GB2043545A - Rendered structural features and an element for use in such features - Google Patents

Abstract

A method of forming a rendered structural feature divided into a plurality of areas comprises: cutting a plurality of lengths from a strip element (preferably an extruded plastics element); securing the strips together by push-in connectors to form a grid; embedding the grid in a rendering leaving the top edges of the grid exposed, and allowing the rendering to harden so that the grid is permanently embedded in it. The specification disclosed a preferred shape of extruded plastics strip element and methods of forming rendered structural features wherein (i) the strip element is pressed into rendering in the doughy state and becomes anchored therein and (ii) the strip element is secured to a headed anchor member secured in a substrate, before applying the rendering. The strip element may also be temporarily secured to wall shuttering whereby on removal of the shuttering the strip element is left embedded in the cast wall. <IMAGE>

Description

SPECIFICATION Rendered structural features and an element for use in such features The expression "rendered structural feature" as used herein is intended to include such features as: element rendered walls, internal or external; -plastered walls (usually internal); poured concrete walls; poured cement paths, patios and pavements.

The invention is capable of use with any such rendered structural feature, wherein the rendering is applied or moulded when in a plastic or paste-like state, and becomes hard when set.

The object of the first aspect of the invention is to provide an extruded strip element which can be used in the production of a rendered structural feature to produce a special decorative effect. The object of the second aspect of the invention is to provide a method of producing a rendered structural feature with a special decorative effect.

According to one aspect of the invention an extruded strip element for use in a rendered structural feature comprises a channel with a substantially tubular excrescence along the inside of one of its flanges. Preferably the excrescence is disposed adjacent to the end of the flange. It is further preferred that an internal lip is provided on the same flange as the tubular excrescence the lip projecting towards the other flange by approximately the same distance as the tubular excrescence.

According to a further preferred feature of this aspect of the invention a series of longitudinally spaced holes is formed laterally through the strip element, passing through both flanges and through the tubular excrescence. Shallow grooves may be formed along the outside of one or both flanges and/or the web of the strip element.

According to a second aspect of this invention the exposed surface of a rendered structural feature is divided into a plurality of areas by strip elements permanently secured in the rendering so that they are visible as part of the said exposed surface. Preferably the strip elements are formed as plastics extrusions.

According to a preferred feature of the invention the strip elements are secured in the rendering by means of anchor members located in holes in the strip elements, but projecting laterally therefrom, the anchor members being totally embedded in the rendering. The strip elements may themselves be formed with recesses and/or holes in which rendering can engage as a means of securing the strip elements in the rendering.

The invention also includes rendered structural features made in accordance with the second aspect of the invention.

An extruded strip element in accordance with the first aspect of the invention, and several structural features made in accordance with the second aspect, together with alternative extruded strip elements which can also be used in the second aspect of the invention, will now be described by way of examples only, with reference to the accompanying drawings, in which:: Figure 1 is a cross-section through a strip element in accordance with the first aspect of the invention, Figure 2 is a section through part of a rendered structural feature, Figure 3 is an elevation showing a butt joint between two strip elements of the kind shown in Fig. 1, Figure 4 is a plan view showing a stage in the construction of a paved area, Figure 5 is an end view of a shuttering member employing a strip element of the kind shown in Fig. 1, Figure 6 is an elevation of a corner joint in shuttering comprising members as shown in Fig. 5, Figure 7 is a view similar to Fig. 6, but showing an alternative shuttering member, Figure 8 is an end view of a strip element of the kind shown in Fig. 1 at one stage in the rendering of an existing wall, Figure 9 is a view similar to Fig. 8, but showing a method used with a wall of weaker construction, Figure 10 is an end view showing a method of securing a strip element of the kind shown in Fig. 1 in a cast concrete wall, Figure 11 is a view similar to Fig. 10 but shown an alternative method of securing the strip element in a cast concrete wall, Figure 12 is an end view showing a method of securing a perpendicularly arranged strip element in a cast concrete wall, Figures 1 3a to 13j are cross-sections through alternative forms of strip element not in accordance with the first aspect of the invention but which can be used in the second aspect of the invention, Figure 14 is a cross-section through another form of strip element again not in accordance with the first aspect of the invention, but which can be used in the second aspect of the invention, and Figure 15 is a cross-section through a paved area showing the use of strip elements as illustrated in Fig. 14.

As will become apparent hereinafter, the invention is applicable to the construction of a wide variety of rendered structural features (as hereinbefore defined) and in particular is of use in the construction of paths, drives, patios and internal paved or rendered floor areas (which might be described broadly as "horizontal" applications) and in the construction of cast concrete walls, cement rendered exte rior or interior walls, plastered walls or even rendered decorative panels for walls (all of which might be described as "vertical" applications). It is to be understood however that the words "horizontal" and "vertical" are only used in a very general sense to facilitate the explanation, and the invention is not restricted to features which are necessarily horizontal or vertical.

The strip element 10 shown in Fig. 1 is made as a plastics extrusion, and may for example, be made in uPVC as used in the manufacture of gutters, pipes and the like for building construction. The element could however be extruded in other plastics materials or indeed in metal, but plastics is preferred, because the strip is left in situ and will be subject to corrosive attack which would destroy most metals.

Basically, the element 10 comprises two flanges 1 2 and 14 joined at one end by a web 1 6 so that the element is in the form of a channel open along one side. The external faces of the flanges and the web are scored as shown at 18, but the scoring is not an essential feature. A tubular excrescence 20 is formed along the lower marginal portion of the inside of the flange 12, and an internal lip 22 is also formed on the inside of the flange 12, this lip being spaced above the excresence 20 and below the web 16.

Although the dimensions of the extruded strip element are not critical, the dimensions of a particular element will be given to further a better understanding of the invention. The depth of this particular element is 1 5 millimetres; the width 10 millimetres; the thickness of the flanges, web, wall of the tubular excrescence and lip, 1.2 millimetres and the bore of the tubular portion 2.5 millimetres.

The gap between the outside of the tubular portion and the opposite internal face of the flange 14 is 3 millimetres, and there is approximately the same gap between the extremity of the lip 22 and the flange 14.

Since the strip element 10 is made by an extrusion process, it is of constant cross-section throughout its length, but a series of transverse holes 24 approximately 2.5 millimetres diameter is formed through the lower part of the element at approximately 360 millimetre spacings along the length thereof, each hole 24 passing through the two flanges and the tubular portion 20. The purpose of all the features of the element 10 will appear from the following description of ways in which the element can be used in accordance with the second aspect of the invention. It should be understood that the element will be supplied in long lengths, ready for cutting to the required length on site.

Assuming that it is intended to lay a concrete path 30 (see Fig. 4) suh-divided into a series of discrete areas (e.g. 32, 34, 36, 38, 40, 42, 44, 46 and 48) in simulation of a ''crazy-paved''path, shuttering (not shown) may be placed in position to define the edges 50 and 52 of the path, and then short divider strips 54, 56, 58, 60, 62, 64, 66, and 68 of the element 10 are cut to the required lengths so that they can be laid out in the area between the shuttering edges in a pattern such as that shown in Fig. 4. In fact, it will probably be advisable to lay out the desired pattern of divider strips in this way to assess the aesthetic effect of the pattern before any concrete is poured.

The concrete/aggregate mix is then poured between the edge shutterings in the conventional manner as would be the case if a unitary concrete path were required. Each divider strip is then fitted with anchors 70 in the form of 50 millimetre nails pushed into the holes 24 and left projecting from each side of the element as shown in Fig. 2, and then, whilst the concrete is still wet and soft, each divider strip is pressed into the concrete until the top surface of its web 1 6 is flush with the top of the concrete and the flanges 1 2 and 14 and the nails 70 are embedded into the concrete. This position is illustrated in Fig. 2 of the drawings. At the appropriate time, the concrete is levelled in the conventional manner leaving the top surfaces of the webs 16 exposed.

It will be appreciated that the result is a path of very pleasing appearance which is a monolithic concrete structure, but having its top surface divided into a series of "paved" areas by the divider strips 54 to 68. Moreover, the divider strips will not deteriorate and there will be no growth of weeds between the "paved" areas. The divider strips will be well secured to the concrete due to the anchoring effect of the nails 70 and due to concrete entering the channel section so that both the tubular portion 20 and the lip 22 provide additional anchors. If the flanges 1 2 and 14 are scored, as shown at 18, the slight recesses formed by this scoring also provide keys. Indeed, it may not be necessary to employ the nails 70, or if they are used it may not be necessary to fit a nail in every one of the transverse holes 24.

It is possible to form secure butt joints where the end of one piece of strip element 80 abuts another strip element 82 as shown in Fig. 3. It is only necessary to force a nail 83 which has a diameter such that it is a push-fit in the bcre of the tubular portion 20, through one of the holes 24 in the element 82 and into the tubular portion 20 of the element 80. This not only secures the two elements to each other, it also ensures that their top surfaces are in the same plane. A right angle butt joint of this kind is shown at the junction of the divider strips 56 and 58 in Fig. 4.It is possible to form butt joints at other angles (for instance the joint between the divider strips 54 and 56) but in that case a hole must be formed through one of the strips at an angle to receive the nail and preferably, the end of the other strip should be cut an angle to form a neat butt joint.

It should also be mentioned that the strip element 10 can be bent to form curved divider walls, and if it is required to reinforce such a curved strip against self-straightening forces, this can be done by inserting a steel wire bent to the required configuration in the bore of the tubular portion 20.

Referring now to Fig. 5, there is shown a strip element 90 of the same kind as that shown in Fig. 1, attached to' one edge of a strip of shuttering material 92, which may be made of hardboard. The top edge of the hard board can be wedged between the flange 14 on the one hand and the tubular portion 20 and the lip 22 on the other hand. In addition, anchor nails 94 may be driven through the, or some of the transverse holes 24 and through the hardboard strip 92 and left projecting on both sides as shown in Fig.

5. With this arrangement, the shuttering in the form of divider strips can be placed on an area prepared for the paving of concrete with the lower edge of each hard board strip resting on the ground or on prepared foundation pads, care being taken to ensure that the top surfaces of all the divider strips are in the same plane. In this way a complete framework of the shuttering is produced. The concrete is then poured and levelled, leaving the top edges of the divider strips exposed as described with reference to Fig. 4. The hardboard shuttering is thus left in the concrete where it will be subjected to organic decomposition, but this will not affect the plastics strip dividers which will remain anchored by the nails 94 and by concrete embedded in the strip itself.

One advantage of the method shown in Fig.

5 is that it enables various depths of concrete to be employed (by presetecting the depth of the hardboard 92) and since the areas divided by the shuttering are completely separated, it is possible to use concrete of different colours in the several paved areas, thus providing an exceptionally visually pleasing effect. Also, the separate paving slabs will be tied together by the plastics divider strips, and this assists in combating the effect of frost on the paved area.

It will be appreciated that the shuttering strip 92 could be made in any one of a variety of materials so long as it is able to provide the necessary shuttering effect during paving of the concrete. If the hard board strip is replaced by a piece cut from a sheet of plastics material for example, then the shuttering could be used to provide permanent path edging. For example, it could be used to provide the edges 50 and 52 of the paved area 30 illustrated in Fig. 4.

Fig. 6 illustrates a method of forming a butt or corner joint from two shuttering strips similar to that shown in Fig. 5. The strip 100 is made exactly as described with reference to Fig. 5 and comprises-a strip 102 of hardboard, with an extruded plastics element 104 fitted to its top edge. The strip 106 is made in a similar fashion, and comprises a hardboard strip 108 and an extruded element 11 0. In addition, the strip 106 is fitted with an additional short length 11 2 of the extruded plastics element which is pressed on to the bottom edge of the hardboard strip at the end where the joint is to be formed.A self-tapping screw 11 4 is passed through one of the transverse holes in strip 100 and into the tubular portion of the element 11 0. Another self-tapping screw 11 6 is forced through a hole in in the hard board strip 102 and into the tubular portion of the element 11 2. In this manner, a very secure butt or corner joint is formed which will resist the separating force set up during pouring of the concrete.

Again, it will be appreciated that it may not always be necessary to employ the lower element 11 2 and the screw 116.

In the joint shown in Fig. 6, the flange 12 of the element 104 with its tubular portion 20 is on the outside of the joint. In some instances it may be necessary to construct a butt joint with the flange 1 2 on the inside, as shown in Fig. 7 (in which all the parts have the same reference numerals as in Fig. 6). In that case, a corner piece is cut away from the strip 110 and from the hardboard strip 108 is indicated at 11 8 to accommodate the element 1 04. If it is necessary to provide temporary reinforcement for the shuttering during construction of the path this can be done by driving tent pegs, skewers or the like into the ground on the outside of the shuttering.

The methods of manufacture described with reference to Figs. 2 to 7 all relate to horizontal applications of the invention. Fig. 8 shows a method used in the rendering of an existing wall 1 20. It will be assumed that the wall 1 20 is an external wall of a building and that cement rendering is to be applied to the wall.

However, the same constructional method could be used on an internal wall which is to be rendered with mortar or plaster.

Where a horizontal divider is required on the rendered wall, a horizontal line is first marked on the wall and then a series of masonary nails 1 22 is driven into the wall at spaced apart position along the marked line.

Reference to Fig. 8 will show that each nail 1 22 is left projecting about 7 millimetres from the face of the wall. The flange 1 2 of an extruded strip element 1 24 is then laid against the face of the wall 1 20 with the tubular portion 20 resting on the protruding portions of the nails 1 22 between the surface of the wall and the heads of the nails. The strip element 1 24 is then turned in a clockwise direction about its tubular portion until it has turned through 90". (The position of the element 1 24 part-way through this turning motion is shown in dotted lines in Fig.

8, and its final position is shown in full lines).

The head of each nail 1 22 is then located in the channel as illustrated. A series of 50 millimetre nails 1 26 is then pushed through the holes 24 in the strip element 1 24 and left projecting above and below that element. It is then impossible to turn the strip element to release from the heads of the nails 1 22 so that is becomes permanently secured to the wall.

Cement rendering can than be applied to the exposed surface of the wall 120, in the conventional manner, until the cement rendering is flush with the exposed surfaces of the elements 1 24. In this way, the elements 1 24 divide the rendering into a series of horizontal strips.

Some walls might not be adequate to accept masonary nails such as those illustrated in Fig. 8. For example, a so-called Paramount partition wall which is manufactured from two sheets of plaster board separated and connected by an "eggbox" arrangement between the sheets. Such a wall normally only has timber uprights at intervals of 1 250 millimetres, and consequently there is no timber or anything else which is adequate to receive nails, except around the perimeters of the sheets of partitioning wall. However, a method of utilising the extruded strip members made in accordance with the first aspect of the invention, on such a wall, is illustrated in Fig. 9.Part of one of the plaster boards 130 is illustrated, and an extruded strip element 1 32 of the kind shown in Fig. 1 is placed against the exposed surface of the plaster board 130, with the edges of the flanges 1 2 and 1 4 resting against that exposed surface. A 50 millimetre nail 1 34 is pushed through each of the holes 24 in the element 132, leaving parts of the nail 1 34 projecting above and below the strip element.

Wire staples 1 36 and 1 38 are then forced into the plaster board 1 30 around the extending portions of the nail 134, and these are sufficient to hold the nail and the strip element in position on the wall ready for the application of a plaster or mortar rendering.

It is to be noted, that when the strip element is used on a vertical wall as illustrated in Figs. 8 and 9, the depth of the strip element, is approximately the same as the thickness of cement or plaster rendering normally applied to walls, so that only the same thickness of rendering will be used as in a conventional construction, to leave the exposed edges of the strip elements flush with the rendering.

It has been mentioned, that the invention is also applicable to cast vertical concrete walls, in which case, the concrete wall itself becomes the rendered feature. A method of manufacturing such a concrete wall, will now be described with reference to Fig. 10, which illustrates part of a sheet of plywood 140 forming the vertical shuttering on one side of the poured concrete wall.

Before the shuttering is erected, the pattern of a "bond" which is required to appear in the exposed vertical surface of the wall is first marked on the inside face of the plywood shuttering 140. Two small holes 142 and 1 46 are then formed through the plywood 140, on each side of each line, at spaced apart positions-say every 360 millimetres along the length of each line.

The extruded strip made in accordance with Fig. 1, is cut into short lengths one of which is shown at 148, corresponding to the lengths of the lines marked on the inside face of the shuttering 1 40. Each such cut strip is then placed on its line, with the web 1 6 engaging with the surface of the shuttering, and a selftapping screw 1 50 is then screwed into the channel of the strip element 148, at each position where there is a pair of holes 142 and 146 formed through the shuttering. If the self-tapping screw is of the correct dimension, it will bite into the flange 14, and into the tubular portion 20 and the lip 22 of the strip element, so as to become tightly fixed in the element.One end of a piece of copper wire 152, is then wrapped around the stem of the self-tapping screw 150, in an anti-clockwise direction. The other end of the wire is taken along the top of the strip 148, through the hole 142, down the outside of the shuttering 140, back through the hole 146, along the bottom side of the strip element 148, and is then wrapped around the stem of the screw in a clockwise direction. The two ends of the wire 1 52 may then be twisted together as illustrated in the drawing.When the screw is again turned, to force it into the strip element, the wire 1 52 will tighten up on itself, and cause the face of the extrusion to be pulled tight against the face of the plywood shutter ing 1 40. In addition, the open end of the channel formation of the strip element 148 will tend to close on itself, ensuring that the self tapping screw cuts the necessary threads into the element.

After all the strip elements 148 have been fitted to the inside of the shuttering 140 to create the aritificial "bond" the shuttering is erected and the concrete poured in the conventional manner. When the concrete has set, the strip elements 148 will all be thoroughly embedded in the concrete, with the upper surfaces of the webs 1 6 exposed in the verti cal surface of the concrete wall. The strip elements will be thoroughly anchored, by the heads of the screws 1 50 being embedded in the concrete, and in addition concrete will flow into the channel formation of the strip element itself.It is then only necessary to cut away the exposed portions of the wire 152, in order to leave a wall which has the appear ance of being constructed from a series of blocks, separated by the plastics strip elements.

Fig. 11 shows a similar method to that just described with reference to Fig. 10, and the same references have been used. However, in this construction, each of the self-tapping screws 1 50 is passed through the hole 24 formed in the strip element 148, and the ends of the copper wire 1 52 are wrapped around the portions of the screw 1 50 which project above and below the strip element 158, before being twisted together.

Fig. 1 2 illustrates the arrnhgement which is used in manufacturing a poured concrete wall, where besides horizontal dividers, it is also necessary to provide vertical dividers. In this method, there is a piece of plywood shuttering 1 60 on which the "bond" is first marked, but in this method, small holes 162 and 164 are only formed above and below the markings for a horizontal row of "blocks". Two extruded strip elements 1 66 and 1 68 are positioned on parallel horizontal lines of the "bond" and a vertical divider strip 1 70 also made of the extruded strip element illustrated in Fig. 1, is placed in position between the strips 166 and 168.A 50 millimetre nail 172 is passed down through the hole 24 in the upper strip 166, into the tubular portion 20 of the strip 1 70. A self-tapping screw 1 74 is passed upwardly through the hole 24 in the lower strip 168, and into the bore of the tubular portion 20 of the vertical strip element 1 70. A piece of copper wire 1 76 is coiled around the upper extension of the nail 1 72, taken through the upper hole 1 62 in the shuttering 160, down the outside of the shuttering, back through the hole 164, under the strip 1 68 where it is coiled around the exposed portion of the screw 174, and then the ends of the copper wire are twisted together on the inside.

Pouring of the concrete wall is carried out in the conventional manner, and it will be appreciated that when the shuttering is removed, and the exposed portions of the copper wire cut away, then the exposed surface of the wall has both horizontal and vertical divider strips.

It will be understood, that in the arrangement illustrated in Fig. 12, it is possible to use two nails instead of the nail and screw, or alternatively two screws. It is also possible, that in all the arrangements described with reference to Figs. 10,11 and 12, it may be possible to simply rely on twisting the wire tightly around the strip elements, by using pliers.

Turning now to Figs. 1 3a to 1 3j, there are illustrated a series of plastics extruded strip elements 200, 202, 204, 206, 208, 210, 212, 214 and 216, each of which can be employed for the purpose of creating plastics dividers, in a rendered surface. For example, taking the strip 200 which is illustrated in Fig.

13a, it will be observed that this is generally T-shaped in cross-section, in that it has a web 220 with a somewhat rounded upper surface, and a depending flange 222 formed with horizontal serrations along its faces. If a horizontal cement area has been poured, then it is possible to force a strip element 200 into the concrete whilst it is still in the wet state, until the undersurface of the web 220 is just under the top surface of the concrete. The flange 222 will then become embedded in the concrete as the latter sets, and will be anchored in position, due to the serrated formation of the flange. When the concrete has set, the curved upper surface of the strip element 200 will be exposed, providing a neat divider.

Similarly, the strip element 202 illustrated in Fig. 1 3b, has a web 224 and a serrated flange 226. In this case, the web 224 is generally rectangular in cross-section, and it would be possible to push the strip element 202 into the poured and wet concrete, until the upper surface of the web 224 is flush with the upper surface of the concrete.

The strip element 204 illustrated in Fig.

13c, is somewhat different, in that the web 228 is arcuate in form, although it still has a depending flange 230 which is somewhat serrated. The flange 230 could only be forced into the concrete until the extremities of the web 228 were engaging in the concrete, leaving a pronounced arcuate divider strip in the finished surface. The strip element 206 illustrated in Fig. 1 3d by way of constrast has a web 232 which has only a very shallow arcuate form, but again there is a serrated flange 234 for forcing into the concrete.

The strip element 208 illustrated in Fig.

13e, is smaller than those shown in Figs. 1 3a to 13d, and its web 236 is partly arcuate, but exhibits a flat central portion. This strip element also has a depending flange 238 which is serrated for anchoring into the concrete.

The strip element illustrated in Fig. 13f, has a more decorative web 240 formed after the fashion of a moulding for use in buildings, and this illustrates that the surface of the strip element which is to be exposed in the finished structure, can if necessary itself have a patterned formation. An alternative pattern formation is illustrated by the strip element 212 shown in Fig. 13g.

The strip elements 214 and 216 illustrated in 1 3h and 1 3j respectively, only show variations on the form of the web in each case.

An alternative form of extruded plastics strip element 250, for use in the second aspect of the invention, is illustrated in Fig. 14. The overall height of the element 250 is approximately equal to the depth of standard concrete paving as used for paths, patios and the like. Essentially, the element 250 comprises a vertical flange 252, and upper and lower webs 254 and 256, each of which is pro vided with a pair of edge strips 258 so that each web 254 and 256 takes the form of an I-section turned on its side. In addition, there are inclined strips 260, which produce in effect arrow heads facing each other, near to the horizontal centre-line of the element 250.

The method of using the strip elements 250 is illustrated in Fig. 15, which shows that each of the lower webs 256 rests on the foundation prepared for the paved area, and that the cement/aggregate mixture 262 is then poured, and levelled off with the top edges of the strips 258 on the upper webs 254 of the elements 250. It will be appreciated, that the strips 250 become permanently anchored in the poured concrete area. The division of the paved area, is similar to that which is obtained by the method described with reference to Fig. 4 of the drawings, except that with the extruded strip element 250, there is no provision for using anchoring nails or screws.

An important feature of the strip illustrated in Fig. 14, is that it can be split horizontally between the two arrow heads formed by the strips 260, because the strip 250 is symmetrical about a horizontal axis. When thus divided into two strip elements, it will be appreciated that there is produced extruded strip material which can be used in similar fashion to the strip elements illustrated in Figs. 1 3a to 13j, and of course one has twice the length of this strip material as the original strip element 250.

It is also to be understood, that features described with reference to some of the accompanying drawings, could be combined with features shown in other drawings. For example, in any particular construction it may be desirable to use one kind of strip element for say horizontal dividers, and another kind of strip element for vertical dividers.

Claims (12)

1. A method of forming a rendered structural feature divided into a plurality of areas comprising the steps of: (i) cutting a plurality of lengths from a strip element; (ii) securing these strip lengths together by push-in connectors to form a grid; (iii) embedding the grid so formed in a rendering whilst the latter is in a doughy state, but leaving the top edges of the grid exposed, and (iv) allowing the rendering to harden so that the grid becomes permanently embedded in it with the top surfaces of the grid exposed.

2. A method of forming a rendered structural feature as claimed in Claim 1, including the further step of locating anchor members in holes formed in at least some of the strip lengths forming the grid, with parts of the anchor members projecting from the strip lengths, so that the anchor members become totally embedded in the rendering.

3. A method of forming a rendered structural feature as claimed in Claim 1 or Claim 2, in which the rendering is also engaged in recesses and/or holes formed in the strip length .

4. A method of forming a rendered structural feature as claimed in any one of Claims 1 to 3, in which shuttering elements are engaged in hollow formations in at least some of the strip lengths to increase the effective depth of the grid by the depth of the shuttering elements and both the grid and the shuttering elements are embedded in the rendering.

5. A method of forming a rendered structural feature substantially as herein described with reference to Figs. 1 to 4 or Figs. 1 to 4 as modified by Fig. 5 or Fig. 6 of the accompanying drawings.

6. A method of forming a rendered structural feature comprising the steps of: convering an area with rendering and, whilst the rendering is in. a doughy state, pressing into it one or more strip elements each of which has at least one keying formation, leaving the top edge of each strip element exposed, and allowing the rendering to harden, whereby each strip element becomes permanently embedded in the rendering with its top surface exposed.

7. A method of forming a grid as claimed in Claim 6, wherein the strip element is constructed substantially in accordance with any one of Figs. 1, 13a to 13j, 14 or 15 of the accompanying drawings.

8. An extruded strip element for use in a rendered structural feature comprising a channel with a substantially circular cross-section excrescence along the inside of one of its flanges.

9. An extruded strip element as claimed in Claim 8, in which the excrescence is substantially tubular.

10. An extruded strip element as claimed in Claim 8 or Claim 9, in which the excrescence is disposed adjacent to the end of the flange.

11. An extruded strip element as claimed in any one of Claims 8 to 10, in which an internal lip is provided on the same flange as the excrescence the lip projecting towards the other flange by approximately the same distance as the excrescence.

12. An extruded strip element as claimed in any one of Claims 8 to 11, in which a series of longitudinally spaced holes is formed laterally through the strip element, passing through both flanges and through the excrescence.

1 3. An extruded strip element as claimed in any one of Claims 8 to 12, in which shallow grooves are formed along the outside of one or both flanges and/or the web of the strip element.

1 4. An extruded strip element constructed and arranged substantially as herein described with reference to Fig. 1 of the accompanying drawings.

1 5. A method of rendering a structural substrate presenting a surface to be rendered, comprising the steps of: securing a plurality of headed anchor members in the substrate with the heads thereof projecting from the said surface of the substrate; attaching one or more strip elements to the headed anchor members so that each such strip element is at least temporarily secured to the substrate by engagement on the heads of the anchor members; rendering the said surface leaving the top edge of each strip element exposed, so that each strip element becomes embedded in the rendering, and allowing the rendering to harden so that the strip element becomes permanently embedded in it with its top surface exposed.

1 6. A method of rendering a structural substrate as claimed in Claim 1 5 substantially as herein described with reference to Fig. 8 of the accompanying drawings.