WO2023144547A1

WO2023144547A1 - Structural panel and system

Info

Publication number: WO2023144547A1
Application number: PCT/GB2023/050180
Authority: WO
Inventors: Philip William BAGNALL; Paul Arthur BAGNALL; Lewis William BAGNALL
Original assignee: Matrix Gmoc Ltd
Priority date: 2022-01-28
Filing date: 2023-01-27
Publication date: 2023-08-03

Abstract

A structural panel (10) for building construction comprises a first surface layer (1), a second surface layer (2), an insulation material (3) disposed between the first surface layer and the second surface layer, and a frame structure. The frame structure comprises a first frame (11) fixed to the first surface layer and a second frame (12) fixed to the second surface layer, wherein the first frame is connected to the second frame via a non-metal connector (4). A system of structural panels comprises a first such structural panel (10) and a second such structural panel (10), in which a first end of the first structural panel engages with a second end of the second structural panel.

Description

STRUCTURAL PANEL AND SYSTEM

The present invention relates to a structural panel for building construction, and a system of structural panels. In particular, the invention relates to structural panels usable in the construction industry to construct walls or buildings, including load-bearing structures.

Background

Structural panels, which may alternatively be called building panels, can be used for the construction of buildings, such as for commercial or residential buildings. Instead of constructing the building using conventional construction techniques, by forming a foundation and then constructing walls on site using either bricks and mortar or studwork and cladding, structural panels can be pre-fabricated and connected together on site in modular fashion to form the walls of the building. This allows the construction of buildings in an extremely quick and straightforward manner compared to conventional building methods, as the modular panels can be installed in a very short timeframe. These advantages make structural panels extremely suitable for building in environments where normal building methods are too slow, such as in disaster zones, or in remote locations where skilled builders are not available.

Structural building panels typically comprise a timber or steel frame with an insulating core, and external panel boards forming the flat faces of the panels. One significant problem facing structural panels in the prior art is that of cold bridging, whereby cold outside temperatures are conducted through the panels, leading to cold or damp inside the buildings. In order to minimise cold-bridging, prior art structural panels typically contain an air cavity between the faces of the panel, which mimics the cavity in conventional cavitywall construction.

Another drawback associated with prior art panels is that the joints between panel-ends are typically a point of structural weakness, and can experience problems with cold bridging and of cold air entering buildings through the panel joints if the joints are not air-tight.

In order to assemble multiple structural panels to build a wall, expertise and specialist tools and fasteners are typically required to connect adjacent panels to one another. In order to construct joints that are sufficiently strong for load-bearing walls, most prior art panels are fixed together using mechanical connections such as bolts, or by complex interconnection systems. Most prior art interconnection systems are designed to be inaccessible after the panels are connected, making it impossible to disconnect panels after assembly. While this is intended to be an advantage for permanent buildings, this can be a disadvantage for temporary constructions that may need to be either removed or reconfigured after they are built.

It is desirable to provide structural wall panels that reduce or eliminate cold bridging between panel faces, and that may be connected to one another with ease.

Summary of the Invention

The invention provides a structural panel and a system of structural panels as defined in the appended independent claims, to which reference should now be made. Preferred or advantageous features of the invention are set out in dependent sub-claims.

According to a first aspect of the present disclosure a structural panel for building construction may comprise a first surface layer, a second surface layer, and an insulation material disposed between the first surface layer and the second surface layer. The structural panel may comprise a frame structure comprising a first frame fixed to the first surface layer and a second frame fixed to the second surface layer, wherein the first frame is connected to the second frame via a non-metal connector.

Structural panels may also be known as building panels, construction panels or prefabricated wall panels. Structural panels are panels suitable for building structures or buildings. These structural panels are suitable for forming load-bearing portions of those structures or buildings. Insulated cladding panels for example would not be suitable for bearing the loads that are required in building construction.

The structural panels may be of different shapes and sizes depending on the intended building construction project. The structural panels may be square or rectangular. Typically, the first and second surface layer may comprise a top edge, bottom edge, a first end and a second end. The frame structure may be the same shape as the first and second surface layers, with a top edge, bottom edge, a first end and a second end, corresponding to the edges and ends of the surface layer. The size of the structural panel may depend on its use in building construction, for example in the case of a structural panel being used in the construction of a wall for a house, the panels may be a standard height corresponding to the height of a single storey. For example, the panel height may be between 2.3 m and 3 m. More preferably, the panels may be 2.4 m in height. The corresponding width of the panels may be between 1 and 1 .5 m, preferably 1 .2 m. The panels may have a depth or thickness (the distance between the first surface layer and the second surface layer) of between 0.2 m and 0.4 m, preferably 0.24 m.

The first frame and second frame may advantageously ensure that the structural panel has sufficient strength to allow the structural panel to be used as a load-bearing component in the construction of buildings such as residential buildings.

The non-metal connector is configured to provide a connection between the first frame and second frame. The non-metal connector connects the frames and increases the strength and rigidity of the frame structure by bracing the first and second frames to prevent relative movement between the two frames.

The use of a non-metal connector instead of conventional metallic frame components advantageously reduces or even prevents cold bridging between the first frame and second frame. In metal-framed panels of the prior art, metal braces were used to create rigidity and strength in the panel frame. However, metal braces extending from the exterior side of a panel to the interior side of the panel are a cause of cold-bridging, as heat is conducted through the metal braces from the warmer interior side of the panel to the colder exterior of the panel. This significantly reduces the thermal efficiency of prior art wall panels, and has presented a hurdle to the wider adoption of modular structural panels as a building technique.

The non-metal connector may have a thermal conductivity of less than 25 W/(m.K), or less than 10 W/(m.K), or less than 5 W/(m.K), or less than 1 W/(m.K), particularly preferably less than 0.5 W/(m.K). This is significantly lower than the thermal conductivity of metals such as steel (thermal conductivity approximately 45 W/(m.K)) that have been used to brace panel frames in the prior art. The thermal conductivity of the non-metal connector can be measured by guarded hot-plate apparatus as defined in ISO 8302: Thermal Insulation - Determination of steady state thermal resistance and related properties - Guarded hot plate apparatus.

The low thermal conductivity of the non-metal connector significantly restricts the transfer of heat from the first frame to the second frame and therefore from the first surface layer to the second surface layer. When the structural panel is part of a building, this reduces the heat transfer from the outside of the building to the inside, reducing cold or damp inside the building and increasing the energy efficiency of the building.

The connector preferably takes the form of a flat sheet of non-metal material. For example the connector may be a rectangular sheet of material, which is configured to extend from one frame to another and to be held flat against the edge of the insulation material.

The non-metal connector may be connected to the first metal frame at a first end of the non-metal connector, and to the second metal frame at a second end of the non-metal connector. The non-metal connector may comprise a plurality of mounting holes corresponding to a plurality of fixing holes in the frame structure. A mechanical fixing means, for example a bolt, may be inserted through the mounting hole and through the corresponding hole in the frame structure to attach the connector to the frame structure. The mounting holes are preferably situated at least 20 mm from any edge of the non-metal connector to ensure a strong connection between the connector and the frame.

The non-metal connector may be a polymer connector. The non-metal connector may preferably be a rigid polymer connector. The non-metal connector may be a PVC connector. The non-metal connector may have a thickness of at least 2 mm. For example the non-metal connector may have a thickness of between 2 mm and 20 mm, or between 5 mm and 10 mm. The length of the connector may correspond to the thickness of the panel, or the separation between the first frame and the second frame across the thickness of the panel. The width of the non-metal connector is preferably at least 100 mm. For example the non-metal connector may have a width of between 100 mm and 300 mm, or between 120 mm and 200 mm, or between 130 mm and 150 mm. Although the thermal conductivity of the connectors is very low compared to metallic connectors, by restricting the width of the connectors the thermal conduction through the connectors is reduced even further. Non- metal connectors of these dimensions may advantageously be strong enough to keep the frame structure rigid without bending or warping.

The first surface layer may comprise a magnesium oxide board or a cement board. Alternatively, or in addition the second surface layer may comprise a magnesium oxide board or a cement board. Preferably the first surface layer and second surface layer may be made of the same material. When the structural panel is used in building construction, either the first surface layer or the second surface layer may form an internal wall of the building, and the other may form an external wall. The use of cement board or magnesium oxide board as a surface layer of the panel advantageously means that as soon as a wall is constructed, the internal surface of the panel that forms the interior wall of the building may be ready to decorate with paint or by tiling. This avoids the need for any additional treatment, making the construction and decoration process both quick and efficient. The cement board or magnesium oxide board forming an external surface of the wall of the building may also be ready to finish as soon as the wall has been constructed. For example the external surface may be finished with at least one of paint, render, bricks, or cladding as soon as the wall has been constructed. The paint, render, brick, or cladding finish may be applied directly to the cement board or magnesium oxide board.

The insulation material may comprise a solid block of thermally insulating material. The solid block of insulating material preferably provides increased structural stability to the structural panel. The insulation material may comprise a polymer foam, for example expanded polystyrene (EPS) or polyurethane (PU) foam. These materials advantageously provide good thermal insulation, are readily available, and relatively lightweight allowing the structural panels to be manoeuvrable. In particular these insulation materials set as a solid block providing stability to the structural panel.

The thermal insulation material is preferably in contact with both the first surface layer and the second surface layer of the panel. In other words, the thermal insulation preferably fills the internal volume of the panel, extending the entire thickness of the panel from the first surface layer to the second layer. The insulation material may be attached to the first surface layer and second surface layer by adhesive.

Structural panels of the prior art typically contain an air cavity between the faces of the panel, which mimics the cavity in conventional cavity-wall construction and reduces heat loss through the panel. The structural panel of the present invention, however, preferably does not comprise an air-filled cavity between the first surface layer and the second surface layer. Having no cavity may advantageously increase the stability and strength of the structural panel, and the use of a non-metal connector between the frames may advantageously mean that heat loss through the panel is sufficiently low that no cavity is required. The frame structure preferably defines a perimeter of the panel, and extends around a perimeter of the insulation material. The first frame and the second frame are preferably metal frames, particularly preferably steel frames. Metal frames advantageously provide strength to the structural panels, but the use of one or more non-metal connectors to connect the two frames together means that there is very little or no cold bridging between the two metal frames.

In a preferred embodiment, the first frame is connected to the second frame via a plurality of non-metal connectors. The plurality of non-metal connectors may be spaced apart around the perimeter of the panel, so that the first frame and the second frame are connected at a plurality of positions around the frame structure. Having a plurality of non- metal connectors may advantageously increase the stability and rigidity of the frame structure.

The plurality of non-metal connectors may be spaced apart around the frame structure. Preferably a plurality of connectors are provided on each of the four edges of the panel. The separation between adjacent connectors may depend on the size of the structural panel. For example, the separation between adjacent connectors along the side of the frame structure may be between 100 mm and 500 mm, or between 150 mm and 300 mm. In preferred embodiments, at least two connectors are provided per linear metre of frame structure.

The non-metal connectors maintain a separation between the first frame and the second frame, such that the first frame is not in physical contact with the second frame except via the non-metal connectors. All of the connections between the first frame and the second frame are made by non-metal connectors. This means that there are no thermally conductive routes through the thickness of the panel, as at all points the frames are separated by insulation material or non-metal connectors. This advantageously reduces cold bridging across the panel.

In an alternative embodiment, each edge of the panel may comprise a single non-metal connector which connects the first frame to the second frame along that edge. For example the connector may be a continuous strip of non-metal material that extends along the entire length of the panel edge, and is affixed to the first frame and the second frame at multiple locations along the connector. The first frame and the second frame may comprise face portions, which are arranged parallel to the first and second surface layers, and edge portions which are arranged to extend inwards from the face portions of the frame towards the central plane of the panel. In other words, the first and second frames may have an L-shaped cross section, with a first branch of the L forming the face portion, and the second branch of the L forming the edge portion. The first surface layer and the second surface layer may be fixed to the frame structure by adhesive and/or mechanical fixings such as screws, bolts, or rivets. Preferably the first and second surface layers may be fixed to the face portions of the first and second frames, respectively.

The building panels are preferably connectable to one another using tongue-and-groove connections on the panel ends. The tongue-and-groove system advantageously both helps with the alignment of the panel ends during construction, and also provides additional strength to the joint between the panels, as the tongue and groove resist relative lateral movement of the two panels along the length of the joint.

A first end of the frame structure may comprise a tongue which extends in a longitudinal direction along the frame end, and a second end of the frame structure may comprise a corresponding groove, such that the panel is connectable to a corresponding second panel by connecting the tongue of the panel to the groove in the second panel. The ends of the first and second panel being identical advantageously allows any number of panels being joined in this way to form a wall.

The first and second structural panels preferably each comprise identical first and second panel ends. The first and second panels may be identical. Alternatively the first and second building panels may be of different lengths, as long as the panel ends have corresponding tongue and groove connections that are connectable to one another. This design allows panels to be connected end to end in modular fashion, with the number of panels suited to whatever structure is being built.

The tongue may be formed by first ends of the first and second frames, and the groove may be formed by second ends of the first and second frames. The tongue and groove may be symmetrical about the centre plane of the panel, so that the panels may be connected either way up, in two possible vertical orientations. Advantageously, this means connecting a structural panel to a second structural panel and therefore connecting a series of panels to form a wall can be done more quickly, and the risk of mistakes may be reduced.

The first ends of the first and second metal frames may comprise a tongue shoulder section that extends inwards from the face portions of the frame towards the central plane of the panel, and a tongue section extending out of the panel from the tongue shoulder section and forming an angle of between 15 and 90 degrees from the plane of the tongue shoulder section.

The second ends of the first and second metal frames may comprise a groove shoulder section that extends inwards from the face portions of the frame towards the central plane of the panel, and a groove section extending into the panel from the groove shoulder section and forming an angle of between 15 and 90 degrees from the plane of the groove shoulder section. The angle formed between the groove section and the groove shoulder section is preferably the same as the angle formed between the tongue section and the tongue shoulder section, so that when the panels are end-to-end the tongue section and the groove section contact one another, and the tongue shoulder section and the groove shoulder section contact one another.

When the first end of the structural panel is aligned with the second end of an identical second panel the tongue shoulder section of the first end of the structural panel and the groove shoulder section of the second end of the identical second panel may be aligned and in contact with one another. The tongue shoulder section of the first end of the structural panel and the groove shoulder section of the second end of the identical second panel may prevent the first end of the structural panel from sliding too far into the second end of an identical second panel compared to a tongue and groove section alone.

The first end of the structural panel may be fastenable to the second end of a second panel by a fastener which may be configured to receive a portion of the first end of the panel, and a portion of the second end of the second panel. The fastener may hold the first panel in connection with the second panel. Preferably the fastener may clamp the first panel to the second panel, forming a tight joint. The first panel may not be removed from the second panel without first removing the fastening member.

The first end of the panel preferably comprises a first connection member, and the second end of the panel preferably comprises a second connection member. The first and second connection members are preferably configured to contact one another when the panels are positioned end-to-end, so that the panel ends may be fastened together by fastening the first and second connection members together.

The first and second connection members are preferably formed on sections of the frame on the panel ends. The connection members may be attached to sections of the first and/or second frames on the panel ends, or alternatively formed from sections of the frames themselves.

In a preferred embodiment, the first end of the first building panel comprises a plurality of first connection members, and the second end of the second building panel comprises a plurality of second connection members, such that the first and second building panels are fastenable to one another in a plurality of positions.

In preferred embodiments, the connection members are elongate projections with a fixed end which are connected to the first and/or second frames, and a free end over which the clamping portion of the fastener can pass during application of the fastener. The elongate connection members are preferably aligned with the plane of the panel ends, with their free ends pointing outwards towards a top edge or a bottom edge of the panel.

Particularly preferably the connection members are elongate “fingers” formed from the panel frame, which is itself typically formed from sheet metal such as steel. The connection members preferably have a length of between 60 mm and 80 mm from end to end, corresponding approximately to the preferred size of the fastener, so that when the connection members are received in the clamping portion of the fastener, the clamping portions extend along the whole length of the clamping portion. In this arrangement, the clamping portion clamps the connection members together over its length of at least 50 mm. This has been found to provide a high level of support and rigidity to the joint, particularly in preferred embodiments in which two or four or more pairs of connection members and fasteners are used to fasten a single panel joint.

In a particularly preferred embodiment, the first panel comprises a top first connection member located at a top end of the first end and a bottom first connection member located at a bottom end of the first end. A top second connection member is located at a top end of the second end and a bottom second connection member located at a bottom end of the second end. The two top connection members are fastenable together by a top fastener, and the two bottom connection members are fastenable together by a bottom fastener. By fastening the panels together with fasteners at both the top and bottom of the panel joint, the panel system is made significantly stronger and more rigid, which is of key importance when the panels are to be used in structural or load-bearing applications.

The top first connection member and the top second connection member are positioned at the top of the panel ends, and arranged so that the free ends of the top connection members extend towards the top edge of the panels, such that the top fastener can be applied over the free ends of the top connection members from the top edge of the panels. Likewise, the bottom first connection member and the bottom second connection member are positioned at the bottom of the panel ends, and arranged so that the free ends of the bottom connection members extend towards the bottom edge of the panels, such that the bottom fastener can be applied over the free ends of the bottom connection members from the bottom edge of the panels.

A particular benefit of fastening panel ends together at their top and bottom edges is that the fasteners are simple to fix in place, and also removable to allow the panels to be separated again at a later date.

In use, in the system of the present invention the first and second panels are positioned with their ends together and then a top fastener may be urged over the top connection members from the top edge of the panel joint, and a bottom fastener may be urged over the bottom connection members of the panel joint from the bottom edge of the panel joint.

In a particularly preferred embodiment, top connection members and bottom connection members are provided on both the first frame and the second frame, so that each panel end comprises two top connection members and two bottom connection members. Panel ends are thus connected using four fasteners to clamp four pairs of connection members at each joint, which creates a particularly strong and rigid joint between adjacent panels.

The first connection member on the first end of the panel may be a tongue connection member, which extends in the direction of the tongue along the panel end, preferably in which the tongue connection member may be a portion of the tongue section. The second connection member on the second end of the panel may be a groove connection member, which extends in the direction of the groove along the panel end, preferably in which the groove connection member may be a portion of the groove section. Preferably the tongue connection member and the groove connection members are formed from and connected to portions of the tongue section and groove sections respectively.

The first end of the panel may be fastenable to the second end of the second panel by positioning the fastener around the tongue connection member and the groove connection member, so that the connection members may be held together by the fastener. Preferably the tongue connection member and the groove connection member have a length of between 60 mm and 80 mm to correspond to the length of the fastener.

The tongue connection member may be formed at the top end and/or bottom end of the tongue section, and the groove connection member is formed at the top end and/or bottom end of the groove section, such that the tongue and groove connection members abut one another when the tongue of the panel is received in the groove of the second panel. The panel preferably comprises a tongue connection member and a groove connection member formed at corresponding positions on the panel ends, so that the tongue and groove connection members abut one another, or are positioned adjacent to one another, when the ends of adjacent panels are connected. The tongue connection member may be formed at the top end of the tongue section, and the groove connection member may be formed at the top end of the groove section, such that the tongue and groove connection members abut one another when the tongue of the panel is received in the groove of the second panel. Alternatively the tongue connection member may be formed at the bottom end of the tongue section, and the groove connection member may be formed at the bottom end of the groove section, such that the tongue and groove connection members abut one another when the tongue of the panel is received in the groove of the second panel.

In a preferred embodiment, each tongue section comprises tongue connection members at both the top and bottom ends of the tongue section, and each groove section comprises groove connection members at both the top and bottom ends of the groove section. Having the tongue connection member and groove connection member formed at both the top and bottom of the tongue section and groove section respectively advantageously provides a strong joint between panels. Panel ends may thus be fastenable to one another by two connections at the panel top, and two connections at the panel bottom. Four connections on each end of the panel advantageously provides a strong joint between the two panels. The tongue connection members and groove connection members are preferably accessible at the top and bottom of the tongue and groove connection when the panel ends may be connected together, such that the fasteners can be both fixed and removed when the panel ends are connected. The top and bottom of the tongue section and groove section may be situated at the top and bottom edges of the panels. Advantageously, this makes the fastener easily accessible during connection of the structural panel to the identical second panel or during disassembly of the second panel from the structural panel. The fastener may be removable from the panels to allow the panels to be separated.

The fastener preferably comprises a clamping portion configured to surround a first connection member on a first end of the first building panel and a second connection member on a second end of an adjacent second building panel. The clamping portion of the fastener is configured to hold the first connection member and the second connection member together in the clamping portion. The fastener preferably also comprises a ramped guide-in portion configured to guide at least one of the connection members into the clamping portion.

The fastener is configured to fasten together modular building panels. The fastener is preferably configured to fasten together structural building panels usable for load-bearing applications such as forming external walls, floors, ceilings or roofs of houses or other buildings. In use, a structure such as a wall may be constructed by arranging a plurality of such panels end-to-end, and fastening the panels to one another at the joints between adjacent panels.

The use of the fastener will be described herein in the context of a joint between two panels - the first panel and the second panel - but it will be readily understood that most structures built using such modular building panels comprise a large number of panels, and that the fastener may be used to hold together any panel joints in the modular structure.

The fastener is configured to hold the first connection member (which is attached to the first panel) and the second connection member (which is attached to the second panel) together in the clamping portion of the fastener. The fastener holds, or clamps, the first and second connection members tightly together so that they cannot move apart - this holds the first end of the first panel tightly against the second end of the second panel, creating a joint that is both tight and structurally strong. The ramped guide-in portion of the fastener provides the significant advantage of guiding connection members into the clamping portion as the fastener is put in position over the connection members. In use, when the fastener is applied over the first and second connection members by urging the fastener onto the connection members, the fastener is oriented so that the ramped guide-in portion acts as the leading edge, and comes into contact with at least one of the connection members as the fastener is urged towards and onto the connection members. As the fastener moves further onto the connection members, the slope of the ramped guide-in portion biases at least one of the connection members sideways towards the centre of the clamping portion, which also urges the two panel ends into closer contact with one another.

The ramped guide-in portion may be configured to guide a connection member into the clamping portion as the connection member is moved in a first direction towards the clamping portion.

In order to hold the connection members together in a tight joint between panel ends, the fit of the two connection members into the clamping members is intentionally tight, so that once they are received in the clamping portion the two panel ends are unable to move relative to one another. This tight fit can make it challenging to insert both connection members into the clamping portion, so the ramped guide-in portion of the fastener helpfully directs at least one of the connection members inwards towards the clamping portion alongside the other connection member. As the panels may be large and difficult to handle manually, this helps to tighten the panel joint automatically when the fastener is applied.

The clamping portion is preferably tubular in shape, so that the first and second connection members are receivable in the hollow core of the tubular clamping member.

The clamping portion of the fastener preferably comprises a passage or aperture configured to receive both the first connection member and second connection member therein. When the fastener is in position, the first connection member and second connection member are both contained within the passage or aperture, such that they are held together. The clamping portion may comprise a hollow core forming the passage, so that the first and second connection members are received in the hollow core and held there by the body of the clamping portion surrounding the hollow core. The clamping portion may have a lateral cross-section that is oval in shape. Preferably the clamping portion may have a 0 shaped cross-section formed by the clamping portion fully surrounding a passage for receiving the connection members, or a C shaped cross-section formed by the clamping portion partially surrounding the passage for receiving the connection members.

The guide-in portion of the fastener is a ramped, or angled, or sloped, portion of the fastener which is configured to guide at least one of the connection members into the clamping portion. The slope, or angle, or ramp of the guide-in portion is directed towards the clamping portion, so that a connection member moving towards the fastener is encouraged towards the clamping portion by the slope of the guide-in portion. In order to obtain a tight joint between the panel ends - ideally an air-tight joint to eliminate loss of heat due to air flow between panel ends - the panel ends must be held very tightly together by the fastener. The ramped guide-in portion of the fastener helps to achieve this.

In use, when the panel ends are positioned together so that the first and second connection members are positioned close to one another. The fastener is then applied by forcing the clamping portion of the fastener over the first and second connection members to bring them together and hold them in the clamping portion. As the clamping portion is configured to be a tight fit over the connection members, the ramped guide-in portion helps to urge the connection members together as the fastener is driven onto the connection members. The ramp of the guide-in portion is directed to slope towards the passage in the clamping portion, to guide the connection members tightly together as they are forced into the passage.

The fastener can be used to connect two panels together in a non-destructive manner. The fastener may be removed and the panels separated without causing any permanent changes or damage, such as may be caused by trying to separate panels that have been nailed or glued together. Both the panels and the fastener may then be re-used. For example, the panels may be moved to a different location and then re-connected by the fastener.

The guide-in portion may be configured to guide a connection member into the clamping portion from a first side of the fastener, and/or from a second side of the fastener. The fastener may comprise only one ramped guide-in portion, or alternatively the fastener may comprise a plurality of ramped guide-in portions. For example, the fastener may have two ramped guide-in portions, configured to guide-in connection members from either side of the fastener. As the fastener is typically applied to the panel joint between the two panel ends, this may help to pull the two panel ends together tightly enough so that the first and second connection members both fit into the clamping portion of the fastener.

The guide-in portion of the fastener may be positioned at a first end of the passage and configured to guide a connection member into the passage from the first end. The guide-in portion of the fastener should be positioned at the leading-end of the fastener, i.e. the end of the fastener that faces towards the connection members when the fastener is applied. In some preferred embodiments, the ramped guide-in portion extends at an angle of at least 10 degrees, or at least 15 degrees, or at least 20 degrees, relative to a longitudinal axis of the clamping portion. Preferably the ramped guide-in portion may extend at an angle of between 10 degrees and 40 degrees, preferably between 15 degrees and 30 degrees, or between 20 and 25 degrees, relative to the axis of the passage in the clamping portion. These angles have been found to be suitably steep for urging the connection members together without presenting too much resistance as the fastener is urged onto the connection members.

In a particularly preferred embodiment the fastener is formed from a single piece of metal. Preferably the fastener is formed from steel. Particularly preferably the fastener is formed from steel with a thickness of at least 2 mm, in order to give the fastener sufficient strength to connect panels used for load-bearing applications.

The fastener may be formed from a single piece of sheet metal having two wings which are folded together to form the clamping portion. For example the two wings may be curved towards one another to enclose the passage of the clamping portion. A tongue extending longitudinally from an end of the passage formed by the wings may me angled outwards to form the ramped guide-in portion sloping towards the passage.

The clamping portion of the fastener preferably has a length of at least 50 mm in order to provide sufficient strength and rigidity to the panel joint. The clamping portion may have a length of between 50 mm and 120 mm, preferably between 55 mm and 100 mm, or between 60 mm and 80 mm.

The fastener preferably has a length of between 60 mm and 80 mm from end to end, including the length of the clamping portion and the ramped guide-in portion. The inventors have found that fasteners in this size range provide the best balance of being sufficiently easy to apply and remove, while being long enough to provide strength and rigidity to the panel joint. In some prior art systems, panel connectors have been designed to extend the entire length of the panel joint, but this has typically made such fasteners difficult to fit and difficult or impossible to remove once in place in the joint.

Structural Panel System

According to a second aspect, the invention may provide a structural panel system comprising a first structural panel and a second structural panel. The first and second structural panels are preferably structural panels as described above according to the first aspect of the invention. A first end of the first structural panel may engage with a second end of the second structural panel.

The first and second panels are preferably structural building panels usable for loadbearing applications such as forming external walls, floors, ceilings or roofs of houses or other buildings. In use, a structure such as a wall may be constructed by arranging a plurality of such building panels end-to-end, and fastening the panels to one another at the joints between adjacent panels. Such building panels have different requirements from non-structural panelling products, for example external cladding panels or are panels which are decorative and potentially thermally insulating, but are not usable as integral loadbearing parts of a structure.

The first and second building panels preferably each comprise identical first and second panel ends. The first and second building panels may be identical. Alternatively the first and second building panels may be of different lengths, as long as the panel ends are connectable to one another. Thus both building panels have a first end with a first connection member and a second end with a second connection member - this design allows panels to be connected end to end in modular fashion, with the number of panels suited to whatever structure is being built.

As described above, in building construction two or more structural panels are connected end-to-end to form a wall. It is also necessary during the construction of buildings to form a corner, to allow fully modular construction of a building. In order to enable the panel system to be constructed around corners, the system may comprise a corner section.

Two structural panels and a corner section may form a corner. The corner may be a rightangle corner. A structural panel may be attached to a second structural panel to form a corner. An end of the structural panel may be at 45 degrees to a surface of the structural panel. A first panel with an end at 45 degrees to a surface layer may abut a second panel with an end at 45 degrees to a surface layer, forming a corner. A corner may also be formed when the ends of the structural panel are at right-angles to a surface of the structural panel. An additional corner panel may be attached between a first end of the first panel and a second end of the second panel to form a corner. The corner panel may comprise a tongue and groove corresponding to a tongue of the first panel and groove of the second panel. This may allow the corner panel to easily connect and form a strong joint with the first structural panel and a second identical panel.

Method of Constructing a Structural Panel System

In a third aspect the invention may provide a method of constructing a structural panel. The method may comprise assembling a first frame, assembling a second frame, and then connecting the first frame to the second frame using a non-metal connector. An insulation material is positioned between the first and second frames, and first and second surface layers are attached to the frames on either side of the insulation material.

The non-metal connector may be mechanically fixed to the first frame and second frame, forming a frame structure. The frame structure may have a top edge, a bottom edge, a first end and a second end.

The internal portion of the frame structure is filled with an insulation material. The insulation material may be a solid insulation material, preferably a rigid block of insulation material. The insulation material may be EPS or PU foam.

An adhesive is preferably applied to a first face of the insulation material, and to a face portion of the first frame. A first surface layer of cement board or MgO board is then applied to the adhesive-covered first face of the insulation material and mechanically fixed to the first frame, for example by rivets. An adhesive may be applied to a second side of the insulation material. An adhesive may then be applied to a face portion of the second frame and to the second face of the insulation. A second surface layer of cement board or MgO board is then applied to the adhesive-covered second face of the insulation material and mechanically fixed to the second frame, for example by rivets.

This process advantageously creates a solid and rigid insulated panel which is highly thermally insulating, avoids cold bridging, and is structurally strong enough to be used as a load-bearing panel in the wall, ceiling, roof, or floor of a building.

Fastener

In a fourth aspect the invention may provide a building panel fastener for fastening a first building panel to a second building panel. The fastener comprises a clamping portion configured to surround a first connection member on a first end of the first building panel and a second connection member on a second end of the second building panel. The clamping portion of the fastener is configured to hold the first connection member and the second connection member together in the clamping portion. The fastener also comprises a ramped guide-in portion configured to guide at least one of the connection members into the clamping portion.

The fastener is preferably a fastener configured to fasten together modular building panels as described above in relation to the preceding aspects of the invention, and may have any of the features described therein in relation to a fastener for fastening a first building panel to a second building panel

The features described above in relation to the first, second, third and fourth aspects of the invention may all be applied to the other aspects of the invention.

if ic Embodiments and Best Mode of the Invention

Specific embodiments of the invention will now be described by way of example, with reference to the accompanying drawings in which:

Figure 1 shows a perspective view of a structural panel frame usable in a preferred embodiment of the present invention;

Figure 2 shows an enlarged perspective view of an end of the frame of Figure 1 ; Figure 3 shows a perspective view of a structural panel;

Figure 4 shows a top view of a structural panel of Figure 3;

Figure 5 shows a cross-sectional view of a first end of a first frame of a frame structure and a second end of a first frame of a frame structure;

Figure 6 shows a cross-sectional view of a first embodiment of a tongue and groove;

Figures 7A and 7B shows cross-sectional views of a second embodiment of a tongue and groove;

Figure 7C is a photograph taken from above a building panel according to a preferred embodiment of the invention, looking along a panel end comprising a groove;

Figure 7D is a photograph taken from above a building panel according to a preferred embodiment of the invention, looking along a panel end comprising a tongue;

Figure 8A shows a perspective view of a fastener;

Figure 8B is a photograph showing the fastener of Figure 6A from two different angles;

Figure 9 shows a cross-sectional view of the second embodiment of the tongue and groove with a fastener;

Figure 10 shows a perspective view of the second embodiment of the tongue and groove with a fastener;

Figure 11A is a photograph taken from above a building panel joint between the panel ends of Figures 7C and 7D, connected by two of the fasteners of Figure 8A & 8B;

Figure 11 B is a photograph of a fastener located over a bottom connection member on a panel end;

Figure 11C is a photograph of two fasteners located over two bottom connection members on a panel end; Figure 12 shows a cross-sectional view of the first embodiment of the tongue and groove with a fastener;

Figure 13 shows a perspective view of the first embodiment of the tongue and groove with a fastener;

Figure 14 shows a perspective view of two structural panels connected together end-to- end;

Figure 15 shows a top view of two structural panels assembled to form a corner; and

Figure 16 shows a perspective view of two structural panels assembled to form a corner.

Figures 1 and 2 show a structural panel frame 5 for a structural panel system according to the present invention. The panel frame 5 is rectangular in shape, and formed by a first rectangular steel frame 11 and a second rectangular steel frame 12 which are connected to one another by regularly spaced non-metal connectors 4. The connectors brace the frames 11 , 12 and provide rigidity to the frame and hold the two frames 11 , 12 at constant separation.

The rectangular panel frame 5 has a top edge 16, a bottom edge 18, a first end 19 and a second end 22. The panel frame 5 extends around a rectangular aperture which in use is filled with insulation material (not shown in Figures 1 and 2), preferably a rigid polymer foam insulation material. When the frame is filled with insulation material, first and second surface layers (not shown in Figures 1 and 2) are fixed to the first steel frame 11 and the second steel frame 12, so that the surface layers form opposite surfaces of the structural panel. The first and second surface layers can be cement board or magnesium oxide boards, for example, which can be affixed to the first and second steel frames 11 , 12 by adhesive and/or mechanical fixings.

The structural panels 10 are connectable to other such panels in a modular fashion, to create structures of a variety of shapes and sizes in a straightforward manner. Unlike the insulated cladding panels or decorative panels of the prior art, the structural panels 10 are sufficiently strong, rigid and thermally-insulating to be used as load-bearing components such as external walls of temporary or permanent buildings. In order to make the structural panels 10 reliable for load-bearing applications, it is of vital importance that the panels are connected to one another strongly, and without leaving gaps through which cold air can flow to the interior of the building.

In order to ensure a strong and reliable connection between adjacent panels, the structural panels 10 are provided with a tongue-and-groove system on the first and second panel ends 19, 22.

In order to prevent cold-bridging, the panel ends 19, 22 are formed by two separate steel frames 11 , 12, which are mirror images of one another about the central plane of the panel. The tongue-and-groove system is thus formed in two halves, with a half tongue and a half groove on each steel frame 11 , 12.

Figure 3 shows a perspective view of a structural building panel according to a first embodiment of the invention. The structural panel 10 has a first surface layer 1 and a second surface layer 2, and an insulation material 3 is disposed between the first surface layer 1 and the second surface layer 2. The first surface layer 1 and the second surface layer 2 are rectangular layers of cement boards or magnesium oxide boards. Preferably, the first surface layer 1 and the second surface layer are made of the same material. The insulation material is a solid block of insulating polymer, for example EPS or PU foam. The thermal insulation 3 is in contact with and adhered to both the first surface layer 1 and the second surface layer 2 by adhesive, and the thermal insulation fills the entire volume between the first and second surface layers. The structural panel 10 does not have a cavity between the first surface layer 1 and the second surface layer 2. The structural panel may be between 2 and 3 m in height, for example it can be 2.5 m in height for residential building construction. The width and thickness of the panel 10 may vary depending on the requirements of any given modular building project. As an example, the panels may have a depth or thickness (the distance between the first surface layer and the second surface layer) of between 0.2 m and 0.4 m, preferably 0.24 m.

The structural panel has a frame structure formed from two separate frames - a first frame 11 fixed to the first surface layer 1 and a second frame 12 fixed to the second surface layer 2. The first and second frames are mirror images of one another, and are connected to one another by a plurality of non-metal connectors 4. The connectors brace the frames 11 , 12 and provide rigidity to the frame and hold the two frames 11 , 12 at constant separation. The non-metal connectors are made of a rigid PVC polymer, and have a thermal conductivity of less than less than 0.5 W/(m.K). The non-metal connectors are in the form of flat sheets of PVC with a thickness of at least 2 mm and a width of at least 100 mm. The non-metal connectors are connected to the first metal frame 11 at a first connector end and the second metal frame 12 at a second connector end, so that the length of the connectors determines the separation between the first and second frames 11 , 12 and therefore the thickness of the panel 10.

The frame structure formed by the first frame 11 , the second frame 12 and the connectors 4 is rectangular in shape and has a top edge, a bottom edge, a first end and a second end. The frame extends around the perimeter of a rectangular aperture which in use is entirely filled by a rectangular block of insulation material 3. In the illustrated example, an additional piece of insulation material 3 is situated between the first surface layer 1 and the second surface layer 2 but external to the perimeter of the frame structure, such that the frame structure is not visible on the panel end in Figure 3.

The first frame 11 and the second frame 12 are metal frames. In this example they are steel frames. The first frame 11 is connected to the second frame 12 via a plurality of non- metal connectors 4. The plurality of non-metal connectors 4 are spaced apart around the perimeter of the panel to provide rigidity. Three such connectors are visible on the top edge of the frame in Figure 3. The non-metal connectors 4 maintain a separation between the first frame 11 and the second frame 12, so that the first frame 11 is not in physical contact with the second frame 12 except via the non-metal connectors 4.

The first frame 11 and the second frame 12 are formed from steel struts with an L-shaped cross-section, such that the first and second frames comprise face portions 20, which are arranged parallel to the first 1 and second 2 surface layers, and edge portions 30 which are arranged to extend inwards from the face portions of the frame towards the central plane of the panel. The first and second surface layers are fixed to the face portions 20 of the first and second frames respectively by adhesive and/or mechanical fixings such as rivets.

Figure 4 shows a top view of a structural panel of Figure 3. A first end of the frame structure comprises a tongue 40 which extends in a longitudinal direction along the frame end. A second end of the frame structure comprises a corresponding groove 50, such that the panel is connectable to an identical second panel by connecting the tongue 40 of the panel to the groove 50 in the second panel. The tongue 40 is formed by first ends of the first and second frames, and the groove 50 is formed by second ends of the first and second frames. The tongue and groove are symmetrical about the centre plane of the panel, so that the panels can be connected either way up.

Figure 5 shows an enlarged view of a first end of a first panel and a second end of a second panel. Only the ends of the first frames and the insulation material are visible in Figure 5.

The first end of the first and second metal frames comprise a tongue shoulder section 42 that extends inwards from the face portions 20 of the frame towards the central plane of the panel, and a tongue section 45 extending out of the panel from the tongue shoulder section. In this example the tongue section 45 forms an angle of 90 degrees from the plane of the tongue shoulder section 42. The second ends of the first and second metal frames comprise a groove shoulder section 52 that extends inwards from the face portions 20 of the frame towards the central plane of the panel, and a groove section 55 extending into the panel from the groove shoulder section 52. In this example, the groove section 55 forms an angle of 90 degrees from the plane of the groove shoulder section 52.

The tongue shoulder section, the tongue section, the groove shoulder section and the groove section are all formed integrally with the first frames of the panels. As the panel frames are metal, these sections are also formed from the same metal.

Figure 6 shows a cross-sectional view of a first embodiment of a tongue and groove connection between two metal frame struts. A first strut 57 forms an end of the first frame of a first panel, while a second strut 58 forms an end of the first frame of a second panel. The first strut 57 comprises a tongue section 45, while the second strut comprises a groove section 55. In this embodiment the tongue section 45 forms an angle of 90 degrees from the plane of the tongue shoulder section 42. The groove section 55 forms an angle of 90 degrees from the plane of the groove shoulder section 52. In use the wall panel 10 is connectable to an identical second panel by connecting the tongue 40 of the panel 10 to the groove 50 in the second panel.

Figures 7A and 7B show a second embodiment of a tongue 60 and groove 70. In this embodiment, a tongue shoulder section 62 extends inwards from the face portions of the frame towards the central plane of the panel, and a tongue section 65 extends out of the panel from the tongue shoulder section. The tongue section 65 forms an angle of 20 degrees from the plane of the tongue shoulder section 62. A groove shoulder section 72 extends inwards from the face portions of the frame towards the central plane of the panel, and a groove section 75 extend into the panel from the groove shoulder section 72. In this embodiment, forming an angle of 20 degrees from the plane of the groove shoulder section 72.

Figure 7A shows the cross section of a steel strut forming half of the first frame end. The strut comprises a half-tongue, so that the two opposing steel frames 1 1 , 12 form a whole tongue on the first end of a panel.

A tongue shoulder section 62 extends inwards from the faces of the panel towards the central plane of the panel, and a tongue section 65 extends outwards (out of the panel end) at an angle of 20 degrees from the tongue shoulder section 62.

Figure 7B shows the cross section of a steel strut forming half of a second frame end. The strut comprises a half-groove, so that the two opposing steel frames 1 1 , 12 form a whole groove on the second end of a panel.

A groove shoulder section 72 extends inwards from the faces of the panel towards the central plane of the panel, and a groove section 75 extends inwards (into the panel end) at an angle of 20 degrees from the groove shoulder section 72.

When the ends of adjacent panels are brought into contact with one another, the tongue shoulder sections 62 of the first panel abuts the groove shoulder sections 72 of the second panel, and the tongue sections 65 of the first panel extend into the groove formed in the end of the second panel by the groove sections 75 on either frame of the second panel. The presence of the tongue and groove shoulder sections 62, 72 advantageously limits the distance that the tongue can be forced into the groove, ensuring consistent separation and strengthening the joint between the panels.

In order to allow the panel ends to be held together once the panels are in position, connection members are formed on the panel ends. The connection members may take a variety of forms, but in preferred embodiments the connection members are sections of the frame that are arranged to be clamped to a corresponding member of an adjacent panel end using a fastener. The steel frames 1 1 , 12 are preferably formed from sheet steel, and in the illustrated embodiment the connection members are formed by fingers of the frame that are arranged to point towards the ends of the panel joint.

In use, these connection members can then be clamped to a corresponding connection member on another panel end by sliding a fastener down from the joint end over the “fingers” formed in the metal frames. The fastener then holds together a connection member on the end of a first panel to another connection member on the end of a second panel, and prevents them from separating as long as the fastener remains in place. This ensures a strong and tight joint between panel ends, in particular in combination with the tongue-and-groove system.

In the preferred embodiment illustrated, there are four connection members on each panel end: a top connection member at the top of the panel end on each of the first and second steel frames 11 , 12, and a bottom connection member at the bottom of the panel end on each of the first and second steel frames 11 , 12.

The connection members located on the first end of the panel may be termed first connection members, while the connection members located on the second end of the panel may be termed second connection members.

As shown in the Figures, the first connection members are formed from a top portion and a bottom portion of the tongue sections 65, so that the first end of the frame comprises two first top connection members 32 and two bottom first connection members 34.

The second connection members are formed from a top portion and a bottom portion of the groove sections 75, so that the second end of the frame comprises two second top connection members 36 and two bottom first connection members 38.

Figure 7C shows a second panel end with a groove, with two second top connection members 36 visible at the top end of the groove, while Figure 7D shows a first panel end with a tongue, with two first top connection members 32 visible at the top end of the tongue. Insulation material 40 is also shown inside the frame ends. The panels of Figures 7C and 7D are shown fastened together in Figures 9, 10 and 1 1 , with the two first top connection members 32 fastened to the two second top connection members 36 by two fasteners 500. Figures 8A and 8B show the structure of a fastener 500 usable to connect panel ends in a preferred embodiment of the invention.

In the illustrated embodiment, the fastener 500 is formed from a single piece of sheet metal, preferably sheet steel with a thickness of at least 2 mm. The fastener is made up of a tubular clamping portion 520, which is formed by two metal wings curved towards one another to form an open-sided tube with a roughly oval cross-section. A hollow passage is formed inside the clamping portion, the size of which corresponds very closely to the size of two of the panel connection members. The fastener 500 also has a ramped, or sloping, guide-in portion 540, which acts as the leading-edge of the fastener when it is used. The ramped guide-in portion 540 is located at a first end of the clamping portion on one side of the oval tubular clamping portion, and is formed by a tab of metal which is angled away from the axis of the passage through the clamping portion 520.

In use, the fastener is applied over a pair of connection members (one on each of a pair of panels) to hold the connection members together. When the panel ends are in position up against one another, with the tongue-and-groove system already located, the first connection members on the first panel are in contact with the second connection members on the second panel. As shown in Figures 9 and 10, the top edge of the first and second frames (and the bottom edge, which is a mirror image of the top edge) is shaped so that the tops of the top connection members are visible from above when the panels are end-to- end. This means that the connection members are accessible to position the fastener 500 over the connection members.

The fastener 50 is always applied with the ramped guide-in portion 540 directed towards the connection members, so that the guide-in portion acts as the leading-edge of the fastener. The fastener is urged onto the free end of the connection member “fingers” - as the passage of the clamping portion 520 is deliberately sized to be a tight fit over two connection members, the ramped guide-in portion 540 acts to contact one of the connection members and to urge it inwards towards the other connection member as the fastener 500 is driven down onto the connection members. As the fastener 500 is urged onto the connection members, the two connection members are thus automatically squeezed together and clamped inside the passage of the clamping portion 520.

To connect the connection members at the bottom of the joint, the fasteners 500 are placed in position on the bottom connection members of the first panel as shown in Figures 11 B and 11 C, with the ramped guide-in portions 540 facing upwards and out of the joint towards the second panel (not yet in position). The second panel may then be brought into position against the first panel end and dropped so that the downward-facing “fingers” of the bottom connection members are guided into the clamping portion 520 of the fastener under the weight of the panel. Thus, the panel bottoms may be fastened together using no tools, with the ramped guide-in portions helping to create extremely tight connections between panel ends. Once the panel bottoms are fastened together, two more fasteners may then be applied over the top connection members to fasten the top of the panels together securely.

The fastener may be forced onto the connection members by hand, or optionally using a hammer or mallet, but no specialised tools or power sources are necessary. The simple design of the fastener is advantageously very strong, and creates a very tight and strong joint between adjacent panel ends, especially when four fasteners 500 are used (two at the top, two at the bottom) to fasten every panel joint.

The travel of the fasteners 500 into the joint is limited by the length of the connection members, and the fasteners remain accessible at the joint ends so that they can be removed in the event that it is ever desirable to disassemble the panel structure after it is assembled.

In the illustrated embodiment, the fastener only has a ramped guide-in portion 540 on one side of the passage, but in alternative embodiments a second ramped guide-in portion could be provided on the opposite side of the passage, to urge both connection members inwards to fit into the clamping portion.

Figures 12 and 13 show a panel fastened to a second panel by a fastener 500. In the embodiment shown in Figures 12 and 13, the panel frames have tongue and groove sections of the embodiment shown in Figure 4.

The first end of the panel is fastenable to the second end of an identical second panel by the fastener 500 which is configured to receive a connection member on the first end of the panel, and a connection member on the second end of the second panel.

In this example the tongue section 45 forms an angle of 90 degrees from the plane of the tongue shoulder section 42. The groove section 55 forms an angle of 90 degrees from the plane of the groove shoulder section 52. The first end of the panel comprises a tongue connection member 43, which extends in the direction of the tongue 40 along the panel end. The tongue connection member 43 is a portion of the tongue section 45. The second end of the panel comprises a groove connection member 53, which extends in the direction of the groove 50 along the panel end. The groove connection member 53 is a portion of the groove section 55. Separate tongue connection members 43 are formed at the top end and bottom end of the tongue section. Two corresponding groove connection members 53 are formed at the top end and bottom end of the groove section. Figure 12 only shows the top end of the tongue section and the groove section. The tongue and groove connection members 43, 53 abut one another when the tongue 40 of the panel 10 is received in the groove 50 of the second panel. The first end of the panel is fastenable to the second end of the second panel by positioning the fastener 500 around the tongue connection member 43 and the groove connection member 53, so that the connection members are held together in the clamping portion of the fastener 500.

Figure 13 shows a perspective view of the panels and fastener of Figure 12. Figure 13 shows the tongue and groove connection with a fastener 500 at the top of the panel. An identical tongue and groove connection with a fastener 500 can also be found at the bottom of the panel (although not shown in Figure 13). The first ends of the first and second metal frames each comprise a tongue connection member 43 at the top of the tongue and a tongue connection member 43 at the bottom of the tongue, and the second ends of the first and second frames each comprise a groove connection member 53 at the top of the groove and a groove connection member 53 at the bottom of the groove, so that panel ends are fastenable to one another by two connections at the panel top, and two connections at the panel bottom.

The tongue connection members 43 and groove connection members 53 are accessible at the top and bottom of the tongue and groove connection when the panel ends are connected together. The fasteners 500 can be both placed into position and removed when the panel ends are connected.

Figure 14 shows a perspective view of two structural panels connected together end-to- end. The first structural panel 10 is connected to an identical second structural panel 100 by a groove of the first structural panel received a tongue of the second panel. This arrangement allows at least two panels to be connected and form a wall. Further panels could be connected to the panels illustrated in Figure 14 to extend the wall as desired. The building panels of the present invention can advantageously be provided in a variety of shapes and sizes, so that they can be combined in modular fashion to construct a variety of structures of different designs. Apertures for windows and doors may be provided in the panels and surrounded by steel frames similar to those provided around the panel perimeter.

Figure 15 and 16 show two structural panels assembled to form a corner using a prefabricated corner panel 90 connected to two structural panels. The corner panel 90 is connected to the structural panels by a tongue and groove connection, as described above for the structural panels. For example, the corner panel 90 has a tongue formed at a first end of the corner panel 90 and a groove formed at a second end of the corner panel 90. The tongue and groove of the corner panel 90 correspond to the tongue and groove of the structural panels, allowing connection to flat panels on either side of the corner.

Claims

1 . A structural panel for building construction, the structural panel comprising: a first surface layer; a second surface layer; an insulation material disposed between the first surface layer and the second surface layer; and a frame structure comprising a first frame fixed to the first surface layer and a second frame fixed to the second surface layer, wherein the first frame is connected to the second frame via a non-metal connector.

2. A structural panel according to claim 1 , in which the non-metal connector is a polymer connector, preferably a PVC connector.

3. A structural panel according to claim 1 or 2, in which the connector is connected to the first metal frame at a first connector end, and to the second metal frame at a second connector end.

4. A structural panel according to any preceding claim, in which the first surface layer comprises magnesium oxide or cement board, and/or wherein the second surface layer comprises magnesium oxide or cement board, preferably wherein the first surface layer and second surface layer are made of the same material.

5. A structural panel according to any preceding claim, in which the insulation material comprises a solid block of insulating material.

6. A structural panel according to any preceding claim, in which the thermal insulation material is in contact with both the first surface layer and the second surface layer.

7. A structural panel according to any preceding claim, in which the structural panel does not comprise a cavity between the first surface layer and the second surface layer.

8. A structural panel according to any preceding claim, in which the first frame and the second frame are metal frames, preferably steel frames.

9. A structural panel according to any preceding claim, in which the first frame is connected to the second frame via a plurality of non-metal connectors.

10. A structural panel according to any preceding claim, in which the non-metal connectors maintain a separation between the first frame and the second frame, so that the first frame is not in physical contact with the second frame except via the non-metal connectors.

11. A structural panel according to any preceding claim, in which the first frame and the second frame comprise face portions, which are arranged parallel to the first and second surface layers, and edge portions which are arranged to extend inwards from the face portions of the frame towards the central plane of the panel.

12. A structural panel according to claim 11 , in which the first surface layer and the second surface layer are fixed to the frame structure by adhesive and/or mechanical fixings, preferably in which the first and second surface layers are fixed to the face portions of the first and second frames, respectively.

13. A structural panel according to any preceding claim, in which a first end of the frame structure comprises a tongue which extends in a longitudinal direction along the frame end, and a second end of the frame structure comprises a corresponding groove, such that the panel is connectable to a corresponding second panel by connecting the tongue of the panel to the groove in the second panel.

14. A structural panel according to claim 13, in which the tongue is formed by first ends of the first and second frames, and the groove is formed by second ends of the first and second frames.

15. A structural panel according to claim 13 or 14, in which the tongue and groove are symmetrical about the centre plane of the panel, so that the panels can be connected either way up.

16. A structural panel according to any of claims 13 to 15, in which the first ends of the first and second metal frames comprise a tongue shoulder section that extends inwards from the face portions of the frame towards the central plane of the panel, and a tongue section extending out of the panel from the tongue shoulder section and forming an angle of between 15 and 90 degrees from the plane of the tongue shoulder section.

17. A structural panel according to any of claims 13 to 16, in which the second ends of the first and second metal frames comprise a groove shoulder section that extends inwards from the face portions of the frame towards the central plane of the panel, and a groove section extending into the panel from the groove shoulder section and forming an angle of between 15 and 90 degrees from the plane of the groove shoulder section.

18. A structural panel according to any preceding claim, in which the first end of the panel is fastenable to the second end of an identical second panel by a fastener which is configured to receive a portion of the first end of the panel, and a portion of the second end of the second panel.

19. A structural panel according to any of claims 13 to 18, in which the first end of the panel comprises a tongue connection member, which extends in the direction of the tongue along the panel end, preferably in which the tongue connection member is a portion of the tongue section.

20. A structural panel according to claim 19, in which the second end of the panel comprises a groove connection member, which extends in the direction of the groove along the panel end, preferably in which the groove connection member is a portion of the groove section.

21 . A structural panel according to claim 20, in which the tongue connection member is formed at the top end and/or bottom end of the tongue section, and in which the groove connection member is formed at the top end and/or bottom end of the groove section, such that the tongue and groove connection members abut one another when the tongue of the panel is received in the groove of the second panel.

22. A structural panel according to claim 21 , in which the first end of the panel is fastenable to the second end of the second panel by positioning the fastener around the tongue connection member and the groove connection member, so that the connection members are held together by the fastener.

23. A structural panel according to claim 22, in which the tongue connection members and groove connection members are accessible at the top and bottom of the tongue and groove connection when the panel ends are connected together, such that the fasteners can be both fixed and removed when the panel ends are connected.

24. A structural panel according to any of claims 13 to 23, in which the first ends of the first and second metal frames each comprise a tongue connection member at the top of the tongue and a tongue connection member at the bottom of the tongue, and the second ends of the first and second frames each comprise a groove connection member at the top of the groove and a groove connection member at the bottom of the groove, so that panel ends are fastenable to one another by two connections at the panel top, and two connections at the panel bottom.

25. A system of structural panels, comprising: a first structural panel according to any preceding claim; and a second structural panel according to any preceding claim, in which a first end of the first structural panel engages with a second end of the second structural panel.