GB2102469A - Cladding of roofs and walls - Google Patents

Abstract

A cladding assembly in which sheets of external cladding material 26 are fixed to frame members of a building, such as purlins 10. The cladding assembly consists of I- section support beams 20 which extend transversely to the purlins 10 and which support sheets 22 of thermally insulating material. Spacers 24 engage the support beams 20, each spacer being aligned with one of the purlins 10. The cladding 26 is laid against the spacers 24 and held in place by fixing elements such as self- tapping screws 28 extending through the cladding, spacers 24 and insulating sheets 22 and engaging the purlins 10. Since the cladding 26 is held spaced from the insulating sheets 22, which support only their own weight, insulating material of low structural strength, such as polyisocyanurate board, can be used. The fixing elements 28 can be inserted from outside, thus facilitating installation of the assembly. <IMAGE>

Description

SPECIFICATION Improvements in or relating to the cladding of roofs and walls This invention relates to the cladding of roofs and walls.

The invention is particularly concerned with cladding of the kind in which sheets of external cladding material such as corrugated asbestos or plastics coated steel sheet are secured to frame members of a building. It is desirable to provide a layer of thermally insulating material beneath the external cladding to reduce heat losses through the roof or wall. There have in recent years been developed boards of expanded foam plastics material having very good thermal insulating properties, such as "isocyanurate" boards, consisting of a sheet of polyisocyanurate foam with a layer of metal foil bonded to each surface.

Such boards have very little structural strength and this causes problems in the use of such boards in roofing. For example, if the external cladding is laid directly on top of a board of insulating material, there is a danger of the board being fractured if the external cladding is deflected downwards due for example to the effect of wind. Problems have also arisen in fixing such insulating boards in position.

It is an object of this invention to provide a cladding assembly for roofs or walls which overcomes these problems.

This invention consists in a cladding assembly for roofs or walls of a building, the assembly comprising a series of parallel support beams engaging frame members of the building, sheets of thermal insulating material extending between and supported by pairs of the support beams, a series of spacer members extending transversely to the support beams and each aligned with one of the said frame members, the spacer members engaging the support beams or frame members, sheets of external cladding material engaging the spacer members so that the cladding material is held spaced from the sheets of thermal insulating material, and fixing elements each extending through aligned holes in the external cladding material and the insulating material and engaging one of the frame members thereby to secure the cladding assembly to the frame members.

Preferably, each support beam is of Section, the section providing two laterally open channels to receive the peripheral portions of the sheets of thermal insulating material.

The thermal insulating material is preferably rigid or semi-rigid, pre-faced board of expanded foam plastics, such as polyisocyanurate.

The fixing elements may be self-tapping screws.

In the cladding assembly of the invention, the external cladding material is separated by the spacer members from the sheets of thermal insulating material, so that there is no danger of the external cladding damaging the insulating material. These sheets of insulating material are subjected to no force other than their own weight.

The invention enables the cladding to be fixed as an over-purlin or outside-rail assembly, which facilitates installation of the assembly.

This invention also includes a method of cladding wails or roofs, comprising the steps of positioning a series of support beams against frame members of a building, fitting sheets of thermal insulating material into position so that each sheet extends between and is supported by pairs of the support beams, positioning spacer members in engagement with the support beams or the frame members so that each spacer member extends transversely to the support beams and is aligned with one of the frame members of the building, positioning sheets of external cladding material against the spacer members so that the sheets of cladding material are held spaced from the sheets of thermal insulating material, and passing fixing elements through aligned holes in the external cladding material and sheets of insulating material to engage the frame members thereby to secure the cladding assembly to the frame members.

The invention will now be described, by way of example, with reference to the accompanying diagrammatic drawings in which: Figure 1 is a fragmentary perspective view of a cladding assembly for a roof, in accordance with the invention, Figure 2 is a cross-section through part of the cladding assembly, Figure 3 is a section on linelll-lll of Figure 2, Figure 4 is a cross-section, on a larger scale, through a support beam forming part of the cladding assembly, Figure 5 is a view similar to Figure 2, on a larger scale, showing a fixing element, Figure 6 is a side elevation of a drill used in constructing a cladding assembly in accordance with the invention, Figure 7 is an exploded view showing the attachment of the drill bit to the shaft of the drill of Figure 5.

Figure 8 is a cross-section through part of a cladding assembly in accordance with a second embodiment of the invention.

Referring to the drawings, Figures 1 to 3 show a typical roof assembly in accordance with the invention. The roof is supported by steel purlins 10 which form part of the frame of the building to be roofed. The roof assembly comprises a series of support beams 20, each consisting of an Isection beam of galvanised steel, as described in more detail below. Each beam 20 extends across, and is supported on, a number of the purlins 10.

The beams 20 are at right angles to the purlins 10, and are spaced apart from one another at regular intervals. Suspended between each pair of beams 20 is a thermally insulating board 22, the board fitting into the channels in the sides of the beams so that each board is supported by the beams. The board 22 may be a glass fibre reinforced polyisocyanurate foam faced with aluminium foil, such as that sold under the trade mark "CELOTEX double-R" by Celotex Corporation. The channels may have an inside dimension slightly larger than the thickness of the board, to facilitate insertion of the boards into the channels during assembly. For example, for boards of 1 7 mm thickness the channel may be 20 mm wide.

A series of spacers 24, each consisting of a length of timber rectangular cross-section, are supported on top of the support beams 20. Each spacer 24 is perpendicular to the beams 20 and lies vertically above one of the purlins 10. External cladding, in the form of sheets 26, e.g. of asbestos or plastics coated steel, is supported on the spacers 24. The roof assembly is held in position by means of self-tapping screws 28 each extending through aligned holes drilled in the external cladding 26, spacer 24, insulating board 22 and screwed into a purlin 10. A plastic washer and cap 30 (Figure 5) may be fitted over the head of each screw to provide a weatherproof seal.

In assembling the described roof, the support beams 20, having been cut to the appropriate length, are positioned on the purlins at a spacing dependent on the width of the insulating boards 22. For example, with isocyanurate board of 27 mm thickness, boards of 1200 mm width could be employed, the strength of the board being adequate to support its own weight at such a width. The insulating boards 22 are fitted into position, and the spacers 24 are then positioned on top of the beams 20. If it is necessary to use more than one length of timber to form a spacer 24, the lengths are arranged to abut one another at the location of one of the support beams 20, as shown at 25 in Figure 3, so that each spacer is properly suported at its end. The external cladding 26 is then laid in position on the spacers.Holes are then drilled at suitable intervals vertically downwards through the external cladding, spacers 24, insulating board 22 and purlin 10, and the self-tapping screws 38 are inserted and screwed into the purlins to secure the assembly in position.

In the described assembly, the weight of the external cladding 26 is transmitted through the spacers 24 and support beams 20 to the purlins 10. No forces are exerted on the insulating boards 22, apart from their own weight. Moreover, since there is a clearance between the external cladding 26 and the insulating boards 22, there is no danger of damage to the boards by deflection of the cladding caused, for example, by wind.

As shown in Figure 4, each support beam 20 is rolled from steel strip and has upper and lower flanges 32 and 34 joined by a web 36 perpendicular to the flanges. The strip extends in a single thickness from one edge 38 of the upper flange 32 and is folded over at the opposite edge 40 of the flange, so that the part of the flange 40 on that side of the web 36 is of double thickness. The strip then continues through 90 to form the central web 36, which is of single thickness. The lower flange 34 is similar to the upper flange 32, the strip being folded over at one edge 42 and extending to the opposite edge 44. The strip is also folded over a short distance at each of the extreme edges 38 and 44 to form welts which strengthen the beam at those edges and also provide smooth edges.

As compared with the conventional construction of such a beam, in which the beam would be symmetrical about the central web, the strip being folded over itself at two opposite edges of one of the flanges and extending in double thickness along the central web and then in single thicknesses to the opposite edges of the other flange, the described beam uses less material and so is of less weight for a given size, and is less expensive. The strength of the described beam also enables steel of less thickness to be used, reducing the weight still further. For example, a beam of conventional construction typically uses steel of at least 0.8 mm nominal thickness, whereas the described beam can be made from steel of 0.55 mm nominal thickness.The beam also has the advantage that the outer face of the lower flange 34, as well as that of the upper flange 32 has a smooth finish with no central crease due to folding of the strip.

It will be appreciated that the described beam could be used in applications other than the described cladding assembly. The beam is the subject of copending British patent application No.8122986.

If the external cladding material 26 is asbestos, it is necessary for the hole 48 (Figure 5) through which the fixing screw 28 passes to be of larger diameter than the screw, to allow for thermal expansion of the screw. This creates problems in drilling the aligned holes in the asbestos cladding, spacers 24, insulating boards 22 and purlins 10.

To deal with this problem, the novel drill shown in Figures 6 and 7 is provided. The drill comprises a cylindrical shaft 50 of silver steel and a replaceable twist drill bit 52 secured to the shaft 50. The shank 54 of the dril bit 52 fits into a cylindrical recessed bore 58 in the shaft 50, and is held in place by two grub screws 60 fitting into threaded lateral bores in the shaft and engaging in two notches 62 in the shank 54, so that the bit 52 rotates with the shaft 50. Four tungsten tipped cutting blades 64 are fixed to the ends of the shaft 50, spaced around the recessed bore 58.

The blades 64 may for example be fitted into slots in the shaft 50 and brazed in position.

The drill bit 52, which may be a split point bit, is of the appropriate diameter to drill holes to receive the size of screw 28 to be used, and the length of bit projecting from the shaft 52 is somewhat less than the distance between the "peaks" of the corrugated asbestos and the spacers 24. The diameter of the shaft 50 and cutting blades 64 is such as to provide a clearance hole 48 of the desired diameter.

In use, with the drill fitted to a suitable handheld drilling tool, the bit 52 first drills a pilot hole in the asbestos sheet 26, and the cutting blades 64 then cut the clearance hole 48. The drill is moved further so that the bit 52 drills through the spacer 24, insulating board 20 and purlin 10.

The weight and rigidity of the shaft 50 help to hold the drill straight during the drilling operation.

The drill bit 52 can be readily replaced by loosening the grub screws 60, withdrawing the bit from the shaft 50 and inserting the new bit.

Use of the described drill enables the cladding assembly for a roof to be fixed in position by operating from above, so facilitating the fixture operation and minimising the risks to operators which can arise, for example in using conventional U- or J-bolts which have to be inserted from below. It will be appreciated that the described drill can be used in other applications where it is necessary to fix in position sheets of asbestos or similar material, or various types of metal sheet.

The drill is the subject of copending British patent application No. 8122985.

Figure 8 illustrates an alternative embodiment of the invention in which spacers 120 in the form of steel beams are used in place of the timber spacers 24 of the first embodiment. Each spacer 120 is an I-section beam, which may be of the same construction, apart from its dimensions, as the support beams 20. Each spacer 120 is supported directly on the purlin 10, rather than on the support beam 24. The support beam 24 is divided at the spacer 120, the two sections of the support beam resting on the lower flanges 122 of the spacer. The web 126 of the spacer extends upwards between the support beam sections and has a vertical dimension greater than that of the support beams 24 so that the cladding 26 is spaced from the support beams 24. The cladding assembly is secured by self-tapping screws 28 extending through aligned holes in the cladding 26, in the flanges 122 and 124 of the spacer 120 and in the insulating board 22 and engaging the purlin 10. A strip of plastics 130 may be interposed between the upper flange 124 of the spacer 120 and the cladding 26 to provide a thermal break.

An advantage of the embodiment of Figure 8 is that both the support beams 24 and spacers 120 are made of non-combustible materials. It will be appreciated that the spacer beams 120 could have other cross-sections instead of the I-section illustrated.

It will be appreciated that the cladding system of this invention can be used for cladding in the horizontal or vertical plane, or in an inclined plane.

The system can thus be used not only for horizontal or pitched roofs but also for cladding vertical walls.

Claims (10)

Claims

1. A cladding assembly for roofs or walls of a building, the assembly comprising a series of parallel support beams engaging frame members of the building, sheets of thermal insulating material extending between and supported by pairs of the support beams, a series of spacer members extending transversely to the support beams and each aligned with one of the said frame members, the spacer members engaging the support beams or frame members, sheets of external cladding material engaging the spacer members so that the cladding material is held spaced from the sheets of thermal insulating material, and fixing elements each extending through aligned holes in the external cladding material and the insulating material and engaging one of the frame members thereby to secure the cladding assembly to the frame members.

2. A cladding assembly as claimed in claim 1, in which each support beam is of Section, the section providing two laterally open channels to receive peripheral portions of the sheets of insulating material.

3. A cladding assembly as claimed in claim 2, in which the width of each of the laterally open channels is greater than the thickness of the sheets of insulating material.

4. A cladding assembly as claimed in any preceding claim, in which each fixing element extends also through one of the spacer members.

5. A cladding assembly as claimed in claim 4, in which the fixing elements are self-tapping screws each having its head positioned on the outside of the external cladding material.

6. A cladding assembly as claimed in any preceding claim, in which each spacer member engages the support beams on the sides remote from the said frame members.

7. A cladding assembly as claimed in claim 6, in which the spacer members comprise lengths of timber of rectangular cross-section.

8. A cladding assembly as claimed in any one of claims 1 to 5, in which each spacer member comprises a beam having a first flange which engages one of the said frame members, a second flange which is engaged by the external cladding material, and a web connecting the two flanges and positioned between the ends of adjacent sections of a support beam, the sections of support beam engaging the said first flange of the spacer member.

9. A cladding assembly as claimed in any preceding claim, in which the thermal insulating material is a pre-faced foam plastics sheet.

10. A method of cladding walls or roofs, comprising the steps of positioning a series of support beams against frame members of a building, fitting sheets of thermal insulating material into position so that each sheet extends between and is supported by pairs of the support beams, positioning spacer members in engagement with the support beams or the frame members so that each spacer member extends transversely to the support beams and is aligned with one of the frame members of the building, positioning sheets of external cladding material against the spacer members so that the sheets of cladding material are held spaced from the sheets of thermal insulating material, and passing fixing elements through aligned holes in the external cladding material and sheets of insulating material to engage the frame members thereby to secure the cladding assembly to the frame members.