GB2204339A

GB2204339A - A ventilator for a roof structure and method of ventilating a roof structure

Info

Publication number: GB2204339A
Application number: GB08810278A
Authority: GB
Inventors: Colin Frederick Gibson; David Bottomore
Original assignee: Glidevale Building and Products Ltd
Current assignee: Glidevale Building and Products Ltd
Priority date: 1987-05-01
Filing date: 1988-04-29
Publication date: 1988-11-09
Anticipated expiration: 2008-04-29
Also published as: GB2204339B; GB8810278D0

Abstract

A ventilator 110 for a roof structure 130 of the type which is arranged in abutment with a wall 128 and having first and second cladding materials 132, 136 which may be disposed in overlapping relationship with one another. The ventilator 110 comprising a spacing means 112, 114, 116 adapted to space the first and second cladding materials from the wall and adapted to space the first and second cladding materials from one another. <IMAGE>

Description

A VENTILATOR FOR A ROOF STRUCTURE AND METHOD OF VENTILATING A ROOF STRUCTURE This invention relates to a ventilator for a roof structure, and to a method of ventilating a roof structure.

More particularly the invention is concerned with a ventilator for a roof structure of the type which is arranged in abutment with a wall, for example, when an extension building is provided on a main building.

The roof structure may be flat roof structure or a pitched roof structure.

In roof structures of this type a gap is usually provided between the roof structure and the wall; typically the gap is about 5mm. This gap can be used to provide ventilation to the interior of the roof structure. Such ventilation to the interior is advisable in order to minimise the risk of condensation within the roof structure.

In this type of roof structure it is common to provide a cladding material in the form of flashing. An upper flashing is secured to the main wall and extends downwardly toward the roof structure; a lower flashing is secured to the roof structure and extends upwardly toward the main wall. It is usually preferable that the two flashings overlap one another.

GB-A-2,138,466 relates to a roof flashing unit for use in this type of roof structure. The roof flashing unit disclosed provides a ventilation path from the external environment to the interior of the roof structure and is intended to replace the conventional roof flashing materials. - Moreover, if conventional roof flashing were provided on top of the unit, it would not be possible for the flashings to overlap without risking blockage of the ventilation path.

Other ventilators for providing ventilation to the interior of a roof structure of this type are described in GB-A-2,142,947 and GB-A-2,153,067.

According to one aspect of the present invention there is provided a ventilator for a roof structure of the type which is arranged in abutment with a wall and having first and second cladding materials which may be disposed in overlapping relationship with one another, said ventilator comprising spacing means adapted to space the first and second cladding materials from the wall and adapted to spce tlBe first and second cladding materials frrlm one anetiler.

Advantageously the spacing means is adapted to be secured to the wall. This can be achieved by the provision ef one or more apertures through which fixing means, such as nails or screws, can be passed into the wall.

Preferably the spacing means comprises first and second spacing members adapted to space the first and second cladding respectively from the wall.

In the preferred construction, the first and second claddings overlap. In this construction, there is provided first and second ventilation paths: the first ventilation path communicates at one end with an interior of the roof structure and at the other end with the second ventilation path, and may be defined between the first cladding and the wall; the second ventilation path communicates at one end with the first ventilation path and at the other end with an external environment, and may be defined between the first and second claddings.

In a first embodiment it is preferred that the first and second spacing members are integral; the integral structure ensures that the first and second spacing members are disposed at the correct position relative to one another. The integral ventilator may be a plastics material formed by injection moulding.

In this embodiment the first spacing member may comprise a plurality of first positioning formations, one edge of which can receive or retain the first cladding, and the other edge of which can abut against the wall; -the thickness of the first positioning formations is substantially equal to the distance of the first cladding from the wall.

The first positioning formations may all be connected to a first panel. The first panel may be disposed so that it can abut the first cladding, or can abut the wall, or it can be disposed intermediate the thickness of the first positioning formations.

Also in this embodiment, the second spacing member may comprise a plurality of second positioning formations, one edge of which can receive or retain the second cladding, and the other edge of which can abut against the first cladding; the distance between the first and second claddings will be substantially equal to the thickness (i.e. the distance between the edges) of the second positioning formations.

The second positioning formations may all be connected to a second panel. The second panel may be disposed so that it can abut the second cladding, or can abut the first cladding, or it can be disposed intermediate the thickness of the second of the second positioning formations.

In a second embodiment the ventilator comprises the first and second spacing members together with a positioning member which can be secured to the wall or the roof structure. In this embodiment the first and second spacing members are secured to the positioning member.

Advantageously the positioning member comprises a body provided with first and second positioning formations. The first spacing member can be secured to the first positioning formation, and the second spacing member can be secured to the second positioning formation.

Preferably the first positioning formation and the first spacing member are provided with cooperating formations to facilitate the securing; it is preferred that the cooperating formations provide a snap-fit between the first spacing member and the first positioning formation.

Preferably the second positioning formation and the second. spacing member are provided with cooperating formations to facilitate the securing; it is preferred that the cooperating formations provide a snap-fit between the second spacing member and the second positioning formation.

One or more apertures can be provided in the positioning member to facilitate securing to the wall or roof structure by fixing means such as nails or screws.

The relative position of the positioning formations can be arranged such that when the first and second spacing members are attached, they can space the first and second claddings at the required distances from one another and from the wall.

A rear surface of the body can be abutted against the wall, so the distance between the rear surface and the first and second positioning formations determines the dimensions of the ventilation paths.

The second positioning formation is preferably provided on an upper part of the body, whilst the first positioning formation is preferably provided on a lower part of the bods.

Desirably the body includes a third positioning formation adapted to be disposed between the first and second spacing members in order to assist with the positioning of said spacing members.

The third positioning member may be movable relative to the rest of the body to facilitate securing the first spacing member to the first positioning formation.

Preferably the third positioning member is pivotably mounted to the body; the third positioning member may be mounted to the body at a position between the first and second positioning formation.

Thus, the third positioning formation can be pivoted away from the first positioning formation whilst the first spacing member is secured thereto. The third positioning formation can then be pivoted back towards the first positioning formation so that it can engage the first spacing member. The second spacing member can then be secured to the second positioning formation in such a manner that it is in engagement with the opposite side of the third positioning member to the first spacing member.

The positioning member and the first and second spacing members may be a plastics material. It is preferred that first and second spacing members are formed by extrusion and that the positioning member is formed by injection moulding.

The positioning member is preferably of elongate configuration with the longitudinal axis being arranged, in use, substantially vertically.

A plurality of the positioning members can be arranged in a row at intervals along the wall, and the first and second spacing members can be secured thereto.

Several positioning members may have secured to them only one first spacing member and only one second spacing member.

In both the above embodiments it is possible for the first and second spacing members to be arranged, without a break, along the wall. In this case either a continuous single first and second spacing member can be used, or a plurality of first and second spacing members can be arranged in juxtaposition with one another.

According to another aspect of the invention there is provided a method of ventilating a roof structure of the type which is arranged in abutment with a wall and having first and second cladding materials which may be disposed in overlapping relationship with one another.

said method comprising: (a) securing a positioning member to the wall; (b) securing the first cladding to a first spacing member and securing the first spacing member to the positioning member to define a first ventilation path between the first cladding and the wall, said first ventilation path nmmunic,ztinji at one end witch an interior of the roof structure; (c) seel1ring the second cladding to a second spacing member and securing the second spacing member to the positioning member to define a second ventilation path between the second cladding and the first cladding, said second ventilation path communicating at one end with an external environment and at the other end with the first ventilation path.

The first cladding is preferably secured to the first spacing member before the first spacing member is secured to the positioning member.

The second cladding is preferably secured to the second spacing member before the second spacing member is secured to the position member.

The first and second claddings are typically flashing. The flashing may be, for example, lead flashing, bitumen flashing or plastics flashing.

According to another aspect of the present invention there is provided a ventilator for use in the ventilation of a roof structure of the type which is arranged in abutment with a wall, said ventilator comprising first and second ventilation members and a positioning member, the positioning member comprising a body and first and second positioning formations, the positioning member being adapted to be secured to the roof structure or the wall, the first positioning formation being adapted to position the first ventilation member from the wall to define a first ventilation path between the wall and the first member, and the second positioning formation being adapted to position the second ventilation member from the first ventilation member to define a second ventilation path between the first and second ventilation members, wherein the first ventilation path communicates at one end with the second ventilation path and at the other end with an interior of the roof structure, and the second ventilation path communicates at one end with the first ventilation path and at the other end with an external environment.

The positioning member may be provided with ans combination of the features of the positioning member described above.

When first and second cladding materials are used, as described above, then the first ventilation member can act as a first spacing member, as described above, and the second ventilation member can act as a second spacing member, as described above.

The ventilator according to this aspect of the invention may be a plastics material. The positioning member is preferably injection moulded whilst the ventilation members are preferable extruded.

It is possible for the ventilation members themselves comprise first and second claddings.

Reference is now made to the accompanying drawings, in which: Figure 1 is a front view of one embodiment of a ventilator according to the invention; Figure 2 is a view on lines 2-2 of Figure 1; Figure 3 is a plan view of the ventilator shown in Figure 1; Figure 4 is a view from the underneath of the ventilator shown in Figure 1; Figure 5 is a rear view of the ventilator shown in Figure 1; Figure 6 is a perspective view showing a roof structure incorporating the ventilator shown in Figures 1 to Figure D; Figure 7 is a cross-sectional view through the roof structure shown in Figure ; Figure 8 is a front view of another embodiment of ventilator according to the invention; Figure 9 is a cross-sectional view showing the ventilator of Figure 8 in a roof structure; ; Figure 10 is a cross-sectional view of another embodiment of ventilator according to the invention, positioned in a roof structure; Figure 11 is a perspective view of a positioning member of the ventilator shown in figure 11; Figure 12 is a cross-sectional view of a further embodiment of positioning member, of a ventilator according to the invention, secured to a wall; Figure 13 is a perspective view of the positioning member shown in Figure 13; Figures 14 to 17 are cross-sectional views showing how a ventilator according to the invention can be provided on a wall; Figure 18 is a cross-sectional view of another embodiment of ventilator according to the invention in a roof structure; Figure 19 is a perspective view of the embodiment shown in Figure 18.

Figures 20 and 21 show modifications to the ventilator shown in Figures 10 and 11; Figure 22 is a perspective view of a flyscreen for use in the ventilator shown in Figures 20 and 21.

Figure 23 is a perspective view of a clip for use in the ventilator according to the invention.

Referring to Figures 1 to 5 a ventilator generally designated 10 comprises a first spacing member in the form of a first panel 12 having a plurality of first positioning formations 14 arranged in a row.

The ventilator 10 further includes second spacing member in the form of a second panel 16 having a plurality of second positioning formations 18 arranged in a row. The row of second positioning formations 18 is substantially parallel to the row of first positioning formations 14.

A gap 20 is provided between the first and second positioning formations 14 and 18; a first cladding material in the form of flashing 22 (see Figure 6) can be received in the gap 20.

The size of the gap 20 at the outermost ends of the ventilator 10 is sufficient to receive at least a single thickness of flashing 22. However, the size of the gap 20 between the ends is large enough to receive at least two thicknesses of flashing 22. This enables adjacent strips of the flashing 22 to be overlapped.

A first ventilation path A is defined between the flashing 22 and the first panel 12 (see Figure 7). A second ventilation path B, which is substantially parallel to the first ventilation path A, is defined between the flashing 22 and the second panel 16.

The first and second ventilation paths A and B communicate with one another at the uppermost part of the ventilator 10 where the first panel 12 is connected to the second panel 16, to provide an integral structure.

The first and second positioning formations 14 and 18 serve to position the flashing 22 from the second panel 16 and the first panel 12, and also divide the ventilation paths A and B into a plurality of channels.

The first panel 12 is provided with apertures 24 through which fixing means in the form of nails or screws 26 (see Figure 7) may be passed in order to secure the ventilator 10 to a wall 36.

In Figures 6 and 7 the ventilator 10 is shown in positioned in a pitched roof structure. It will be appreciated that the ventilator 10 can also be used in flat roof structures.

The roof structure comprises roof tiles 28 which are secured to battens 3G by nails 32; sarking felt 34 is arranged underneath the roof tiles 28 and the battens 30.

The roof structure is arranged in abutment with the wall 36 of a main building.

The ventilator 20 serves to provide ventilation from the exterior environment to an interior 38 of the roof structure; the ventilation is provided through a gap between the wall 36 and the roof structure.

The first ventilation path A is in communication with the interior 38 of the roof structure, whilst the second ventilation path B is in communication with the exterior environment.

A second cladding material in the form of flashing 46 extends over the second panel 16 and is in overlapping relationship with the flashing 22; the flashing 46 is secured to the wall 36.

The second positioning formations 18 serve to space the flashing 22 from the flashing 46 in order to define the second ventilation path B therebetween.

A further embodiment of ventilator 50 is shown in Figures 8 and 9. The ventilator 50 is similar to the ventilator 10 and like parts have been designated with like reference numerals.

The differences are as follows. The ventilator 50 is provided with a first panel 52a which is disposed at the edge of the first positioning formations 14 opposite the wall 36. The ventilator 50 is also provided with a second panel 52b which is disposed at the edge of the second positioning formations 18 closest to the wall 36.

The panels 52a and 52b are connected at the top to define a fork-shaped structure. The panels 52a and 52b define a gap 48 which receives the first flashing 22.

The ventilator 50 is provided with a further panel 56 which is considerably shorter than the second panel 16 of the ventilator 10. The second flashing 46 extends over the further panel 56 and onto the second positioning formations 18. Thus, the second flashing 46 is in direct engagement with the second positioning formations 18.

Pins 58 are provided on the second panel 52b between the second positioning formations 18, and serve to help prevent the second flashing 46 from blocking the second ventilation path B.

The upper part of the panels 52a and 52b, where they join together, is provided with apertures 60 which can receive the nails or screws 26; the apertures 24 (shown in Figure 1) are not necessary.

It will be appreciated that in both the above embodiments the direction of the air flow indicated by arrows A and B can be reversed.

Referring to Figures 10 and 11 a ventilator generally designated 110 comprises a first spacing member 112, a second spacing member 114 and a positioning member 116.

The positioning member 116 comprises a body 118, a first positioning formation 120 and a second positioning formation 122.

The body 118 is provided with an aperture 124 through which a nail or screw 126 can be passed to secure the body 118 to a wall 128. A rear surface 118a of the body 118 abuts the wall 128. A roof structure generally designated 130 is disposed adjacent the wall 128 beneath the ventilator 110.

The first spacing member 112 and the first positioning formation 120 are provided with cooperating formations 132 and 134 respectively; the cooperation formations 132 and 134 provide a snap-fit between the first spacing member 112 and the first positioning formation 120.

The second spacing member 114 and the second positioning formation 122 are provided with cooperating formations 136 and 138 respectively; the cooperating formations 136 and 138 provide a snap-fit between the second spacing member 114 and the second positioning formation 122.

A first flashing 140 is provided over the first spacing member 112 and is spaced from the wall 128 by a distance equal to the distance between the first positioning formation 120 and the rear surface 118a. The first flashing 140 extends downwardly onto the roof structure 130.

A second flashing 142 is provided over the second spacing member 114, and is spaced from the wall 128 by a distance equal to the distance between the second positioning formation 122 and the rear surface 118a, The second flashing 142 extends upwardly into the wall 128.

The distance of the second positioning formation 122 from the wall 128 is greater than the distance of the first positioning formation 120 from the wall 128.

A first ventilation path C is defined between the firs spacing member 112 and the wall 128. A second ventilation path D is defined between the second spacing member 114 and the first spacing member 112. The first ventilation path C communicates at one end with an interior of the roof structure and at the other end with the second ventilation path D. The second ventilation path D communicates at one end with the first ventilation path C and at the other end with the external environment.

The positioning member 116 is of generally elongate configuration, and a plurality of said positioning members 116 can be arranged at intervals in a row along the wall 128; thus, the first ventilation path C is defined between adjacent positioning members 116.

It will be appreciated that the direction of air flow through ventilation paths C and D can be reversed.

The first and second spacing members 112 and 114 may be arranged along the wall 128 either continuously or at intervals.

The first and second flashings 140 and 142 are each arranged in adjacent strips, and the adjacent strips overlap at the edges to produce a region having a double thickness of flashing. The distance between the first and second positioning formations 120 and 122 is large enough that the second ventilation path D is not blocked by the double thickness of the first flashing 140.

One method of providing the ventilator 110 on the roof structure is as follows.

First, the positioning member 116 is secured to the wall 128 at a selected position above the roof structure 130.

The first flashing 140 is then secured to the first spacing member 112, and the first spacing member 112 is snap-fitted onto the first positioning formation 120.

The second flashing 142 is then secured to the second spacing member 114, and the second spacing member 114 is snap-fitted onto the second positioning formation 122.

Referring to Figures 12 and 13 a positioning member generally designated 210 comprises a body 212 having first and second positioning formations 214 and 216 respectively provided thereon.

The first positioning formation 214 is provided on a lower portion of the body 212 and the second positioning formation 216 is provided on an upper portion of the body 212.

The body 212 is provided with a rear surface 218 which is adapted to engage a wall 220. The bod 212 is also provided with a front surface 222, opposite to the rear surface 218, and the first and second positioning formations 214 and 216 are provided on the front surface 222.

The body 212 is provided with an aperture 224 through which a nail or screw 226 can be passed in order to ecure the positioning member 210 to the wall 220 (for clarity the wall 220 is not shown in Figures 12 to 1;).

The body 212 is also provided with a third positioning formation 228 the purpose of which will be described hereinafter. The third positioning formation 228 is pivotally secured to the rest of the body 212 by moans of a hinge 230.

In Figures 14 to 17 a method of providing a ventilator according to the invention on a roof structure is shown. The first step is to secure the positioning member 210 at a selected position to the wall 220 by means of the nail or screw 226.

A first spacing member 232 is then secured to the first positioning formation 214. The first spacing member 232 is provided with cooperating formation 234 which are a snap-fit with cooperating formations 214a and 214b on the first positioning formation 214.

As shown in Figures 15, a first flashing 236 is then provided over the surface of the first spacing member 232 in close contact therewith.

The third positioning formation 228 is then pivoted towards the first flashing 236 and the first spacing member 232 until it comes into engagement with the outer surface of the first flashing 236; this is shown in Figure 16.

A second spacing member 238 is then secured to the second positioning formation 216.

The second spacing member 238 is provided with cooperating formations 242 which are a snap-fit with cooperating formations 216a and 216b on the second positioning formation 216.

A first ventilation path E, which communicates at one end with an interior of the roof structure, is defined between the first spacing member 232 and the wall 220. A second ventilation path F, which communicates at one end with the first ventilation path E and at the other end with the external environment, is defined between the first and second spacing members 232 and 238.

It wil] 1 be appreciated that the direction of air flow through the ventilation paths E and F can be reversed.

As can be seen in Figure 17, the third positioning formation 228 helps to position the first spacing member 232 from second spacing member 238 to define the second path F therebetween; the body 212 spaces the first spacing member 232 from the wall 220 in order to define the first ventilating path E therebetween.

It will be observed that the first and second spacing members 232 and 238 serve to space the overlapping flashing 236 and 240 thereby providing the second ventilation path F therebetween.

Another embodiment of ventilator according to the invention is shown in Figures 18 and 19.

In Figures 18 and 19 the positioning member 210 is the same as the positioning member 210 shown in Figures 12 to 17. Furthermore, the second spacing member 238 and the upper flashing 240 are the same as those shown in Figure 17, and they have not been illustrated in Figures 18 and 19 in order to increase the clarity.

In Figures 18 and 19 the first spacing member 232 is replaced by a combined flashing and spacing member 244 which is preferably injection moulded.

The flashing and spacing member 244 has apertures 246 provided therein through which the nails or screws 226 can be passed in order to secure both the flashing and spacing member 244 and the body 212 to the wall 220.

It will be appreciated that the flashing and spacing member 244 could be provided with a cooperating formation adapted to he secured to the cooperating formations 214a and 214b of the first positioning formation 214.

The flashing and spacing member 244 is provided with projections 248 thereon which serve to keep the flashing and spacing member 244 spaced from the wall 220.

The flashing and spacing member 244 is provided with a roof engaging portion 250 which engages tiles 252 of the roof structure. The lower edge of the roof engaging portion 250 is provided with a flange 254 which engages the tiles 252. The provision of the flange 254 enables the flashing and spacing member 244 to be used with different roof pitches.

A first ventilation path G, which communicates at one end with an interior of the roof structure, is defined between the flashing and spacing member 244, and the wall 220. A second ventilation path H, which communicates at one end with the first ventilation path G and at the other end with the external environment, is defined between the flashing and spacing member 232, and the second spacing member 238. It will be appreciated that the direction of air flow through the ventilation paths G and H can be reversed.

It is possible for the second spacing member 238 to be replaced by a combined flashing and spacing member. To this end, the upper flashing 240 may be moulded, and may be provided with cooperating formations adapted to be secured to the cooperating formations 216a and 216b of the second positioning formation 216.

Figures 20 and 21 show a ventilator which is similar to the ventilator shown in Figures 10 and 11; like parts have been designated with like reference numerals.

In Figure 20 a flyscreen 150 is disposed in the second ventilation path D so that it extends between the second spacing member 114 and the flashing 140.

The flyscreen 150 is shown in greater detail in Figure 22. The flyscreen 150 comprises an elongate plastics extrusion having fixing apertures 152 and slotshaped apertures 154 along its length. The fixing apertures can receive the nails or screws 126 to secure the flyscreen 150 to the rest of the ventilator 110. The slot-shaped apertures are dimensioned such that adequate ventilation is maintained whilst preventing the ingress of insects and vermin.

Figure 1 shows the flyscreen 150 positioned in the first ventilation path C. The flyscreen can, if desired, be positioned in both ventilation paths C and D.

It will be appreciated that in order to be effective the flyscreen 150 should extend along substantially the entire length of the wall 128.

The arrangement of the apertures 124, 152 and 154 in the ventilator can be modified, depending upon where it is desired to fit the flyscreen 150.

The flyscreen 150 may be in the form of a mesh, grille or other perforated article.

In Figures 20 and 21 the flashing 142 is connected to the second spacing member 114 by means of a clip 160, which is shown in greater detail in Figure 23.

The clip 160 comprises a base 162 having two legs 164 extending therefrom. The legs 164 converge in a direction away from the base 162, and are resiliently deformable. Each leg 164 is provided with a projection 166 which can act as a barb. The end of the second spacing member 114 and the flashing 142 are received between the legs 164 and are gripped thereby; the projection 166 help to prevent the clip 160 from becoming displaced.

It will be appreciated that the clip 160 can also be used to secure the flashing 140 to the first spacing member 112. .Also, the clip 160 can be used in an of the other embodiments described above.

In the above embodiments shown in Figure 1 to 23, if the first and second claddings are not provided then the spacing members can act as the ventilation members described above.

Claims

1. A ventilator for a roof structure of the type which is arranged in abutment with a wall and having first and second cladding materials which may be disposed in overlapping relationship with one another, said ventilator comprising spacing means adapted to space the first and second cladding materials from the wall and adapted to space the first and second cladding materials from one another.

2. A ventilator according to claim 1 wherein the spacing means is adapted to be secured to the wall.

3. A ventilator according to claim 1 or 2, wherein the spacing means comprises first and second spacing members adapted to space the first and second claddings respectively from the wall.

4. A ventilator according to claim 1, 2 or 3, wherein the first and second spacing members are also adapted to space the first and second claddings from one another.

5. A ventilator according to any preceding claim, wherein the first and second spacing members are integral.

6. A ventilator according to claim 5, wherein the first spacing member comprises a plurality of first positioning formations, one edge of which can receive or retain the first cladding, and the other edge of which can abut against the wall.

7. A ventilator according to claim 6, wherein the first positioning formations are connected to a first panel.

8. A ventilator according to claim 5, 6 or 7, wherein the second spacing member comprises a plurality of second positioning formations, one edge of which can receive or retain the second cladding, and the other edge of which can abut against the first cladding.

9. A ventilator according to claim 8, wherein the second positioning formations are connected to a second panel.

10. A ventilator according to any of claims 1 to 4, further comprising a positioning member which can be secured to the wall or the roof structure.

11. A ventilator according to claim 10, when dependent upon claim 3, wherein the first and second spacing members are secured to the positioning member.

12. A ventilator according to claim 10 or 11, wherein the positioning member comprises a body provided with first and second positioning formations.

13. A ventilator according to claim 12, when dependent upon claim li, wherein the first spacing member is secured to the first positioning formation.

14. A ventilator according to claim 12 or 13, when dependent upon claim 11, wherein the second spacing member is secured to the second positioning formation.

15. A ventilator according to any of claims 12 to 14, when dependent upon claim 11, wherein the first positioning formation and the first spacing member are provided with cooperating formations to facilitate securing to one another.

16. A ventilator according to claim 15, wherein the cooperating formations provide a snap-fit between the first spacing member and the first positioning formation.

17. A ventilator according to any of claims 12 to 16, when dependent upon claim 11, wherein the second positioning formation and the second spacing member are provided with cooperating formations to facilitate securing to one another.

18. A ventilator according to claim 17, wherein the cooperating formations provide a snap-fit between the second spacing member and the second positioning formation.

19. A ventilator according to any of claims 10 to 18, wherein the positioning member is provided with at least one aperture to facilitate securing to the wall or roof structure by fixing means.

20. A ventilator according to any of claims 10 to 19, when dependent upon claim 11, wherein the relative position of the positioning formations on the body is such that when the first and second spacing members are attached thereto, the first and second spacing members can space the first and second claddings at the required distances from one another and from the wall.

21. A ventilator according to any of claims 10 to 20, when dependent upon claim 11, wherein the body of the positioning member further includes a third positioning formation disposed between the first and second positioning formations, said third positioning formation assisting with the spacing of said first and second spacing members from one another.

22. A ventilator according to claim 21, wherein the third positioning formation is movable relative to the rest of the body.

23. A ventilator according to claim 22, wherein the third positioning formation is pivotably mounted to the body.

24. A method of ventilating a roof structure of the type which is arranged in abutment with a wall and having first and second cladding materials which may be disposed in overlapping relationship with one another, said method comprising: (a) securing a positioning member to the wall; (b) securing the first cladding to a first spacing member and securing the first spacing member to the positioning member to define a first ventilation path between the first cladding and the wall, said first ventilation path communicating at one end with an interior of the roof structure; and (c) securing the second cladding to a second spacing member and securing the second spacing member to the positioning member, to define a second ventilation path between the second cladding and the first cladding, said second ventilation path communicating at one end with an external environment and at the other end with the first ventilation path.

25. A ventilator according to claim 24, wherein the first cladding is secured to the first spacing member before the first spacing member is secured to the positioning member.

26. A method according to claim 24 or 25, wherein the second cladding is secured to the second spacing member before the second spacing member is secured to the positioning member.

27. A ventilator for use in the ventilation of a roof structure of the type which is arranged in abutment with q ;all, said ventilator comprising first and second ventilation members and a positioning member, the positioning member comprising a body and first and second positioning formations, the positioning member being adapted to be secured to the roof structure or the wall, the first positioning formation being adapted to position the first ventilation member from the wall to define a first ventilation path between the wall and the first ventilation member, and the second positioning formation being adapted to position the second ventilation member from the first ventilation member to define a second ventilation path between the first and second ventilation members, where the first ventilation path communicates at one end with the second ventilation path and at the other end with an interior of the roof structure, and the second ventilation path communicates at one end with the first ventilation path and at the other end with an external environment.

28. A ventilator according to claim 27, wherein the first positioning formation and the first ventilation member are provided with cooperating formations facilitate securing to one another.

29. A ventilator according to claim 28, wherein the cooperating formations provide a snap-fit between the first venti1ation member and ke first positioning formation.

30. A ventilator according to claim 27, 28 or 29, wherein the second positioning formation and the second ventilation member are provided with cooperating formations to facilitate securing to one another.

31. A ventilator according to claim 30, wherein the cooperating formations provide a snap-fit between the second ventilation member and the second positioning formation.

32. ventilator according to any of claims 27 to 31, wherein the positioning member is provided with at least one aperture to facilitate securing to the wall or roof structure by fixing means.

33. A ventilator according to any of claims 27 to 32, wherein the relative position of the positioning formations on the body is such that when the first and second ventilation members are attached thereto, the first and second ventilation members are spaced at the required distances from one another and from the wall.

34. A ventilator according to any of claims 27 to 33, wherein the body of the positioning member further includes a third positioning formation disposed between the first and second positioning formation, said third positioning formation assisting with the spacing of said first and second ventilation members from one another.

35. A ventilator according to claim 34, wherein the third positioning formation is movable relative to the rest of the body.

36. A ventilator according to claim 35, wherein the positioning member is pivotably mounted to the body.

37. A ventilator substantially as herein described with reference to and as shown in the accompanying drawings.

38. A method of ventilating a roof structure substantially as herein described with reference to and as shown in the accompanying drawings.