GB2244298A

GB2244298A - Insulated cavity closers

Info

Publication number: GB2244298A
Application number: GB9016674A
Authority: GB
Inventors: George Molyneux
Original assignee: Radway Plastics Ltd
Current assignee: Radway Plastics Ltd
Priority date: 1990-02-15
Filing date: 1990-07-30
Publication date: 1991-11-27
Anticipated expiration: 2010-07-30
Also published as: GB9003425D0; GB2244298B; GB9016674D0

Abstract

A cavity closer 70 is shown for closing the end of a cavity wall of a building, adjacent to an opening for a door or a window frame. The closer comprises a strip of corrosion-resistant, liquid-impermeable material, having a cavity entering part 80 adapted to fit within the end portion of a wall cavity and a location rib 72 adapted to provide location for a frame element of a door or a window frame in either the internal or external sense. A layer of thermal insulation material 144 is provided, which is located at least partly within the cavity entering portion and the position of the location rib is such that at least part of a frame element abutting that rib will overlie the thermal insulation layer. <IMAGE>

Description

STRUCTURAL ASSEMBLIES AND CAVITY CLOSERS.

The invention relates to cavity wall buildings and is applicable to either the traditional cavity wall construction in which the internal leaf of the wall is made of building blocks or to timber frame type buildings, in which the internal leaf comprises a dry clad frame of timber. Modern building techniques, and perhaps especially thermal insulation techniques, have led to an increased awareness of the problems of cold bridges, which occur particularly around the openings in the wall for doors and windows.

Building Regulations and recommendations (such as those published by the Building Research Establishment) now specify the minimum thermal insulation to be provided in various details of building construction. This is specified as a thermal resistance of 0.65 M2K/W which corresponds to a U value of 1.2 W/M2S. Throughout this specification thermal resistance values will be employed.

For example, common brickwork has a thermal insulation value of 0.14 whereas a 19 millimetres thick layer of ESP (Styrene) insulation material has a thermal insulation value of 0.53. Where the most direct cold bridge from the exterior of the wall to the interior of any cladding on the interior of the internal leaf is perpendicular to the faces of the wall, it is relatively easy to calculate the thermal insulation value of a wall by summating the insulation values of the wall "components (external leaf; cavity; internal leaf; plaster - for example).

One of the reasons for cold bridging in the vicinity of window or door openings is that there can be a heat transfer path through the structure, which is curved and which passes through only a relatively small thickness of one or more of the "components" so that the full thermal insulation value of all the "components" is not effective. A possible method of attempting to provide adequate thermal insulation around a window frame, is to use both a 19 millimetres thick ESP insulation panel and a 12 millimetres thick plasterboard, one on top of the other.Together with the thickness of any adhesive material required to secure the insulation material to the blocks of the internal leaf and to secure the plasterboard to the insulation material, this renders the thickness of the window frame which can be seen on the inside of the building ("sight line") to something below the level of acceptable aesthetics.

It is the object of the present invention to provide a cavity closer which can be used in a structural assembly within a cavity wall adjacent to an opening in the wall for a door or window frame which allows a construction which will meet thermal insulation requirements and help to eliminate cold bridging in these areas.

In order to explain the invention, it is necessary to refer to certain spatial relationships, which will now be defined. Throughout the specification, the two leaves of the cavity wall will be referred to as the internal and external leaves respectively, and hence the thickness of the wall is measured in the internal/external direction.

This is to avoid referring to "outside" and "inside" which as will appear, are used for a different purpose.

The opening in a wall for a door or window frame has ends adjacent which are located the various frame elements head, jamb or sill. These ends are therefore considered to face "inwardly" (i.e. inwardly towards the frame) and each frame element has an "outer" face which fits against the end of the wall as well as "internal" and "external" faces which face respectively in the internal and external directions as previously defined.

Thus the expressions "internal" and "external" refer to the spatial relationship of the leaves of the wall, whereas the expressions "outer" and "inner", or "outside" and "inside" refer to the window or door frame as seen from the front or rear.

According to a first aspect of the invention, a cavity closer for closing the end of a cavity wall of a building adjacent to an opening for a door or window frame, comprises a strip of corrosion-resistant, liquidimpermeable material, having a cavity entering part adapted to fit within the end portion of a wall cavity and a location rib adapted to provide location for a frame element of a door or window frame in the internal/external sense; there being a layer of thermal insulation material located at least partly within the cavity entering portion, the position of the location rib being such that at least part of the frame element abutting that rib will overlie the thermal insulation layer.

Cavity closers in the form of strips of water-resistant, moisture impermeable material (e.g. plastics) are now well known (see United Kingdom Patent Specifications 1 302 694, 1 302 695, 1 302 696 and 2 158 478 for examples).

Although these cavity closers have many advantages over traditional methods of closing the ends of cavities, they provide only a relatively thin layer of usually plastics material between the frame member of the door or window and the leaves of the cavity wall, and even if the reveal on the inside of the frame is covered with plasterboard, there is a curved heat transfer path through the plasterboard, then through the cavity and then through the outer leaf of the wall, which provides only a relatively poor thermal resistance.

It has also been proposed (see, for example, United Kingdom Patent Specification No. 1 399 456) to provide a cavity closer made of plastics material, in which part of the cavity closer is filled with thermal insulation material, as a means of attempting to increase the thermal resistivity of the construction, between the outer leaf of the wall, and the plaster reveal.However, in those constructions, the door or window frame is located entirely on the outer leaf of the cavity wall, so that the plastered reveal inside the door or window frame, where it abuts against the inner face of the door or window frame, is only separated from the outer leaf of the wall by the thickness of a part of the extruded cavity closer, or in some later forms of thermally insulated cavity closers, by a very small triangular web of thermal insulation material, which has very little, if any, effect on the minimum thermal resistance of the structure around the door or window frame.

One of the essential features of the present invention is that the cavity closer is so constructed, that at least part of the frame element which abuts against the location rib of the cavity closer, actually overlies the thermal insulation material which forms part of the cavity closer, so that there is a substantial thickness of thermal insulation material located on the external side of the plaster reveal, and hence the thermal insulation properties of the construction are considerably enhanced.

Indeed, in a preferred construction, the location rib is so located that the frame element of the door or window frame will overlie approximately 10 mm of the thermal insulation material.

Preferably, the location rib projects inwardly from the cavity entering part, but is offset to one side of that part, so that alternative frame location positions (with respect to the thickness of the wall) are offered by inverting the closer. All known cavity closers are adapted to be employed in a single orientation, that is to say one edge is always the external edge and the other edge is always the internal edge, or the cavity closer is symmetrical about its vertical longitudinal median plan, so that it is immaterial which edge of the closer is used as the external edge. In contradistinction to these known cavity closers, the cavity closer in accordance with the first aspect of the invention exhibits greater versatility, in that it can be employed in one of two orientations.In the first orientation, one edge is on the external side, and the other edge is on the internal side, but when the cavity closer is inverted from this first orientation, the other edge is on the external side and the one edge is then on the internal side. Since the location rib is offset to one side of the cavity entering part, by the simple process of inverting the cavity closer before it is used, one is able to obtain two possible locations of the frame element of the door or window frame. This is obviously a great advantage, because one of the snags of known cavity closers is that it is necessary for the stockist to hold stocks of a number of types of cavity closer to deal with a variety of constructions, but this number can be reduced, in that the single cavity closer can be employed in two different orientations. As will appear hereinafter, the cavity closer in accordance with preferred embodiments of the invention is even more versatile, in that it can be used in a series of possible locations and with cavities of various widths.

According to another preferred feature of the invention, the cavity entering part includes a channel cross-section, the web of which extends in the internal/external sense, there being a frame engaging flange adapted to receive and abut a frame element of a door or window frame, this flange being substantially parallel with the web of the cavity entering part and extending (in one orientation of the strip) externally of the cavity entering part, and further extending partway only across the "open" side of the cavity entering part, the location rib projecting from the part of the frame-engaging flange which extends over the cavity entering part. Preferably, there is a second frame-engaging flange in substantial continuation of the first frame-engaging flange, but extending (in the one orientation of the strip) internally of the cavity entering part.It is further preferred that the second frame-engaging flange also extends partway only across the "open" side of the cavity entering part.

The frame-engaging flange or flanges is or are adapted to abut against the end or ends of the leaves of the cavity wall, and provide a means whereby the cavity closer can be conveniently secured to the frame element, by nailing or screwing through the frame-engaging part or flanges.

Moreover, since the frame-engaging flange or flanges is or are made of liquid-impermeable material, they provide an effective dampproof course between the end of the wall (particularly the external leaf of the wall) and the frame element. This is especially important, where the door or window frame is made of timber, because the external leaf of a cavity wall is frequently damp for long periods, especially in climatic conditions where there is likely to be a relatively long period of the year in which there is rain on almost every day, and sometimes the external leaf of the wall is quite wet for some weeks on end. It is well known, that one source of rotting of a timber window or door frame is moisture migrating from the external leaf of the wall into the jamb of the door or window frame.

This is, of course, entirely prevented when the frameengaging flange separates the end of the wall from the frame element.

According to another preferred feature of the invention, the first and second frame-engaging flanges extend by substantially the same distance in the internal/externals sense from the location rib. Thus, although the location rib is offset with respect to the cavity entering portion, it is central of the overall width of the cavity closer between the ends of the frame-engaging flanges. Hence, no matter on which side of the locating rib the frame element is engaged, the frame-engaging flange at that side will extend to the same distance externally relatively to the door or window frame.

According to another preferred feature of the first aspect of the invention, the layer of thermal insulation material is a preformed element, and the cavity entering part of the strip is capable of being distended to allow the insulation material to be inserted through the "open" side. This is another significant feature of the invention. Some known cavity closers locate thermal insulation material in an enclosed insulating space, so that it is relatively difficult to fit the insulation material into that space. It is possible to fit strips of thermal insulating material into the cavity closer with a totally enclosed space, by threading it through one end, but then this usually has to be carried out on site, and is an added complication in the building process.The advantage of the construction according to the preferred feature of the invention is that the thermal insulation material can be made separately in strips, and applied in the manufacturing workshop by the simple expedient of distending the cavity entering portion of the closer, putting the insulating element into the cavity entering portion, and allowing that part to re-close onto the insulating material.

Preferably the thermal insulation layer substantially fills the cavity entering part.

According to another preferred feature of the invention, an anchorage for a wall tie is available at all positions along the length of the cavity entering part. Preferably, a wall tie anchorage is available on the internal face of the internal flange of the channel-shaped cavity entering portion (in the one orientation of the strip). Such an anchorage allows a wall tie to extend from the internal face of the internal flange into the internal leaf of the cavity wall when the closer is used in the one orientation or, alternatively, if the closer is inverted, it allows a similar wall tie to be employed between the internal flange of the channel-shaped cavity entering portion and the external leaf of the cavity wall.

It is further preferred, that two wall tie anchorages are available at all positions along the length of the cavity entering part at the outer end of that part. This is a particularly advantageous construction, in that it allows two sets of wall ties to be employed between the outer end of the cavity entering part of the closer and the two leaves of the wall, one set being attached to each of the two anchorages at the outer end of the cavity entering part. It will be appreciated, that a particularly firm construction is provided if there are two sets of wall ties, one engaging in each leaf of the wall, and this has the effect of firmly tying the two leaves of the wall together at a position adjacent to the door or window frame, which is normally rather a weak part of the cavity wall construction.

Wherever wall tie anchorages are provided, they preferably take the form of undercut recesses in cross-section.

It is further preferred, that a moisture trap is formed in the inner (frame-engaging) face of the frame engaging flange. Further, a moisture trap is preferably formed in the inner (frame-engaging) face of the second frameengaging flange. Such a moisture trap may comprise a series of closely juxtaposed grooves with relatively sharp longitudinal edges between them. The provision of moisture traps of this kind on the inner face or faces of the frame-engaging flange or flanges has the effect of preventing moisture migrating across the joint between the cavity closer and the frame element, from the exterior of the frame to the plaster reveal on the interior of the frame.

According to another preferred feature of the invention, the depth of the thermal insulation layer from the inside to the outside is not less than 15 mm. It has been found that this gives a useful degree of thermal insulation.

Preferably also, the distance in the internal/external sense between the external edge of the cavity entering part and the external face of the location rib is approximately 10 mm.

In one form of this aspect of the invention, a wall tie anchorage is available at all positions along the length of the frame-engaging flange. In yet another form of this aspect of the invention, a wall tie anchorage is available at all positions along the length of the second frameengaging flange. The or each such wall tie anchorage may take the form of an undercut recess in cross-section.

In a form of this aspect of the invention, which is intended to be used with a cavity having a width of more than 50 mm, a second thermal insulation layer is provided in the angle between the internal face of the cavity entering part and the outside face of the second frameengaging flange. In yet another form of the invention, also intended to be used with a cavity wider than 50 mm, a third thermal insulation layer is provided in the angle between the external face of the cavity entering part and the outside face of the frame-engaging flange.

According to yet another possible feature of this first aspect of the invention, there is an additional flange in substantial continuation of the web of the cavity entering part extending in the same direction and parallel with the frame-engaging flange to permit a further layer of thermal insulation material to be located between this additional flange and the frame-engaging flange.

Preferably, the cavity closer takes the form of an extrusion. It may be made in plastics material, and in a preferred construction it is made in polyvinylchloride.

According to a second aspect of the invention, a structural assembly comprises a cavity wall having internal and external leaves, with a cavity between them; a frame element of a door or window frame located adjacent to an end of the cavity wall; a cavity closer between the end of the wall and the frame element, the cavity closer (i) bridging the cavity; (ii) locating a layer of thermal insulation material across at least a substantial part of the cavity, and (iii) providing a location for the frame element in the internal/external sense, which locates the frame element so that at least part of it overlies the thermal insulation layer.

It will be appreciated that the structural assembly in accordance with this aspect of the invention exhibits the same advantages as the first aspect of the invention, particularly with regard to the provision of an adequate thermal insulation of the detail at the end of the cavity wall where the door or window frame is fitted.

Preferably, the cavity closer comprises a strip of corrosion-resistant, liquid-impermeable material, having a cavity entering part which fits within the end portion of the cavity, so that the thermal insulation layer is located substantially entirely within the cavity, and a location rib which projects inwardly from the cavity entering part, the frame element abutting a face of this rib. It is further preferred that the locating rib is offset to one side of the cavity entering part so that (in one orientation of the closer) the frame element extends only a relatively short way across the cavity, but (in the inverted orientation of the closer) the frame element extends across the greater part of the width of the cavity.

According to another preferred feature of this second aspect of the invention, the cavity entering part of the closer is of channel-shaped cross-section, the web extending across the width of the cavity, there being a frame-engaging flange locating between the end of the external leaf and the frame element and also extending part way across the "open" inner end of the cavity entering part, the location rib projecting from the part of the frame-engaging flange which extends over the cavity entering part. Preferably the closer has a second frameengaging flange in substantial continuation of the first frame-engaging flange, but locating on the end of the inner leaf of the cavity wall in the said one orientation of the closure. The second frame-engaging flange may also extend part way only across the "open" side of the cavity entering part.

It is further preferred, that the thermal insulation layer is a preformed element which is fitted into the cavity entering part by distending that part to allow the thermal insulation layer to be pushed into the cavity entering part through the "open" side thereof.

In the preferred construction, the thermal insulating layer substantially fills the cavity entering part.

Furthermore, the inner face of the thermal insulating layer is preferably substantially in alignment with the ends of the leaves of the wall. This is a significant feature of this second aspect of the invention, because it ensures that none of the plaster which forms the plaster reveal on the interior of the window or door frame actually enters the cavity. If any plaster does enter the cavity, it is inevitably closer to the external leaf of the wall, than if it is kept entirely outside the cavity, and therefore by ensuring that the plaster does not enter the cavity, the thermal insulation value of the detail is increased.

According to another preferred feature of the second aspect of the invention, the closer provides anchorage for wall ties on the internal flange of the cavity entering part of the closer at all positions along its length and at least one wall tie is attached to the anchorage and extends between two of the courses of the adjacent leaf of the wall. Preferably the closer provides two alternative anchorages for wall ties on the web of the cavity entering part of the closer at all positions along its length; at least one wall tie attached to one of these anchorages extends between two courses of the external leaf of the wall and at least one other wall tie attached to the other of these anchorages extends between two courses of the internal leaf of the wall.The or each wall tie anchorage is preferably in the form of an undercut recess and the or each wall tie has a root portion, which is adapted to fit in the undercut recess either by sliding along the closer strip from one end or by inserting the root portion with the tie turned about its own longitudinal axis away from the operative orientation, so that the root portion can be inserted through the open side of the undercut recess and then turning the tie to its operative orientation.

In the preferred construction, the frame-engaging flange has a moisture trap in the face which engages with the frame element. Further, the second frame-engaging flange preferably has a moisture trap in the face which engages with the frame element. It is preferred that the moisture trap comprises a series of closely juxtaposed grooves with relatively sharp longitudinal edges between them.

According to another preferred feature of this second aspect of the invention, the depth of the thermal insulation layer from the inside to the outside is not less than 15 mm. It is further preferred that the distance in the internal/external direction between the external edge of the cavity entering part and the external face of the location rib is approximately 10 mm.

According to yet another preferred feature of this aspect of the invention, a wall tie anchorage is available at all positions along the length of the closer in the outside face of the first frame-engaging flange and at least one wall tie attached to that anchorage extends between courses of the adjacent leaf of the wall. Preferably, a wall tie anchorage is available at all positions along the length of the closer in the outside face of the second frame-engaging flange and at least one wall tie attached to that anchorage extends between courses of the adjacent leaf of the wall.Thus, in addition to any wall ties used between the cavity entering portion of the closer and the internal and external leaves of the wall (or as alternatives thereto) one or more wall ties can be used to secure the closer by extending from the anchorages on the frame-engaging flanges into the adjacent leaves of the wall.

In a particular form of the second aspect of the invention, in which the cavity is wider than the cavity entering part, that part is located against the internal face of the external leaf of the wall and a second thermal insulation element is located in the angle between the internal face of the cavity entering part and the second frame-engaging flange, the second insulating layer substantially filling the width between the cavity entering part and the internal leaf of the wall.

In another construction, in which the cavity is wider than the cavity entering part, that part is located against the external face of the internal leaf of the wall and a third thermal insulating layer is located in the angle between the external face of the cavity entering part and the first frame-engaging flange, the third insulating layer substantially filling the space between the cavity entering part and the external leaf of the wall.

According to another preferred construction, a structural assembly in accordance with the second aspect of the invention, has a cavity closer which comprises a strip of water-resistant, moisture-impermeable material, the strip having substantially parallel internal and external webs, the external web engaging with the outside face of the frame element and on the end of the external leaf of the wall, the internal web being offset outwardly of the external web and engaging on the end of the internal leaf of the wall, the offsetting of the webs with respect to each other defining an internal checked reveal between the two leaves of the wall, and an end strut engaging between and connecting the internal and external webs at a position such that a socket is formed, bounded by overlapping parts of the two webs and the strut, the socket opening into the reveal; the thermal insulation layer covering at least part of the inside face of the internal web and having its external end located in the socket, at least part of the insulation layer which is in the socket being thereby located on the outside of the frame element and attachment means securing the cavity closer to at least one of the internal and external leaves of the wall.

It will be appreciated that this is quite a different construction to some of those which have been described already, in that there is strictly speaking no cavity entering part of the closer, but instead, a checked reveal construction is used, and the construction of the closer is such that the insulation material extends across the width of the end of the cavity.

Preferably, the position of the frame element relatively to the thickness (interior to exterior) of the cavity wall is assured by engagement of the frame element with a location flange on the external web of the cavity closer.

It is further preferred, that the spacing in the wall thickness direction between the strut and the location flange is such that when the external edge of the insulation layer is engaged with the strut, the length of that part of the insulation layer which is on the outside of the frame element in the wall thickness direction is at least substantially equal to the thickness of the insulation layer.

Preferably, a cavity entering formation extends from the outer face of the internal web and is of such a crosssection that it provides a dampproof course within the cavity between the two leaves. Preferably the cavity entering formation is in the form of a flange projecting outwardly substantially perpendicular to the internal web.

It is further preferred that the cavity entering flange projects at least 50 mm from the internal web.

According to another preferred feature, the internal web is provided with a moisture barrier adapted to resist moisture migration across the internal web between the two leaves of the wall. The moisture barrier may comprise a series of longitudinal grooves in the outer face of the internal web.

According to yet another preferred feature of the invention, the means securing the cavity closer to at least one of the leaves of the wall comprises one or more wall ties anchored to the internal web and projecting from that web into one or more mortar joints between the courses of the internal leaf.

According to another preferred feature, the means securing the cavity closer to at least one of the leaves of the wall comprises one or more angled wall ties, each being anchored to the external side of the strut by one limb, the other (angled) limb projecting in the outward direction away from the frame element and into a mortar joint between two courses of the external leaf.

It is further preferred that there is a moisture barrier formation on the inside face of the outer web to resist migration of moisture across the joint between the frame element and the external leaf.

According to yet another preferred feature of the invention, the external web and the frame element are located substantially entirely aligned with the external leaf of the wall, the socket of the cavity closer being received in a cutaway part of the external leaf.

Preferably, the cavity entering flange abuts the internal face of the external leaf of the wall and retains any mortar which is squeezed out of the external leaf into the cutaway for the socket.

The socket formation may be located on the internal side of the external leaf and the cavity entering flange may be located at a position intermediate the width of the cavity. Alternatively, the cavity entering flange may abut the external face of the internal leaf of the wall, the external web extending across substantially the entire width of the cavity and resting on the end of the external leaf.

The invention will be better understood from the following description of the problems of ensuring correct thermal insulation of a building adjacent to a door or window frame and structural assemblies and cavity closers for use with such assemblies which ensure that the thermal insulation is adequate, all of which are described by way of examples only, with reference to the accompanying drawings, in which:: Figure 1 shows the detail of a cavity wall adjacent to a window frame where a known type of cavity closer made of insulation material is employed, Figure 2 is a detail of a cavity wall adjacent to a window frame showing a somewhat unsatisfactory way of achieving a required thermal insulation, Figure 3 is a detail similar to Figure 1, but showing another construction which does not give adequate thermal insulation, Figure 4 is a cross-section through a cavity closer and dampproof course in accordance with the invention, Figure 5 is a cross-section through an alternative design of cavity closer and dampproof course, Figure 6 is a detail of a cavity wall adjacent to a window frame using a cavity closer as shown in Figure 4, to provide an adequate thermal insulation, Figures 7 and 8 are views similar to Figure 6, but showing the window frame in different location, Figure 9 is a detail through a cavity wall adjacent to the head of a window frame showing the difficulty of providing adequate thermal insulation, Figure 10 is a section through a cavity closer and dampproof element for use over the head of a window frame, Figure 11 is a detail similar to Figure 9, but showing the use of the cavity closer illustrated in Figure 10, Figure 12 is a section through an insulation layer, Figure 13 is a detail similar to Figure 8, but showing the use of the insulation layer illustrated in Figure 12, Figure 14 is a cross-section through part of a cavity wall construction at a window frame, showing a conventional construction and, in particular, the location of the window frame and its sill relatively to the external leaf of the wall, Figure 15 is a cross-section through a cavity closer in accordance with this invention, Figure 16 is a plan view of a wall tie adapted for use with the cavity closure shown in Figure 15, Figure 17 is a cross-section through part of a cavity wall adjacent to an opening for a window frame, showing a jamb of a window frame, and the employment of a cavity closer of the type shown in Figure 15, Figure 18 is a view similar to Figure 17, but showing an alternative construction, Figure 19 is another view similar to Figure 17, but showing another alternative construction, Figure 20 is another view similar to Figure 17, but showing yet another alternative construction, Figure 21 is another view similar to Figure 17, but showing a further alternative construction, Figure 22 is another view similar to Figure 17, but showing yet another alternative construction, Figure 23 is a view similar to Figure 17, but showing a construction in which the cavity closer of Figure 16 is used in an inverted orientation, Figure 24 is a view similar to Figure 23, but showing an alternative construction, Figure 25 is another view similar to Figure 23, but showing another construction, Figure 26 is another view similar to Figure 23, but showing yet another construction, Figure 27 is another view similar to Figure 23, but showing another alternative construction, Figure 28 is another view similar to Figure 23, but showing another alternative construction, Figure 29 is another view similar to Figure 23, but showing yet another alternative construction, Figure 30 is another view similar to Figure 23, but showing another alternative construction, Figure 31 is another view similar to Figure 23, but showing a construction with a very wide cavity, Figure 32 is a cross-section through an alternative form of cavity closer, Figure 33 is a plan view of another form of wall tie for use with a cavity closer such as that shown in Figure 32, Figure 34 is a cross-section through an alternative form of cavity closer in accordance with the invention, Figure 35 is a plan view of yet another form of wall tie for use with the cavity closer illustrated in Figure 34, Figure 36 is a cross-section through part of a cavity wall, showing use of a cavity closer of the type illustrated in Figure 34, Figure 37 is a view similar to Figure 36, but showing an alternative use of the cavity closer shown in Figure 34, Figure 38 is a cross-section through yet another form of cavity closer in accordance with the invention, Figure 39 is a cross-section through part of a wall, showing use of the cavity closer illustrated in Figure 38, Figure 40 is a view similar to Figure 39, but showing use of the cavity closer of Figure 38 in a different orientation, Figure 41 is a cross-section through another form of cavity closer, Figure 42 is a diagrammatic representation of a cavity wall, showing uses of the cavity clcser illustrated in Figure 41, Figure 43 is another diagrammatic view of cavity walls, showing an alternative way of using the cavity closer illustrated in Figure 41, and Figure 44 is a cross-section through another construction of cavity wall, with a check reveal showing another use of the cavity closer illustrated in Figure 38.

In Figure 1 there is illustrated a conventional cavity wall of a building comprising an external leaf 10, which is usually constructed in bricks and an internal leaf 12 which is usually constructed in building blocks such as breeze blocks. A cavity 14 is formed between the two leaves of the wall and in Figure 1, the cavity is of conventional 50 millimetres width. It is to be understood that the two leaves of the wall may be made in any known building material, and in particular, if the building is of timber frame construction, the internal leaf 12 will be made of a timber frame clad internally with plasterboard.

The part of the wall which is shown in Figure 1 is at an end adjacent to an opening for a window frame, and one of the timber jambs 16 of the window frame is shown.

However, similar considerations to those which will be discussed in relation to this construction apply to door frames and to the heads and sills of window and door frames. For convenience however, throughout the specific examples herein described, reference will be made to the jamb or head of a window frame, though it must be clearly understood that the invention is not restricted to window frames. Also, the frame may be made of metal or plastics, although timber frames are illustrated herein.

It is to be noted that in the Figure 1 construction, the window frame is located in the cavity wall so that the jamb 16 substantially bridges the cavity. This is a desirable position because it provides good protection for the frame against weather, but it is not often favoured by builders, because it requires the fitting of a wide sill -(not shown). The end of the cavity 14 is closed by the jamb 16 so that no other cavity closer is needed. However, in this particular example, the end of the cavity is filled with a 50 millimetres square block of thermal insulation material, for example E.S.P (styrene) material.

The construction is completed by a layer of plasterboard 20 (conventionally 12 millimetres thick) which lines the reveal on the interior of the window frame and which is secured to the end of the internal block leaf 12 by plaster dabs 22, and by a layer of plaster or plasterboard 24 on the internal face of the internal leaf 12.

Now if one considers the heat transfer path which passes through the plasterboard 20; the internal leaf 12; the insulated cavity closer 18 and the external leaf 10, the thermal insulation appears to be adequate. However, there is a heat transfer path, illustrated by the chain dotted line 26 which circumvents the ESP insulation by passing through the cavity on the outside of the cavity closer. The thermal insulation provided by this path 26 can be shown to be: Plasterboard 20 0.08 50 millimetres internal leaf assuming this to be building block with a density of 100 kilograms/m3) 0.15 50 millimetres cavity air space 0.18 70 millimetres external brick wall (assuming this to have a density of 1600 kilograms/m3) 0.095 Total 0.505 This falls well short of a recommended (Building Research Establishment) figure of 0.65 for the thermal insulation.

In Figure 2 there is shown an arrangement which in many respects is similar to that shown in Figure 1 and therefore detailed description is unnecessary. Again there is a cavity wall comprising an external leaf 30, an internal block leaf 32 with a 50 millimetres wide cavity 34 between them. In this construction, the jamb 36 of the window frame is located entirely on the external leaf and although this exposes the window frame more than the location shown in Figure 1, it is more frequently used.

The end of the cavity 34 is closed by cut bricks 38, which is a very traditional method, and there is a vertical dampproof course 40 of bitumastic material between the cut bricks and the external leaf 10.

In this construction, in order to comply with the thermal insulation requirements, a layer of ESP insulation material 42 is laid over the end of the internal leaf 32 and over the ends of the cut bricks 38, this layer 42 abutting the internal face of the jamb 36. A 12 millimetres plasterboard layer 44 is then laid over the inside face of the ESP layer and this plasterboard is skimmed as shown at 46. The internal face of the internal leaf 32 may also be covered with plasterboard 48 which is also skimmed.

It will be apparent that with this structure, the heat transfer path from the inside of the window reveal must pass through the 19 millimetres layer of ESP and this will ensure that the thermal insulation will meet the minimum requirements. However, a severe aesthetic problem has been created. The width of the jamb 36 on the interior is typically 50 millimetres. The minimum thickness of the insulation layer 42; plasterboard 44 and skim 46 is 34 millimetres, leaving the maximum free width of the jamb 36 visible on the inside of the building (this is called the "sight line") of 16 millimetres. In practice, this will be reduced, because dabs of plaster or adhesive will be applied underneath the ESP layer 42 and under the plasterboard layer 44, so that the sight line may be well below 15 millimetres. Anything so shallow would be totally unacceptable aesthetically.

In Figure 3, there is shown another possible construction in which the cavity wall comprises an external brick work leaf 50; an internal block leaf 52; a cavity 54 and a window frame jamb 56 located entirely on the external leaf 50. The construction differs from that shown in Figure 2 in that the end of the cavity 54 is closed by a hollow plastics cavity closer 58 shown only diagrammatically filled with ESP insulation material.

The reveal on the interior of the window frame is covered with plasterboard 60, which will be skimmed and the internal face of the internal leaf 52 is covered with plasterboard 62.

The use of the insulation filled cavity closer 58 would appear to solve the thermal insulation problem, but in practice it does not, because there is a curved heat transfer path, shown bounded by the curved line 64 and 66, which provides a cold bridge. It can be shown that the thermal insulation value of this path is: 12 millimetres plasterboard 0.08 Average of 9 millimetres ESP insulation (across the corner shown at 68) 0.25 70 millimetres external brickwork 0.095 Total 0.425 This is only about 70% of the recommended minimum insulation value.

It has been shown therefore by reference to Figures 1 to 3, that the builder is faced with a dilemma. Even with a thermal insulation filled cavity closer, he cannot achieve the required total thermal insulation value except by putting a layer of ESP across the internal window reveal and that, together with the plasterboard, reduces the sight line to an unacceptable width.

This dilemma is solved by the use of a cavity closer, one form of which is shown at 70 in Figure 4. This cavity closer is made in the form of an extruded strip of unsaturated polyvinylchloride (uPVC) of a similar grade to that conventionally used in the building industry for gutters, fallpipes and the like. The material from which the cavity closer 70 is made ensures that it is waterresistant and moisture-impermeable, characteristics which enable it to be used as a dampproof course as well as a cavity closer. Because it is extruded, it can be made economically and it is of constant cross-section throughout its length. It is possible to take relatively long lengths of the cavity closer to a building site and then to cut the required lengths on site.Plastics cavity closers in themselves are now well known and for a general description of such closers, reference is made to the specifications of U.K. Patents No. 1 302 694; 1 302 695; 1 302 696 and 2 158 478. The principle elements of the cavity closer and dampproof course 70 are: an external web 72; an internal web 74; a strut 76; a locating flange 78 and a cavity entering flange 80. The external web 72 is generally planar with a flat underside (as seen in Figure 4). The locating flange 78 is a relatively narrow perpendicular upstand from the internal end of the web 72. The top or inside face of the internal web is formed with a series of longitudinal shallow grooves 82 which are so closely juxtaposed that a relatively sharp or pointed cross-section rib 84 is formed between each adjacent pair of grooves. This arrangement of the grooves 82 provides a very effective moisture trap, because it is almost impossible for moisture to migrate across the grooved inside face of the external web 72, especially when that web is located vertically, as it will be when the cavity closer 70 is used alongside a jamb of a door or window frame.

The internal web 74 is also generally planar with a flat top or inside surface 86. The web 74 is parallel with the external web 72, but is considerably wider, and as is clear from Figure 4, there is overlap between the two webs. In a typical example, the external web will be approximately 70 millimetres wide, but the internal web may be approximately 130 millimetres wide and there is an overlap of about 20 to 25 millimetres between the two webs. The strut 76 connects the two webs and is about 20 millimetres deep, so that a socket 88 is formed which is bounded by the overlapping parts of the two webs and the strut 76 and which is open on the internal side. As will hereinafter appear, this socket is adapted to receive and locate part of a standard 19 millimetres thick ESP insulation layer.

The internal web 74 projects slightly on the external side of the strut 76 to form a rib 90 and there is an inturned lip 92 on the end of this rib. A corresponding out turned lip 94 is formed on the outside of the external web 72, leaving a gap 96 between the two lips.

In effect, this provides an undercut recess on the external face of the strut 76.

The cavity entering flange 80 is a flat sided planar flange approximately 50 millimetres wide perpendicular to the internal web 74 and aligned with the locating flange 78 on the external web. All that part of the internal web which is on the external side of the flange 80 and approximately 50 millimetres width of the internal web on the internal side of the flange 80 is formed with a series of closely juxtaposed longitudinally extending grooves 98 to provide moisture barriers on the outside of the web 74 similar to the moisture barrier on the inside of the web 72.

Two pairs of inclined ribs 100 are provided on the outside of the internal web 74, one pair adjacent to the internal edge of the web and the other pair adjacent to the internal edge of the moisture barrier 98. Each pair of ribs 100 forms an effective dovetail shaped undercut recess which provides an anchorage for the root of a wall tie as will hereinafter appear.

The cavity closer shown in Figure 4 can be employed with a variety of window frame fixing arrangements and one such arrangement is shown in Figure 6. A cavity wall comprises an external leaf 110 made of bricks and an internal building block leaf 112 with a 50 millimetres wide cavity 114 between them. One feature of the construction to be noted is that the two leaves 110 and 112 are built up so that there is an internal checked reveal about 20 millimetres wide, that is to say, the external leaf 110 projects about 20 millimetres further into the window opening than the internal leaf. Cavity walls formed with checked reveals are well known and no further description of this is required.Another significant feature to be noted is that during the construction of the end of the wall around the window opening, the internal corners of the bricks of the external leaf are cut off as shown at 116. This cutting will probably be done by the brick layer using his trowel, but specially prepared (cut, moulded or ground) bricks could be employed.

The jamb of the window frame is shown at 118 and it is to be noted that it is located entirely within the external leaf 110, that is to say, its internal face is aligned with the internal face of the external leaf of the wall.

Before the window frame is offered up to the wall, cut lengths of the cavity closer 70 are fastened to the outside faces of the window frame jambs. This is done by locating the jamb with its outside face resting on the grooved inside face of the external web 72 and its internal face resting against the locating flange 78. It will be appreciated that it is very easy to locate the cavity closer on the jamb 118 in this way. Nails 120 are then driven through the web 72 into the jamb 118 to secure the cavity closer to the window frame.

As the wall is built up to the sill level, the window frame is placed in position on the sill aligned with the external leaf. The internal leaf is then built up and the internal leaf 74 rests on the end of the internal leaf 112. Special wall ties 122 are fitted at heights corresponding to the mortar courses in the internal leaf.

The ties 122 are of a known kind and each simply comprises a plastics moulding in the form of a flat bar (say 3 millimetres thick) with a flared outer end 126 in which there is a large generally triangular hole 128 and a dovetail shaped route portion 130, with a central notch 132. The dovetail route portion 130 is a tight fit in either of the recesses formed by the ribs 100 on the internal flange 74 of the cavity closer 70. To fit one of the ties 122, the tie is turned through 900 about its longitudinal axis from the position illustrated in Figure 6, so that the width of the tie is in a vertical plane.

The route portion 130 is then inserted between the ribs 100 of the dovetail recess nearest to the internal end of the internal web 74, and then the tie is turned about its longitudinal axis into the position illustrated, where its route engages tightly in the recess in the web 74.

The tie will then be pressed into mortar between two courses of the bricks of the internal leaf 112 of the wall. Some mortar will flow into the hole 128 to provide a positive key for the tie in the mortar and in any case, the flaring of the outer end of the tie helps to key it in the mortar. The root cannot detach from the web 74 once the mortar has set to prevent the tie turning, so that the internal web becomes firmly anchored to the internal leaf 112. This ties the cavity closer 70 and the window frame to the internal leaf.

The external leaf is then built up locating the internal faces of the end bricks against the flange 80 of the cavity closer. The closer then bridges the cavity and part of its external web rests on the end of the external leaf. The checked reveal is automatically produced.

Special ties 124 are used to secure the cavity closer to the external leaf of the wall. The ties 124 are also formed as moulded plastics flat plates, but each has a short lateral arm 134 joined at right angles to a longer longitudinal arm 136. At its internal end, there are notches 138 forming an anchoring root 140 which fills the space 96 between the strut 76 and the lips 92 and 94 of the cavity closer 70. A series of holes 142 is formed in both arms of the tie 124. The tie 124 is fitted in similar manner to that described for the tie 122, to bring the root 140 into anchoring engagement with the strut 76, and the tie is held in position by mortar engaging in the holes 142.

It will be appreciated therefore, that as the wall is completed alongside the window opening, the window frame is firmly secured to the wall by the cavity closer 70 and the ties 122 and 124. The internal face of the jamb 118 is aligned with the internal face of the external leaf by virtue of the alignment of the locating flange 78 with the cavity entering flange 80. It is also to be noted that the socket 88 formed in the cavity closer is located in the space formed by cutting away the corners of the bricks in the external leaf. The spaces around the socket in the external leaf are filled with mortar squeezed out from between the courses of bricks in the external leaf and this mortar is retained on the internal side by the cavity entering flange 80.

Besides closing the end of the cavity and securing the jamb 118 to the two leaves of the cavity wall, the cavity closer and dampproof course element 70 also provides dampproofing arrangements. To begin with, it will be seen that the external web 72 separates the external leaf of the wall from the jamb 118, and thereby provides a very effective dampproof course between the brickwork of the external leaf and the jamb 118. It is well known, that one source of timber frame deterioration is damp migrating from the external brickwork into the jamb of the frame. This of course is entirely prevented by the dampproof course constituted by the external leaf 72.

Furthermore, it is virtually impossible for moisture to migrate from the outside of the building across the joint between the external leaf 72 and the jamb 118, by virtue of the moisture barrier provided by the grooves 82 and the ribs 84.

The cavity entering flange 80 provides a moisture barrier intended to prevent moisture travelling across the cavity itself at the end of the cavity wall, and in addition, in the arrangement illustrated in Figure 6, the moisture barrier provided by the grooves 98 on the outside face of the internal leaf 74 provide a further means of preventing moisture travelling across the cavity from the external leaf to the internal leaf.

Once the window frame is fitted, it is then possible to complete the detail illustrated in Figure 6 first by fitting a 19 millimetres thick layer of ESP insulation 144, and then by covering the insulation layer with a 12 millimetres thick plasterboard 146. Now it is to be noted that the ESP insulation layer is cut to such a size, that when it is pushed into the socket 88, and into engagement with the strut 76 of the cavity closer, its internal end is in alignment with the internal face of the internal leaf 112 of the cavity wall. It will be appreciated, that the engagement of the external end of the ESP insulation layer in the socket 88 helps to locate the insulation layer, but of course dabs of plaster or adhesive will be applied to the outside face of the ESP insulation layer, to secure it to the inside face of the internal web 74 of the cavity closer.Similarly, dabs of plaster will be applied to the outside face of the plasterboard 146, to secure it to the insulation layer 144. The external end of the plasterboard 146 is pressed against the internal face of the locating flange 78. The entire detail can then be completed by a layer of plasterboard 149 covering the internal face of the internal leaf 112, and the internal end of the insulation layer 144.

It will be apparent, that the only reduction in the "sight line" on the inside of the jamb 118 is created by the plasterboard 146, and it is quite conventional to have a layer of plasterboard in this position, so that the "sight line" is quite acceptable. There are two possible heat transfer paths from the interior of the building to the exterior adjacent to the window frame.

The first of these is illustrated by the arrows 148. It passes through the plasterboard, then through the ESP insulation layer, across the corner of the cavity 114, and through the external leaf of the wall. It can be shown that this heat transfer path has a thermal insulation value of 0.705, which is greater than the minimum recommended value. The curved heat transfer path illustrated by the continuous arrowed line 150 can also be shown to have a thermal insulation value of 0.68, which again is greater than the recommended minimum value.The significant difference between this arrangement illustrated in Figure 6 and that illustrated for instance in Figure 3 is that part of the ESP insulation has been brought to the outside of the jamb itself in the socket 88, so that whichever heat transfer path is considered, either that at 148 or that at 150, it is necessary to travel through the full thickness of the ESP insulation or a length of the ESP insulation equivalent to or greater than its full thickness. It will be appreciated from this therefore, that it is desirable, that the thickness of the socket 88 (measured from the interior to the exterior) should be at least equal to the thickness of the ESP insulation material, to ensure that the heat transfer path which follows the curved line 150 through the ESP insulation is at least as long as the straight path 148 through that insulation.

Turning now to Figure 7, there is illustrated another arrangement, which in many ways is similar to that illustrated in Figure 6, and indeed, the same reference numerals have been used for equivalent parts. The difference is that the cavity closer 70 is located with the lips 92 and 94 in engagement with the internal face of the external leaf 110, so that it is unnecessary to cut away parts of the bricks of the external leaf. Also, this positions the cavity entering flange 80 at about the mid position across the width of the cavity 114, and of course the socket 88, is then contained entirely within the internal reveal between the two leaves of the wall.

The construction of the detail is exactly as previously described, with the exception that there is no cutting of the bricks of the external leaf, and the location of the cavity closer, and consequently the location of the jamb 118 is different to the extent described and illustrated.

It will be noted, that this has the effect of locating the jamb 118 partly over the cavity 114 and partly over the external leaf 110 of the wall. Also, with this construction, it may be preferable to fit the straight wall ties 122 in the undercut recess of the web 74 which is nearer to the cavity. All the securing and dampproofing advantages described with reference to Figure 6 are provided by the construction illustrated in Figure 7, although it should be mentioned, that the dampproofing between the two leaves of the wall is now effected by the cavity entering flange 80 and the moisture barrier provided by the grooves 98 on both sides of the flange 80.

There are again two possible heat transfer paths from the interior of the building to the exterior. One of these is illustrated by the arrows 152 and it passes through the plasterboard 146, the ESP insulation layer 144, the cavity 114 and the external brickwork 110. It can be shown that the thermal insulation value of this path is 0.85 which is well above the minimum recommended value.

The alternative curved heat path is illustrated by the arrows 154, and again, the cost of the ESP insulation material contained in the socket 88, this path has to pass through a length of that insulating material which is at least equal to the thickness of the insulation material, and in fact it can be shown that the insulation value of this curved heat transfer path is 0.67, which is above the recommended minimum value.

In Figure 8, there is illustrated another arrangement using the cavity closer 70 illustrated in Figure 4, and again this is so similar to the construction illustrated in Figure 6, that the same reference numerals have been used for equivalent parts. In this construction, the wall is built up, with the cavity entering flange 80 located against the external face of the internal leaf 112, and this has the effect of locating the jamb 118 of the window frame in a position where it substantially bridges the cavity 114, and only a small portion of the jamb 118 is within the external leaf 110 of the wall.

Once again, the securing and dampproofing properties of the cavity closer 70 are all utilised though in this case, the dampproof course between the two leaves of the wall is provided by the moisture barrier on the internal web 74 which lies on the external side of the flange 80, and by the flange 80 itself. Furthermore, the straight ties 122 will be fitted in the undercut recess of the internal web 74 which is nearest to the cavity, and indeed it might be necessary to cut off the undercut recess at the internal end of the web 74, if part of that web would otherwise project on the internal side of the internal leaf 112.

Once again, the "sight line" is satisfactory, and with this construction, the minimum values of the heat transfer paths are even greater. The heat transfer path shown by the arrows 156 passing through the plasterboard 146, the ESP insulation 144, the corner of the internal leaf 112, the cavity 114 and the external leaf 110 has a total thermal insulation value of 0.82. The curved heat transfer path following the arrows 158 once again has to pass through a length of the ESP insulation material at least equal to the thickness of that material, and it can be shown that the total thermal insulation value of this curved path 158 is 0.81, which again is extremely satisfactory.

It will be appreciated, that other arrangements than those shown in Figures 6, 7 and 8 are possible, the significant feature being the provision of the socket 88 for the ESP insulation material on the outside of the jamb 118, so that there is no heat transfer path from the interior to the exterior of the building which avoids passing through the ESP insulation material.

Returning now to Figure 5 of the drawings, there is shown an alternative construction of cavity closer and dampproof course 160. In general, this cavity closer is formed as an extrusion in uPVC material similar to that described with reference to Figure 4. Again, it has an external leaf 162 with a locating flange 164 which is identical with the external leaf 82 and locating flange 78 of the cavity closer 70. However, in this construction, a plasterboard retaining lip 166 projects in the internal direction from the inside edge of the locating flange 164 for the purpose of providing a location for the plasterboard which covers the ESP insulation on the window frame reveal.

As with the cavity closer 70, there is an internal web 168 parallel with the external web 162, and a strut 170 joining the two webs, and providing the insulation receiving socket 172. Also, lips 174 and 176 formed on the strut 170 provide a socket for the root portion of an angled wall tie in the same manner as that which is provided on the cavity closer 70. There is also a cavity entering flange 80.

The main difference between the cavity closer shown in Figure 5 and that shown in Figure 4 is that the internal web 168 is formed as a series of "reversed dovetail" formations providing dovetail shaped undercut recesses 178, 180 and 182 on the outside face of the web 168, in any of which the root portions of wall ties can be secured. Also, there are provided by this construction dovetail shaped undercut recesses 184 and 186 on the inside face of the internal flange 168, and these may be used as anchorages for plaster dabs used to secure the ESP insulation layer in position.

It should also be understood, that the invention is not limited to the use of 19 millimetres thick insulation layers. Other types of insulation material could be used, such as 13 millimetres thick polyurethane, because that could still be received in the socket 88 or 172 of the cavity closer 70 or 160, and the plasterboard covering the insulation material would then cover even less of the internal face of the jamb 118 - in other words the "sight line" would be improved.

Figure 9 shows a conventional detail at the head of a window frame, where the external brick work leaf is shown at 170 and a popular type of hollow metal lintel 172 is used, part of which forms part of the internal leaf of the wall (not otherwise illustrated) and part of which extends across the cavity 174, there being a horizontal flange 176 of the lintel supporting the external leaf 170. A sheet of "expanded metal" 178 is secured to the underside of the lintel 172 to provide a key for the plaster which in the conventional construction - not shown - is applied to the underside of the lintel. The head of the window frame is shown at 180, part of the opening casement being illustrated at 182. It will be seen that the head 180 is in alignment with the external leaf of the wall, that is to say, it is in the location equivalent to those shown in Figures 4 and 6 of the drawings.

For thermal insulation purposes, the hollow lintel 172 can be filled with insulation material, but it will be apparent from the previous discussion, that this will not ensure the correct thermal insulation value because the insulation filled lintel is in the same position at the head of a window frame as is an insulation filled cavity closer alongside the jamb of the frame. Therefore, the only known way to achieve adequate thermal insulation is to fit both a layer of ESP or similar insulation material as shown at 184 (securing it to the expanded metal by plaster dabs) and to cover this with plasterboard 186, again secured by plaster dabs and completed by skimming.

Now it will be seen that this presents the problem of reducing the "sight line" on the inside of the window frame head to an unacceptable level - as was the case with the construction shown in Figure 2.

With a view to solving the dilemma of lack of thermal insulation on the one hand or loss of sight line on the other hand, a special extruded plastics cavity closer 190 is provided as shown in Figures 10 and 11.

The cavity closer 190 comprises a top web 192, a bottom web 194, an end strut 196 and a divider strut 198. The top web 192 is generally planar and is wide enough to extend across the full width of the widest cavity with which the closer 190 is to be used, plus the width of the head 180 of the window frame. With a 50 millimetres wide cavity, the top web will be approximately 120 millimetres wide. An external portion of the top web 192 is formed with a moisture barrier comprising a series of closely juxtapositioned longitudinal grooves 200.

The bottom web 194 is of the same width as the top web and is parallel to the top web, but spaced therefrom by a depth of 19 millimetres. The connection and spacing of the two webs is assured by the two struts 196 and 198, the external strut being slightly concave for improved appearance and the two struts with the portions of the webs between them defining a hollow box 202. The remaining portions of the webs and the strut 198 define a socket 204 open at the internal end. The underside of the bottom web has a moisture barrier 206 (formed by closely juxtaposed shallow grooves) and a series of T shaped ribs 208 which form undercut recesses 210.

The manner in which the cavity closer 190 can be used with a cavity wall construction similar to that shown in Figure 9, is illustrated in Figure 11. The same elements have the same reference numerals as those used in Figure 9. It will be noted, that it is not necessary to provide a checked reveal at the head of the window space, and indeed this -would not be possible utilising the hollow lintel 172. However, it should be explained, that the depth of the window opening is made greater than the depth of the window frame by the overall thickness of the flange 176 of the lintel and the thickness of the cavity closer 190.During the construction of the building, a length of the cavity closer 190 is secured across the top of the head 180, aligning the external strut 196 with the external face of the head 180, and driving nails 212 through the hollow box portion 202 of the cavity closer closely adjacent to the divider strut 198. The hollow box section 202 is provided mainly to accept the nails 212, and the box section gives the cavity closer a good degree of rigidity at the point where the nails are used.

The wall is then completed over the head of the window frame, fitting the lintel 172, but after the window frame has been fitted, a layer of ESP insulation board 214 is slid into the socket 204 from the internal end, until it completely fills the socket 204. In this position, the insulation board extends across the underside of the cavity 174, but very importantly, it also extends part way across the top of the head 180, and in this sense it provides exactly the same insulation effect as the ESP insulation 144 illustrated in Figure 6.Once the insulation board 214 has been fitted into the socket 204, plaster or mortar rendering 216 can then be used to fill up the shallow reveal on the internal side of the insulation board; plaster dabs can be pushed into the recesses 210 on the underside of the bottom web 206 of the cavity closer and also applied to the underside of the plaster or mortar rendering, and the detail completed by the fitting of a 12 millimetre thick plasterboard 218, which will be skimmed in the conventional manner.

It can be shown, that because of the location of the insulation board 214 across the cavity and above the head 180 of the window frame, the minimum thermal insulation is provided even if one takes into account the shortest heat transfer path through the detail, and on the other hand, the sight line at the head 180 is acceptable, because it is only reduced from the full depth of the frame head at the internal face thereof by the depth of the ribs 208 plus the thickness of the plasterboard 218 and any skimming on it. The total covered depth is unlikely to exceed 20 millimetres, leaving at least 30 millimetres of the window frame head 180 visible. This is important not only for aesthetic reasons, but because the head 180 is sometimes used to provide attachment means for curtain rails or curtain hooks.

In several of the constructions which have been described herein, it is necessary to apply a layer of plasterboard (usually 12 millimetres thick) to a layer of ESP insulation material or similar insulation material.

Typical of this is the construction shown in Figure 8, where the layer of plasterboard 146 has to be secured to the layer of ESP insulation material 144. The method of securing the plasterboard to the insulation material likely to occur to most plasterers, is the use of plaster dabs, since this is the method traditionally used for securing plasterboard for example to building blocks.

There could however be a problem, because ESP insulation and similar insulation materials lack porosity, and hence the plaster dabs may not effectively key into the insulation material. A method of tackling this problem is illustrated in Figures 12 and 13. Figure 12 illustrates a special form of ESP insulation material, which is made 19 millimetres thick, and is in all respects identical with the ESP insulation material illustrated for example in Figure 8, excepting that its inside surface is formed during manufacture with a series of three longitudinally extending dovetail cross-section recesses 230, 232 and 234.

Figure 13 shows a construction identical with that in Figure 8, and therefore the same reference numerals have been used, but the ESP insulation layer 144 illustrated in Figure 12 has been employed. The plaster dabs used for securing the plasterboard 146 can then be pressed into the undercut recesses 230, 232 and 234, and this will provide a mechanical keying of the plaster dabs to the insulation board, which will be effective, even if the lack of porosity in the insulation material would not allow the plaster dabs to secure themselves in the conventional manner.

Turning to Figure 14, there is shown the cross-section through a cavity wall at the window opening, the detail of which is conventional and which represents good practice when the window frame is mounted on the outer leaf of the cavity wall. In Figure 14, a cavity wall is illustrated comprising an external leaf 300 made of bricks and an internal leaf 302 made of building blocks, with a cavity 304 between them. The wall illustrated has the conventional 50 mm wide cavity without thermal insulation. With the conventional construction, the end of the cavity 304 at the opening for the window will be closed with cut bricks 305 but a strip 306 of conventional dampproof material (e.g. bitumastic material) is sandwiched between the external leaf 302 and the cut bricks closing the end of the cavity, adjacent to the end of the wall. This dampproof course 306 prevents moisture in the external leaf from migrating across the cavity at the end of the wall.

The sill of a timber window frame is shown at 308 and it will be seen that this rests on a bed of mortar in the outer leaf 300 of the wall. In this particular example, the sill is of standard 140 mm width in the internal/external direction. Part of one of the jambs of the window frame is shown at 310. Attention is drawn to two features of the location of the window frame within the outer leaf of the wall; firstly, the outer edge of the sill overhangs the external face of the external leaf by about 28 mm (to give the required drip clearance) and, secondly, the internal face of the window frame is on the internal side of the dampproof course 306, in fact it is approximately 12 mm on the internal side of the internal face of the outer leaf 300.The window frame is said to "break" the vertical dampproof course 306 (i.e. extend to its internal side) so as to ensure that plaster (not shown) in the internal reveal of the window opening, which abuts the internal faces of the window frame jambs and sill, cannot come into contact with the outer leaf of the wall. It will be appreciated that, on the one hand, the window frame should extend as far as possible to the internal side of the vertical dampproof course 306, but, on the other hand, this has to be balanced against the necessity to maintain a good drip overhang on the external side of the external leaf.An arrangement as shown in Figure 14, wherein the window frame extends about 10 to 15 mm to the internal side of the external leaf is quite acceptable, and this location of the window frame relatively to the cavity and external leaf is utilised in the following specific embodiments of the invention.

One form of cavity closer in accordance with the first aspect of the invention is shown in Figure 15, which is a cross-section through the closer 310. This closer is formed as an extrusion in unsaturated polyvinylchloride (uPVC) of a grade similar to that used for other building components such as drainpipes, gutters and gulleys. The extrusion technique means that the closer is made in the form of a strip of constant cross-section throughout its length. This also enables the strip to be produced economically and in long lengths, which can be cut to the required shorter lengths on site.

As is apparent from Figure 15, the closer 310 comprises a channel part 312 with external and internal frame-engaging flanges 314 and 316 extending from it. The channel part 312 comprises a cavity entering part of the closer and in the specific embodiment illustrated, it is approximately 50 mm wide in the internal/external direction and approximately 25 mm deep in the inner/outer direction. It will be observed that the cavity entering part is of rectangular configuration, having a web 318 and flanges 320 and 322, but there are inturned lips 324 and 326 on the inner ends of the flanges 320 and 322 - leaving a wide gap between the lips, at the "open" inner side of the cavity entering part 312.

The cavity entering part 312 is filled by a layer 328 of thermal insulation material. This may take the form of expanded polystyrene or it may be the ESP (styrene) thermal insulation material now commonly used as a lining for the cavity of a cavity wall constructed building. It will be appreciated that other thermal insulating material may be employed to fill the cavity entering part 312.

Although the layer 328 of insulation material may be fitted in any way, in the specific embodiment being described, it is made separately as a long strip of the required rectangular cross-section. This strip could be fitted by threading it into the part 312 from one end, but the construction of the flanges 320 and 322 is such that they can be forced apart (distended) to such an extent that the space between the lips 324 and 326 will allow the layer 328 to pass between them into the cavity entering part. Alternatively, the flanges could be partly distended to facilitate threading of the insulation layer from one end.When the flanges 320 and 322 are subsequently released, they spring back to the free positions at right angles to the web 318 and the lips 324 and 326 then partly close the "open" side of the channelshaped cavity entering part to retain the thermal insulation layer 328 in position. It may be sufficient to rely on the lips 324 and 326 to hold the layer of insulation material in the cavity closer, but if desired, adhesive may be applied to the layer and/or to the inside walls of the cavity entering part so that the insulation layer 328 adheres to the cavity entering part.

The external frame-engaging flange 314 is of double-walled construction (the overall thickness being about 8 mm) and it will be observed that it forms an undercut recess 330 facing outwardly towards the external end of the flange, and another undercut recess 332 facing inwardly towards the internal end of the flange. It will also be seen that the lip 324 is in continuation of the inner wall of the double-walled construction and that a location rib 334 is turned inwardly from the internal end of the lip 324, the distance between the external face of the cavity entering part 312 and the external face of the locating rib 334 being approximately 12 mm.

The internal frame-engaging flange 316 is of similar double-walled construction to the external flange 314, but it is shorter and has only a single undercut recess 336, which faces outwardly. It is an important feature of the construction, that the distance from the external edge of the flange 314 to the external face of the rib 334 is approximately equal to the distance from the internal edge of the internal flange 316 to the internal face of the locating rib 334. However, because the rib 334 is offset to the exterior of the cavity entering part 312, this results in the external frame-engaging flange being much longer than the internal frame-engaging flange - an asymmetrical feature of some importance as will appear.

In the specific example, the rib 334 is 2 mm thick (as are all the walls of the closer 310) and the distance from the faces of that rib to each of the external and internal edges of the flanges 314 and 316 is approximately 65 mm.

On the outer face of the web of the cavity entering part 318 there is a formation 338 providing an undercut recess 339 facing outwardly, and a moisture trap 340 comprising a plurality of closely juxtaposed shallow grooves 342, with sharp longitudinally extending ribs between them. It will be appreciated that, when the closer is standing vertically (as it is when in position at the end of a cavity wall) it is virtually impossible for moisture to migrate across the moisture trap 340, even if it is being driven by a wind, because at each sharp edge, the moisture is deflected downwardly and it then flows down the grooves 342 under gravity.

It should be mentioned that the formations providing the undercut recesses 330; 332; 336 and 339 have similar dimensions, particularly as regards the width of the mouth of the recess; the thickness of the walls of the ribs and walls forming the recess and the depth of the recess.

Referring now to Figure 16, there is shown a wall tie 350 capable of use with the cavity closer shown in Figure 15.

The wall tie 350 is made as an injection moulding in relatively rigid uPVC and it is flat with a thickness of about 2 mm. Generally, the tie takes the form of a straight bar 352, through which is formed a series of holes 354. At the righthand end, there is a root portion comprising a T-piece 356, the shape of which is such that it is a slight interference fit in any one of the undercut recesses 330; 332; 336 and 339. In order to fit the root portion 356 in say the recess 330, the tie 350 could be slid along the length of the closer strip 310 to the required location, but this is time consuming, particularly because of the tight fit of the root portion in the recess.However, if the tie 350 is turned about its own longitudinal axis through 900, so that the width of the tie is in the same direction as the length of the closer 310, the head of the T-piece can then easily be passed between the lips forming the mouth of the undercut recess to bring the head portion of the tie into the undercut recess (and into engagement with the closed side of the recess) at the position along the length of the closer strip 310 where the tie is required. The tie can then be turned about its own longitudinal axis through 900 to bring the head of the T-piece into the plane where it fills the undercut recess. It may be necessary to distend the parts of the closer around the recess, to allow the head of the T-piece to occupy this position, but that enable the root portion of the tie 350 to be held tightly in the selected position.

At the other end of the tie 350, there is a short cranked part 358 with a T-piece root 360 of the same dimensions as the root 356, but because of the crank portion, this root faces one side of the tie.

Turning now to Figure 17, there is illustrated part of a cavity wall construction, in which a cavity closer as described with reference to Figure 15 is employed. The cavity wall itself comprises an external leaf 370, an internal leaf 372 and a 50 mm wide cavity 374 between them. During the construction of the building, the cavity wall is built up to the level where the bricks of the external leaf 370 and the blocks of the internal leaf 372 are starting to form the end of the opening for a window frame, and at that stage, strips of the cavity closer 310 are cut to the length of the jambs of the window frame, one of which is illustrated at 376.Each cavity closer 310 is then offered up to its respective jamb 376, by engaging the inner wall of the external frame-engaging flange 314 with the outer face of the jamb 376, and engaging the location rib 334 against the internal face of the jamb 376, so that the jamb becomes located in the angle between the flange 314 and the rib 334. The closer 310 is then secured to the jamb by nails 378 driven through the flange 314 and nails 380 driven through the rib 334. Holes (not shown) may be preformed through the flange 314 and/or the rib 334 to accept nails or screws.

With the cavity closers thus secured to the jambs of the window frame, the latter is then offered up to the opening in the cavity wall, so that the cavity entering part 312 of each of the closers 310 enters its respective cavity, and so that the outer faces of the flanges 314 and 316 engage respectively with the inner faces of the external leaf 370 and the internal leaf 372. It is to be observed, that this provides a particularly neat arrangement, because the cavity entering portion 312 just fills the full width of the cavity 374, and the frame-engaging flanges 314 and 316 locate the frame against the end of the cavity wall.

The bricks and blocks continue to be built up, and during this building up of the internal and external leaves, wall ties 382 and 384 of the type illustrated in Figure 16, are fitted between courses of the leaves of the wall. The tie 382 is fitted to the undercut recess 330 of the flange 314, and then extends parallel with the length of the external leaf 370 into that leaf, so that mortar added between the courses of bricks in the external leaf flows into the holes 354 and also engages with the root portion 360 at the outer end of the tie 382, for the purpose of anchoring the tie in the external leaf of the wall. Thus, as the external leaf is built up, any ties between courses of bricks in that leaf in the position illustrated at 382, firmly tie the frame-engaging flange 314 of the cavity closer 310 to the external leaf.

Another tie 384 is shown used with the internal leaf of the wall and, in that case, the root portion 360 at the cranked end of the tie is engaged in the undercut recess 339 on the web 318, but whereas the tie 382 extends longitudinally of the external leaf of the wall, the tie 384 extends transversely to the internal leaf 372. It will be appreciated, that when ties are used in both the positions illustrated in Figure 17, the cavity closer 310 is very effectively tied to the end of the cavity wall.

The internal reveal of the detail is completed by fitting a plasterboard reveal 390, which is located in the angle between the locating rib 334 and the inner wall of the frame-engaging flange 316, there being dabs or a layer of mortar 392 securing the plasterboard 390 to the end of the blocks building up the internal leaf 372. If desired, a finishing bead 394, illustrated in dotted lines in Figure 17, may be fitted in the angle between the internal face of the jamb 376 and the inner face of the plasterboard reveal 390.

With the construction illustrated, all the advantages of a modern cavity closer are obtained, that is to say, the end of the cavity is effectively closed by the cavity entering portion; that portion provides a vertical dampproof course between the two leaves of the wall, especially by virtue of the moisture trap 312; a dampproof course is provided between the end of the external leaf 370 of the wall and the jamb 376 of the window frame; the window frame is tied to the end of the cavity wall, and the two leaves of the wall are tied together at the end where there is the opening for the window - which is otherwise a weak part of the wall construction.In addition to all these advantages, the layer of thermal insulation material 328 provides thermal insulation between the plaster on the internal reveal of the window opening, and the external leaf 370 of the wall, so that the minimum U-value of the detail is relatively high.

This is particularly the case, because of the overlapping of the jamb 376 on to the thermal insulation material 328, caused by the location of the rib 334 which is used to locate the window frame. Because of this overlapping arrangement, the shortest thermal root from the interior to the exterior has to pass through the plasterboard 390, then through a substantial thickness of the thermal insulation material 328 and then through the external leaf 370. Moreover, as has been shown with reference to Figure 14, this location of the window frame is quite satisfactory from the point of view of providing a sufficient drip overhang.

Another advantage arises from the use of the closer 310 with an "open" inner side of the cavity entering part.

When the closer is used around a door frame, the shocks of slamming the door are not transmitted directly from the external flange 314 to the internal flange 316 (and hence directly to the plaster in the internal reveal). Such shocks would have to travel around the channel section of the cavity entering part 312, where they are absorbed by the channel construction.

There is an important advantage in the provision of the frame location rib 334, in that the window frame is correctly located relatively to the width of the cavity.

In the absence of internal/external location window frames are sometimes wrongly fitted, so that they do not break the vertical dampproof course.

Attention is now directed to Figure 18 of the drawings, in which an alternative type of cavity wall construction is illustrated, comprising an external leaf 400, an internal leaf 402 and a 75 mm wide cavity 404 with a batt 406 of thermal insulation material such as ESP adhering to the external face of the internal leaf 402. Thus, although the overall width of the cavity is 75 mm, the open space in the cavity between the internal face of the external leaf and the external face of the ESP thermal insulation material 406 is approximately 50 mm.

A cavity closer 310 identical with that illustrated in Figures 15 and 17 is employed for the purpose of closing the end of the cavity and securing the jamb 376 of a window frame in exactly the same position relatively to the external leaf of the wall as that illustrated in Figure 17. Consequently, the flange 320 of the cavity entering part 312 of the closer is located in engagement with the internal face of the external leaf 400, and the cavity entering part 312 fills the open space between the external leaf and the batt 406 of thermal insulation material, the internal frame-engaging flange 316 overlying the end of the thermal insulation material 406, and just reaching onto the internal leaf 402 of the wall.

All the other features of the construction, including the arrangement of the wall ties 382 and 384 are exactly the same as described with relation to the construction illustrated in Figure 17. Consequently, the cavity closer 310 performs all the functions previously mentioned with reference to Figure 17, and the window frame is located in exactly the same position with regard to the external leaf of the wall. It will be appreciated, that the cavity closer 310 is used in the same orientation in both Figures 17 and 18, the only difference being that the flange 316 does not overlap the internal leaf 402.

In Figure 19, there is illustrated another cavity wall construction detail, comprising an external leaf 410, and internal leaf 412 and a 75 mm wide cavity between the two leaves. However, this construction differs from that in Figure 18, in that there is no batt of thermal insulation material within the cavity 414, so that the full width of the cavity is open at the end. The end of the cavity is closed by a cavity closer 310 located and secured in exactly the same manner as that illustrated in Figure 18.

However, in this construction, an additional layer 416 of the E.S.P. thermal insulation material is secured to the outside of the cavity closer 310 in the angle between the flange 322 and the outer wall of the internal flange 316.

This layer of thermal insulation material therefore closes the space on the outside of the flange 316, to ensure that there is virtual continuity of thermal insulation material across the full width of the cavity. The layer 416 may be fitted to the extrusion strip forming the cavity closer at the factory where the cavity closer is made and the layer 328 fitted or, alternatively, it may be simply cut from long lengths of ESP strips on site, and adhered to the cavity closer by the application of adhesive on site. It will be appreciated that, in the arrangement illustrated in Figure 19, the cavity closer 310 is used in exactly the same orientation as in Figures 17 and 18, and that the location of the cavity closer relatively to the cavity is exactly the same as that illustrated in Figure 18.

As an alternative to the use of adhesive, or in addition thereto, for securing the insulation layer 416 to the closer, the layer 416 may be formed with a cross-section which includes a "root" adapted to key into the undercut recess 336 in the flange 316.

Figure 20 illustrates another cavity wall construction, comprising an external leaf 420 and an internal leaf 422, with a 65 mm wide cavity 424 between them. The drawing also illustrates the use of a 25 mm batt 426 of ESP thermal insulation material adhering to the external face of the internal leaf 422, but this is optional, and in this construction, if a batt of thermal insulation is employed, it must terminate at the position indicated at 428, on the outer side of the cavity closer 310. The latter is fitted in exactly the same location as shown in Figure 19, excepting that, since the cavity in this arrangement is only 65 mm wide, the internal frameengaging flange 316 will overlap on to the internal leaf 422 to a greater extent than in the Figure 19 construction.Also, a layer of ESP thermal insulation material 430, which is fitted into the angle between the flange 322 of the cavity entering part and the outer wall of the flange 316, is only approximately 15 mm wide, in order to fill up the space between the cavity entering part 310 and the external face of the internal leaf 422.

As with the previous construction, the layer of thermal insulation material 430 may be fitted either at the factory where the extrusion for the cavity closer is produced or, alternatively, it may be cut from a length of material and fitted on site.

Turning now to Figure 21, there is illustrated yet another cavity wall construction, comprising an external leaf 440 and an internal leaf 442, with a 65 mm wide cavity 444 between them. As illustrated in Figure 21, a layer 446 of thermal insulation material is fitted to the external face of the internal leaf 442, that is to say, it fills part of the width of the cavity 444. Also, a cavity closer 310 is employed to close the end of the cavity and to secure the jamb 376 of a timber window frame to the end of the wall, and it will be observed that the orientation of the cavity closer 310 is exactly the same as that illustrated in Figures 17, 18, 19 and 20.However, in this arrangement, the cavity closer is located so that its flange 322 engages with the external face of the internal wall 442, that is to say, the whole cavity closer is taken to a position which is to the interior of that illustrated in Figures 18 to 20, so that as with the construction illustrated in Figure 17, the internal frame-engaging flange 316 lies entirely over the end of the internal leaf 442, but the external flange 314 does not extend so far over the end of the external leaf 440, as is the case, for example, with the construction illustrated in Figure 20.

However, the cavity closer 310 is secured to the internal and external leaves of the wall by the ties 382 and 384 fitted in exactly the same manner as described with reference to the construction illustrated in Figure 17, save that the tie 382 will be somewhat nearer to the cavity than in the Figure 17 construction.

It will be seen that the jamb 376 of the window frame is still located against the location rib 334, but because the cavity closer is in a more inward position than previously described, the window frame is now in a more inward position, that is it extends by a greater amount over the cavity itself. Some builders prefer this location of the window frame to one such as that illustrated in Figure 14, although it necessitates the employment of a wider sill or an alternative sill construction. It will also be seen that it is desirable to ensure the continuity of the thermal insulation material across the width of the cavity by fitting a layer 448 of thermal insulation material (which may be applied at a factory where the extrusion strip is manufactured or fitted on site) in the angle between the flange 320 of the cavity entering part and the outer wall of the flange 314.

Once again, the cavity closer performs all the functions of the cavity closer described with reference to Figure 17, and in particular, it ensures that there is a good thermal insulation between the plasterboard in the reveal of the window opening, and the external leaf 440 of the cavity wall.

Figure 22 illustrates another cavity wall construction comprising an external leaf 450 and an internal leaf 452 with a 75 mm wide cavity between them, there being a layer 456 of thermal insulation material adhering to the external face of the internal leaf 452. In fact, the cavity wall is constructed in the same way as that illustrated in Figure 18, excepting that the layer 456 of thermal insulation material terminates at 458, short of the outer end of the cavity wall.

A cavity wall closer 310 is employed to close the end of the cavity, and it is in the same orientation as in the previous constructions, with the internal flange 322 abutting against the external face of the internal leaf 452 of the cavity wall. Because of this, the jamb 376 of the window frame, which still locates against the rib 334, is taken even further inwardly than in the arrangement illustrated in Figure 21, and it is necessary to fill up the space between the internal face of the external leaf 450 and the flange 320 of the cavity entering part of the cavity closer, by a layer 458 of the ESP thermal insulation material located in the angle between the flange 320 and the outer wall of the flange 314.Once again, the cavity closer performs all the functions of the closer described with reference to Figure 17 and, again, there is a good thermal insulation provided between the plasterboard on the internal reveal of the window frame opening and the external leaf 450 of the wall.

In Figure 23, there is illustrated another cavity wall construction comprising an external leaf 460 and an internal leaf 462, with a 50 mm wide cavity 464 between them. The end of the cavity is closed by a cavity closer 310, which is of exactly the same construction as that described with reference to Figure 15, but the difference between this construction and those described with reference to Figures 17 to 22 is that the closer 310 has been inverted, which has the effect of bringing the external flange 314 to the internal side of the cavity, and putting the internal flange 316 on the external side of the cavity. The ability of the cavity closer to be used in this inverted orientation, greatly improves the versatility of the cavity closer.In fact, the construction is quite similar to that illustrated in Figure 17, excepting that, since the location rib 334 is considerably offset with respect to the width of the cavity entering part 312, the engagement of the jamb 376 with the rib 334 has the effect of placing the window frame in a position much to the interior of that illustrated in Figure 17, where, in fact, most of the window frame is across the end of the cavity 464. This is a position which some builders regard as being superior to that illustrated in Figure 17, although it will be appreciated that it involves the use of a much wider sill, or an alternative sill arrangement.

Another difference between the construction illustrated in Figure 23 and that in Figure 17 is that the tie 382 is much closer to the cavity, and the tie 384, instead of being attached to the flange 314 by means of the cranked end 360, is attached by the straight end 356 and, consequently, the tie 384 extends longitudinally of the inner leaf of the wall, parallel with the tie 382. Figure 23 shows that it is also possible with this construction to increase the rigidity of the tying effect by fitting another tie 383 in a position indicated by the dotted lines, where the crank end of the tie is fitted into the undercut recess 339 on the rib of the cavity entering part of the cavity closer and the main portion of the tie 383 extends laterally of the wall into the external leaf.

The function of the cavity closer illustrated in Figure 23 is exactly the same as that illustrated in Figure 17, the only difference being the alternative location of the window frame.

In Figure 24, there is illustrated a cavity wall which is identical to that illustrated in Figure 18, that is to say, it comprises an external leaf 470, and an internal leaf 472 with a 75 mm wide cavity 474 between them, but a layer of ESP thermal insulation material 476 is adhered to the external face of the internal leaf 472. Again, a cavity closer 310 is employed, but the orientation of the cavity closer is the same as that illustrated in Figure 23, and the cavity entering part 312 fits snugly between the internal face of the external leaf 470, and the external face of the thermal insulation material 476.

Moreover, the frame-engaging flange 314 extends over the end of the thermal insulation 476 and partway over the end of the internal leaf 472 (allowing the tie 384 to be used in a position where it extends longitudinally of the wall), whilst the flange 316 extends a short distance over the end of the external leaf 470 (allowing the tie 382 to be used in the longitudinally extending position). A tie 383 may be used in the position where it is anchored to the undercut recess 339 on the web of the cavity entering part of the closer as an alternative or in addition to ties in the position indicated at 382.The construction is very similar to that described with reference to Figure 18, excepting that the location of the locating rib 334 causes the window frame to be at the inner location where it extends most of the way across the open part of the cavity 474, as was the case with the construction described with reference to Figure 23.

Figure 25 illustrates another cavity wall construction, which is similar to that illustrated in Figure 19, that is to say, it comprises an external leaf 480 and an internal leaf 482, with a 75 mm wide cavity 484 between them. The cavity closer 310 is employed in the same orientation as that illustrated in Figures 23 and 24, and with the flange 320 of the cavity entering portion engaging against the internal face of the external leaf 480 of the wall. With this construction, it is necessary to fill the gap between the flange 320 of the cavity entering portion and the external face of the internal leaf 482 by means of a strip of ESP thermal insulation material 486, secured to the outside of the flange 314 and in the angle between that flange and the flange 320 of the cavity entering part.

The ties 382 and 384 can be fitted in positions similar to those illustrated in Figure 24 and, again, there is the option of fitting ties in the position illustrated at 383.

The function of the cavity closer is exactly as previously described and, in particular, it provides the good thermal insulation between the plaster reveal on the interior of the window frame, and the external leaf 480 of the cavity wall. However, it locates the window frame in the inner position illustrated in Figures 23 and 24.

Figure 26 shows another cavity wall construction which is similar to that shown in Figure 22, in that it comprises an external leaf 490, an internal leaf 492 with a 75 mm wide cavity between them, in which a layer of ESP thermal insulation material 496 is secured to the external face of the internal leaf 492 of the wall. This thermal insulation 496 terminates short of the inner end of the cavity wall.

A cavity closer 310 is employed in the same orientation as that shown in Figures 23, 24 and 25, and the only difference between this construction and that illustrated in Figures 25 is that a layer of thermal insulation material 498, which is fitted in the angle between the flange 314 and the flange 320 is thinner than the insulation material 486 shown in Figure 25, because the cavity is narrower.

In Figure 27, there is illustrated a construction of a cavity wall which is similar to that shown in Figure 21, in that it comprises an external leaf 500 and an internal leaf 502 with a 65 mm cavity between them, which is partly filled by a layer 506 of ESP thermal insulation material, which terminates at 508, short of the inner end of the cavity wall. A cavity closer 310 is employed in the same orientation as that illustrated in Figures 23 to 26, but in this arrangement, the flange 320 of the cavity entering part 312 of the cavity closer is in engagement with the external face of the inner leaf 502 of the wall, so that it is necessary to fit a layer 510 of thermal insulation material in the angle between the flange 322 and the flange 316 of the closer, in order to fill the full width of the cavity with insulation material at the closed end.

Otherwise, the construction is quite similar to previous constructions, it being noted that it is necessary to employ the tie 382 in the position where its cranked end engages in the undercut recess 339 on the web of the cavity entering part of the closer, and for that tie to extend tránsversely of the external leaf of the wall, because the flange 316 only just overlies the end of the external leaf, and it is not possible to fit a tie into the undercut recess 336 in that flange. The construction operates in the same manner as described with reference to previous arrangements but, in this case, it will be noted that the timber frame 376 extends almost to the internal side of the cavity 504, since the internal face of the jamb 376 is still in engagement with the location rib 334, which in this construction is located as far to the interior as is possible.

Figure 28 illustrates yet another cavity wall construction, in which there is a 75 mm wide cavity 524 between an external leaf 520 and an internal leaf 522, there being a layer 526 of ESP thermal insulation material adhering to the external face of the internal leaf 522, and terminating short of the inner end of the cavity wall.

The cavity closer 310 is used in the same orientation as that illustrated in Figure 27 and, indeed, its flange 320 locates against the external face of the internal leaf 522 in exactly the same manner as that illustrated in Figure 27, so that the window frame is located at an internal position, where it almost entirely extends across the end of the cavity. However, the flange 316 just abuts onto the end of the external leaf 520, and the space between that leaf and the flange 322 of the cavity entering part of the closer 310 is showed by a layer 528 of insulation material fitted in the angle between the flange 316 and the flange 322.

In Figure 29 there is illustrated a cavity wall construction, in which there is an external leaf 530 and an internal leaf 532, but the cavity 534 between the two leaves is very wide, being approximately 100 mm in width.

As illustrated in Figure 29, however, a layer of ESP thermal insulation material 536 adheres to the external face of the internal leaf 532, and as this layer is approximately 25 mm thick, the effective width of the cavity is reduced to 75 mm. A cavity closer 310 is employed in the same orientation as that illustrated in Figure 28. However, the cavity entering portion 312 enters the cavity, with the flange 320 in engagement with the external face of the thermal insulation material 536 (which it will be noted extends to the end of the cavity wall) and with the frame-engaging flange 314 engaging on the end of the thermal insulation 536 and just sufficiently on to the end of the internal leaf 532, to allow the tie 384 to be fitted into the undercut recess 330 in the flange 314, and to extend longitudinally of the internal leaf 532.Because of the width of the cavity, the flange 316 only just engages on the end of the external leaf 530, and the gap between the internal face of the external leaf 530 and the flange 322 of the cavity entering part of the cavity closer 310 is filled by a layer of thermal insulation material 538. Hence, the entire width of the cavity across the end of the cavity is filled by thermal insulation material (excepting for the thickness of the flanges 320 and 322), which provides the very good thermal insulation qualities of the detail. In addition, the tie 382 can be used in the position where its crank end is engaged in the undercut recess 339 on the web 312 of the cavity closer 310, the tie 382 extending substantially into the external leaf of the wall.

The jamb 376 of the window frame abuts against the locating rib 334, so that the window frame is located in a position where most of it extends over the end of the cavity 534.

Turning now to Figure 30, there is illustrated another cavity wall comprising an external leaf 540, an internal leaf 542 and a cavity 544 between them which is 100 mm wide. In this construction, a layer 546 of ESP insulation material is fitted to the external face of the internal leaf 542 of the wall, and this insulation layer extends to the inner end of the cavity wall. A cavity closer 310 is fitted in the same orientation as that illustrated in Figure 29, excepting that the flange 322 abuts against the internal face of the external leaf 540, so that the flange 316 is entirely in line with the end of the external leaf 540, and it is possible to fit a wall tie 382 in the undercut recess 336 of the flange 316, so that the tie extends longitudinally of the wall. It is, of course, also possible to fit a tie in the position indicated at 383, where its cranked end is anchored in the undercut recess 339 on the web of the cavity entering part of the closer, and the tie extends transversely into the external leaf 540.

In this construction, the flange 314 extends across the end of the thermal insulation layer 546, but only just touches on to the end of the internal leaf 542 of the wall. The space between the flange 320 and the external face of the layer of thermal insulation 546 is closed by an additional layer of thermal insulation 548 secured to the flanges 320 and 314 of the cavity closer. This ensures that there is a complete wall of thermal insulation material, save for the thickness of the flanges 322 and 320 bridging the end of the cavity and providing the good thermal insulation characteristics between the plasterboard in the reveal of the window frame and the external leaf 540.In this construction, the jamb 376 abuts against the rib 334, which is about in the centre of the width of the cavity, so that the window frame extends to a considerable extent over the width of the cavity, and there is a relatively large overlap between the frame and the thermal insulation layer 328 in the cavity entering part of the cavity closer.

As a means of tying the flange 314 to the internal leaf 542, a wall tie 384 has its cranked end engaged in the undercut recess 330 of the flange 314, the main portion of the tie extending laterally of the internal leaf 542 near to the outer end of that leaf.

A final possible position of the cavity closer 310 described with reference to Figure 15 is illustrated in Figure 31, where again there is a cavity wall comprising an outer leaf 550 and an inner internal leaf 552 with a 100 mm wide cavity 554 between them and a layer of ESP thermal insulation material 556 fitted to the external face of the internal leaf 552, this layer of insulation material extending to the end of the cavity wall.

In this arrangement, the cavity closer 310 is used in the first orientation, that is the one which is described in detail with reference to Figure 17. The flange 322 of the cavity entering part is in abutment with the external face of the layer of thermal insulation material 556, so that the flange 314 extends over the end of the external leaf 550 a sufficient distance to allow a wall tie 382 to be fitted in the position shown in the undercut recess 330, and for that tie to extend longitudinally with respect to the outer leaf. However, the flange 316 extends across the end of the insulation material 556 but only just engages on the inner end of the internal leaf 552 of the wall. The gap between the external leaf 550 and the flange 320 of the cavity closer is filled by a layer 558 of thermal insulation material fitted in the angle between the flanges 320 and 314.In order to secure the cavity closer 310 to the internal leaf, a tie 384 is fitted with its cranked end engaged in the undercut recess 339 on the web of the cavity entering portion of the cavity closer, so that the tie extends transversely into the internal leaf 552. In this construction, the location rib 334 is again approximately mid-way across the width of the cavity 554, so that the jamb 376 extends partly across the end of the external leaf 550 and partway across the end of the cavity 554. There is a substantial amount of thermal insulation material comprising part of that fitted within the cavity entering part of the closer and the layer 558 on the outside of the jamb 376 to improve the thermal insulation qualities of the detail.

Figure 32 illustrates a different form of cavity closer 600, which is intended to perform all the functions of the cavity closer 310 previously described, and which is made by a similar extrusion process in uPVC material. In general, therefore, it is unnecessary to describe the cavity closer 600 in the same detail as was used with the closer 310.

Essentially, the closer 600 comprises a generally rectangular channel-shaped cavity entering portion 602, which is identical with the cavity entering portion 312 of the closer 310, including the provision of an undercut recess 604 and a moisture trap 606 on the web 608. Also, there are inturned lips 610 and 612 on the flanges 614 and 616, as there are with the closer 310, and a location rib 618 is provided on the lip 612. The difference between the construction illustrated in Figure 32 and that illustrated in Figure 15 is that the external flange 620 comprises an outer wall 622 with a dovetail-shaped end portion 624 which provides an undercut recess 626 facing outwardly.There are also two T-shaped ribs 628 and 630 projecting from the inside of the wall 622 and a rib 632 in continuation of the lip 612, the lip 612, rib 632, heads of the ribs 628 and 630 and the base of the dovetail-shaped portion 624 are all in the same plane, and form in effect an inner wall of the flange 620.

A flange 634, shorter than the flange 620, extends on the opposite side of the cavity entering portion of the closer, and essentially comprises a dovetail-shaped arrangement providing an undercut recess on the outside, spaced slightly from the flange 614 of the cavity entering part by a short outer wall 636.

Figure 33 illustrates a wall tie suitable for use with the cavity closer illustrated in Figure 32. This wall tie 638 is generally similar to the wall tie 350 illustrated in Figure 16, in that it is made as a plastics moulding and is mainly in the form of a straight bar, which is relatively thin, and which is formed with a series of holes 640. Moreover, at one end there is a cranked portion with a root portion 642, which is identical with the cranked portion 358 and root 360 on the tie 350.

At the other end, however, instead of the T-shaped root portion, there is a root portion comprising a pair of splayed apart teeth 644 and 646, which together form an effective dovetail, which is a tight fit in either of the undercut recesses provided by the formation 624 and 634 on the cavity closer 600. The dovetail-shaped root portion on the tie 638 can be fitted into either of these undercut recesses in the cavity closer by the same method as that described for the T-shaped root portions, and the dividing of the teeth 644 and 646 ensures that the root portion can be squeezed somewhat, so that it is possible to make it as an interference fit within the dovetail-shaped undercut recesses.It will be appreciated that the tie 638 is used with the dovetail-shaped recesses provided by the formation 624 and 634 on the cavity closer 600 in any of the ways described with reference to Figures 17 to 32, and that the root portion 642 at the cranked end of the tie can be fitted into the undercut recess 339 on the web portion of a cavity closer 310 or the undercut recess 604 on the cavity closer 600.

Figure 34 illustrates another form of cavity closer 700 which is made by a similar process as that described for the manufacture of the cavity closer 310 and, again, there is a rectangular channel-shaped cavity entering portion 702, filled with a layer of ESP thermal insulation material 704, retaining lips 706 and 708, which can be sprung apart by distending the cavity entering portion to allow the insulation material 704 to be fitted through the "open" side of the cavity entering portion, and a location rib 710. The only difference between the cavity entering portion of the cavity closer 700 and the cavity entering portion 312 of the cavity closer 310, is that instead of the moisture trap formation on the outer end of the cavity entering portion, there are two undercut recess formations 712 and 714, and a short rib 716 which forms part of both these undercut recesses 712 and 714 is itself formed with a moisture trap arrangement comprising a series of longitudinally extending closely juxtaposed shallow grooves, with sharp longitudinally extending ridges between them.

However, in this construction, instead of the doublewalled frame-engaging flanges 314 and 316, there are single thickness flanges 718 and 720, although the width of these flanges in the internal/external direction is precisely the same as the width of the flanges 314 and 316, so that the location rib 710 occupies the same offset relationship to the cavity entering part 702 as does the rib 334, and the flanges 718 and 720 extend by the same distance (in the specific example approximately 65 mm) on opposite sides of the location rib 710. Another feature of the cavity closer illustrated in Figure 34, is that there are moisture traps formed in the inner faces of both the flanges 718 and 720, each of these moisture traps comprising a similar arrangement of longitudinally extending grooves to that illustrated at 318 in Figure 15.

In Figure 35, there is illustrated a wall tie 722 intended for use with the cavity closer 700, and it will be seen that this is generally very similar to the wall tie 350 in its construction, in that it is in the form of a straight bar, with holes 724 formed through it and a cranked end with a T-shaped root portion 726 at one end. However, in this construction, the wall tie is cut off at right angles at the other end, without the provision of a root portion.

In Figure 36, there is illustrated a cavity wall comprising an external leaf 730 and an internal leaf 732, with a 50 mm wide cavity 734 between them. A cavity wall closer 700, of the kind described with reference to Figure 34, is attached to the jamb 736 of a door frame, by first locating the corner between internal face and the outer face of the jamb 736 in the corner between the flange 718 and the locating rib 710, and then securing the cavity closer to the jamb 736 by nails 738 driven through the flange 718 or through pre-drilled holes in the flange.

This has the effect of attaching the cavity closer 700 to the jamb of the door frame, and it provides a dampproof course between the end of the external leaf 730 of the cavity wall and the door frame. In addition, the moisture trap provided along the width of the flange 718 prevents the migration of moisture between the flange 718 and the door frame across the joint of the door frame and the end of the wall.

The cavity entering portion 702 of the cavity closer 700 is fitted into the end of the cavity in exactly the same way as described with reference to Figure 17, and this provides the closure of the end of the cavity, the moisture trap between the two leaves of the cavity wall, and also provides the thermal insulation within the cavity, which extends behind the jamb 736, where the insulation material overlaps the part of the jamb which enters the corner between the flange 718 and the rib 710.

The flange 720 rests against the inner end of the internal leaf 732.

For securing the cavity closer 700 to the leaves of the wall, two of the wall ties 722 illustrated in Figure 35 are employed, and each of them has its root portion 726 engaged in a respective one of the undercut recesses 712 and 714 of the cavity entering part of the closer, the two wall ties then extending apart, as illustrated in Figure 36, so that one enters between the courses of the external leaf and the other enters between the courses of the internal leaf. This has the effect of tying the cavity closer to the leaves of the wall, without the necessity to provide undercut recesses in the flanges 718 and 720.

Consequently, those flanges can be quite thin, and this is desirable in some situations because it reduces the thickness of the sight line between the jamb 736 and the end of the wall. The detail is completed by the fitting of plasterboard 740 in the internal reveal, and when it is completed, the construction exhibits all the advantages of other constructions previously described.

In Figure 37, there is illustrated another cavity wall construction, comprising an external leaf 750 and an internal leaf 752, with a 50 mm wide cavity 754 between them. The construction is very similar to that illustrated in Figure 36, excepting that the cavity closer 700 is used in the inverted position with respect to that shown in Figure 36, so that the flange 718 is on the internal side and extends a considerable distance over the inner end of the internal leaf 752, and the flange 720 is on the external side. The position of the location rib 710 is in this orientation displaced to the internal side of that illustrated in Figure 36 and, consequently, the jamb 736 of the door frame is located in a position where it extends a greater distance across the end of the width of the cavity 754.Again, ties 722 are employed engaging in both the undercut recesses 712 and 714 on the cavity entering part of the closer, to secure the closer to the wall.

It will be appreciated, that it is possible to use the cavity closer 700 in any of the cavity wall configurations described with reference to Figures 17 to 30 of the drawings, since, in effect, the flanges 718 and 720 simply replace the flanged 314 and 316 of the cavity closer illustrated in Figure 15.

In Figure 38, there is illustrated another cavity closer 800, which is very similar in construction to the cavity closer 700 illustrated in Figure 34. Indeed, it exhibits all the features and characteristics of the cavity closer 700, excepting that the length of the cavity entering part 802 is somewhat shorter than that of the cavity entering part 702 and, consequently, the length of the thermal insulation layer 804 is also shorter. In this specific embodiment, the overall length of the cavity entering part from the inner face of the flanges 818 and 820 to the outer face of the web of the cavity entering part is approximately 20 mm.

Also, the cavity closer 800 is formed with undercut recesses 812 and 814 for the reception of the root portions of wall ties 722 in the same way as is the cavity closer 700. The difference is that at the internal side of the cavity entering part of the closer (in the orientation illustrated in Figure 36), there is an additional formation 822, which provides an undercut recess formation 824 on the flange 826 at the internal side of the cavity entering part.

The manner in which a cavity closer 800 can be used is illustrated in Figure 39, which shows a cavity wall comprising an external leaf 830, an internal leaf 832 with a 50 mm wide cavity 834 between them, and a cavity closer 800, as described with reference to Figure 36, engaging in the end of the cavity, and securing the jamb 376 of a window frame to the end of the cavity wall. It is not necessary to describe the general method of fixing the cavity closer in position in detail, since this is so similar to the previous descriptions. However, it will be noted that the arrangement provides for three possible locations for wall ties of the type shown at 350 in Figure 16.Two of these are fitted with their root portions at the cranked ends in the undercut recesses at the outer end of the cavity entering part of the closer 800, and these extend respectively into the external leaf 830 and the internal leaf 832. In addition, however, or possibly as an alternative to the tie which extends into the internal leaf 832 from the undercut recess 814, a further tie of the type shown at 350 in Figure 16, may be fitted with its root portion at the non-cranked end engaged in the undercut recess 824, the tie then extending transversely of the internal leaf of the cavity wall, closely adjacent to the end of the cavity wall.

In Figure 40, there is illustrated an alternative way of using a cavity closer in accordance with that described with reference to Figure 38, in which there is a cavity wall comprising an external leaf 840, with an internal leaf 842 and a 50 mm wide cavity 844 between them. The cavity closer 800 is inverted from the orientation shown in Figure 39, and then engaged in the cavity, so that its flange 718 rests against the inner end of the internal leaf 842, and the flange 720 rests against the inner end of the external leaf 840. Again, two wall ties 350 are fitted into the undercut recesses 812 and 814, but, in addition, a further wall tie 350 has its root portion at the non-cranked end fitted into the undercut recess 824 and, in this orientation, that wall tie then extends transversely into the external leaf 840, close to the end of that leaf as illustrated in Figure 40.

In Figure 41, there is illustrated yet another form of cavity closer 900, which is produced by extrusion in uPVC material, and generally exhibits many of the characteristics of the previously described cavity closers. In particular, it has a channel-shaped cavity entering portion 902, which is very similar to the cavity entering portion 802 of the cavity closer 800 described with reference to Figure 38. This cavity entering portion is filled with a layer of ESP thermal insulation material 904. The similarity with the cavity closer 800 is continued, in that there are undercut recesses 906 and 908 on the web portion of the cavity entering part, and a moisture trap 910 on the part separating these undercut recesses.The cavity closer also has a frame-engaging flange 912, which is of similar dimensions to the flange 818, and is formed with a locating rib 914, and a shorter frame-engaging flange 916. As is clear from Figure 41, there are moisture trap formations on the inside faces of the flanges 912 and 916. Moreover, there is an undercut recess arrangement 918 at the same side of the cavity entering portion 902 as the short flange 916.

Where this closure differs from previously described closers, is that there is an additional flange 920 extending in continuation of the web of the cavity entering part 902, and parallel with the flange 912, but terminating short of the extremity of the flange 912.

Moreover, there are formations on the outer side of the flange 920, which provide undercut recesses 922 and 924 for the reception of root portions at the end of wall ties.

With this construction of cavity closer, in addition to the thermal insulation material 904, it is possible to fit a similar layer of thermal insulation material indicated in dotted lines at 926 between the flanges 912 and 920.

Referring now to Figure 42, there is shown diagrammatically, a cavity wall arrangement, in which there is an external leaf 930 but the internal leaf is not illustrated and, instead, the locations of the external faces of possible internal leaves are indicated at 932, 934, 936, 938 and 940, for cavity widths of 50 mm, 65 mm, 75 mm, 90 mm and 100 mm. It will be seen that the cavity closer 900 can be used with any of these cavity widths, so long as part of the flange 920 and the insulation 926 is cut away where necessary, so as to avoid fouling the internal leaf of the wall. Hence, with this construction, whatever the width of the cavity, there is a substantially full width of thermal insulation material provided in the cavity closer itself.

In Figure 43, there is illustrated diagrammatically a construction employing an internal leaf 950, with an external leaf, the internal faces of which are indicated at 952, 954 and 956, for cavities of 50 mm, 65 mm and 75 mm width. A cavity closer of the type illustrated at 900 in Figure 41 is employed, but it is inverted as compared with the closer shown in Figure 42, so that the jamb 376 of the window frame engaging with the location rib 914 extends approximately 10 mm over the width of a 50 mm cavity; approximately 25 mm over a 65 mm wide cavity, and approximately 35 mm over a 75 mm wide cavity. Figure 43 also illustrates how it is necessary to cut away part of the flange 920 and the insulation 926, in order to accommodate the cavity closer 900 to a cavity width of 75 mm.More of this flange would need to be cut away if the closer were used with a cavity of only 65 mm or 50 mm width, but if the cavity were of 100 mm width, it would not be necessary to cut away any part of the flange 920 and the insulation 926.

In Figure 44, there is illustrated an arrangement comprising an external leaf 960 and an internal leaf 962, with a cavity of 50 mm between them. (In the upper part of Figure 44, there is illustrated an alternative arrangement, in which the cavity is 75 mm wide, but a layer of ESP thermal insulation material is fitted to the external face of the internal leaf 962.) It should be observed, however, that the inner end of the external leaf 960 projects beyond the inner end of the internal leaf 962, so forming what is called a check reveal. Check reveal wall constructions are known in themselves, and therefore no further description is necessary. A cavity closer 800 is fitted with its cavity entering part pushed into the end of the cavity, and with the flange 818 engaging with the end of the internal leaf 962. Also, there are wall ties 350 used as described with reference to other examples. The difference is that the location rib has been cut away, and so has the flange 820 on the outside of the formation 822 for the undercut recess 824.

This enables the jamb 376 to be located against the internal face of the external leaf of the wall, i.e. by the reveal provided by the external leaf. Otherwise, the construction functions as described with reference to previous examples.

Claims

1. A cavity closer for closing the end of a cavity wall of a building adjacent to an opening for a door or window frame, comprising a strip of corrosion resistant, liquid-impermeable material, having a cavity entering part adapted to fit within the end portion of a wall cavity and a location rib adapted to provide location for a frame element of a door or window frame in the internal/external sense; there being a layer of thermal insulation material located at least partly within the cavity entering portion, the position of the location rib being such that at least part of a frame element abutting that rib will overlie the thermal insulation layer.

2. A cavity closer as claimed in Claim 1, in which the location rib projects inwardly from the cavity entering part, but is offset to one side of that part, so that alternative frame location positions (with respect to the thickness of the wall) are offered by inverting the closer.

3. A cavity closer as claimed in Claim 1 or Claim 2, in which the cavity entering part includes a channel cross-section, the web of which extends in the internal/external direction, there being a frame engaging flange adapted to receive and abut a frame element of a door or window frame, this flange being substantially parallel with the web of the cavity entering part and extending (in one orientation of the strip) externally of the cavity entering part, and further extending partway only across the "open" side of the cavity entering part, the location rib projecting from the part of the frame engaging flange which extends over the cavity entering part.

4. A cavity closer as claimed in Claim 3, in which there is a second frame-engaging flange in substantial continuation of the first frame-engaging flange, but extending (in the one orientation of the strip) internally of the cavity entering part.

5. A cavity closer as claimed in Claim 4, in which the second frame-engaging flange also extends partway only across the "open" side of the cavity entering part.

6. A cavity closer as claimed in Claim 4 or Claim 5, in which the first and second frame-engaging flanges extend by substantially the same distance in the internal/external sense from the location rib.

7. A cavity closer as claimed in any one of Claims 2 to 6, in which the layer of thermal insulation material is a preformed element, and the cavity entering part of the strip is capable of being distended to allow the insulation material to be inserted through the "open" side.

8. A cavity closer as claimed in any one of Claims 1 to 7, in which the thermal insulation layer substantially fills the cavity entering part.

9. A cavity closer as claimed in any one of Claims 1 to 8, in which an anchorage for a wall tie is available at all positions along the length of the cavity entering part.

10. A cavity closer as claimed in Claim 3, or any one of Claims 4 to 9, so far as they depend from Claim 3, in which a wall tie anchorage is available on the internal face of the internal flange of the channel shaped cavity entering portion (in the one orientation of the strip).

11. A cavity closer as claimed in any one of Claims 1 to 10, in which two wall tie anchorages are available at all positions along the length of the cavity entering part at the outer end of that part.

12. A cavity closer as claimed in any one of Claims 8 to 11, in which the or each wall tie anchorage is in the form of an undercut recess in cross-section.

13. A cavity closer as claimed in Claim 3, or any one of Claims 4 to 12, so far as they depend from Claim 3, in which a moisture trap is formed on the inner (frame-engaging) face of the frame-engaging flange.

14. A cavity closer as claimed in Claim 4 or Claim 5, in which a moisture trap is formed on the inner (frame engaging) face of the second frame-engaging flange.

15. A cavity closer as claimed in Claim 13 or Claim 14, in which the moisture trap comprises a series of closely juxtaposed grooves with relatively sharp longitudinal edges between them.

16. A cavity closer as claimed in any one of Claims 1 to 15, in which the depth of the thermal insulation layer from the inside to the outside is not less than 15 mm.

17. A cavity closer as claimed in any one of Claims 1 to 16, in which the distance in the internal/external sense between the external edge of the cavity entering part and the external face of the location rib is approximately 10 mm.

18. A cavity closer as claimed in Claim 3, or any one of Claims 4 to 17, so far as they depend from Claim 3, in which a wall tie anchorage is available at all positions along the length of the frame-engaging flange.

19. A cavity closer as claimed in Claim 4, or any one of Claims 5 to 18, so far as they depend from Claim 4, in which a wall tie anchorage is available at all positions along the length of the second frame engaging flange.

20. A cavity closer as claimed in Claim 18 or Claim 19, in which the or each wall tie anchorage is in the form of an undercut recess in cross-section.

21. A cavity closer as claimed in Claim 4, or any one of Claims 5 to 20, so far as they depend from Claim 4, in which a second thermal insulation layer is provided in the angle between the internal face of the cavity entering part and the outside face of the second frame-engaging flange.

22. A cavity closer as claimed in Claim 3, or any one of Claims 4 to 21, so far as they depend from Claim 3, in which a third thermal insulation layer is provided in the angle between the external face of the cavity entering part and the outside face of the frame engaging flange.

23. A cavity closer as claimed in Claim 3, or any one of Claims 4 to 22, so far as they depend from Claim 3, in which there is an additional flange in substantial continuation of the web of the cavity entering part extending in the same direction and parallel with the frame-engaging flange to permit a further layer of thermal insulation material to be located between this additional flange and the frame-engaging flange.

24. A cavity closer as claimed in any one of Claims 1 to 23, which is in the form of an extrusion.

25. A cavity closer as claimed in Claim 24, which is made in plastics material.

26. A cavity closer as claimed in Claim 25, which is made in polyvinylchloride.

27. A structural assembly comprising a cavity wall having internal and external leaves, with a cavity between them; a frame element of a door or window frame located adjacent to an end of the cavity wall; a cavity closer between the end of the wall and the frame element, the cavity closer (i) bridging the cavity; (ii) locating a layer of thermal insulation material across at least a substantial part of the cavity and (iii) providing a location for the frame element in the internal/external sense, which locates the frame element so that at least part of it overlies the thermal insulation layer.

28. A structural assembly as claimed in Claim 27, in which the cavity closer comprises a strip of corrosion-resistant, liquid-impermeable material, having a cavity entering part which fits within the end portion of the cavity so that the thermal insulation layer is located substantially entirely within the cavity, and a location rib which projects outwardly from the cavity entering part, the frame element abutting a face of this rib.

29. A structural assembly as claimed in Claim 28, in which the locating rib is offset to one side of the cavity entering part so that (in one orientation of the closer) the frame element extends only a relatively short way across the cavity, but (in the inverted orientation of the closer) the frame element extends across the greater part of the width of the cavity.

30. A structural assembly as claimed in Claim 29, in which the cavity entering part of the closer is of channel-shaped cross-section, the web extending across the width of the cavity, there being a frame engaging flange locating between the end of the outer leaf of the wall and the frame element and also extending partway across the "open" outer end of the cavity entering part, the location rib projecting from the part of the frame-engaging flange which extends over the cavity entering part.

31. A structural assembly as claimed in Claim 30, in which the closer has a second frame-engaging flange in substantial continuation of the first frame engaging flange but locating on the end of the inner leaf of the cavity wall in the said one orientation of the closer.

32. A structural assembly as claimed in Claim 31, in which the second frame-engaging flange also extends partway only across the "open" side of the cavity entering part.

33. A structural assembly as claimed in any one of Claims 30 to 32, in which the thermal insulation layer is a preformed element which is fitted into the cavity entering part by distending that part to allow the thermal insulation layer to be pushed into the cavity entering part through the "open" side thereof.

34. A structural assembly as claimed in any one of Claims 28 to 33, in which the thermal insulation layer substantially fills the cavity entering part.

35. A structural assembly as claimed in any one of Claims 28 to 34, in which the inner face of the thermal insulation layer is substantially in alignment with the ends of the leaves of the wall.

36. A structural assembly as claimed in Claim 30, or any one of Claims 31 to 35, so far as they depend from Claim 30, in which the closer provides anchorage for wall ties on the inner flange of the cavity entering part of the closer at all positions along its length and at least one wall tie attached to this anchorage extends between two of the courses of the adjacent leaf of the wall.

37. A structural assembly as claimed in Claim 30, or any one of Claims 31 to 36, so far as they depend from Claim 30, in which the closer provides two alternative anchorages for wall ties on the web of the cavity entering part of the closer at all positions along its length; at least wall tie attached to one of these anchorages extends between two courses of the external leaf of the wall and at least one other wall tie attached to the other of these anchorages extends between two courses of the internal leaf of the wall.

38. A structural assembly as claimed in Claim 36 or Claim 37, in which the or each wall tie anchorage is in the form of an undercut recess and the or each wall tie has a root portion which is adapted to fit in the undercut recess either by sliding along the closer strip from one end thereof, or by inserting the root portion with the tie turned about its own longitudinal axis away from the operative orientation, so that the root portion can be inserted through the open side of the undercut recess and then turning the tie to its operative orientation.

39. A structural assembly as claimed in Claim 30, or any one of Claims 31 to 38, so far as they depend from Claim 30, in which the frame-engaging flange has a moisture trap in the face which engages with the frame element.

40. A structural assembly as claimed in Claim 31, or any one of Claims 32 to 39, so far as they depend from Claim 31, in which the second frame-engaging flange has a moisture trap in the face which engages with the frame element.

41. A structural assembly as claimed in Claim 39 or Claim 40, in which the moisture trap comprises a series of closely juxtaposed grooves with relatively sharp longitudinal edges between them.

42. A structural assembly as claimed in any one of Claims 28 to 41, in which the depth of the thermal insulation layer from the inside to the outside is not less than 15 mm.

43. A structural assembly as claimed in any one of Claims 28 to 42, in which the distance in the internal/external sense between the external edge of the cavity entering part and the external face of the location rib is approximately 10 mm.

44. A structural assembly as claimed in Claim 30, or any one of Claims 31 to 43, so far as they depend from Claim 30, in which a wall tie anchorage is available at all positions along the length of the closer in the outside face of the first frame-engaging flange and at least one wall tie attached to that anchorage extends between courses of the adjacent leaf of the wall.

45. A structural assembly as claimed in Claim 31, or any one of Claims 32 to 44, so far as they depend from Claim 31, in which a wall tie anchorage is available at all positions along the length of the closer in the outside face of the second frame-engaging flange and at least one wall tie attached to that anchorage extends between courses of the adjacent leaf of the wall.

46. A structural assembly as claimed in Claim 30, or any one of Claims 31 to 45, so far as they depend from Claim 30, in which the cavity is wider than the cavity entering part, that part is located against the internal face of the external leaf of the wall and a second thermal insulation element is located in the angle between the internal face of the cavity entering part and the second frame-engaging flange, the second insulation layer substantially filling the width between the cavity entering part and the internal leaf of the wall.

47. A structural assembly as claimed in Claim 30, or any one of Claims 31 to 46, so far as they depend from Claim 30, in which the cavity is wider than the cavity entering part, that part is located against the external face of the inner leaf of the wall and a third thermal insulation layer is located in the angle between the external face of the cavity entering part and the first frame-engaging flange, the third insulation layer substantially filling the space between the cavity entering part and the outer leaf of the wall.

48. A structural assembly as claimed in Claim 27, in which the cavity closer comprises a strip of water resistant, moisture-impermeable material, the strip having substantially parallel internal and external webs, the external web engaging with the outside face of the frame element and on the end of the external leaf of the wall, the internal web being offset outwardly of the external web and engaging on the end of the internal leaf of the wall, the offsetting of the webs with respect to each other defining an internal checked reveal between the two leaves of the wall, and an end strut engaging between and connecting the internal and external webs at a position such that a socket is formed bounded by overlapping parts of the two webs and the strut, the socket opening into the reveal; the thermal insulation layer covering at least part of the inside face of the internal web and having its external end located in the socket, at least part of the insulation layer which is in the socket being thereby located on the outside of the frame element and attachment means securing the cavity closer to at least one of the internal and external leaves of the wall.

49. A structural assembly as claimed in Claim 48, in which the position of the frame element relatively to the thickness (interior to exterior) of the cavity wall is assured by engagement of the frame element with a location flange on the external web of the cavity closer.

50. A structural assembly as claimed in Claim 49, in which the spacing in the wall thickness direction between the strut and the location flange is such that when the external edge of the insulation layer is engaged with the strut, the length of that part of the insulation layer which is on the outside of the frame element in the wall thickness direction is at least substantially equal to the thickness of the insulation layer.

51. A structural assembly as claimed in any one of Claims 48 to 50, in which a cavity-entering formation extends from the outer face of the internal web and is of such a cross-section that it provides a dampproof course within the cavity between the two leaves.

52. A structural assembly as claimed in Claim 51, in which the cavity entering formation is in the form of a flange projecting outwardly substantially perpendicular to the internal web.

53. A structural assembly as claimed in Claim 52, in which the cavity entering flange projects at least 50 mm from the internal web.

54. A structural assembly as claimed in any one of Claims 48 to 53, in which the internal web is provided with a moisture barrier adapted to resist moisture migration across the internal web between the two leaves of the wall.

55. A structural assembly as claimed in Claim 54, in which the moisture barrier comprises a series of longitudinal grooves in the outer face of the internal web.

56. A structural assembly as claimed in any one of Claims 48 to 55, in which the means securing the cavity closer to at least one of the leaves of the wall comprises one or more wall ties anchored to the internal web and projecting from that web into one or more mortar joints between courses of the inner leaf.

57. A structural assembly as claimed in any one of Claims 48 to 56, in which the means securing the cavity closer to at least one of the leaves of the wall comprises one or more angled wall ties each being anchored to the external side of the strut by one limb, the other (angled) limb projecting in the outward direction away from the frame element and into a mortar joint between two courses of the external leaf.

58. A structural assembly as claimed in any one of Claims 48 to 57, in which there is a moisture barrier formation on the inside face of the outer web to resist migration of moisture across the joint between the frame element and the external leaf.

59. A structural assembly as claimed in any one of Claims 48 to 58, in which the external web and the frame element are located substantially entirely aligned with the outer leaf of the wall, the socket of the cavity closer being received in a cut away part of the external leaf.

60. A structural assembly as claimed in Claim 52, or any one of Claims 53 to 58, so far as it depends from Claim 52 and Claim 59, in which the cavity entering flange abuts the internal face of the external leaf of the wall and retains any mortar which is squeezed out of the external leaf into the cut away for the socket.

61. A structural assembly as claimed in Claim 52, or any one of Claims 53 to 58, so far as it depends from Claim 52, in which the socket formation is located on the internal side of the external leaf and the cavity entering flange is located at a position intermediate the width of the cavity.

62. A structural assembly as claimed in Claim 52, or any one of Claims 53 to 58 so far as it depends from Claim 52, in which the cavity entering flange abuts the external face of the internal leaf of the wall and the external web extends across substantially the entire width of the cavity and rests on the end of the external leaf.

63. A structural assembly as claimed in any one of Claims 27 to 62, wherein the cavity closer is of constant cross-section throughout its length.

64. A structural assembly as claimed in Claim 63, in which the closer is made by an extrusion process.

65. A structural assembly as claimed in Claim 64, in which the closer is made of polyvinylchloride.

66. A cavity closer for closing the end of a cavity wall constructed and arranged substantially as herein described with reference to any one of Figures 4, 5, 6, 10, 13, 15, 32, 33, 36, 40 or 43 of the accompanying drawings.

67. A structural assembly constructed and arranged substantially as herein described with reference to any one of Figures 6, 7, 8, 11, 13, 14, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29, 30, 31, 34, 35, 37, 38, 41, 42 and 43 of the accompanying drawings.