Roofing system

Abstract

 A method of constructing a roof on top of a building, the method comprising: fixing two lower spandrels, one on each of two opposite sides of the top of the building, the lower spandrels each having an upper and a lower parallel side and two sloping sides; fixing ceiling panels to the upper parallel sides of both of the spandrels to form a platform; fitting upper spandrels above the respective lower spandrels on the ceiling panels; and fitting gable to gable roofing panels to bridge the gap between the sloping sides of the spandrels to form a roof.

Description

Introduction

[0001] The present invention relates to a roofing system and to a method of constructing a roof and a roofing panel.

Background

[0002] Traditionally roofs are made by positioning a series of roof rafters at spaced intervals across the roof line of a building, connecting them to a wallplate and tying the heads of the wallplate together with a ceiling joist which in turn supports the ceiling lining. An alternative and more popular approach is the use of trussed rafters which are prefabricated offsite and which sit on and are fixed to the wallplate and braced with diagonal and longitudinal braces to keep the trussed rafters vertical and to distribute the forces back to flanking walls. An outer pitched surface is then sometimes boarded and is then covered with weatherproof roofing material such as roofing felt and tiles.

[0003] Traditional trussed rafters can be heavy and take up a large amount of space because the webs forming the trusses in the loft area render it unusable for living accommodation. Insulation is usually added piece by piece after the roof is constructed, preferably between the bases of the trusses and under the roofing material and this is time consuming on site.

[0004] There is an increasing need for lower cost housing in which a larger proportion of a building is useable as living space. There is also an increasing need for better insulated buildings and constructions in which a minimum of non-living space is heated, so as to make heating more economical and to reduce the carbon footprint of new buildings both from an ecological point of view and to meet modern legal standards.

[0005] A roofing system is described in GB 2391026 in which two spandrels are positioned on opposite sides of a building at the roof line and ready prepared insulated and lined panels are used to construct the roof. They are fastened to one or both of the sloping edges of the spandrels. Intermediate panels do not span the spandrels but rest on the other panels and provide openings for window frames to be fitted. This modular system is relatively quick to assemble compared to using trusses and has the advantage that insulation can be built into the panels in the factory. However tolerances with such a system are critically important and the system requires a considerable amount of screwing and nailing to restrain the panels from sliding down the roof line. This is a particular problem because the preconstruction with boarding and insulation makes them heavy. Thus this known system is labour intensive and time consuming to assemble.

Summary of the Invention

[0006] According to the present invention, there is provided a method of constructing a roof on top of a building, the method comprising: fixing two lower spandrels, one on each of two opposite sides of the top of the building, the lower spandrels each having an upper and a lower parallel side and two sloping sides; fixing ceiling panels to the upper parallel sides of both of the spandrels to form a platform; fitting upper spandrels above the respective lower spandrels on the ceiling panels; and fitting gable to gable roofing panels to bridge the gap between the sloping sides of the spandrels to form a roof.

[0007] Preferably a small wall is constructed along the other two sides of the top of the building and the sloping sides of the spandrels are stubbed to match the height of the small walls.

[0008] In one embodiment the ceiling panels are closed panels with insulation inside them.

[0009] A groove may be provided in the sloping edge of one of the spandrels to locate the roofing panels.

[0010] Advantageously at least one roofing panel has an opening to accommodate a window.

[0011] In addition the roofing panel may have at least one flitch beam screwed through to the spandrel to transfer the load. This may comprise a sheet of steel sandwiched between two wooden beams and it is preferably located in the plane of the panel. Located across the top of a window opening it will resist bending of the panel in the plane of the panel, and located perpendicular to the top of the window, within the panel, will resist bending of the panel out of the plane of the panel. Preferably flitch beams in both orientations are provided.

[0012] Advantageously the roofing panels are butt jointed and are fastened together by long screws driven through from the underside to pull the panels together.

[0013] Roofs constructed with these panels have a cavity running along their length which can accommodate insulation.

[0014] The deeper the panel the more insulation can be installed in a roof, increasing the thermal resistance of the roof panel and decreasing the U value to meet modern building standards. Using the invention allows the roof panel depths to be increased without using thicker timbers, with consequent savings in cost and weight.

Specific embodiments

[0015] For a better understanding of the present invention and to show how the same may be carried into effect, reference will now be made, by way of example, to the accompanying drawings, in which:

Figures 1 to 11 illustrate successive steps in the roofing method according to the invention in perspective views of the top of a building;

Figures 4 and 6 show detail of part of Figure 5; and

Figure 12 is a cross section through roofing panels according to the invention.

Detailed description of drawings

[0016] Figure 1 illustrates the top of a building 20 before a roof has been added. The building 20 is constructed to have a generally flat and level top surface 21. On top of this a plurality of beams 60 are laid spanning the top edges 71, 72 of the long parallel sides of the building 20. These beams 60 each comprise two elongate parallel timbers 81, 82 joined together along their length by V-shaped metal struts 83. At each end is a double timber connecting plate 84 and a timber spacer 85 is fixed in the middle of long beams to prevent sagging.

[0017] The beams 60 are preferably pre-prepared in a factory so that they can simply be hoisted into position on site saving construction time and allowing for more accurate manufacturing tolerances and consistency. This also makes it easier to construct the top of the building to be level and square. Hence an improved base is provided on which to construct a roof and makes a level floor for any living space in the roof. The beams are then decked with boards 76 as shown in Figure 2.

[0018] The beams 60 may also be pre-grouped in a factory into modular floor cassettes which can be pre-booked and optionally insulated to save time on site. A hole 19 is provided for a staircase (not shown).

[0019] The next step in construction of the roof is to build two relatively low timber frame walls 22 on opposite short sides of the building 20.

[0020] As shown in Figure 3 two lower spandrels 23 are then put into position along the long edges of the top of the building 20, abutting the side walls 22. Each of these spandrels have two horizontal generally parallel sides 24 and 25 and two sloping sides 26 and 27. The sloping sides 26 and 27 are stubbed at 70 where they meet the timber frame walls 22.

[0021] The building 20 illustrated is an end of terrace building and in Figure 3 the left-hand spandrel is an external one. This external spandrel 23 is constructed in three ply timber typically with 97mm inner and outer top chords and a 72mm internal top chord resulting in a locater channel 28 as shown more clearly in the enlarged drawing shown in Figure 4.

[0022] Subsequently a decked ceiling cassette 29 is craned into position and located using the locator channel 28 on the external spandrel 23 as shown in Figure 5. This ceiling cassette 29 is preferably pre-insulated and decked with boards 76. Preferably ceiling noggins 87 which meet the roof panels are angle cut, as shown in Figures 5 and 6, and capped with OSB. Making the ceiling cassette 29 fully insulted makes the roof space above into a cold roof space and avoids unnecessary heating of the loft space in the building.

[0023] Upper spandrels 30a and 30b are then lifted into position as shown in Figure 7. The outer upper spandrel 30a also comprises a middle locator groove 90. The upper spandrels 30a and 30b are triangular shaped.

[0024] Figure 8 shows a first roof panel 31 positioned to bridge the gap between the two spandrels 23.

[0025] In Figure 9 a second roof panel 33 is positioned above the first panel 31, again bridging the two lower spandrels 23 and also the two upper spandrels 30a and 30b. This second roof panel 33 abuts the first panel and has two openings 34 for installation of dormer windows.

[0026] A third roof panel 35 is then lifted into place again bridging the two upper spandrels 30a, 30b, and abutting the second roof panel 33. An eaves panel 37 and an apex panel 39 are then positioned. The panels are preferably pre-boarded as shown in the Figures. Corresponding roof panels are positioned along the other sloping side of the roof until all of the roof panels are in place as shown in Figure 11.

[0027] A cross section of a roofing panel is shown in Figure 12. In the example shown the eaves panel 32 and the apex panel 39 are relatively small, i.e. less high; the third panel 35 is of a standard size; and the second panel 33 is extra large so as to accommodate a dormer window opening or openings 34. To provide additional strength for window openings flitch beams 37 and 38 are provided. These are screwed through the timber and the OSB. Flitch beam 37 is arranged in the plane of the panel above and across the dormer window opening 34 to prevent sagging of the panel in the line of the roof. Flitch beam 38 is provided perpendicular to flitch beam 37 in the plane of the panel to prevent sagging of the panel components into the roof space. These flitch beams are composed of a thin steel sheet sandwiched between two timber posts. The butt connection between roofing panels is shown for example at 91 and a locator piece is shown at 92. This is a thin elongate piece adjacent the spandrels.

[0028] Dormer windows are then installed in the relevant openings such as 34 and the whole roof is then completed with felting and weatherproof roofing material such as tiles.

Claims

1. A method of constructing a roof on top of a building, the method comprising:

fixing two lower spandrels, one on each of two opposite sides of the top of the building, the lower spandrels each having an upper and a lower parallel side and two sloping sides;

fixing ceiling panels to the upper parallel sides of both of the spandrels to form a platform;

fitting upper spandrels above the respective lower spandrels on the ceiling panels; and

fitting gable to gable roofing panels to bridge the gap between the sloping sides of the spandrels to form a roof.

2. A method according to claim 1 comprising constructing a small wall along each of the two other opposite sides of the top of the building.

3. A method according to claim 2 wherein the sloping sides of the spandrels are stubbed to match the height of the small walls.

4. A method according to claim 1, 2 or 3 wherein the ceiling panels are closed panels with insulation inside them.

5. A method according to claim 1, 2, 3 or 4 wherein a groove is provided in the sloping edge of one of the spandrels to locate the roofing panels.

6. A method according to any one of the preceding claims wherein at least one roofing panel has an opening to accommodate a window.

7. A method according to claim 6 wherein the roofing panel has at least one flitch beam screwed through to the spandrel to transfer the load.

8. A method according to claim 7 wherein the flitch beam comprises a sheet of steel sandwiched between two wooden beams.

9. A method according to claim 7 or 8 wherein one flitch beam is located across the top of a window opening to resist bending of the panel in the plane of the panel.

10. A method according to claim 7, 8 or 9 wherein one flitch beam is located perpendicular to the top of a window opening within the panel, to resist bending of the panel out of the plane of the panel.

11. A method according to any one of the preceding claims wherein the roofing panels are butt jointed.

12. A method according to any one of the preceding claims wherein the roofing panels are fastened together by long screws driven through from the underside to pull the panels together.

Drawing