GB2160557A

GB2160557A - Clad roof construction

Info

Publication number: GB2160557A
Application number: GB08415655A
Authority: GB
Inventors: Malcolm Robert Wallis; David Anthony Ward
Original assignee: WARD BROTHERS
Current assignee: WARD BROTHERS
Priority date: 1984-06-19
Filing date: 1984-06-19
Publication date: 1985-12-24
Also published as: GB8415655D0

Abstract

A clad roof construction comprises a plurality of spaced parallel purlins (13), outer cladding (34), inner cladding (30) and thermal insulating material (33) between the inner and outer cladding, and at least one support element (14, 15) extending between a pair of adjacent purlins (13) and controlling movement of the adjacent purlins towards and away from each other; the inner cladding (30) being supported by the or each support element (14, 15). <IMAGE>

Description

SPECIFICATION Clad roof construction Description of invention This invention relates to a clad roof construction, hereinafter referred to as being of the kind specified, comprising a plurality of spaced parallel purlins, outer cladding, inner cladding and theremal insulating material between the inner and outer cladding.

Hitherto such a clad roof construction has usually comprised an inner cladding next to the purlin, a spacer supported on the inner cladding, thermal insulating material next to the inner cladding and extending over the spacer and the outer cladding being next to the insulating material, and fastening means, such as a hook bolt, extending through the outer cladding, insulation and inner cladding to engage with a lip on the purlin to fix the cladding thereto. Such a clad roof construction is generally known as an "over purlin" type.

Whilst this prior construction permits of fixing from above, without the need to allow access from within the building, a problem is encountered with the increasing need for high insulation properties in the external envelope of buildings. If efforts are made to increase the insulation value, with an "over purlin" clad roof construction as described above, by simply increasing the amount of insulating material and hence the gap between the inner and outer cladding, this leads to instability of the construction both during the erection and in service under applied loads.

It is accordingly an object of the invention to provide a clad roof construction which permits of desired thermal insulation properties, together with adequate stability, ease of erection and economical use of material.

This aim is achieved according to the present invention by providing a clad roof construction comprising a plurality of spaced parallel purlins, outer cladding, inner cladding and thermal insulating material between the inner and outer cladding, wherein at least one support element extends between a pair of adjacent purlins and the inner cladding is supported by the or each support element.

Usually the or each support element controls movement between the purl ins of said pair towards and away from each other.

The thermal insulating material may be supported by the inner cladding.

The outer cladding may be supported by the purlins.

The support element may extend between the purlins parallel to a plane containing parts of the purlins which support the outer cladding.

The support element may have opposite end parts each engaged in an aperture in the associated purlin and the wall of each aperture being received between a pair of abutments, the abutments of said pair being spaced apart longitudinally of said axis of the support element so that the purlins are restrained against rotation about an axis coincident with or parallel to the longitudinal axis thereof and are held in parallel relation.

The support elements may be connected to the purlins at approximately the mid-point of the web or at a position which is closer to the lower flange than the mid-point of the web.

The support element may comprise an elongate body having a longitudinal axis, a web, and an outwardly extending limb at each longitudinal edge of the web, each end part of the body having first and second pairs of abutments, the abutments of each pair being spaced apart longitudinally of said axis of the support element, the abutments comprising the edges of slots formed in said limbs and/or the web, so that the abutments of the first pair are spaced apart from the abutments of the second pair in a direction transverse to the longitudinal axis of the purlins, each of the purlins of said pair of purlins having at least one aperture therein, which receives one of said end parts of the support element with the web of the support element extending transversely of the longitudinal axis of the purlin, the abutments of said first and second pairs of abutments of each end part engaging opposite faces of a wall on the associated structural member around said aperture so that each of the purlins are restrained against rotation about an axis coincident with, or parallel to, the longitudinal axis thereof and are held in parallel relation.

At least one pair of said abutments may be spaced from the longitudinal axis of the purlin in a direction towards the lower side thereof.

The support element may have resilient means associated therewith to retain said abutments in engagement with said faces of the purlin.

The purlin may comprise a pair of spaced generally parallel flanges interconnected by a web.

The upwardly facing surface of the upper flange of the purlin may support the outer cladding.

The inner cladding may comprise a liner tray.

The inner cladding may be fastened to the support element by suitable fastening means, for example by pop rivets, to rivet the inner cladding to a flange of the support element.

Alternatively, a further member may extend between the purlins above the inner cladding to trap the inner cladding between the further members and the support elements.

The further members may also serve as additional support elements.

The outer cladding may be fastened to the purlins by suitable fastening means such as self-tapping screws or clips, and the fastening means may fasten the outer cladding to the upper flange of the purlin.

Further, alternatively, the liner tray may be secured in position by providing a thermally insulating block on top of the thermal insulating material to engage with the underside of the outer cladding so as to trap the inner cladding between the support element and the thermal insulating material.

The thermal insulating material may be supported on the inner cladding.

A vapour barrier may be provided between the inner cladding and the thermal insulating material.

A thermal spacer may be provided between the purlin and the outer cladding to prevent or to reduce cold bridging.

The thermal insulating material may extend between the purlin and the outer cladding or alternatively may not do so.

In the roof construction according to the present invention, the outer cladding is located either directly in contact with the upper surface of the purlins, or closely spaced therefrom by virtue of the presence of a thermal spacer, but in either case, is not widely spaced above the purlins. This is because the inner cladding and thermal insulating material are located below the part of the purlin which supports the outer cladding and hence the stability of the clad roof construction is good and the only constraint imposed upon the distance between the inner cladding and the outer cladding, and thus available to be occupied by thermal insulating material, is the distance available between the upper surface of the purlin and the upper surface of the support element which is typically half the height of the purlin but can be greater where the support element is connected to the purlin closer to the lower side thereof.

In addition, because the outer cladding is secured directly to the top of the purlin or is secured thereto with only the imposition of a relatively low thermal spacer, the outer cladding provides further stability to the purlins to restrain them from rotation about their longitudinal axis or an axis parallel thereto and to restrain them in parallel relationship, and of course the support elements give stability to the purlins erection and additional stability in service so that the combination of stability provided by the support elements and the cladding in service provides a very stable clad roof construction.

The invention will now be described in more detail by way of example, with reference to the accompanying drawings, wherein: Figure 1 is a perspective view, partly broken away, of a roof structure prior to cladding to provide a clad roof construction embodying the invention; Figure 2 is a fragmentary perspective view showing the interconnection of two support elements and purlins of Figure 1; Figure 3 is a fragmentary cross-sections view on the line 3-3 of Figure 2; Figure 4 is a fragmentary side elevation of the purlin of Figure 2; Figure 5 is a side view of an end part of one of the support elements of Figures 2 and 3; and Figure 6 is a fragmentary perspective view to an enlarged scale of part of the roof structure shown in Figure 1 during cladding with parts omitted for clarity.

Referring to the drawings, a roof structure of a building construction comprises three roof trusses each indicated generally at 10 supported by vertical column supports 11. The trusses provide roof principals 12 on which rest purlins, some of which are shown at 13, the purlins 13 each being in the form of cold-rolled steel joists of stigma section.

The purlins 13 are interconnected by support elements which comprise restraint ties 14, 15 which serve to support the purlins 13 so that adjacent purlins 13 are parallel along their length between adjacent roof principles 12, (which provide support members), and also, as hereinafter to be described, to prevent rotation of the purlins 13 about their longitudinal axes one of which is indicated at A1. In Figure 1, the interconnection of the restraint ties 14, 15 and purlins 13 is illustrated diagrammatically but is shown in more detail in Figures 2-5 which are now referred to.

Each purlin 13 is provided in a web 13a thereof, with an aperture 16 at the locations to where it is desired to connect the restraint ties 14, 15. Each aperture 16 is of rectangular configuration having its major axis vertical.

Each restraint tie 14, 15 is of channel configuration comprising a web part 17 interconnecting parallel spaced flanges 18. An end part 19 of each restraint tie 14, 15 is provided with a narrow rectangular slot 15 in each limb 17, the edges of one slot 20 providing a first pair of abutment surfaces 21, 22 which are spaced apart longitudinally of the longitudinal axis A2 of the restraint tie, and the edges of the other slot 20 provide a second pair of abutment surfaces 21a, 22a similarly spaced apart longitudinally and spaced laterally of the axis A2 from the first pair 21, 22.

One of the restraint ties, in the present example the restraint tie 15, is provided with a resilient biasing means in the form of a leaf spring 23 fixed at one end 24 to the end part of the restraint tie.

The limbs 18 reduce in height towards the free end 25 of their associated restraint tie 14, 15 from a position 26 adjacent to but spaced from the slots 20 towards the free end 25.

In use, a restraint tie 15 is introduced into the aperture 16 until the part of the wall 27 of the web 17 surrounding the aperture 16 is aligned with the slots 20 and the wall part 27 is then caused to enter the slots 20 so that the abutment surfaces 21, 22 engage oppositely facing surfaces of the wall part 27.

A second restraint tie 14 is then introduced into the aperture 16 from the opposite side and is forced by the leaf spring 23 against the opposite side of the aperture 16 in engagement with the restraint tie 15 until the wall part 27 becomes aligned with the slots 20 in the restraint tie 14, whereupon the wall part 27 is caused to enter the slots 20 so that again the abutments 21, 22 engage oppositely facing surfaces of the wall part 27.

The abutments 21, 22 are retained in engagement with their associated surfaces of the wall 27 by means of the leaf spring 23.

It will be seen that the abutments 21, 22 of said one pair engage the wall part 27 at positions which are spaced laterally relative to the axis A1 from the abutments 21a, 22a of said second pair, as indicated at 28, 29 in Figure 2.

Because of the engagement of opposite surfaces of the wall part 27 of the purlin 13 by abutments 21, 22 at positions which are spaced transversely relative to the axis A1, considerable resistance to rotation of the purlin 13 about the axis A1 or any axis thereto, is achieved. This is particularly important before cladding is affixed and is an important advantage of the invention compared with previously known systems which do not give adequate stability to the structural members before cladding.

Referring now to Figure 6, the roof structure thus erected as described hereinbefore is clad by positioning inner cladding 30 so as to be supported on the top flange of each restraint tie 14, 15. The inner cladding is in the form of a liner tray comprising a sheet of plastics or other suitable material of generally corrugated configuration, the corrugations being of trapezoidal configuration as shown in Figure 6. The liner trays are secured to the restraint ties by pop rivets 31. Alternatively, the inner cladding may be secured in position by providing further restraint ties, of generally similar configuration to the restraint ties 14 and 15 but of smaller crosssection and made of thinner material, and positioned above the liner trays so as to trap the liner trays between such further restraint ties and the associated restraint tie 14, 15 upon which the liner tray is supported.

A sheet of material 32 impervious to water vapour is then laid on the inner cladding 30 to provide a vapour barrier.

On top of the vapour barrier 32 is provided a layer of thermal insulating material 33. (When further restraint ties are provided to secure the inner cladding in position, they may extend above or below the thermal insulating material 33).

In the present example, the thermal insulating material 33 extends over the upper flange 13b of the purlins. There is then positioned on top of the insulating material covering the flanges 13b, outer cladding 34, with the interposition, if desired, of suitable thermal insulating blocks 35.

The outer cladding comprises, in the present example, a metal sheet provided with edge flanges which co-operate to provide a generally corrugated appearance to the upper surface of the roof, the corrugations again having trapezoidal configuration. The panels of which the outer cladding is made are secured to the purlins 13 by means of self-tapping screws 36 passed downwardly through the cladding 34 and into the upper flange 13b of the associated purlin 13. Alternatively, if desired, the outer cladding panels 34 may be clipped to the flanges 13b of the purlins 13 by clips 37 which If desired, the thermal blocks 35 may be omitted if adequate thermal insulation is provided by the compressed insulation material 33 between the flange 13b and the outer cladding.

Further alternatively, the insulation material 33 may not extend over the flange 13b in which case the outer cladding may be fixed directly to the flange 13b where a thermal break therebetween is not required, or with the interposition of a thermal block 35.

The inner cladding may be made of any suitable material such as metal, plasterboard, semi-rigid fibreglass or mineral wool, with a suitable layer of facing, polyurethane, polystyrene insulating boards or other materials. The outer cladding may be made of metal, plastics coated metal, plastics material, asbestos cement or any other suitable material, and both the inner and outer claddings may be made of any desired configuration.

The thermal insulating material 33, in the present example comprises a glass fibre quilt but may be made of any other suitable thermal insulating material.

Because the outer cladding 36 is spaced closely above the flanges 13b of the purlins 13, the resulting clad roof construction is mechanically stable and the outer cladding 34 contributes to maintaining the purlins stable, i.e. restraining them from rotation about their longitudinal axes or an axis parallel thereto and also to maintain them mutally parallel and of course the restraint ties 14 and 15 also contribute to this. At the same time, a high degree of insulation can be attained because there is sufficient space between the upper flange 18 of the restraint ties 14, 15 and the undersurface of the cladding 34 to accommodate the liner tray and a relatively great thickness of thermal insulating material.

Although in the present example the restraint ties have been shown connected to the purlins so that the central longitudinal axis of the purlins and restraint ties intersect, if desired, the restraint ties could be connected to the purlins at a position closer to the lower sides thereof to increase still further the space available for thermal insulation material.

Moreover, the restraint ties may be connected to the purlins in a manner different to that described, but it is preferred that the restraint ties extend parallel to a plane containing part of the purlins which supports the outer cladding. If the purlins are inclined to such a plane, then spacers or inner cladding of appropriate configuration is required so that the inner cladding can be supported on such inclined restraint ties. Where the restraint ties are not parallel to said plane, the space available for thermal insulating material is material is reduced at least at the higher end of each restraint tie and throughout the area where spacers or inner cladding panels shaped to provide an upper surface generally parallel to said plane are provided.

In the present example, restraint ties are provided at intervals of between 2000mm and 2400mm which is a relatively close spacing, and further contributes to the mechanical stability of the roof construction.

In the above example the support elements serve also as restraint ties (sag rods). However in certain cases the purlins may not require to be restrained by the support elements and in this case the support elements serve solely to support the inner cladding. In such cases, their connection to the purlins may be such that they are incapable of serving also as restraint ties.

The features disclosed in the foregoing description, or the accompanying drawings, expressed in their specific forms or in terms of a means for performing the disclosed function, or a method or process for attaining the disclosed result, or a class or group of substances or compositions, as appro priate, may, separately or in any combination of such features, be utilised for realising the invention in diverse forms thereof.

Claims

1. A clad roof construction comprising a pluraiity of spaced parallel purlins, outer cladding, inner cladding and thermal insulating material between the inner and outer cladding, at least one support element extending between a pair of adjacent purlins and controlling movement between the purlins of said pair towards and away from each other, the inner cladding being supported by the or each support element.

2. A roof construction according to Claim 1 wherein the thermal insulating material is supported by the inner cladding.

3. A roof construction according to Claim 1 or Claim 2 wherein the outer cladding is supported by the purlins.

4. A roof construction according to Claim 3 wherein the or each support element extends between the purlins parallel to a plane containing parts of the purlins which support the outer cladding.

5. A roof construction according to any one of Claims 1 to 4 wherein the support element has opposite end parts each engaged in an aperture in the associated purlin and the wall of each aperture is received between a pair of abutments of the respective end part, the abutments of said pair being spaced apart longitudinally of said axis of the support element so that the purlins are restrained against rotation about an axis coincident with or parallel to the longitudinal axis thereof and are held in parallel relation.

6. A roof construction according to any one of the preceding claims wherein the support element is connected to the purlins at approximately the mid-point of the web or at a position of each purl in which is closer to the lower flange than the midpoint of the web.

7. A roof construction according to any one of the preceding claims wherein the support element comprises an elongate body having a longitudinal axis, a web, and an outwardly extending limb at each longitudinal edge of the web, each end part of the body having first and second pairs of abutments, the abutments of each pair being spaced apart longitudinally of said axis of the support element, the abutments comprising the edges of slots formed in said limbs andfor the web, so that the abutments of the first pair are spaced apart from the abutments of the second pair in a direction transverse to the longitudinal axis of the purlins, each of the purlins of said pair of purlins having at least one aperture therein, which receives one of said end parts of the support element with the web of the support element extending transversely of the longitudinal axis of the purlin, the abutments of said first and second pairs of abutments of each end part engaging opposite faces of a wall on the associated structural member around said aperture so that each of the purlins are restrained against rotation about an axis coincident with, or parallel to, the longitudinal axis thereof and are held in parallel relation.

8. A roof construction according to Claim 7 wherein at least one pair of said abutments is spaced from the longitudinal axis of the purlin in a direction towards the lower side thereof.

9. A roof according to Claim 7 or Claim 8 wherein the support element has resilient means associated therewith to retain said abutments in engasgement with said faces of the purlin.

10. A roof construction according to any one of the preceding claims wherein the purlins comprise a pair of spaced generally parallel flanges interconnected by a web.

11. A roof construction according to Claim 10 wherein the upwardly facing surface of the upper flange of the purlin supports the outer cladding.

12. A roof construction according to any one of the preceding claims wherein the inner cladding comprises a liner tray.

13. A roof construction according to any one of the preceding claims wherein the inner cladding is fastened to the support element by fastening means.

14. A roof construction according to Claim 13 wherein said fastening, means comprises pop rivets, to rivet the inner cladding to a flange of the support element.

15. A roof construction according to Claim 13 wherein said fastening means comprise a further member which extends between the purl ins above the inner cladding to trap the inner cladding between the further members and the support elements.

16. A roof construction according to Claim 15 wherein the further members serve as additional support elements.

17. A roof construction according to any one of the preceding claims wherein the outer cladding is fastened to the purlins by fastening means.

18. A roof construction according to Claim 17 wherein the fastening means fasten the outer cladding to an upper flange of the purlin.

19. A roof construction according to Claim 12 wherein the liner tray is secured in position by providing a thermally insulating block on top of the thermal insulating material to engage with the underside of the outer cladding so as to trap the inner cladding between the support element and the thermal insulating material.

20 .A roof construction according to any one of the preceding claims wherein the thermal insuiating material is supported on the inner cladding.

21. A roof construction according to Claim 19 wherein a vapour barrier is provided between the inner cladding and the thermal insulating material.

22. A roof construction according to any one of the preceding claims wherein a thermal spacer is provided between the purlins and the outer cladding to prevent or to reduce cold bridging.

23. A roof construction according to Claim 21 wherein the thermal insulating material extends between the purlins and the outer cladding.

24. A roof construction substantially as her einbefore described with reference to and as shown in the accompanying drawings.

25. Any novel feature or novel combination of features disclosed herein and/or shown in the accompanying drawings.