GB2293874A

GB2293874A - Roof valley ventilation

Info

Publication number: GB2293874A
Application number: GB9512423A
Authority: GB
Inventors: Neil Rideout; Mark Laurence Hesketh
Original assignee: Willan Building Services Ltd
Current assignee: Willan Building Services Ltd
Priority date: 1994-07-21
Filing date: 1995-06-19
Publication date: 1996-04-10
Anticipated expiration: 2015-06-19
Also published as: GB9512423D0; GB9414719D0; GB2293874B

Abstract

The space between rafters 1 is ventilated at a roof valley 2 by interposing a rigid structure 12 between the valley floor and a roof covering 5, 6 overlying the rafters. The rigid structure 12 is shaped to define an air duct between an inner end 17 in communication with the inter-rafter space, and an outer end 18 in communication with the exterior of the roof at the valley. The structure may be formed by a shaped sheet which may have parallel spacer ribs 14 which define the air duct, and a transverse channel 16 which passes over a valley batten 4 of the roof to accommodate the batten 4 and also to act as an obstruction to prevent ingress of moisture. <IMAGE>

Description

VENTILATION STRUCTURE This invention relates to a ventilation structure for roofing.

It is common practice to provide ventilation for roof spaces in modern houses. This is necessary to prevent undue accumulation of condensation in insulated roof spaces.

Where insulation is provided only on the floor of a roof space and the rafters are exposed it is only necessary to provide ventilation for the roof space.

In some cases, however, it is the practice to attach plaster-board immediately beneath the rafters so that they are enclosed between this plaster board on the inside and the usual tile underlay on the outside. Where insulation is sited immediately above the plasterboard it is necessary to ventilate the spaces above the insulation immediately between the rafters.

Where the rafter ends are readily accessible it is possible to provide ventilation openings between such ends. However, a problem arises in the case of valley constructions. The rafter ends of one roof are joined at the valley to rafter ends of an adjacent roof and it is common practice to seal the valley with a trough structure overlying the rafter ends. Access to the rafter ends for ventilation purposes is therefore limited.

An object of the invention is to overcome this problem by providing a ventilation structure insertable in the vicinity of rafter ends at a roof valley.

According to one aspect of the invention therefore there is provided a method of ventilating a space between rafters at a roof valley, wherein a rigid structure is interposed between the valley floor and a roof covering overlying said rafters, said ventilation structure having inner and outer open ends respectively in communication with the said space and with the exterior of the roof at the valley, and said structure defining a duct permitting flow of air between said open ends thereof.

With this arrangement, the rigid structure permits ventilation of the space between rafters in a convenient manner without requiring an unduly obtrusive or unsightly structure. Due to the rigid nature of the structure, ventilation can be achieved without prejudice to the structural integrity or strength of the roof or the valley construction.

In a particularly preferred embodiment, the rigid structure incorporates spacers engageable with the valley floor to define the said duct between the valley floor and an upper wall of the rigid structure.

The spacers may comprise side-by-side ribs which may run throughout at least a major part of the extent of the rigid structure between its ends.

The ribs may be parallel. The ribs may be formed as integral parts of the rigid structure and may be defined by convolutions of sheet material pressed or moulded therefrom.

The rigid structure may be shaped to conform to structural members of the roof between the said ends of the rigid structure. In particular, the rigid structure may have a transverse channel portion between its ends to pass over and around a transverse valley batten of the roof.

The rigid structure is preferably configured and/or installed so as to avoid or minimise ingress of rain or moisture collecting in or blown back from the valley. The shaping and arrangement of the structure as mentioned in the preceding paragraph will normally be sufficient to achieve this. If desired however any other suitable shaping and/or arrangement may be utilised to avoid or substantially eliminate a direct line, un-obstructed passageway between the ends of the structure.

The top surface of at least the outer end portion of the rigid structure may be roughened or configured, e.g. by incorporation of a sand strip, to provide purchase for mortar or other building material or adhesive used to seal and/or bond an overlying tile thereto. The rigid structure may have an upwardly directed transverse channel at said end portion to receive said building material or adhesive.

The rigid structure may be interposed at its inner end beneath the usual tile underlay and the adjacent end of any tiling batten. At its outer end the rigid structure may overlay any suitable surface or valley structure at or adjacent to the valley terminating beneath or projecting from the tile or other roof covering at the valley.

However, in a particularly preferred embodiment, the rigid structure overlays a sealing valley trough of the kind comprising a rigid or semi-rigid sheet of V-shaped configuration adapted to correspond to the valley floor.

The rigid structure used in the method of the invention may be formed from plastics, or glass-fibre or other reinforced resin, or metal or any other suitable material using any suitable moulding, forming or pressing operation as appropriate.

In use, multiple like rigid ventilation structures may be deployed side-by-side on both side of the valley.

The invention also provides a rigid ventilation structure for use in the method described above comprising a shaped rigid sheet structure having a top wall and depending spacer constructions defining below the top wall at least one duct running between inner and outer ends thereof, said inner end comprising a lower projecting part adapted to fit beneath the roof covering, said outer end having a lower projecting part for communication with the exterior of the roof at the valley, and there being an upwardly displaced transverse section between said lower projecting parts to pass over and around a valley batten of the roof.

The invention further provides the combination of a valley trough and at least one rigid structure adapted to overlay a side of the trough to provide thereat a ventilation duct to permit flow therealong between the valley trough and the roof beneath a roof covering thereof.

The invention will now be described further by way of example only and with reference to the accompanying drawings in which: Fig. 1 is a sectional view of a roof valley fitted with a valley trough, and also rigid ventilation structures in accordance with one embodiment of the invention; Fig. 2 is a perspective view showing one of the rigid structures of Fig.1.

The roof valley is of conventional construction and is defined by rafters 1 of two adjoining sloping roofs which are joined at an angle to define a V-shaped valley 2 therebetween.

Each roof has multiple, parallel, longitudinal tiling battens 3 terminating at a position spaced from the valley, and a transverse valley batten 4 extending closely beneath the lower ends of the battens 3. The battens 3, 4 are fixed to the rafters 1. The longitudinal battens are fixed over a sheet of waterproof roofing underlay 5.

Tiles of any suitable kind are fixed on top of the battens 3 in conventional manner. These tiles 6 terminate close to, but spaced from the valley 2.

Within the valley there is fixed a valley trough 7 (or rather a row of end to end valley troughs depending on the length of the valley) of conventional form comprising a glass-fibre reinforced water-impermeable plastics sheet shaped to provide a generally V-shaped structure with a central longitudinal upwardly displaced ridge 8 and two side longitudinal upwardly displaced ridges all being mutually parallel.

The side edge portions 10 of the valley trough 7 are stepped upwardly to fit on top of the valley battens 4 with the remaining V-shaped central portion of the trough in contact with the rafters 1 at the valley.

The valley trough 7 in conventional manner acts to seal the rafters 1 at the valley against ingress of water. The central ridge 8 facilitates drainage. The side ridges 9 normally provide mortar-retention checks as explained hereinafter. The top surface of the valley trough 7 is provided with sand strips 11 between each ridge 9 and the adjacent stepped edge portion 10, normally to facilitate mortar adhesion, also as explained hereinafter.

At each side edge portion of the valley trough there is a respective rigid ventilation structure 1 2 (or rather a row of side-by-side such structures depending on the length of the valley). This structure comprises a sheet of water impermeable material such as glass fibre reinforced plastics formed with multiple parallel side-by-side narrow channels 13 which define spacer ribs 14 depending below a top wall 15 of the sheet.

The structure 1 2 is shaped with a central transverse stepped portion 16 defining a downwardly directed wide channel extending perpendicularly to the ribs 14, a lower projecting part 1 7 at an inner end of the structure 1 2 in the form of a downwardly turned edge region, and a lower, stepped projecting part 18 at the opposite outer end defining a shallow downwardly directed transverse channel 19 terminating in a straight edge portion 20.

Each structure 1 2 overlays the respective side region of the valley trough 7 so that the channel 16 fits over and around the stepped end part 10 of the trough 7 and the valley batten 4, and the shallow channel 19 fits over the pertaining ridge check 9.

In this position, as shown, the inner end lower projecting part 1 7 fits beneath the roofing underlay 5 and the ends of the tiling battens 3, and the straight edge portion 20 at the outer end projects towards the valley 2 slightly free of the adjacent edge of the tiling 6.

In this position, the ribs 14 contact the top surface of the valley trough 7 and act as spacers to hold the top wall 15 of the structure 12 above the trough surface. There is thereby defined a duct, between the parallel ribs 14 running between the open outer end of the structure 1 2 close to the valley 2 and the open inner end of the structure 12 beneath the roofing underlay.

Free flow of air can therefore take place between the space between adjacent rafters 1 and the exterior of the roof. Adequate ventilation of the inter-rafter spaces can therefore be ensured even if the rafter space is sealed from below with plaster-board or other material.

As shown, the edge region of the tiling 6 adjacent the valley 2 is fixed in position and sealed by means of mortar 21 between the tiling 6 and the top surface of the rigid structure 1 2 in the region between the central channel 16 and the edge of the shallow stepped part 18 adjacent the projecting part 20, which edge acts as a check for the mortar.

In order to facilitate adhesion of the mortar 21 to the structure 12 a transverse strip of sand 22 is fixed to the trough surface e.g. in the form of resin bonded sand.

The ridges 9 and sand strips 11 of the trough 7 are therefore not used, and indeed these structures may be omitted if desired.

With the arrangement described the rigid structures 1 2 provide efficient ventilation in a convenient manner and without being obtrusive or unsightly. The structures 1 2 fit on a conventional valley trough 7 without disturbing the sealing properties of the trough 7 or the structural integrity and strength of the valley construction of the roof.

Efficient ventilation is assured without serious risk of ingress of water through the ventilation duct, blow back of rain being prevented by the convoluted shape of the central channel portion 16.

Since the structure 1 2 conforms closely to the floor of the valley and the overlying valley batten 4, the structure can be used with any suitable kind and shape of tile or slate or other roofing elements.

It is of course to be understood that the invention is not intended to be restricted to the details of the above embodiment which are described by way of example only.

Claims

1. A method of ventilating a space between rafters at a roof valley, wherein a rigid structure is interposed between the valley floor and a roof covering overlying said rafters, said ventilation structure having inner and outer open ends respectively in communication with the said space and with the exterior of the roof at the valley, and said structure defining a duct permitting flow of air between said open ends thereof.

2. A method according to claim 1 wherein the rigid structure incorporates spacers engageable with the valley floor to define the said duct between the valley floor and an upper wall of the rigid structure.

3. A method according to claim 1 or 2 wherein the spacers comprise side-by-side ribs which run throughout at least a major part of the extent of the rigid structure between its ends.

4. A method according to claim 3 wherein the ribs are parallel to each other.

5. A method according to claim 3 or 4 wherein the ribs are formed as integral parts of the rigid structure.

6. A method according to claim 5 wherein the ribs are defined by convolution of sheet material.

7. A method according to any one of claims 1 to 6 wherein the rigid structure is shaped to conform to structural members of the roof between the said ends of the rigid structure.

8. A method according to claim 7 wherein the rigid structure has a transverse channel portion between its ends to pass over and around a transverse valley batten of the roof.

9. A method according to any one of claims 1 to 8 wherein the rigid structure is arranged to give an obstructed passageway between the ends of the structure to obstruct ingress of moisture from the valley.

10. A method according to any one of claims 1 to 9 wherein the top surface of at least the outer end portion of the rigid structure is configured to provide purchase for sealing or bonding material.

11. A method according to claim 10 wherein the rigid structure has an upwardly directed transverse channel at said end portion to receive said material.

12. A method according to any one of claims 1 to 11 wherein the rigid structure is interposed at its inner end beneath a tile underlay.

13. A method according to any one of claims 1 to 12 wherein the rigid structure overlays a sealing valley trough adapted to correspond to the valley floor.

14. A method according to any one of claims 1 to 13 wherein multiple like rigid ventilation structures are deployed side-by-side on both sides of the valley.

15. A rigid ventilation structure for use in the method described above comprising a shaped rigid sheet structure having a top wall and depending spacer constructions defining below the top wall at least one duct running between inner and outer ends thereof, said inner end comprising a lower projecting part adapted to fit beneath the roof covering, said outer end having a lower projecting part for communication with the exterior of the roof at the valley, and there being an upwardly displaced transverse section between said lower projecting parts to pass over and around a valley batten of the roof.

16. A rigid structure according to claim 15 wherein the spacer construction comprise side-by-side ribs which run throughout at least a major part of the extent of the rigid structure between its ends.

17. A rigid structure according to claim 16 wherein the ribs are parallel to each other.

18. A rigid structure according to claim 16 or 17 wherein the ribs are formed as integral parts of the rigid structure.

19. A rigid structure according to claim 18 wherein the ribs are defined by convolution of sheet material.

20. A rigid structure according to any one of claims 15 to 19 wherein the top surface of at least the outer end portion of the rigid structure is configured to provide purchase for sealing or bonding material.

21. A rigid structure according to claim 20 wherein the rigid structure has an upwardly directed transverse channel at said end portion to receive said material.

22. A combination of a valley trough and at least one rigid structure adapted to overlay a side of the trough to provide thereat a ventilation duct to permit flow therealong between the valley trough and the roof beneath a roof covering thereof.

23. A combination according to claim 22 wherein the rigid structure is as claimed in any one of claims 15 to 21.

24. A method according to claim 1 substantially as hereinbefore described by way of example only.

25. A rigid structure according to claim 15 substantially as hereinbefore described with reference to and as illustrated in the accompanying drawings.

26. A combination according to claim 22 substantially as hereinbefore described with reference to and as illustrated in the accompanying drawings.