Background to the Invention Roofs fall into two categories, namely pitched roofs and flat roofs. Pitched roofs are advantageous insofar as water runs off them more easily, they have few maintenance requirements, and are generally thought to be leasing to the eye. The advantages of flat roofs are that they are cheap to install, and can be used where there is a height restriction on the building which would not allow the building to function properly and have a roof pitched sufficiently to provide for the run off of water. Also, the building does not need to be of such substantial construction if a flat roof is to be used, because a flat roof is much lighter in weight than a traditional pitched roof.

Flat roofs have very high maintenance costs, because the weatherproof material with which they are covered (usually roofing felt) needs to be replace regularly, typically once every ten years. As well as being costly, such work disturbs the users of the building, and is dangerous. Leaking flat roofs tend to rot, making it unsafe to walk on any unsupported part of the roof. It is not uncommon for a roofer to fall through a rotten roof. The likelihood of a building having a flat roof suffering leakage is far greater than that of a pitched roof and therefore, in many cases the owners of buildings with flat roofs would like to have them converted to pitched roofs. Often this is not possible, either because the building is not constructed to withstand the weight of a pitched roof, or because the constraints of the building would not allow a pitched roof to have sufficient pitch to provide for run off of water.

When the angle of pitch of a pitched roof falls below a certain limit, capillary action tends to cause water, which should run off the roof, to seep back between the overlapping roofing panels or sheets. It is the angle at which this capillary action occurs which is one factor determining the lowest angle of pitch.

Another disadvantage of known roofs, both pitched and flat, is that a structure must be provided to carry the weight of the weather proofing material, be that felt, panels, or sheets. The weather proofing materials do not themselves add significantly to

the strength of the assembled roof. Additionally, many pitched roofs are designed for a particular roofing material, slate for example, which may be considerably lighter than other roofing materials. However, when it becomes necessary for the roofing material to be replace the owner of the building may wish to use a different material for reasons of cost, for example concrete panels. This may not be possible without changing the roof structure to carry the additional weight of the different roofing material. Of course, this adds to the cost of replacing the roof.

A further disadvantage of known roofs, both pitched and flat, is that they take a considerable time to erect.

GB 2 094 365 describes a roofing system which attempts to overcome some of the problems mentioned above. However, this roofing system requires the use of mastic between the sheets of roofing material to provide for sealing of the roof.

BE 888 231 describes a roofing system having overlapping panels which simulate tiles. The upper edges of these panels are provided with raised portions which serve to prevent seepage of water by capillary action.

US 4 226 070 discloses plastics roofing panels which simulate the appearance of Spanish or Mission tiles and which fit together with a very small degree of overlap, rendering the likelihood of water seepage very high at low roof pitches.

It would be advantageous to provide a roofing system which does not suffer the disadvantages of known systems.

Summary of the Invention The invention provides a roofing system A roofing system for a roof having a pitch of at least 5°, the system comprising a plurality of lightweight panels fitted together so that a part of one panel rests on and overlaps the next, characterised in that each panel has a downwardly-projecting lip at its lower end and a stepped portion at its upper end, the height of the step being at least equal to the height of the lip, the length of the stepped portion and the height of the lips being sufficient to prevent water seeping upwardly between the panels, in use.

The pitch of the roof may be substantially 10 degrees or greater. It has been found that a roof having a pitch of substantially 10 degrees or greater is more aesthetically leasing than a roof having a smaller angle of pitch.

Preferably, the roofing panel is fabricated from glass reinforced plastic.

Alternatively, the panel could be formed from a suitable metal such as steel or a lightweightalloy.

The panel may be formed in any profile to simulate any desired style of roofing panel or sheet. By forming the panel with at least one raised arch therein, the strength of the panel may be increase.

The length of the downward extending lip may be increased so that it overhangs the wall of the building on which it is mounted to such a degree that it acts as a vermin trap.

The panel may be provided with at least one hole or weakened area to receive a suitable fastening means, such as a roofing nail, for fastening the panel to a lath, a wall, or another panel. One panel is provided with 15 such holes or weakened areas.

One or both sides of the panel may have a downward extending lip.

A further aspect of the invention provides a beam to support a plurality of the said roofing panels.

_Preferably, the beam is fabricated from glass reinforced plastic. Alternatively, the beam could be formed from a suitable metal such as steel or a lightweight alloy.

Preferably, the beam is provided with a series of steps, wherein the shape of a surface of each step corresponds to the shape of a part of the panel.

The beam may be provided with at least one hole or weakened area to receive a suitable fastening means, thereby providing for the fastening of panels to the beam.

The beam may be provided with further fastening means to provide for fastening of the beam to a building. The said fastening means may comprise a bracket, a strap or a block of wood to which a bracket, strap or the like may be attached.

The beam may be provided with a recess or cut away portion to receive a lath.

The beam may further comprise a block of material such as wood to provide for the attachment of other objects to the beam.

The beam may comprise a plurality of beam sections, each beam section being provided with attachment means for attachment of one beam section to another. The attachment means may comprise apertured plates, and a pin or bolt to pass through the apertures of plates of respective beam sections in order to fasten one to another. The

plates at one or both ends of the beam section may be provided with a plurality of apertures to allow for slight adjustment of position of one beam section relative to another.

The beams may be provided with support members extending from the side or sides thereof. The support members may be in the form of flanges, brackets, or clips.

The support members may be formed integrally with the beams.

Another aspect of the invention provides a roofing system comprising a plurality of roofing panels according to the invention, and a plurality of beams, wherein the panels are mounted on the beams.

Preferably, the beams are beams according to the invention.

The roofing system may comprise insulating means mounted between the said beams. The insulating means may be in the form of insulating panels. The insulating panels may be supported by, or attached to the said support members provided on the beams.

Preferably, laths extend between adjacent beams at longitudinally spaced apart locations. Laths may extend through and between a plurality of adjacent beams.

The roofing system may further comprise a vermin trap attachable to a roofing panel and/or the wall of a building.

The roofing system may further comprise a ridge cap. Preferably, the ridge cap is shaped so as to mate with the roofing panels. The ridge cap may have a central flexible portion so that the ridge cap may be used on roofs having different pitches.

The roofing system may further comprise at least one end cap arranged to fit on to a side of the roof. Advantageously, the or each end cap is provided with apertures or points of weakness to facilitate attachment of the or each end cap to a part of the said roof, or to the building supporting the roof.

In order to increase the strength of the beams of the invention, a brace member may be inserted inside the beam. The shape of the brace member may correspond to the shape of the beam, and be so dimensioned as to fit within the said beam. The brace member may be formed from a suitable material, for example wood.

The roofing panels of the invention are lightweight and can be used at low angles of pitch. They are strong and can withstand the weight of a man walking across

them. The beams enable the roofing system of the invention to be constructed in a very short period of time, and also serve to provide a strong roofing structure. They are lightweight and can be easily manipulated, thereby making construction of the roofing system of the invention relatively simple. Furthermore, the roofing panels can be made in any desired style, for example double roman, single roman, pan tile, Spanish tile, Bainbridge, etc.

As well as being useful for replacing traditional flat roofs, the roofing system of the invention can be incorporated in to the architecture of new buildings. The short time taken to erect a roof according to the invention makes the roofing system particularly useful for roofing temporary structures. In addition, the panels can be used to replace existing slated or tiled roofs. In particular, due to the lightweight of the panels of the invention, they can be used to replace slates on a slated roof without the need to strengthen the roof structure.

Brief Description of the Drawings Figure 1 is an isometric projection of a roofing panel of the invention; Figure 1 a is an enlarged sectional view on line A-A in Figure 1; Figure 2 is a schematic representation of a beam for use in a roofing system according to the invention; Figure 3 is a schematic representation of a part of a beam for use in a roofing system according to the invention; Figure 4 is a schematic representation of a roofing system according to the invention; Figure 5 is schematic representation of an end cap for use in a roofing system according to the invention; Figure 6 is a schematic representation of a ridge cap for use with panels, or in a roofing system, of the invention; Figure 7 is a schematic representation of a vermin trap for use with panels, or in a roofing system, of the invention; Figure 8 is a schematic representation of two beam sections for use in a roofing system according to the invention; and

Figure 9 is a schematic representation of a vermin trap comprising a gutter for use with panels, or in a roofing system, of the invention.

Detailed Description of the Preferred Embodiments Referring now to Figure 1 there is shown a roofing panel 1 having an upper portion 3 having a length a, and a lower portion 2 having a length b, with a step 12 therebetween. The panel 1 is formed from glass reinforced plastic, and is moulded so that the upper portion 3 has a plurality of substantially semi-circular ridges 8 and between adjacent ridges planar portions 7. Similarly the lower portion 2 has a plurality of substantially semi-circular ridges 9 and between adjacent ridges planar portions 6.

The lower portion 2 of the panel 1 has a downwardly extending lip 10 provided with a plurality of cut away portions 13 which correspond in shape to the ridges 9 of lower portion 2. When a roof comprising roofing panels according to the invention is assembled, the lower portion 2 of a first roofing panel 1 sits on top of the upper portion 3 of a second roofing panel 1, the cut away portions 13 of the first panel engaging with the ridges 9 of the second panel. The length a of upper portion 3 is such that when two panels 1 are assembled in the above-mentioned manner, seepage due to capillary action does not occur.

The upper portion 3 is provided with a plurality of apertures 4, one in each ridge 8. A shaped grommet 11, illustrated in Figure 1 a, is moulded on to the underside of each ridge 9 in the lower portion of the panel at a position corresponding to that of the aperture 4 of the next panel, so that, when the panels are installed, the grommets 11 fit into the holes 4 to secure the panels together.

The height of step 12 is one determining factor of the pitch of the roof on which the roofing panels 1 may be used. Additionally, the height of the step 12 influences the rigidity of the roofing panel 1. The greater the height of the step, the more rigid the panel will be.

Referring now to Figure 2, there is shown a beam 15 for use with the panel shown in Figure 1 in a roofing system according to the invention. The beam comprises a plurality of stepped portions each having a raised elongate semi-circular portion 20 and to either side thereof planar portions 16,18. A laterally extending flange 27 is located on one or both sides of the beam 15.

A block of wood 24 is provided in the lower end of the beam 15. This is to provide for the fixation of the beam to the building to be covered. Any suitable attachment means, such as a bracket may be used to secure the beam to the building.

Similarly, a second block of wood may be provided at the other end of the beam 15 for securing that end of the beam to the building.

Where a suspended ceiling is required in the building to be roofed using beams and panels according to the invention, it may be desirable to fix wooden blocks into the beam 15 at a number of locations thereon, so as to provide for the attachment of suspension brackets thereto. Alternatively, suspension brackets may be fixed to the beam in the process of moulding the beam, or otherwise fastened thereto.

Figure 3 shows a portion of a beam similar to that shown in Figure 2, but the corner 17 has been cut away so as to provide a recess into which a lath (not shown) may fit. In the embodiment shown in Figure 3, an aperture 23 is provided so that the lath may pass into the beam. This is a simple means of restricting movement of the lath.

Wall 22 prevents reward movement of the lath, planar portion 18 prevents downward movement of the lath, and the upper and forward internal edges of aperture 23 prevent upward and forward movement of the lath. In another embodiment of the invention the opposite corner 17 is also cut away to permit a lath to be passed right through the beam 15. When a plurality of such beams are arranged in side by side spaced apart configuration a lath can be passed through a number of the said beams thereby adding significantly to the strength of the roof. The panels may be nailed to the laths on either side of the portion 20 of each beam 15.

Referring now to Figure 4, there is shown a portion of a roof constructed according to a roofing system of the invention. The roof comprises a plurality of roofing panels 1 mounted on beams 15. It can be seen that the upper portion 3 of each panel sits on a stepped portion of beam 15. The lower portion 2 is laid on the roof so that it over lies the upper portion 3 of the next roofing panel beneath it. Apertures 11, 21 align and a fixing means can be passed therethrough thereby securing two panels 1 to a beam at one point. A vermin trap 25 is also provided. This is provided with apertures 26 so that the vermin trap may be attached to the lower most roofing panels

of the assembled roof. For the sake of clarity, only one lath 36 is shown joining two beams 15.

Referring again to Figure 4, it can be seen that each of the beams 15 is provided on one or both of its sides with outwardly projecting flanges 27. The left outermost beam is provided with a flange 27 projecting inwardly from its right hand edge, the two central beams 15 are provided with flanges projecting from both edges, and the right outermost beam 15 is provided with a flange 27 projecting inwardly from its left hand edge. The purpose of the flanges 27 is to support an insulating layer which may be in the form of a substantially rigid insulating board 28.

Referring now to Figure 5, there is shown the lower portion of an end cap 30 (known in the roofing industry as a verge cap). The end cap 30 can be made to any desired length and may have as many steps as required by the roof to which it is to be fitted. When fitted to a roof, for example the roof shown in Figure 4, the stepped portions 35 fit over the outer most ridges 8,9 of the panels 1. The face 37 of the end cap 30 sits against the outermost structural member of the roof, beam 15 in Figure 4 for example, and is attached thereto by attachment means which pass through apertures 32 in the face 37. The inwardly projecting flange 31 prevents wind blowing underneath the panels 1. The provision of an end cap 30 can be important in order to prevent the panels 1 from being lifted from the roof.

Referring now to Figure 7, there is shown a vermin trap 50 comprising an upper face 51 and a downwardly projecting face 52. The upper face 51 is provided with a plurality of apertures, or points of weakness 54 in order that the vermin trap may be fastened by fastening means to a beam 15 or another part of the roof structure. The downwardly projecting face 52 is provided with apertures or points of weakness 53 and 56. When fitted to a roof, fastening means may be passed through the apertures 53 and into a wall of the building supporting the roof. Many buildings are provided with a wooden board around the top of the walls to facilitate attachment of vermin traps and the like thereto. The apertures 56 are arranged to align with apertures 21 of beams 15 to facilitate attachment of the vermin trap to the beams 15. Any suitable fastening means may be used. Clearly, where panels of the invention are fitted to a roof which

does not comprise beams of the invention the provision of apertures or points of weakness 56 is not necessary and they may not be provided.

The vermin trap shown in Figure 7 can be made to any desired length.

Figure 9 shows another type of vermin trap 60 that has an integral gutter 70.

The trap 60 comprises an upper face 64, a downwardly extending face 63, a lower face 62 and a front face 71, the gutter 70 being an extension of the front face 70. Ridges 65 are arranged to fit the panels 2, while apertures 66 are provided in the ridges so that the vermin trap 60 may be attached, for example by the grommets 11 (Fig 1 a), to a component of the roof. In order to further secure the trap 60 to a roof, fastening means such as nails are passed through apertures 69 and 68 and a wooden lath (not shown for the sake of clarity) is located in the channel shape defined by the faces 62, 63, and 71.

Referring now to Figure 6, there is shown a ridge cap 40 having a central curved portion 45 and outwardly extending flanges 43 having ridges 42 to sit on the ridges 8 of panels 15. The ridge cap 40 is provided with a downwardly extending flange 44.

Grommets similar to those shown in Figure 1 a may be moulded on to the underside of the ridges 42 to fit into the apertures 4 (Fig 1) of the stepped portion 3 of the uppermost panels 2 on the roof. The central curved portion 45 is flexible so that the ridge cap can be used on a roof having any degree of pitch, the angle"x"simply decreasing as the pitch of the roof increase.

Referring now to Figure 8, there is shown two beam sections 80. Each beam section 80 is provided at one end thereof with a pair of outwardly projecting brackets 81 each having an aperture 82, and at the other end thereof with a pair of internally mounted plates 83 having two apertures 84. The beam sections 80 are joined one to another by bringing an end 86 into abutment with an end 87 so that the aperture 82 of a each bracket 81 is aligned with an apertures 84 of a respective one of plates 83. A bolt or pin (not shown) is then passed through the aligned apertures to secure the beam sections 80 one to another. The plates 81,83 are set into the glass reinforced plastics beam section 80 as it is being moulded.