US4372014 for example, describes a membrane covering for a roof or wall panel. The membrane covering includes attachable edge fasteners having male and female coupling means such as parallel longitudinal ribs and grooves which are adapted to interlock with the ribs or grooves of an edge fastener of an adjacent panel when force is applied. US2874652 describes a method for covering the joints between adjacent panels by laying a narrow strip of film over the joint after the panels have been installed.

Insulated membrane based roof decking systems are known. One such system is formed from panels comprising an inner skin, a layer of insulation and an outer membrane bonded to the insulation via a polyester fleece. While such a system is a major advance in low slope roofing technology their application is limited because of a range of issues. The system is not efficient in terms of insulation and mechanical properties. Any imperfection in the surface between the membrane and the foam can lead to ghosting in the membrane and undesirable flexibility in the membrane which makes it prone to indentation by installers. The load capacity of the panel systems is determined by the inner skin section properties-deep profiles are wasteful of insulation and difficult to manufacture, consequentially load capacities tend to be relatively small.

Another known system uses a pre-bonded steel/membrane material in coil form for the outside skin. This is mechanically more efficient and more resistant to surface imperfections. However, joint details are difficult to form in this material and any side joints must be finished with a butt strap. This is time consuming and unreliable.

There is therefore a need for an improved roof panel of this type.

Statements of Invention According to the invention there is provided a roof panel for forming a low pitch or flat roof, having an inner liner, an outer layer, a body of insulation material between the inner liner and the outer layer, comprising a waterproof membrane pre-bonded to the outer layer, the membrane comprising an integral side lap extending sidewardly of at least some of the marginal edges of the outer layer, and the side lap being extendable over the joint between adjacent panels to form a sealed joint between adjacent panels on assembly.

This arrangement advantageously provides waterproof and weatherproof sealed panels and sealed joints between adjacent panels on assembly resulting in an effectively sealed roof structure. The membrane is provided pre-bonded to the panels there is no need for the user to acquire separate covering components for assembly with the roof panels on site in often difficult conditions.

In one embodiment the membrane comprises a unitary sheet of membrane or film.

The membrane does not include any joins or joints or other points of weakness that would typically be susceptible to wear. In addition manufacture and handling of the panel on site is simplified by the provision of the membrane as a unitary component of the required form and dimensions.

In another embodiment the membrane is substantially planar.

In a further embodiment the membrane is of substantially uniform structure and thickness.

The uniformity of the membrane has the advantages that it provides for ease handling.

There is no need to align specific matching parts of the membrane with corresponding interlocking parts of an adjacent membrane.

In one embodiment the membrane has a thickness of between 0.4 mm and 2mm.

In another embodiment the membrane has a thickness of 0.8 mm and 1.8 mm.

In a further embodiment the membrane is of a flexible plastics material.

In one embodiment the outer layer of the panel comprises a generally flat face for receiving the membrane.

In another embodiment the membrane is pre-bonded to the outer layer except at a fixing region at one or more of the marginal edges.

In a further embodiment the side lap of the membrane is extended to cover the fixing region on assembly.

In one embodiment the side lap is bonded to the outer layer on assembly.

In another embodiment the membrane is adhesively bonded to the outer layer.

In a further embodiment the side lap extends for bonding to an adjacent panel on assembly.

In one embodiment the side lap is adhesively bonded to an adjacent panel on assembly.

In another embodiment the adhesive is applied to the panel.

In a further embodiment the adhesive is applied to the membrane.

In one embodiment the adhesive is a polyurethane based adhesive.

In another embodiment the adhesive is a hot melt polyurethane adhesive.

In one embodiment the adhesive is pressure activated.

In another embodiment the adhesive is heat activated.

In one embodiment the membrane side lap comprises a peelable release tape or layer covering the adhesive.

In another embodiment the membrane side lap is folded onto itself covering the adhesive prior to application.

In a further embodiment the fixing region comprises a peelable release layer covering the adhesive.

In one embodiment the panel comprises a fixing region for receiving one or more fasteners for fixing the panel to a support and/or adjacent panel on assembly.

In another embodiment the fixing region comprises the fixing region of the outer layer.

In one embodiment the fixing region comprises one or more grooves recessed from the outer layer for receiving fasteners.

The panel is thus arranged so that the fasteners are located below the face of the outer layer or the panel and do not protrude to place stresses on the membrane or to interfere with bonding of the membrane. In addition the membrane seals over the fasteners on assembly providing waterproof covering and protection for the fasteners too.

In another embodiment the panel has a profiled edge for engagement with an adjacent panel on assembly.

In a further embodiment the panel comprises a profiled edge for interengagement with a corresponding opposed profiled edge of an adjacent panel on assembly.

In one embodiment the panel has a profiled edge on one side and an oppositely profiled edge on an opposed side for interengagement of the profiled edges of adjacent panels.

In another embodiment the profiled edges are configured so that the outer layers of adjacent panels present a generally flat top face on assembly.

The provision of profiled edges provides overall structural integrity and also provides improved ease of handling and installation. The panels are configured so that upon interengagement of the profiled edges the outer layers are arranged as required for effective covering with the membrane.

In a further embodiment one of the profiled edges defines a tongue and the other profiled edge defines a corresponding groove.

In one embodiment the inner liner has a profiled edge for engagement with the inner liner of an adjacent panel, on assembly.

In another embodiment the inner liner has a profiled edge on one side and an oppositely profiled edge on an opposed side for interengagement of the profiled edges of adjacent panels.

In a further embodiment one of the profiled edges defines a tongue and the other profiled edge defines a corresponding groove.

In one embodiment the body of insulation comprises an insulation foam.

In another embodiment the insulation foam is factory formed in situ between the inner liner and the outer layer.

In a further embodiment the inner liner is of metal.

In one embodiment the liner is a profiled liner.

According to another aspect of the invention there is provided a method for manufacturing a roof panel for a low pitch or flat roof comprising the steps of :- providing a membrane; providing an outer layer; bonding the membrane to the layer such that an integral membrane side lap extends sidewardly of at least some of the marginal edges of the outer layer.

In one embodiment the method comprises the step of : bonding the membrane to the outer layer except at one or more of the marginal edges.

In another embodiment the method comprises the steps of :- applying an adhesive to the membrane; applying the outer layer over the adhesive on the membrane; In a further embodiment the method comprises applying the adhesive by coating one side of the membrane with an adhesive.

In one embodiment the adhesive is slot coated onto the membrane.

In another embodiment the method comprises the steps of :- applying an adhesive to the outer layer; applying the membrane over the adhesive on the outer layer; In a further embodiment the method comprises the steps of :- providing an inner liner; providing liquid foam reactants the between the outer layer and the inner liner to form a sandwich structure; and heating the sandwich structure in an oven to expand the foam and form a composite roof panel.

In one embodiment liquid foam reactants are applied to the liner and the outer layer is applied to the liquid foam reactants.

In another embodiment the liquid foam reactants are applied between the face of the outer layer to which the membrane is not bonded and the inner liner.

In a further embodiment the liquid foams reactants are applied between the outer layer and liner after bonding of the membrane.

In one embodiment the liquid foams reactants are applied between the outer layer and liner before bonding of the membrane.

In another embodiment the method comprises the step of profiling at least one side edge of the outer layer.

In one embodiment the side edge is profiled after bonding of the membrane.

In another embodiment the side edge is profiled before bonding of the membrane.

According to a further aspect of the invention there is provided a low pitch or flat roof system comprising a plurality of roof panels, each panel having an inner liner and an outer layer, a body of insulation between the liner and outer layer and comprising: a profiled edge for interengagement with a corresponding profiled edge of an adjacent panel on assembly, a waterproof membrane pre-bonded to the outer layer, the membrane comprising an integral side lap extending sidewardly of at least some of the marginal edges of the outer layer, and the side lap being extended over the joint between adjacent panels to form a sealed joint between adjacent panels on assembly.

In another embodiment each panel comprises a fixing region for receiving one or more fasteners for fixing the panel to a support and/or an adjacent panel on assembly.

In a further embodiment the membrane extends to provide a waterproof seal covering the panel, joint and fasteners on assembly.

Brief Description of the Drawings The invention will be more clearly understood from the following description thereof given by way of example only, in which:- Fig. 1 is a cross sectional view of a joint between roof panels according to the invention; Fig. 2 is a perspective view from above of a roof panel of Fig. 1; Fig. 3 is a cross sectional view of another joint detail between two adjacent roof panels; Fig. 4 is a cross sectional view of a further joint detail; Fig. 5 is a cross sectional view of another joint detail; Fig. 6 is a perspective view from above of a roof panel of Fig. 6; and Fig. 7A and 7B are cross sectional views of further joint details; Detailed Description Referring to the drawings there are illustrated various roof panels according to the invention for use in forming a low pitch or flat roof.

Referring initially to Fig. 1 a roof panel 1 comprises a profiled inner liner or decking 2, an outer layer 3, a body 4 of insulation between the inner liner 2 and outer layer 3, and a waterproof membrane 5 bonded to the outer layer 3.

The membrane 5 comprises a side lap 10 extending sidewardly of at least some of the marginal edges 8 of the outer layer 3 of the panel 1. The side lap 10 is extended over a joint 20 between adjacent panels to form a sealed joint between the adjacent panels on assembly.

The inner liner 2 which may be of painted galvanised steel is formed with trapezoidal portions for improved mechanical and insulation performance.

The outer layer 3 comprises a metal layer, of sheet steel for example, of about 0. 5mm in thickness. The outer or metal layer 3 is generally flat. The insulation may be of any suitable foam material such as a polyisocyanurate foam.

Referring to Fig. 2 the outer or metal layer 3 of the panel comprises a generally flat face defined by the marginal edges 8 for receiving the membrane and comprises a pre- covered region 6 and a fixing region 7. The membrane 5 being pre-bonded to the outer layer 3 except at the fixing region 7. The fixing region 7 lies between the pre- covered region 6 and at least one of the marginal edges 8 of the outer layer 3. The side lap 10 of the membrane is extended to cover the fixing region 7 on assembly.

The side lap 10 comprises a first overlap area 11 which extends over the fixing region 7 and a second projecting area 12 which extends sidewardly of a marginal edge 8 of the panel.

The membrane 5 is manufactured of a unitary sheet of membrane or film. The side lap 10 is integral with the membrane 5 pre-bonded to the panel. The membrane 5 is of substantially uniform structure and thickness throughout and is substantially planar.

The membrane 5 may be of any suitable waterproof material such as flexible plastics or PVC material. Typically the membrane will be between 0.4 and 2mm in thickness and preferably from 0.8 to 1. 8mm in thickness. A membrane of this form has the advantages that it is suitably strong and flexible.

The panels 1 are fixed to underlying supports or purlins and/or adjacent panels by means of fasteners or fixing screws 14. As shown in the drawings when in place the fixing screws extend downwardly either through the full depth of the panel (Figs. 1,3 and 7A) or a portion of the depth of the panel (Figs. 4 and 5) to secure the panel onto the underlying support.

The panel 1 comprises a fixing region for receiving one or more fixing screws 14. The fixing region 7 on the outer or metal layer 3 comprises one or more grooves 13 recessed from the face of the outer layer 3 for receiving a fixing screw 14. The form of the groove 13 is such that the head of the fixing screw 14 is fully accommodated in therein and does not project over the outer layer 3. The arrangement of the groove 13 ensures that the fixing screws 14 do not place stress on the membrane or interfere with bonding of the membrane to the outer layer 3. The panel and membrane are thus arranged so that the membrane extends over the outer or metal layer 3 to cover it and seal it and the one or more fixing screws 14 on assembly.

At least a portion of the membrane is pre-bonded to the outer layer of the panel at the pre-covered area 6. The side lap extends for bonding to the fixing region 7 of the panel and/or the fixing region of an adjacent panel or to a portion of the membrane pre-bonded to an adjacent panel. The side lap may be bonded using adhesive or by other suitable means. Adhesive may be applied to the panel or to the membrane.

The adhesive may be a polyurethane based adhesive for example a hot melt polyurethane adhesive. The adhesive may be pressure or heat activated. The membrane side lap 10 may comprises a peelable release tape or layer covering the adhesive or alternatively may be folded onto itself covering the adhesive prior to

application. Alternatively the fixing region may comprise a peelable release layer covering the adhesive.

A layer 15 of material to assist in preventing slippage at the joint may be applied to the foam edge on one or both sides of the panel. The layer 15 may comprise directional fibres, hook and loop type material such as that known by the Trade Mark Velcro or the like.

The side edges of panel may be profiled to provide any required joint detail. For example, referring to Fig. 3, a panel 31 comprises a profiled inner liner or decking 2, an outer layer 3, a body 4 of insulation between the inner liner 2 and outer layer 3, and a waterproof membrane 5 bonded to the outer layer 3. One side edge of the panel may be profiled to provide a groove feature 32 and the opposite side edge profiled with a corresponding tongue 33 which inter-engage at the joint 20 between adjacent panels on assembly. When the profiled edges are inter-engaged the outer or metal layers 3 of adjacent panels present a generally flat face and as described above the sidelap 10 of the membrane 5 is extended over the joint 20 between adjacent panels for forming a sealed joint on assembly.

In Fig. 4 the insulating foam 4 has interengagable tongue and groove features 50 which interengage on assembly of a joint 20 between adjacent panels. The head of the fixing screw 14 is covered by a projecting portion 51 of the panel at the joint. In this case the membrane side lap 10 is extendable over the joint 20 between adjacent panels to form a sealed joint and over any fixing screws 14.

The joint detail of Fig. 5 is similar to that of Fig. 4 except that in Fig. 5 the inner liner 2 has a more pronounced trapezoidal profile for enhanced structural properties.

Referring to Figs. 5 and 6 the membrane is pre-bonded to substantially the entire area of the outer or metal layer 3 of the panel.

Referring to Fig. 7A there is illustrated another joint detail which includes a countersunk sticher screw 55. Alternatively a flat head sticher screw 56 may be used as illustrated in Fig. 7B. (In the drawings 4A and 4B for clarity the outer metal layers have been illustrated as represented by single lines.) In this embodiment a panel 41 comprises a profiled inner liner or decking 2, an outer or metal layer 3, a body 4 of insulation between the inner liner 2 and outer layer 3, and a waterproof membrane 5 bonded to the outer layer 3 expect at fixing regions 43 and 44 at opposite marginal ends of the panel 41.

The outer layer 3 comprises a projecting metal end lap 42 which extends sidewardly of the side edge 47 of the panel. The projecting metal end lap 42 extends over the joint between adjacent panels and overlaps a portion of the outer metal layer 3 of the adjacent panel at the fixing region 44 thereof. The projecting metal end lap 42 is connected to the outer metal layer 3 of the adjacent panel by means of the sticher screw 55.

The projecting metal end lap 42 comprises one or more recesses or grooves 46 which are received in corresponding recessed grooves 45 provided on the fixing region 44 of the adjacent panel.

The side lap 10 of a first panel extends over the fixing region 43 of the first panel over the joint 40 between the adjacent panels and also over the fixing region 44 of the opposite end of the adjacent panel to form a sealed joint between adjacent panels and to cover and seal the fixing regions and fixing screws of the adjacent panels.

The membrane 5 is pre-bonded or applied to the outer layer 3 of the panel 1 at the site where the panel is manufactured.

In a first step a membrane 5 and outer layer 3 are provided. The membrane is bonded to the outer layer 3 such that an integral membrane side lap extends sidewardly of at

least some of the marginal edges of the outer layer. The membrane 5 may be bonded to the outer layer except at one or more of the marginal edges.

The membrane material is drawn from a supply reel and over a backing roll. A suitable adhesive such as a hot melt polyurethane based adhesive is then applied to the exposed surface of the membrane. For example, the adhesive may be applied by slot coating from an application head. The adhesive may alternatively be applied to outer layer and the membrane applied over the adhesive on the outer layer.

The outer layer is comprised of a metal layer of sheet steel which is drawn from a coil and laid down on top of the adhesive. Pinch rollers may be used to improve bonding.

The steel may have profiled edges which may be formed prior to application to the adhesive coated membrane.

The membrane has a side lap 10 to which the outer layer is not bonded and this side lap may be adhesive-free in this region or the adhesive may be covered with a release tape or the like.

A composite panel is then produced by laying down liquid foam reactants between the outer layer 3 and a liner layer 2. The liquid foam reactants may be poured onto the inner liner 2 and the outer metal layer 3 applied over the liquid foam reactants. The sandwich thus formed is heated in an oven and the liquid foam reactants expand to fill the space between the inner liner 2 and the outer metal layer 3. The liquid foam reactants may be applied between the outer metal layer 3 and the liner either before or after bonding of the membrane.

The panel thus formed is cut to a desired length.

In use, a roof is built up by laying a number of the panels side by side on support purlins. The joints between adjacent panels are sealed by extending the sidelaps 10 over the joints between adjacent panels and by then applying the side or end laps

which may be heat sealed, hot air welded, solvent welded or adhesively bonded to the membrane of an adjacent panel. The overlapping portion of a side or end lap where provided is extended over the free fixing region of the panel and may be similarly sealed to the outer layer.

The panels are formed so that on assembly and interengagement of the profiled edges the top metal layer of adjacent panels present on assembly a generally flat face to enable the membrane cover to be extended to completely cover the panel and joints between adjacent panels on assembly. The fixing member or screw is also covered.

This provides an effective waterproof sealed roof and ensures the integrity of the membrane and avoids surface imperfections at the fixing member or the need to leave a portion of the panel without any membrane to allow for the fixing member to be inserted.

The roof panels of the invention offer considerable advantages both in terms of mechanical performance and thermal efficiency. The metal layer 3 greatly strengthens the panel and provides resistance to foot traffic. The metal layer 3 may be formed of steel for example. Thermal efficiency is improved as the metal face provides an impermeable surface to cell gas from the foam core.

As shown in the drawings the invention provides a low pitch or flat roof system for the installation and assembly of a waterproof sealed roof.

The panels of the various embodiments of the invention are formed to interengage on assembly by virtue of the profiled form of the inner liner and/or the profiled form of opposed side edges.

The panels comprise a membrane pre-bonded to the outer or metal layer and configured to extend over the outer layer of the panel and over joints between adjacent panels to seal the panel and the roof on assembly.

The panels are fixed to an underlying support purlin using fixing means. The fixing means when installed extends the depth of the panel or a part thereof. The panels are formed so that the fixing means is installed below the membrane so that when the membrane is extended to cover the panel and the joint between adjacent panels on assembly the fixing means is also completely sealed, covered and protected.

The components of the invention provide an efficient waterproof sealed roof on assembly. On assembly the membrane provides a highly efficient seal with advantages as follows: the membrane extends to cover the outer layer of the panels and the joints between adjacent panels ; the outer layer presents a substantially face for receiving the membrane there protruding features that might interfere with laying or bonding of the membrane to the outer layer are accommodated in recesses ; the membrane is bonded to the flat face of the outer layer protrusions or uneven formations that might place stress on it are avoided ; and the seal extends over the entire roof assembly-fixing members, joint and panels The provision of a pre-bonded membrane greatly improves the ease of laying the membrane to seal the joints between adjacent panels. The ease of extending out and sealing the membrane side lap is greatly assisted by virtue of there being at least a portion of the membrane pre-bonded to the panel as this provides an anchor and guide for the membrane to ensure that the alignment of the membrane is correct. In addition the provision of a pre-bonded membrane with integral side lap portions eliminates the requirement for the user to have additional membrane pieces for attachment to roofing panels on assembly and for cutting of the membrane on site.

The invention provides a low pitch or flat roof system of excellent structural integrity and having a waterproof covering and which addresses some of the manufacturing issues of the prior art. On the one hand complex joint profiles are difficult to form with a membrane covering extending over the portion on the other hand it is difficult to cover an assembled roof with a membrane covering on site while avoiding surface imperfections. However, the system of the invention addresses these problems.

While in a preferred embodiment the membrane is pre-bonded to the outer metal layer of the panel it will be appreciated that an intermediate coating or layer may be provided on the metal layer of the panel prior to bonding the membrane. The invention is not limited to the embodiments hereinbefore described which may be varied in detail.