GB2251870A - Ventilated flat roofing panels - Google Patents

Abstract

A roofing panel (27) for constructing a warm-type roof is composed of a layer of insulation (28) laminated to a decking sheet (33) and between the decking sheet (33) and the insulation (28) is provided a network of ventilation passages (31), which passages can lead water vapour-laden air away to either lateral or sub-adjacent ventilators. The panels may be secured to joints by helical drive fasteners or screws. <IMAGE>

Description

FLAT ROOFING This invention relates to flat roofing, and in particular to a flat roofing panel, and a flat roofing structure made using that panel.

The problems of low temperature within an unventilated roof leading to condensation of water vapour is well known, in both pitched and flat roofs.

Figs. 1 to 4 illustrate prior art constructions in which there is a greater or lesser degree of problems due to condensation. Fig. 1 shows a typical "cold" roof wherein weatherproofing 10 (usually supported on timbers) lies above a loft space 11 in which is a layer of insulation 12. The loft 11 is cold and in order that the timbers supporting the weatherproof ing 10 do not suffer from condensation and hence rot and/or deterioration due to mould growth, the loft area has to be extensively ventilated. This system is quite efficient and common, particularly in domestic dwellings. The coldness within the loft 11 does not lead to significant heat waste provided the insulation 12 is thick enough. It does mean, however, that the loft space 11 is not ideal for use.

A similar construction is illustrated in Fig. 4 wherein weather proofing 13 overlies support structure comprising a deck 14 and rafters 15.

Between rafters 15 is insulation 16 and beneath the insulation is a lining such as plasterboard 17. The provision of the insulation 16 effectively reduces heat loss from the working space beneath, but creates a situation wherein the deck and the rafters are "cold". This means that water vapour travelling through the roof from the interior can condense on the deck and rafters or even between the deck and the weatherproofing with all the attendant problems.

Fig. 2 shows a first way in which a "warm" roof can be constructed. In Fig. 2 the weatherproof ing 18 is separated from the load bearing structure 19 by insulation 20. Here the structure 19 (which may be a concrete pad, or a deck plus timber construction as shown in Fig. 3 or 4, is on the warm side of the insulation and therefore is very considerably protected against the deleterious effect of interstitial condensation. However, the boundary between the insulation 20 and the waterproofing 18 can become a collecting point for condensed water vapour and even the top part of the insulation 20 might become sufficiently cold to allow water condensation. This can mean that the insulation 20 (particularly at joints) can become wet or partly saturated. This can lead to blistering of the overlying weatherproofing or damage due to freezing in winter.Further, condensation forming on the upper part of the insulation or on the weatherproof ing can drip downwards (particularly in the case of timber structure) causing patches on the underside of the roof which can be unsightly and can lead to mould growth and similar problems.

It has become known to overcome the problem of condensation in or slightly above the insulation by venting the insulation so that any water vapour rising through the support structure or rising from the support structure can be dissipated. Some of these systems incorporate an air permeable layer between the weatherproof ing and the insulation which can allow water vapour to dissipate to the edges of the roof, or to be expelled to ventilators. A further possibility is also illustrated in Fig. 3 wherein a composite panel 21 is provided. This panel 21 includes insulation 22 in whose underside are provided a network of ventilation channels 23 which are interconnected and can be lead either to lateral ventilation means on the sides of a relatively small roof, or, preferably, to spaced-apart ventilators 24.

The panel 21 can have an upper layer (not shown) of weatherproof-compatible material-which can itself serve to weatherproof the insulation. In practice this upper layer will normally be a layer of bituminous felt. After installation of the ventilators 24, additional weatherproof ing such as layers of felt 25 can be applied in conventional manner. In this system any water vapour rising through the roof structure can be conducted away by the channels 23 thus ensuring that the insulation remains free of water pockets. If desired, a permeable membrane can be provided between the weatherproof ing and the insulation to provide a second ventilation layer discouraging the formation of water pockets underneath the weatherproof ing which can lead to bubbling in hot weather.

In relation to the panel 21, it will be appreciated that a roof construction made from such a panel has to be made fairly carefully. For example, typically the lower side of the panel 21 is coated with a layer of lacquered aluminium foil or comparable protective material. This is necessary, because it is impossible to tell, during manufacture, precisely what sort of surface the panel 21 will have to rest upon. The panels 21 are normally adhered to the structure beneath by first priming the structure, for example with a solvent/bitumen based primer, then applying a layer of bitumen by means of brush or mop and then pressing the panels 21 downwards on to the support structure. It will be appreciated that the bitumen has to be applied with care. If too much is applied the channels 23 can become wholly or partially blocked leading to poor ventilation and the usual problems.Further, the application of bitumen to, for example, damp or wet decking can lead to poor adhesion and the possibility of panels lifting during strong wind.

An additional disadvantage of the Fig. 3 structure is that the deck 26 (in the case of a deck and rafter support structure) needs to be sufficiently strong to span the rafter gap and allow at least foot traffic during construction without significant bending and certainly without breaking.

In practice this usually means that the deck 26 has to be constructed from 20mm plywood (which has an allowable span of 600mm) or of other material of equal span. 20mm plywood is relatively expensive.

It is an object of the present invention, therefore, to provide a roofing panel wherein the above described disadvantages can be reduced or minimised.

The invention provides a flat roofing panel including a layer of insulating material bonded to a layer of decking material, a network of ventilation channels being provided in the insulation adjacent the decking material.

A preferred panel of the invention can have one or more of the following features: The panel is provided with spaced apart through apertures for connection to a ventilator.

The face of the panel opposite the decking is provided with a layer of protective material.

The protective material can be a bituminous felt.

Edges of the panel are provided with means whereby lateral ventilation of a constructed roof can be achieved.

The decking has an intrinsic span of less than The composite panel has an intrinsic span of greater than 600mm.

The decking is wood less than 16mm in thickness.

The decking is less than 13mm in thickness.

The decking is llmm particle board.

The decking is Sterling board with The decking is plywood ranging in thickness from 6 to 12mm.

In using the panel of the invention, it will be appreciated that it will normally be laid on spaced timber rafters, perhaps 50 or 65mm wide. This will require fixings to pass through the panel into the joists. Best connection between a roof panel and a joists is achieved when fasteners and/or adhesive effect a mutual connection between the two parts.

This is not the case in relation to headed nails, wherein pressure on the underside of the panels can lift nails from the joists. Wood screws could be used, but unless a pilot hole were drilled through a panel the wood screw would tend, upon contacting the rafter, simply to partially enter the joist and then jack-up the roof panel. Further, both nails and screws have heads which either damage quite an area of the upper protective bitumen layer or project above the deck surface and form domes in the weatherproof ing (which is usually multiple layers of bitumen felt).

Such domes can form air pockets leading to problems.

The invention provides, as a further feature therefore, a roof structure including a plurality of panels each as aforesaid secured to supporting rafters, the panels being secured to the rafters by helical fasteners. The fasteners can be drive fasteners or screws incorporating a large (50mm) diameter washer applied into predrilled holes.

A preferred roof structure can have one or more of the following features.

The drive fasteners have no heads.

The fasteners each consist of a non-circular elongate body of material which has been formed into a helix.

The body of material is cross-shaped, Y-shaped or in the form of a central spine having a plurality of ribs.

The drive fasteners are driven so that upper ends thereof are slightly below the level of the protective coating on the outer side of the panels. The recesses so formed are filled with a sealant.

The sealant is hot fluid bitumen.

The roof structure is completed by applying further weatherproof ing over the panels.

The weatherproofing includes or consists of additional layers of bitumen felt adhered by means of fluid bitumen.

The invention will be described further, by way of example, with reference to the accompanying drawings wherein Figs 1 to 4 are fragmentary cross-sectional sketches illustrating known roof structures and panels; Fig. 5 is a cross-sectional fragmentary sketch view illustrating a preferred roofing panel of the invention; Figs. 6 is a fragmentary vertical cross-section through a preferred roof structure of the invention; Fig. 7 illustrates a pair of unsuitable fasteners; Fig. 8 shows a desirable fastener used in the construction of Fig. 6; Figs. 9 and 10 illustrate alternative constructions for the fastener of Fig. 8; and Fig. 11 illustrates a detail of the structure of Fig. 6 after driving of a fastener such as that shown in Fig. 8.

Fig. 12 shows a screw fixing incorporating a large washer, that can be used as an alternative fixing method.

The various constructions of the functions of the various roofs shown in Figs. 1 to 4 have been previously discussed and will not be discussed further here.

Referring now to Fig. 5, however, it will be seen that a preferred roof panel 27 of the invention includes a layer of insulation 28. The insulation 28 can vary from perhaps 50mm upto 150mm in thickness and is desirably made from a closed-cell polyurethane foam material. A closed-cell form is desired as this reduces the possibility of water penetration into the insulation. Of course, any other convenient insulation can be used provided it has the requisite strength and water-resistant properties. To the upper surface of the insulation 28 is secured a layer of protective material 29 which is waterproof and prevents water contacting the insulation 28 and possibly wetting it to even a slight degree. The protective later 29 does, however, serve a further purpose. It provides an outer layer which is compatible with further weather-proofing layers 30.

As these layers are usually bituminous felt, protective layer 29 is also conveniently of bituminous felt adhered to the insulation by an appropriate adhesive. Where the weatherproof ing layer is to be trowell applied asphalt, the protective layer 29 is an appropriate weight glass tissue layer to obviate bonding of the asphalt to the panel facing. The asphalt has to be allowed to expand or contract independently of insulation.

On its underside the insulation 28 is provided with a network of interconnected ventilation channels 31. These are arranged in a rectangular grid of two sets of parallel channels about 100mm apart. The depth of the channels can conveniently be 5 to l0mm.

Optionally, a layer of aluminium foil 32 can be applied to the outer surface of the insulation and channels as a protective. However, this is not essential and it can be dispensed with.

On to the under surface of the foil 32 is adhered a layer of decking 33.

The decking 33 can be a layer of a particle board1 particularly that type of particle board which is sold under the Trade Mark STERLING BOARD some llmm in thickness. Alternatively, plywood varying in thickness from 8 to 15mm can also be used.

Here it should be noted that the structure is comparable to the built-up structure shown in Fig. 3, but there are very important differences.

Firstly, the decking 33 is significantly less thick than the decking 26. As has been previously mentioned, the decking 26 has to have a minimum spanning capacity of 600mm. In the material of the invention we can use a much thinner decking material having a normal spanning capacity of 400mm when used in an unlaminated state. In the adhered composite form shown in Fig. 5, the panel 27 has a maximum instrinsic spanning capability of over 600mm, far greater than even the decking 26. This is, of course, due to the inherent laminated strength of the panel 27. Thus, this means that a roof structure comparable to that of Fig. 3 can be achieved using much lighter and therefore cheaper material. It can also mean that the roof is lighter and that therefore supporting timbers do not need to be so thick.

There is a further additional great advantage.

Whilst in the Fig. 3 embodiment the panel 21 is applied to the decking on site, the panel of Fig. 5 is factory constructed. This means that the adhesive between the panel 28 and the decking 33 can be applied by machine in a carefully controlled manner and the application pressure between the two components can be chosen to ensure that there is a uniformly optimum bond throughout the entire area of the panel. Further, there can never be too much adhesive applied which might possibly block the channels 31. In the Fig. 3 embodiment the insulation panel and the decking are adhered together by liquid bitumen, mop or brush applied to the plywood deck.

The increasing quality in using a factory-applied adhesive rather than this rather crude method will be much appreciated.

It will, of course, be also appreciated that instead of the decking 33 having to be nailed to joists, the entire thickness of the panel 27 will have to be attached to joists such as 34 (Fig.6). It will be appreciated that the securement of quite a thick panel to rafters 34 by driven fasteners could cause problems. We have found that long round headed nails, such as nails 35 and oval nails such as 36 are unacceptable. The nails 35 do not work because air pressure beneath the panel 27 can lift the nails 35 from the rafters 34. Further the nail has a head.

We have found that use of a helical drive fastener 37 to be particularly effective. Such a fastener can be driven, that is to say installed by means of simple hammer blows. Its helical shank engages both the rafter and the board with a very firm grip and has a much greater gripping power than a nail. Further, the fastener 37 is desirably formed without a head or with only a vestigial head so that it can be driven so that its upper end lies well below the upper surface of the layer 29. (see Fig. 11).

The recess 38 formed by overdriving of the fastener 37, e.g. to 25mm below the surface can very conveniently be filled with liquid bitumen as the selvedge of the layer 29 is adhered to the adjacent panel or as a jointing tape is applied.

As will be seen from-Figs. 9 and 10, the cross-section of the drive fastener can vary from the simple cross-shape of Fig. 37 to a Y-shape, Fig. .9, or a central spine plus a plurality of ribs as in Fig. 10. The panel 27 of the invention and the roof structure of the invention can lead to very efficient roofs which are very carefully constructed and are also easily constructed. The possibility of a bad roof being constructed due to mis-use of materials on site, or the poor performance of specified operations on site is very much reduced. Further, an extra major component of the work of constructing a flat roof is transferred to controlled factory conditions and away from the site. This must lead to a more efficient roofing procedure.

Conventional screws can be used in combination with predrilled holes and large washers, as shown in Fig.

12. Either type of fastener can be covered, after driging, either by selvedge or jointing tape with liquid bitumen.

The invention is not limited to the precise details of the foregoing and variation may be made thereto within the scope of the accompanying claims.

Claims (29)

1. A structural roofing panel including a layer of insulating material bonded to a layer of decking material, ventilation channels being provided between the insulation and the decking material.

2. A panel as claimed in claim 1 wherein the panel is provided with spaced apart through-apertures for connection to a ventilator.

3. A panel as claimed in claim 1 or 2 wherein the face of the panel opposite the decking is provided with a layer of protective material.

4. A panel as claimed in claim 1, 2 or 3 with the ventilation channels from a network.

5. A panel as claimed in any of claims 1 to 4 wherein the ventilation channels are formed in the insulation.

6. A panel as claimed in any of claims 1 to 4 wherein an air-pervious layer is provided between the insulation and decking and ventilation channels are formed by partial bonding of the decking to the insulation through the pervious layer.

7. A panel as claimed in claim 6, wherein the pervious layer is a layer of glass fibre fabric or felt.

8. A panel as claimed in any preceding claim wherein the protective material is a bituminous felt.

9. A panel as claimed in any preceding claim wherein the edges of the panel are provided with means whereby lateral ventilation of a constructed roof can be achieved.

10. A panel as claimed in any preceding claim wherein the decking has an intrinsic span of less than 400mm .

11. A panel as claimed in any preceding claim wherein the composite panel has an instrinsic span of greater than 600mm.

12. A panel as claimed in any preceding claim wherein the decking is wood less than 16mm in thickness.

13. A panel as claimed in claim 12 wherein the decking is less than 13mm in thickness.

14. A panel as claimed in claim 13 wherein the decking is llmm particle board.

15. A panel. as claimed in claim 14 wherein the decking is Sterling board.

16. A panel as claimed in claim 13 wherein the decking is plywood ranging in thickness from 6 to llmm.

17. A roofing panel substantially as described with reference to the Figs. 5 to 11 of the accompanying drawings.

18. A roof structure including a plurality of panels each as claimed in any preceding claim secured to supporting rafters by helical fasteners.

19. A roof structure as claimed in claim 18 wherein the fasteners are helical drive fasteners.

20. A roof structure as claimed in claim 18 wherein the fasteners are screws in combination with large washers.

21. A roof structure as claimed in claim 19 wherein the drive fasteners have no heads.

22. A roof structure as claimed in claim 18, 19 and 21 wherein the fasteners each consist of a non-circular elongate body of material which has been formed into a helix.

23. A roof structure as claimed in claim 22 wherein the body of material is cross-shaped, Y-shaped or in the form of a central spine having a plurality of ribs.

24. A roof structure as claimed in any of claims 18, 19 or 21 or 22 wherein the drive fasteners are driven so that upper ends thereof are slightly below the level of the protective coating on the outer side of the panels.

25. A roof structure as claimed in claim 24, wherein recesses are so formed and are filled with a sealant.

26. A roof structure as claimed in claim 25, wherein the sealant is hot fluid bitumen.

27. A roof structure as claimed in any of claims 18 to 26 wherein the roof structure is completed by applying further weatherproofing over the panels.

28. A roof structure as claimed in claim 27 wherein the weatherproofing includes or consists of additional layers of bitumen felt adhered by means of fluid bitumen.

29. A roof structure substantially as hereinbefore described with reference to the accompany drawings.