GB2147032A

GB2147032A - Ventilation of roof space

Info

Publication number: GB2147032A
Application number: GB08425246A
Authority: GB
Inventors: John Louis Shillabeer
Original assignee: Individual
Current assignee: Individual
Priority date: 1983-10-07
Filing date: 1984-10-05
Publication date: 1985-05-01
Also published as: GB8425246D0; GB2147032B; GB8326851D0

Abstract

An eaves ventilator 22 for connection between adjacent roof trusses 10, 12 beneath the insulation 20 so as to leave a gap between the ventilator and the insulation 20 is rigid and elongate. Thus it can be set carefully in place and then secured. It may be of thin sheet metal, shaped to confer rigidity without substantially interrupting the ventilation gap. For example it may have diagonal tensioning creases 32, concave upwards, and/or marginal down- turned flanges (Fig. 4: 44). Fixing may be by means of flanges 28 with integral securing tongues 30. <IMAGE>

Description

SPECIFICATION Ventilation of roof space The present invention relates to the ventilation of the roof space, e.g. in a pitched roof of a house. In one aspect it relates to an eaves ventilator for use in constructing a ventilated roof. In another aspect it relates to a method of constructing a roof.

In modern house construction, there is commonly a layer of insulating material spread over and between the floor joists, extending right to (and possibly over) the wall plate at the top of the cavity wall. The roof itself has an inner lining of impermeable felt, laid over the roof trusses. The result tends to be that the roof space is totally enclosed by the insulation and the felt. There are fears that this may lead to rotting of the timbers. To avoid this, building regulations now require the roof space to be ventilated.

The usual approach is to provide air inlets at the eaves, e.g. by using ventilating soffits.

Further means are required to maintain air gaps between the felt and the insulation or wall plate. One solution is to use plastics trays. In use, a tray bridges two roof trusses, being nailed to their upper surfaces at its ends. Between the trusses the tray is generally lower than these surfaces. Felt is applied over the trays, and is intended to be taut. Thus there is a gap between the felt and each tray, and this serves for ventilation.

The installation of such trays is rather tiresome. They are of thin, floppy piastics materials, and so have to be held in position until nailed down. Adjacent trays are laid in mutual contact, and so securing the felt involves nailing through the trays. The need to be able to nail through them (for fixing them, the felt and roofing battens), together with considerations of cost, necessitate the use of thin, and hence floppy, material.

According to the present invention there is provided an eaves ventilator comprising a rigid elongate bridging portion for extending between two roof trusses and, at either end, an attachment portion for attachment to a respective truss to hold the bridging portion generally below the top surfaces of the trusses. Preferably the attachment portions have integral securing means. Preferably the ventilator is formed of sheet metal. The attachment portions may then be provided with securing means in the form of turned-over tongues of metal which can be driven into the trusses. An attachment portion may be arranged to extend over less than half the width of a truss, so that there is wood exposed between adjacent ventilators, into which nails for securing the felt etc. can be driven.

The bridging portion may be configured to confer rigidity. Preferably any rigidifying structures do not project substantially upwardly so as to interfere with the ventilation passage over the upper surface. In a preferred form the bridging portion is formed with tensioning creases. For example, a generally rectangular bridging portion may be given a pair of shallow diagonal creases. They may be concave upwardly, so that central portions are slightly below the original plane of the sheet. Alternatively (or additionally) there may be downturned flanges along the length of the bridging portion.

In a second aspect the invention provides a method of constructing a roof, including the step of laying an eaves ventilator as described above so that it bridges two roof trusses, and subsequently securing it to the trusses. Preferably the securing step involves driving securing means fast with the ventilator into the trusses.

Some embodiments of the invention will now be described in greater detail with reference to the accompanying drawings in which: Figure 1 is a perspective view of part of a roof assembly including an eaves ventilator according to a first embodiment of the invention; Figure 2 is a front elevation of the assembly shown in Fig. 1, viewed in the length direction of a roof truss, and with roof felt added; Figure 3 is a vertical transverse section of the assembly on a smaller scale, with the roof complete; and Figure 4 is a perspective view of a second embodiment.

The roof construction of which parts are visible in Figs. 1 to 3 includes a parallel pair of spaced roof trusses 10, 1 2 extending downwardly and forwardly over the top of a cavity wall 14. The wall 14 has on top of it a wall plate 16, which supports joists 1 8. A layer of insulating material 20 lies over and between the joists 18. (The section of Fig. 3 is at a region between joists 1 8. Thus there are joists superimposed on the illustrated material 20, above and beneath the plane of the paper.) A ventilator 22 is formed from a sheet of metal e.g. galvanised steel, by cutting and bending. It has a generally rectangular bridging portion 24, at each end of which there is an upturned wall portion 26 leading to an out-turned flange 28.The two flanges 28 are co-planar and arranged to overlie upper surfaces of roof trusses 10. 1 2. Each has, at one end edge region, a down-turned tongue 30.

The bridging portion 24 has diagonal folds or creases 32 which, viewed from above, are valley folds. They are quite shallow: e.g. for a bridging portion of size 1 8 x 58 cm, the lowest point may be 8 mm beneath the original level. (The depth is exaggerated in Fig. 2.) This suffices to give the thin metal considerable resistance to bending about a transverse axis.

As best seen from Figs. 1 and 2, a ventila tor 22 is placed so as to bridge two trusses 10, 12. Its flanges 28 only overlap the trusses 10, 1 2 to a small extent. The tongues 30 point downwardly into the trusses. The ventilator 22 is self supporting. This a row of them can be swiftly put in place (along the line of the wall plate 16). It is then the work of a moment to secure each one with a tap of a hammer in each top corner region, driving the tongues 30 into the trusses 10, 12. At the eaves, a facia 34 and a ventilating soffit 36 are mounted, either before or after the installation of the ventilators 22. Felt 38 is laid over the trusses 10, 1 2 and ventilators 22, and secured to the trusses 10, 1 2 by nails driven in between adjacent ventilators 22, and to the facia 34.Ideally the felt 38 has final dimensions such that it is taut, as shown, and this forms with a ventilator 22 an unobstructed conduit for air which can thus pass as shown by the arrows 40. To allow for imperfect fitting or the effects of ageing, the ventilators are made deep enough (i.e. with tall enough wall portions 26) to ensure an adequate air passage even if there is some sagging of the felt. Of course, all of the dimensions of the ventilators can be selected to suit particular needs. Preferably the wall portion 26 has a depth of at least 24 mm, and greater depths (e.g. 30 or 35 mm) may give still greater reliability.

Fig. 3 also shows tiles 41 and battens 42 secured over the felt, by means (not shown) including nails driven into trusses 10, 1 2 between ventilators 22.

Fig. 4 shows a second embodiment of a ventilator 22'. It is generally similar to the first embodiment, being made of the same material. Corresponding parts are indicated by the same reference numerals. The bridging portion 24 does not have diagonal creases (32). Instead, rigidity against bending about a transverse axis is conferred by a pair of downturned longitudinal flanges 44. This construction is at present less preferred, since it involves more steps to produce. Of course, many other structures are possible. Ones involving stiffening ribs are not favoured, insofar as they obscure the air passage.

It may not always be desired to fix a ventilator by means of integral tongues 30 the out-turned flanges 28 may have apertures for nailing instead of (or in addition to) such tongues.

Claims

CLAIMS:

1. An eaves ventilator comprising a rigid elongate bridging portion for extending between two roof trusses and, at either end, an attachment portion for attachment to a respective truss to hold the bridging portion generally below the top surfaces of the trusses.

2. An eaves ventilator according to claim 1 wherein the attachment portions have integral securing means.

3. An eaves ventilator according to either preceding claim wherein each attachment portion is dimensioned so as to extend in use over less than half the width of a standard roof truss.

4. An eaves ventilator according to any preceding claim wherein the bridging portion is configured to increase the rigidity over that inherent in the material of which it is made.

5. An eaves ventilator according to claim 4 wherein the rigidifying configuration comprises tensioning creases.

6. An eaves ventilator according to claim 5 wherein the bridging portion has a pair of shallow diagonal creases which are concave upwardly so that central portions are slightly below the original plane of the sheet.

7. An eaves ventilator according to claim 4, 5 or 6 wherein the rigidifying configuration comprises downturned flanges along the length of the bridging portion.

8. An eaves ventilator according to any preceding claim which is of sheet metal.

9. An eaves ventilator according to any preceding claim which is of sheet metal.

9. An eaves ventilator according to claim 8 wherein the attachment portions are provided with securing means in the form of turned-over tongues of metal which can be driven into the trusses.

1 0. An eaves ventilator substantially as herein described with reference to and as illustrated in Figs. 1 to 3 or Fig. 4 of the accompanying drawings.

11. A method of constructing a roof, including the step of laying an eaves ventilator according to any preceding claim so that is bridges two roof trusses, and subsequently securing it to the trusses.

1 2. A method according to claim 11 wherein the eaves ventilator is attached with each attachment portion overlying less than half the width of a respective truss.

13. A method of constructing a roof including a step of laying an eaves ventilator substantially as described herein with reference to Figs. 1-3 or Fig. 4 of the accompanying drawings.