GB2469032A

GB2469032A - Floor and ceiling structures

Info

Publication number: GB2469032A
Application number: GB0905443A
Authority: GB
Inventors: Derek Linton
Original assignee: Individual
Current assignee: Individual
Priority date: 2009-03-30
Filing date: 2009-03-30
Publication date: 2010-10-06
Also published as: GB0905443D0

Abstract

A ceiling or floor structure for a room of a building comprises a plurality of pre-formed parallel, horizontal metallic joists 7 of "C" or "I" section and a plurality of pre-formed parallel horizontal members 8 of "top hat" section extending transversely of the joists only on the side facing towards the room. A ceiling panel 18 (or a floor panel 38, fig.4) is secured to central portions (15, fig.3) of the transversely extending members 8 (or 37, fig.4). A layer of insulating material (28, fig.3) is provided as well as a water resistant membrane (19, fig.3). Also disclosed is a support apparatus formed from two wedges and used to adjust the height of the joists.

Description

Floor and Ceiling Structures This invention relates to floor and ceiling structures for buildings. The invention is particularly, but not exclusively, concerned with structures that use pre-formed components that can be assembled together rapidly, such as metallic members.

GB-A-2 128 219 discloses a floor / ceiling structure or a ceiling / roof structure constructed from metallic elements. Horizontal T' beam joists are secured at either end to an upwardly extending framework. Spaced cross members extend across the tops and bottoms of the joists. The cross members are of top hat section. A floor panel is secured to the cross members on the top of the structure, and a ceiling panel is secured to the cross members on the bottom of the structure. Insulating material can be provided in the space between the two panels. The complete structure can provide a ceiling for a room and a floor for the room above at first floor level for example, or a ceiling for a room and a floor for the roof space above, at second floor

level for example.

The present invention is concerned with an adaptation of this type of structure for use at ceiling I roof space level, and an adaptation of this type of structure for use at ground floor level.

Viewed from one aspect, the present invention provides a ceiling or floor structure for separating a room from another part of a building, the structure comprising a plurality of spaced, substantially parallel, substantially horizontally extending metallic joists, each joist being supported at the two opposed ends thereof by being connected to a framework, and each joist comprising an upwardly extending web, a first portion extending laterally from the web on the side facing towards the room and a second portion extending laterally from the web on the side facing away from the room; a plurality of spaced, substantially horizontally extending metallic members extending transversely of the joists only on the side of the joists facing towards the room, and secured to the first laterally extending portion of at least some of the joists; the transversely extending members each having a pair of horizontal flanges, each of which engages the first laterally extending portion of a joist, a central portion displaced towards the room from the flanges, and connecting portions extending from inner edges of the flanges to edges of the central portion; a panel extending substantially horizontally and secured to the central portions of at least some of the transversely extending members so as to face into the room; a layer of insulating material provided on the side of the panel remote from the room, and a substantially horizontally extending water resistant membrane arranged between the panel and the other part of the building.

The structure may be in the form of a ceiling structure for the room, in which to save material and weight the first laterally extending portion of each joist projects from the web in one direction only, and the second laterally extending portion of each joist projects from the web in one direction only. The first laterally extending portion and the second laterally extending portion of each joist preferably project from the web in the same direction so that the joist is of substantially "C" section.

However, it would be possible for the laterally extending portions to project in opposite directions, so that the joist is of substantially "S" or "Z" section with right angles connecting the portions to the central web.

In a preferred form of ceiling structure, the transversely extending members are secured to the lower laterally extending portions of the joists, the panel is a ceiling panel facing into the room, the waterproof membrane passes over the surfaces of the joists and the transversely extending members, the ceiling panel is secured to the to the central portions of the transversely extending members through the waterproof membrane, and the insulating material is provided above the waterproof membrane.

The ceiling structure may separate the room from a roof space and may be substantially non-load bearing. The preferred form ofjoist for use in a ceiling structure, a single member have a substantially "C" section, provides sufficient strength for a non-load bearing structure, which does not have to carry the weight of people, furniture and so forth.

In an alternative embodiment of the invention, the structure is in the form of a floor structure for separating a room from a base for the building. In this case, preferably the first laterally extending portion of each joist projects from the web in both directions, and the second laterally extending portion of each joist projects from the web in both directions, so that the joist is of substantially "I" section. Each joist may consist of two substantially "C" section portions back to back to form the substantially "I" section. Preferably, there are two separate, substantially "C" section members placed back to back, with their webs connected, to form the "I" section.

An "I" section beam provides sufficient strength for a load bearing floor, which has to carry the weight of people, furniture and so forth. It is simpler and less expensive to cold roll two "C" sections and join them, than to cold roll a complete "I" section.

Nevertheless, the use of an "I" beam, which consists of two "C" sections back to back, in which the "C" sections have been formed integrally rather than separately and joined together, is a possibility.

In the case of a floor structure, in preferred embodiments the waterproof membrane overlies the base, the lower laterally extending portions of the joists overlie the waterproof membrane, the transversely extending members are secured to the upper laterally extending portions of the joists, the panel is a floor panel facing into the room, the floor panel is secured to the to the central portions of the transversely extending members, and the insulating material is provided above the waterproof membrane in the space between the waterproof membrane and the floor panel.

In the case of both floor and ceiling structures, each joist is preferably supported at either end by being secured to one or members of an upwardly extending framework of the building. The framework may, for example, comprise metallic box sections.

It will be appreciated that in the case of both ceiling and floor structures there is a saving in material over the structure disclosed in GB-A-2 128 219, since in accordance with the present invention the transversely extending members are only provided on one side of the structure. This provides a saving in the amount of material required, and thus weight and cost, as well as a saving in fabrication time.

In the case of a ceiling, having lower load bearing requirements than a floor, the use of "C" section members further reduces the amount of material as compared to the use of "I" section members.

In the case of a floor structure, at least some of the joists may be supported on the base at at least one intermediate point between their ends. At least one joist may be supported on the base at an intermediate point between its ends by means of a support of adjustable height. The support of adjustable height may include an upper wedge portion with a substantially horizontally extending upper surface, the upper wedge portion being engaged with a lower wedge portion with a substantially horizontally extending lower surface, the relative positions of the upper and lower wedge portions being adjustable to vary the height between the upper surface of the upper portion, and the lower surface of the lower portion. The wedge portions may be provided with teeth, along their engaging surfaces to assist in interlocking and to resist slippage, and / or across their outer surfaces so as to resist slippage relative to the joists and relative to the base.

In the case of a floor structure, the water resistant membrane will resist moisture rising from the base of the building into the room. The base may be, for example, a concrete raft above the foundations of the building. In the case of a ceiling structure, the water resistant membrane will resist, for example, chemicals from a foam insulation process passing through to the ceiling panel, which may be plasterboard or the like. The waterproof membrane can also be extended upwardly so that portions protect wooden roof rafters or other structural members, preventing chemicals or moisture from a foam process from contacting the wood and leading to

rot, for example.

As noted above, the transversely extending members having a pair of horizontal flanges, a central portion displaced towards the room from the flanges, and connecting portions extending from inner edges of the flanges to edges of the central portion. In all cases the arrangement may be such that the connecting portions incline inwardly from the inner edges of the flanges to the central portion.

The metallic members such as the joists, transversely extending members and box sections may be made from galvanised steel or other materials of suitable strength and corrosion resistance. They may for example be fabricated by cold rolling.

The invention may be viewed from a number of different aspects.

Thus, for example, viewed from another aspect, the invention provides an assembly for use in constructing a ceiling structure as described above, comprising a plurality of spaced, substantially parallel, metallic joists, each joist being of substantially "C" section having an upwardly extending web, an upper laterally extending portion and a lower laterally extending portion; an array of a plurality of spaced, substantially parallel metallic members extending transversely of the joists on the lower side only of.the joists, and secured to the laterally extending portions of the joists on that side, the upper side of the joists being free from an array of transverse members; the transversely extending members each having a pair of horizontal flanges, each of which engages the laterally extending portion of a joist, a central portion displaced downwardly away from the flanges and the laterally extending portion of the joist, and connecting portions extending inwardly and downwardly from inner edges of the flanges to edges of the central portion.

It will be appreciated that references to "upper", "lower" and "downwardly" refer to the intended orientation of the assembly in use, and that the assembly may be constructed, stored or shipped in a different orientation.

Viewed from another aspect, the invention provides a method of constructing a ceiling structure using such an assembly, wherein the assembly is positioned to extend substantially horizontally above a room of a building with the lower sides of the joists facing downwardly towards the room, each joist is supported at the two opposed ends thereof and connected to a framework, a substantially horizontally extending water resistant membrane is positioned over the lower surfaces of the transversely extending members and the lower surfaces of the joists; a ceiling panel is positioned substantially horizontally beneath the water resistant membrane, and secured through the water resistant membrane to the central portions of at least some of the transversely extending members; and a layer of insulating material is provided above the water resistant membrane.

Viewed from another aspect, the invention provides an assembly for use in constructing a floor structure as described above, comprising a plurality of spaced, substantially parallel, metallic joists, each joist being of substantially "I" section having an upwardly extending web, an upper laterally extending portion and a lower laterally extending portion; an array of a plurality of spaced, substantially parallel metallic members extending transversely of the joists on the upper side only of the joists, and secured to the laterally extending portions of the joists on that side, the lower side of the joists being free from an array of transverse members; the transversely extending members each having a pair of horizontal flanges, each of which engages the laterally extending portion of a joist, a central portion displaced away from the flanges and the laterally extending portion of the joist, and connecting portions extending inwardly and upwardly from inner edges of the flanges to edges of the central portion.

It will be appreciated that references to "upper", "lower" and "upwardly" refer to the intended orientation of the assembly in use, and that the assembly may be constructed, stored or shipped in a different orientation.

Viewed from another aspect, the invention provides a method of constructing a floor structure using such an assembly, wherein the assembly is positioned to extend substantially horizontally at the bottom of a room of a building with the upper sides of the joists facing upwardly towards the room, the assembly overlying a base for -7,.

the building, each joist is supported at the two opposed ends thereof and connected to a framework, a substantially horizontally extending water resistant membrane is positioned over the base; a floor panel is positioned over the transversely extending members and secured to the central portions of at least some of the transversely extending members; and a layer of insulating material is provided between the water resistant membrane and the floor panel.

Viewed from a further aspect the invention provides a ceiling structure comprising a plurality of spaced, substantially parallel, substantially horizontally extending metallic joists, each joist being supported at the two opposed ends thereof and connected to an upwardly extending framework, and each joist being of substantially "C" section having an upwardly extending web, an upper laterally extending portion and a lower laterally extending portion; a plurality of spaced, substantially horizontally extending metallic members extending transversely of the joists on the lower surfaces only of the joists, and secured to the lower laterally extending portion of at least some of the joists; the transversely extending members each having a pair of horizontal flanges, each of which engages the lower laterally extending portion of a joist, a central portion displaced downwardly from the flanges, and connecting portions extending downwardly from inner edges of the flanges to edges of the central portion; a substantially horizontally extending water resistant membrane extending over the lower surfaces of the transversely extending members and the lower surfaces of the joists; a ceiling panel extending substantially horizontally beneath the water resistant membrane, and secured through the water resistant membrane to the central portions of at least some of the transversely extending members; and a layer of insulating material above the water resistant membrane.

Viewed from a further aspect, the invention provides a floor structure comprising a substantially horizontally extending base, a substantially horizontally extending water resistant membrane over the base, a plurality of spaced, substantially parallel, substantially horizontally extending metallic joists overlying the base, each joist being supported at the two opposed ends thereof and connected to an upwardly extending framework, and each joist being of substantially "I" section having an upwardly extending web, an upper laterally extending portion and a lower laterally extending portion; a plurality of spaced, substantially horizontally extending metallic members extending transversely of the joists on the upper surfaces only of the joists, and secured to the upper laterally extending portion of at least some of the joists; the transversely extending members each having a pair of horizontal flanges, each of which engages the upper laterally extending portion of a joist, a central portion displaced upwardly from the flanges, and connecting portions extending upwardly from inner edges of the flanges to edges of the central portion; a floor panel extending substantially horizontally and secured to the central portions of at least some of the transversely extending members; and a layer of insulating material beneath the floor panel.

Viewed from another aspect, the invention provides a ceiling structure comprising metallic joists supported at the two opposed ends thereof and connected to an upwardly extending framework, each joist being of substantially "C" section; metallic members extending transversely of the joists on the lower surfaces only of the joists, the transversely extending members each having horizontal flanges, a central portion and connecting portions from inner edges of the flanges to edges of the central portion, a water resistant membrane extending over the lower surfaces of the transversely extending members and the lower surfaces of the joists; a ceiling panel beneath the water resistant membrane, and secured through the water resistant membrane to the central portions of the transversely extending members; and a layer of insulating material above the water resistant membrane.

Viewed from another aspect, the invention provides a floor structure comprising a base, a water resistant membrane over the base, metallic joists supported at the two opposed ends thereof and connected to an upwardly extending framework, each joist being of substantially "I" section; metallic members extending transversely of the joists on the upper surfaces only of the joists, the transversely extending members each having horizontal flanges, a central portion and connecting portions from inner edges of the flanges to edges of the central portion; a floor panel secured to the central portions of the transversely extending members; and a layer of insulating material beneath the floor panel.

Viewed from another aspect the present invention provides a ceiling or floor structure for separating a room from another part of a building, the structure comprising a plurality of spaced, substantially parallel, substantially horizontally extending metallic joists, each joist being supported at the two opposed ends thereof and connected to an upwardly extending framework, and each joist comprising a substantially "C" section portion having an upwardly extending web, a first laterally extending portion on the side facing towards the room and a second laterally extending portion on the side facing away from the room; a plurality of spaced, substantially horizontally extending metallic members extending transversely of the joists only on the side of the joists facing towards the room, and secured to the first laterally extending portion of at least some of the joists; the transversely extending members each having a pair of horizontal flanges, each of which engages the first laterally extending portion of a joist, a central portion displaced towards the room from the flanges, and connecting portions extending from inner edges of the flanges to edges of the central portion; a panel extending substantially horizontally and secured to the central portions of at least some of the transversely extending members so as to face into the room; a layer of insulating material provided on the side of the panel remote from the room, and a substantially horizontally extending water resistant membrane arranged between the panel and the other part of the building.

In the case of a ceiling structure in accordance with this aspect of the invention, each joist consists of a single "C" section member. In the case of a floor structure in accordance with this aspect of the invention, each joist consists of a pair of "C" section members secured to each other back to back to from an "I" section, or an "I" section which in effect consists of a pair of back to back "C" sections formed integrally. -10-

It will be appreciated that the preferred embodiments of the ceiling and floor structures described herein could be modified. For example, there could be transverse members on both sides of the joists in a manner similar to the arrangement in GB-A-2 128 219, but with the structure being novel by virtue of including other features disclosed and claimed in this specification.

Thus, by way of example only, another aspect of the invention extends to a ceiling structure comprising metallic joists supported at the two opposed ends thereof and connected to an upwardly extending framework, each joist being of substantially "C" section; metallic members extending transversely of the joists on the upper and lower surfaces of the joists, the transversely extending members each having horizontal flanges, a central portion and connecting portions from inner edges of the flanges to edges of the central portion, a water resistant membrane extending over the lower surfaces of the lower transversely extending members and the lower surfaces of the joists; a ceiling panel beneath the water resistant membrane, and secured through the water resistant membrane to the central portions of the lower transversely extending members; and a layer of insulating material above the water resistant membrane.

By way of example only, a further aspect of the invention extends to a floor structure comprising a base, a water resistant membrane over the base, metallic joists supported at the two opposed ends thereof and connected to an upwardly extending framework, each joist being of substantially "1" section; metallic members extending transversely of the joists on the upper surfaces and lower surfaces of the joists, the transversely extending members each having horizontal flanges, a central portion and connecting portions from inner edges of the flanges to edges of the central portion; a floor panel secured to the central portions of the upper transversely extending members; and a layer of insulating material beneath the floor panel.

The additional and optional features discussed earlier above in broad terms, and described below in particular in relation to the preferred embodiments with reference to the drawings, may be used also in the contexts of these two additional aspects of the invention and in the contexts of other aspects of the invention.

Some embodiments of the invention will now be described by way of example and with reference to the accompanying drawings in which: Figure 1 is a perspective view of a prior art arrangement which can be used as an intermediate floor in a building which embodies the present invention; Figure 2 is a perspective view of an embodiment of a ceiling structure in accordance with the invention; Figure 3 is a detailed cut-away view of the structure of Figure 2; Figure 4 is a perspective view of an embodiment of a floor structure in accordance with the invention; Figure 5 is an end view of the structure of Figure 4; Figure 6 is a detailed cut-away side view of the structure of Figure 4; Figure 7 is a view of a component for forming a wedge; Figure 8 is a view showing two of the components assembled to form a wedge; and Figure 9 is a view showing the wedge with the two components in an alternative configuration.

Referring now to Figure 1 there is shown a prior art structure 1 as described in GB-A-2 128 219, which can be used as an intermediate, load-bearing floor in a building which embodies the present invention. The building includes a vertically extending steel frame 2, which incorporates a horizontal box section member 3. Steel joists 5 -12 -are supported at either end on a horizontal "C" section member 4 attached to box section member 3 (only one end is illustrated) and form an array of spaced joists.

An upper array of transverse steel members 6 is attached to upper portions of joists 5, and a corresponding array lower array of transverse steel members 6' is attached to the lower portions of joists 5. A floor can be laid on the upper array of transverse members 6, and a ceiling panel can be attached to the lower array of transverse steel members 6'.

Figure 2 shows a ceiling structure in accordance with the invention, for separating a room from a roof space of a building. The building includes a steel frame 2', which in this case include a horizontal steel box section 3' to which is attached a C section member 4'. Parallel, spaced steel joists 7 are supported at their ends by the C section member 4'. The other end of each joist, not shown, is supported in a like manner.

Secured to the underneath of the joists 7 are parallel, spaced, transverse steel members 8. Each joist 7 is provided with apertures 9 along its length to reduce weight, and is of "C" section having an upwardly extending web 10, a lower transverse 11 portion and an upper transverse portion 12. The transverse members 8 are secured to the lower transverse portions 11 of the joists 7. Ceiling panels 18, for example of plasterboard, are secured to the underneath parts of transverse members 8.

As shown in more detail in Figure 3, each transverse member 8 is of inverted "top hat construction, having a first laterally outwardly extending flange 13 on one side of the member, a downwardly and inwardly directed first connecting portion 14 extending from the inner edge of the first flange to a horizontal central portion 15, a second laterally outwardly extending flange 16 on the other side of the member, and a second downwardly and inwardly directed connecting portion 17 extending from the inner edge of the second flange to the central portion 15. A plasterboard ceiling panel 18 is secured at intervals to the central portion 15 of the transverse member, as indicated at 29. It is also secured at the edge of the structure to the box section 3', as indicated at 30.

-13 -Between the plasterboard ceiling panel 18 and the remainder of the structure, is provided a waterproof membrane 19. This is positioned over the transverse members 8 and joists 7 before the plasterboard panel is secured in place. The membrane 19 may be adhered to the transverse members 8, and optionally joists 7, using for example double sided tape.

The joists 7 are attached to timber roof rafters 20, using connector plates 21, screws 22 into the timber rafters, and rivets 23 into the webs 10 of the joists. The "Ca section member 4' is also secured to a timber member 24, using connector plate 25, screws 26 into the timber member 24, and rivets 27 into the box section 3'.

The space above the waterproof membrane is filled with foam insulation 28, up to a depth of about 100 mm, for example.

Figure 4 shows a floor structure in accordance with the invention. The building includes a vertical steel frame 2", which in this case include a horizontal steel box section 3" which carries a "C" section member 4". Parallel, spaced steel joists 31 are supported at their ends by the "C" section member 4". The other end of each joist, not shown, is supported in a like manner. Secured to the top surfaces of the joists 31 are parallel, spaced, transverse steel members 37. Each joist 31 is of "I" section having an upwardly extending web 32, an upper transverse 33 portion projecting in both directions from the web, and a lower transverse portion 34 projecting in both directions from the web. Each joist is provided with apertures 35 along its length to reduce weight. The transverse members 37 are secured to the upper transverse portions 33 of the joists 31. Floor panels 38, for example of chipboard, are secured to the to parts of transverse members 37. At an intermediate point a joist 31 is shown supported on a wedge assembly 36 of adjustable height.

Figure 5 is an end view showing a joist in more detail. The entire structure is supported above a concrete raft 45, as shown in Figure 6. Above this is laid a waterproof membrane 41. The wedge assembly 36 is shown, comprising a lower wedge portion 39 on top of the membrane and thus supported by the concrete raft, -14 -and an upper wedge portion 40, which supports the lower portion 34 of the joist 31.

By arranging the wedge portions so that the upper portion 40 is displaced to the right relative to the lower portion 39, as viewed in the drawing, the overall height of the wedge assembly 36 will be increased. Grooves or the like can be provided on the facing surfaces of the wedge portions so that they will remain in a chosen position.

The joist 31 is provided with apertures 42 to enable it to be connected to another joist or another component, using a suitable connector plate.

Figure 6 shows the concrete raft 45 at the bottom of the building, on which the membrane 41 is laid. The joists are spaced above the concrete raft and the membrane, by being supported at their ends and, optionally, by the intermediate wedge assemblies 36. The space above the membrane and below the floor panel 38 is filled with foam insulation 46, for example to a depth of 100 mm.

Each transverse member 37 is of "top hat" profile, having a first laterally outwardly extending flange 47 on one side of the member, an upwardly and inwardly directed first connecting portion 48 extending from the inner edge of the first flange to a horizontal central portion 49, a second laterally outwardly extending flange 50 on the other side of the member, and a second upwardly and inwardly directed connecting portion 51 extending from the inner edge of the second flange to the central portion 49. The floor panel 18 is secured at intervals to the central portion 49 of the transverse member, as indicated at 52. The rivets 43 and 44 secure the flanges 47 and 50 to the joist 31.

Figure 7 shows a component 53 from which the wedge portions 39 and 40 can be formed. The component has a main wedge portion 54 and a manipulating portion 55 which can be used to manipulate the wedge portion 54 under a joist. The manipulating portion 55, is integrally formed with the wedge portion 54 but there are notches 56 defining a line of weakness, so that the manipulating portion can be snapped off once the wedge portion is in position. The wedge portion 54 is in the form of an isosceles triangle with an upper surface 57 and a lower surface 59. The upper surface 57 has a series of teeth 58 and the lower surface 59 has a series of -15-teeth 60. The notches are optional and the manipulating portion can be left in place once the component is in position. The manipulating portion itself is optional and may be omitted so that there is only a wedge.

An optional feature is a line of weakness 61 part way along the wedge portion 54.

There may be notches at the ends of this line. The wedge portion 54 can then be split into two parts, namely a part to be used as a wedge portion when the height to be covered is relatively small, and a part to be used as a wedge portion when the height to be covered is relatively large.

Figure 8 shows component 53 placed on top of an identical component 53', which has been rotated through 180° about a vertical axis. Lower face 59 of component 53 is in contact with upper face 57' of component 53', with teeth 60 of component 53 engaged with teeth 58' of component 53'. Upper face 57 of component 53 is parallel to lower face 59' of component 53', and the overall height between face 57 and face 59' is hI. Teeth 58 on the component 53 will improve engagement with a joist supported on the assembly of components 53 and 53' so as to resist horizontal movement, and lower face 59' will be supported on the membrane covered base, with teeth 60' resisting horizontal movement.

Figure 9 shows the same assembly of components 53 and 53', but in this configuration the upper component 53 has been displaced in the direction of the arrow D with relative to component 53'. The upper surface 57 and the lower surface 59' remain parallel, but the overall height h2 is greater than height hi. Thus by varying the relative positions the height at which a portion of a joist is supported above the base can be varied. -16-

Claims

CLAIMS1. A ceiling or floor structure for separating a room from another part of a building, the structure comprising a plurality of spaced, substantially parallel, substantially horizontally extending metallic joists, each joist being supported at the two opposed ends thereof by being connected to a framework, and each joist comprising an upwardly extending web, a first portion extending laterally from the web on the side facing towards the room and a second portion extending laterally from the web on the side facing away from the room; a plurality of spaced, substantially horizontally extending metallic members extending transversely of the joists only on the side of the joists facing towards the room, and secured to the first laterally extending portion of at least some of the joists; the transversely extending members each having a pair of horizontal flanges, each of which engages the first laterally extending portion of a joist, a central portion displaced towards the room from the flanges, and connecting portions extending from inner edges of the flanges to edges of the central portion; a panel extending substantially horizontally and secured to the central portions of at least some of the transversely extending members so as to face into the room; a layer of insulating material provided on the side of the panel remote from the room, and a substantially horizontally extending water resistant membrane arranged between the panel and the other part of the building.
2. A structure as claimed in claim 1, in the form of a ceiling structure for the room, wherein the first laterally extending portion of each joist projects from the web in one direction only, and the second laterally extending portion of each joist projects from the web in one direction only.
3. A structure as claimed in claim 2, wherein the first laterally extending portion and the second laterally extending portion of each joist project from the web in the same direction so that the joist is of substantially "C" section.

-17 -
4. A structure as claimed in claim 2 or 3, wherein the transversely extending members are secured to the lower laterally extending portions of the joists, the panel is a ceiling panel facing into the room, the waterproof membrane passes over the surfaces of the joists and the transversely extending members, the ceiling panel is secured to the to the central portions of the transversely extending members through the waterproof membrane, and the insulating material is provided above the waterproof membrane.
5. A structure as claimed in claim 2, 3 or 4, wherein the ceiling structure separates the room from a roof space.
6. A structure as claimed in any of claims 2 to 5, which is substantially non-load bearing.
7. A structure as claimed in claim 1, in the form of a floor structure for separating a room from a base for the building, wherein the first laterally extending portion of each joist projects from the web in both directions, and the second laterally extending portion of each joist projects from the web in both directions, so that the joist is of substantially "F' section.
8. A structure as claimed in claim 1, wherein each joist comprises a portion of substantially "C" section.
9. A structure as claimed in claim 8, in the form of a ceiling structure for the room, wherein each joist is of substantially "C" section.
10. A structure as claimed in claim 8, in the form of a floor structure for separating a room from a base for the building, wherein each joist consists of two substantially "C" section portions back to back so that the joist is of substantially "I" section.
11. A structure as claimed in claim 10, wherein each joist consists of two separate substantially "C" section members placed back to back, with their webs connected, to form the "I" section.
12. A structure as claimed in claim 10, wherein the two substantially "C" sections are integral parts of an "I" beam.
13. A structure as claimed in any of claims 7, 10, 11 or 12 wherein the waterproof membrane overlies the base, the lower laterally extending portions of the joists overlie the waterproof membrane, the transversely extending members are secured to the upper laterally extending portions of the joists, the panel is a floor panel facing into the room, the floor panel is secured to the to the central portions of the transversely extending members, and the insulating material is provided above the waterproof membrane in the space between the waterproof membrane and the floor panel.
14. A structure as claimed in any of claims 7, 10, 11, 12 or 13, wherein at least some of the joists are supported on the base at at least one intermediate point between their ends.
15. A structure as claimed in claim 14, wherein at least one joist is supported on the base at an intermediate point between its ends by means of a support ofadjustable height.
16. A structure as claimed in claim 15, wherein the support of adjustable height includes an upper wedge portion with a substantially horizontally extending upper surface, the upper wedge portion being engaged with a lower wedge portion with a substantially horizontally extending lower surface, the relative positions of the upper and lower wedge portions being adjustable to vary the height between the upper surface of the upper portion, and the lower surface of the lower portion.
17. A structure as claimed in any preceding claim, wherein the framework comprises metallic box sections.
18. A structure as claimed in any preceding claim, wherein the connecting portions of the transversely extending members incline inwardly from the inner edges of the flanges to the central portion.
19. An assembly for use in constructing a ceiling structure as claimed in claim 3, comprising a plurality of spaced, substantially parallel, metallic joists, each joist being of substantially "C" section having an upwardly extending web, an upper laterally extending portion and a lower laterally extending portion; an array of a plurality of spaced, substantially parallel metallic members extending transversely of the joists on the lower side only of the joists, and secured to the laterally extending portions of the joists on that side, the upper side of the joists being free from an array of transverse members; the transversely extending members each having a pair of horizontal flanges, each of which engages the laterally extending portion of a joist, a central portion displaced downwardly away from the flanges and the laterally extending portion of the joist, and connecting portions extending inwardly and downwardly from inner edges of the flanges to edges of the central portion.
20. A method of constructing a ceiling structure using an assembly as claimed in claim 19, wherein the assembly is positioned to extend substantially horizontally above a room of a building with the lower sides of the joists facing downwardly towards the room, each joist is supported at the two opposed ends thereof and connected to a framework, a substantially horizontally extending water resistant membrane is positioned over the lower surfaces of the transversely extending members and the lower surfaces of the joists; a ceiling panel is positioned substantially horizontally beneath the water resistant membrane, and secured through the water resistant membrane to the central portions of at least some of the transversely extending members; and a layer of insulating material is provided above the water resistant membrane.
21. An assembly for use in constructing a floor structure as claimed in claim 7, comprising a plurality of spaced, substantially parallel, metallic joists, each joist being of substantially "I" section having an upwardly extending web, an upper laterally extending portion and a lower laterally extending portion; an array of a plurality of spaced, substantially parallel metallic members extending transversely of the joists on the upper side only of the joists, and secured to the laterally extending portions of the joists on that side, the lower side of the joists being free from an array of transverse members; the transversely extending members each having a pair of horizontal flanges, each of which engages the laterally extending portion of a joist, a central portion displaced away from the flanges and the laterally extending portion of the joist, and connecting portions extending inwardly and upwardly from inner edges of the flanges to edges of the central portion.
22. A method of constructing a floor structure using an assembly as claimed in claim 21, wherein the assembly is positioned to extend substantially horizontally at the bottom of a room of a building with the upper sides of the joists facing upwardly towards the room, the assembly overlying a base for the building, each joist is supported at the two opposed ends thereof and connected to a framework, a substantially horizontally extending water resistant membrane is positioned over the base; a floor panel is positioned over the transversely extending members and secured to the central portions of at least some of the transversely extending members; and a layer of insulating material is provided between the water resistant membrane and the floor panel.
23. A ceiling structure, substantially as hereinbefore described with reference to Figures 2 and 3 of the accompanying drawings.
24. An assembly for use in constructing a ceiling structure, substantially as hereinbefore described with reference to Figures 2 and 3 of the accompanying drawings.

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25. A method of constructing a ceiling structure, substantially as hereinbefore described with reference to Figures 2 and 3 of the accompanying drawings.
26. A floor structure, substantially as hereinbefore described with reference to Figures 4 to 9 of the accompanying drawings.
27. An assembly for use in constructing a floor structure, substantially as hereinbefore described with reference to Figures 4 to 9 of the accompanying drawings.
28. A method of constructing a floor structure, substantially as hereinbefore described with reference to Figures 4 to 9 of the accompanying drawings.