GB2435889A

GB2435889A - Roof Structure

Info

Publication number: GB2435889A
Application number: GB0703414A
Authority: GB
Inventors: Graeme Fugaccia
Original assignee: Eleco PLC
Current assignee: Eleco PLC
Priority date: 2006-03-09
Filing date: 2007-02-22
Publication date: 2007-09-12
Also published as: GB0604717D0; GB0703414D0; WO2007101977A1

Abstract

The invention relates to a roof structure made predominantly of timber comprising a plurality of support means bearing a plurality of rafters 16 or joists to define a roof space. Each support means 14 comprises a plurality of wooden elongate members 18 where each rafter 16 is secured between opposing support means positioned on respective end walls 12 of a building. The entire weight or load of the rafters is borne along a vertical axis defined by the support means 14, allowing the rafters to span greater distances, and allowing a wider internal volume within a roof space without additional internal supporting structures being needed. The support means may further comprise a support pocket (22 figure 2), within which the rafter locates. This is particularly suitable where support along a bottom chord of a rafter is required. In an alternative embodiment, the support means may further comprise at least one support noggin (24 figure 3) having a vertical face which defines a location position of the rafter. Such an arrangement is particularly suitable for top chord supported rafters. A later independent claim relates to a support means for use in a roof structure comprising a plurality of wooden elongate members cut at an uppermost end to conform to the pitch of the roof.

Description

I

Title: Roof Structure

Field of the Invention

This invention relates to a roof structuie and components used within such a roof structure.

Background to the Invention

A variety of traditional roof structures are known, for example roofs made from purlins and rafters, and roofs made from triangular trusses. Increasingly requirements for housing density mean that modern buildings need to utilise as much space within a building volume as possible, and thus ideally to use attic space within a roof structure as living accommodation. One roofing system uses trusses made from parallam timber, with gable or end walls built in brick and blockwork. The trusses are fixed together on site, on the roof, which can delay the rest of the build. Not all of the floor space within the attic is available for living space.

There is also a need to assemble a roof structure in the quickest and most efficient way possible and thus there has been a move to pre-fabrication of roof structures off-site so that roof components are ready to hoist into place and assemble as soon as the supporting walls are built. Another roofing system consists of a metal web floor and large interlocking panels which span from gable to gable of a building. The roof panels are large requiring cranes to be lifted into position and causing problems with storage. The tolerance of the panels and their fit is critical to ensure the integrity of the roof structure.

It is an aim of thc present invention to provide a roof structure, which overcomes at least some of the disadvantages of the prior roof structures.

Summary of the Invent ion

In accordance with one aspect of the present invention, there is provided a roof structure made predominantly of timber comprising a plurality of support means bearing a plurality of rafters or joists to define a roof space wherein each support means comprises a plurality of wooden elongate members and each rafter is secured between opposing support means positioned on respective end walls of a building, the entire weight or load of the rafters borne along a vertical axis defined by the support means. By having the load of the rafters carried entirely along a vertical axis, the rafters are able to span greater distances, so allowing a wider internal volume within a roof space without additional internal supporting structures being needed.

The support means may be a spandrel panel.

In one preferred embodiment, the support means may further comprise a support pocket, within which the rafter locates. This is particularly suitable where support along a bottom chord of a rafter is required.

In an alternative embodiment, the support means may further comprise at least one support noggin having a vertical face which defines a location position of the rafter. Such an arrangement is particularly suitable for top chord supported rafters, Each support means may be made from two, three, four or more wooden elongate members with the support means cut at its uppermost end to conform to the pitch or angle of the roof.

The individual wooden elongate members within the support means are preferably fixed to one another using metal connector plates, although standard fixings such as nails may be used.

Preferably, each support means is braced to ensure it remains upright during assembly of the roof structure. Bracing may be achieved by members extending between adjacent panels.

In accordance with another aspect of the invention, there is provided a support means for use in a roof structure, the support means comprising a plurality of wooden elongate members with the support means cut at its uppermost end to conform to the pitch or angle of a roof.

In one preferred embodiment, the support means may further comprise a support pocket, within which, in use, a rafter locates.

The invention will now be described, by way of example with reference to the accompanying drawings in which: Figure 1 shows a perspective view of a roof structure in accordance with the present invention; Figure 2 shows a cross-section through part of the roof structure illustrating a first embodiment of the invention; Figure 3 shows a perspective view in close-up of a second embodiment of the invention; Figure 4 shows a cross-section of a third embodiment; and Figure 5 shows a cross-sectional view from one end illustrating all the elements within the roof structure once assembled.

Description

A pitched timber-framed 10 roof constructed in accordance with the present invention is shown in Figure 1. The roof 10 is carried on four load bearing walls and has a triangular cross-section, each end or gable wall 12 formed from two triangular spandrel panels 14. The spandrel panels 14 are made from a number of wooden studs, each stud comprsing two or more lengths of timber, and a sheathing board. For the purposes of illustration one panel 14' is shown with the board removed. The number of spandrel panels will depend on the size of the roof; small roofs will only require one spandrel panel for each gable end, large roofs will require more than two panels. The shape of the panels will depend on the roof shape.

A plurality of rafters or joists 16 run horizontally between corresponding studs 18 in respective gable walls. The rafters or joists shown in Figure 1 are typically metal web joists or rafters, formed from two elongate lengths of wood, having identical rectangular cross-sections, spaced apart by metal webs. The rafters are all of the same length, which depends on the building size, and typically have a width of 72mm or 97mm, although other widths may be used. Other forms of rafter or joist may be used, for example a solid timber joist.

Whilst the roof structure is shown in its open condition in Figure 1, the final structure is fully enclosed against the elements with Figure 5 illustrating a cross-section of completed roof structure. The entire structure is watertight upon assembly, each spandrel panel 14 having an external facing of plywood, sheathing board or similar weather-resistant material fixed to it, such that edges of adjacent plywood facings abut one another.

Within the spandrel panels 14 are typically seven studs approximately 0.6m apart. The studs are formed from two, three, four or more lengths of timber. Figure 2 shows upstanding studs 18 comprising four vertically upright timber members 20, 20', 20", 20" affixed to one another by metal connector plates, with the two central timbers 20, 20" cut to be an identical height. lower than the external timbers 20, 20". The external timbers 20, 20" are cut to form a tapered profile at their upper end corresponding to the roof angle required. The four lengths of timber together define a central pocket or void 22 in which a rafter 16 is placed, with the entire weight of the rafter 16 borne along a single vertical axis deimed by the studs of the spandrel panel 14. This improves the load capacity of the rafters 16 compared to rafters loaded in two axes, i.e. rafters which are positioned on the diagonal, parallel to the angle of the roof. As the load of the rafter bears vertically directly down through the studs 18, the rafter can be of a longer length and cross longer spans than is possible where the rafter load is transmitted both vertically and horizontally through a support.

The arrangement shown in Figure 2 is known as a bottom chord support, where the upper and lower beams of the metal web joist are of the same length and the weight of the joist is carried through the lower beam into the stud of the spandrel panel, the lower beam resting on the stud.

The studs 18 are made using lengths of TR26 grade timber, cut to defmed lengths calculated by a computer program using the horizontal roof area defined by the supporting walls and the angle of pitch of the roof. The timber lengths are cut not only to the correct length, but also cut with an appropriate angle at their upper end to support the roofing material. The different timber lengths are fitted onto a jig on a pressing table where metal connector plates are placed over the joints. The plates are pressed into the timber using an industrial roof truss press, the panel turned over and the process repeated on the other side to ensure strength and stability.

On manufacture, the panels 14 are typically covered with 9mm Grade 3 oriented stand board (O.S.B) as a sheathing board to provide additional structural strength. This sheathing board overhangs the panel so that when erected, the sheathing board on adjacent panels abuts forming a continuous waterproof layer. This ensures that upon assembly a waterproof structure can be arrived at within 8-9 hours. Typically breather membrane will be added to the external face of the panel to provide further weather protection.

Instead of using support pockets, alternative embodiments are shown in Figures 3 and 4 which use support noggins. In Figure 3, the stud consists of three timber uprights with support noggin 24' nailed to the tallest length of timber 20' such that its vertical face 26 is positioned on the stud to provide a face against which a rafter is located and retained. A lower support noggin 24" runs from the lower timber 20" to the next stud. A top chord supported metal web rafter 16 is positioned against the vertical face 26 of noggin 24' before being nailed to the stud of spandrel panel 14. The load of the rafter 16 is transferred vertically through the stud in the direction of arrow X. Where there is a top chord supported metal web joist as shown in Figure 3, it will be appreciated that the lower timber of the joist is shortened to provide clearance from the stud, the upper part of the joist resting on the stud.

In Figure 4, the upright stud 18 is made from two lengths of timber 20, 20" with the uppermost end of the timbers tapered in accordance with the roof profile. The support noggins 24 are lengths of timber cut on an angle so that their end faces are upright when the noggins are nailed to the studs.

To construct and assemble a roof structure in accordance with the present invention, first the height and tapering angle of each spandrel panel is calculated on the basis of the roof area defined by the supporting walls and the maximum roof height, which gives the roof angle.

Using triangulation, a computer program calculates how many spandrel panels are required, the height of each spandrel panel, the spacing of the studs within the panel and the angle at which the uppermost part of the spandrel panel must taper to ensure that the roof covering is at the correct angle. The spandrel panels are custom manufactured for the specific area and angle so as to produce a number of spandrel panels which when assembled will form two complete gable ends of a building.

On a building site, the external supporting walls of the building are erected and when at roof height, a floor which will form the internal floor of the roof space is put in place. The floor is constructed in component form using standard floor joists which are fitted in the usual manner, either by fitting between the walls and being supported by a wall plate or joist hangars. The joists are then fully decked with chipboard flooring. This provides a safe supporting structure for workers to stand on whilst assembling the roof structure.

Once the roof space floor is constructed, the spandrel panels 14 are fitted to the building, either directly to wall plates at the gable ends or fixed to the deck of the floor joists. The spandrel panels 14 are typically nailed at designated centres of the studs 18 so as to join to the wall plates or the deck. This is done for each gable end. Noggins 28 to define the pitch or angle of the roof are fixed to the spandrel panels and together with the fixing at the foot of the spandrel panels ensures lateral stability of the upright panels during assembly of the roof.

The spandrel panels 14 either have studs 18 with support pockets 22 as shown in Figure 2, or rely on support noggins 24 attached to the studs as shown in Figures 3 and 4, so as to provide a vertical support for rafters 16. The rafters 16 are nailed into position. The remaining elements of the roof structure are then put in place as shown in Figure 5. Angled timber fillets 30 are fitted to the top and bottom chord of the rafters 16 to allow the internal plasterboard ceiling 32 and the roof sarking felt 34 to be fitted substantially parallel to the pitch of the roof. High performance insulation 36 is retained between either noggins 28 or support noggins 24 and 9mm Grade 3 O.S.B. sheathing board 38 providing a "warm roof' construction where insulation is close to or adjoins the roof tiles. The sheathing board 38 provides structural bracing to stiffen the whole roof structure and is covered by a breathable roof membrane 40 to which are affixed a number of tiling batons 42 which support a standard roof covering such as tiles 44.

Alternatively the high performance insulation 36 is retained between either noggins 28 or support noggins 24 and supported by battens fixed under the rafters 16. This option provides a "cold roof' construction where the insulation is fixed within the internal roof space, such that there is a large air gap between the rafters and the roof tiles.

As the load of the rafters 16 is borne vertically directly through the studs of the spandrel panels, due to the location of the rafters 16 within either the support pockets 22 or in the secure position using the support noggins 24, a roof of equivalent strength to other known roofs can be provided but using less components. The vertical load bearing also permits greater spans so allowing a wider internal volume within a roof space without additional internal supporting structures needed. This ensures that virtually all the volume within the triangular roof structure can be used as a room, the roof structure modified with dormer windows or other design features as is felt appropriate. The spandrel panels 14 provide a pre-configured gable wall which can be assembled in a few hours, enabling the entire roof structure to be put in place in typically 8-9 hours. The individual components of the roof, such as the panels 14 and the rafters 16, are all fairly light being predominantly wood, with the only non-wood parts being metal cormector plates in the spandrel panels, metal webs within the rafters and metal wall plates at the foot of the spandrel panels. The components are not particularly bulky, so are easy to store. Also the use of individual components, for example individual rafters, means that they can be replaced individually if required, as opposed to having to replace entire sect ions of roof.

Claims

Claims 1. A roof structure made predominantly of timber comprising a

plurality of support means bearing a plurality of rafters or joists to defme a roof space, wherein each support means comprises a plurality of wooden elongate members and each rafter is secured between opposing support means positioned on respective end walls of a building, the entire weight or load of the rafters borne along a vertical axis defined by the support means.

2. A roof structure in accordance with claim 1, wherein the support means is a spandrel panel.

3. A roof structure in accordance with claim 1 or 2, wherein the support means further comprises a support pocket, within which the rafter locates.

4. A roof structure in accordance with claim 1 or 2, wherein the support means further comprises at least one support noggin having a vertical face which defines a location position of the rafter.

5. A roof structure in accordance with any of the preceding claims, wherein each support means is made from two, three, four or more wooden elongate members with the support means cut at its uppermost end to conform to the pitch or angle of the roof.

6. A roof structure in accordance with any of the preceding claims, wherein the individual wooden elongate members within the support means are fixed to one another using metal connector plates.

7. A roof structure in accordance with any of the preceding claims, wherein each support means is braced to ensure it remains upright during assembly of the roof structure.

8. A support means for use in a roof structure, the support means comprising a plurality of wooden elongate members with the members cut at an uppermost end to conform to the pitch or angle of a roof.

9. A support means according to claim 8, wherein the support means further comprises a support pocket, within which, in use, a rafter locates.

10. A roof structure and support means substantially as herein particularly described with reference to and as illustrated in the accompanying drawings.