This invention relates to panels for use in structures such as building structures. A panel according to the invention is particularly suitable for use as a roof or wall panel for a building and it will be convenient to hereinafter describe the invention with reference to that example use.

Roofs and walls of buildings are formed in a variety of ways depending upon the size and/or nature of the building. The roofs of domestic dwellings are typically formed by interlocking a series of tiles, or a series of metal sheets. Tiles are generally favoured for aesthetic reasons, but are inconvenient to install and provide weatherproofing problems. Metal sheet is generally easier to install than tiles, but has less aesthetic appeal and suffers a lack of strength such that it can buckle or distort under load.

Most load bearing walls are formed as an integral part of the main structure of the building, or at least they have a frame or core which is so formed. Furthermore, the majority of walls are not constructed as a single unit, but require addition of facing material or some other surface treatment. That is, the wall is formed on site and is generally constructed in stages.

It is an object of the present invention to provide a panel which is relatively strong, is convenient to install and can be coloured and/or patterned as required to have appeal to the eye. It is a further feature of the invention to provide a method of forming such a panel. Still another object of the present invention is to provide a building panel which can be supplied as a complete unit for connection to a building structure. Yet another object of the invention is to provide

such a panel which can form a complete wall or wall section and which is capable of bearing a load.

According to the present invention, there is provided a building panel comprising two relatively rigid layers forming respective oppositely facing broad surfaces of said panel, and a core of foamed polymer interposed between and secured to said layers, at least one said layer being composed of a skin of the same material as said core which is formed integral with said core and which has a density substantially greater than that of said core.

An embodiment of the invention is described in detail in the following passages of the specificaton which refer to the accompanying drawings. The drawings, however, are merely illustrative of how the invention might be put into effect, so that the specific form and arrangement of the various features as shown is not to be understood as limiting on the invention. In the drawings:

Figure 1 is a diagrammatic view of a mould for producing a panel according to the invention, Figure 2 is a perspective view of one form of panel according to the invention and which is shown in semi-diagrammatic form.

Figure 3 is an enlarged cross-sectional view taken along line III-III of Figure 2 and showing the edge portion of a second panel of the same kind as that shown by Figure 2,

Figure 4 is an enlarged cross-sectional view taken along line IV-IV of Figure 2,

Figure 5 is a diagrammatic view of the end portion of a building constructed from panels according to the invention, Figure 6 is an enlarged cross-sectional view taken along

line VI-VI of Figure 5,

Figure 7 is a schematic view of a corner portion of a building structure as shown in Figure 5, but omitting parts for convenience of illustration, Figure 8 is an enlarged cross-sectional view taken along line VIII-VIII of Figure 7,

Figure 9 is an enlarged cross-sectional view taken along line IX-IX of Figure 7,

Figure 10 is an enlarged cross-sectional view taken along line X-X of Figure 7,

Figure 11 is a cross-sectional view of another form of panel according to the invention.

A panel according to the invention is characterised in that it is formed as a composite having relatively rigid and/or dense outer layers and an intervening core of less dense material. Preferably, the core and at least one outer layer are formed of a polymer such as silicate polymer. Such a panel is formed by applying the silicate polymer, for example, to a preformed mould 1 as shown in Figure 1, so as to produce a relatively dense skin against a surface 2 of that mould 1, and then modifying the composition of the polymer so as to produce controlled foaming over that skin. The manner of creating such a composite silicate polymer structure is well known and requires no further explanation in this specification.

Assuming the panel is to be used as a building panel such as a roofing panel, a sheet 3 of relatively rigid material such as plasterboard is preferably applied over the mould 1 prior to the foaming step as shown in Figure 1. The arrangement is such that a cavity 4 of appropriate size and

shape is created between the plasterboard sheet 3 and the mould surface 2 against which the aforementioned skin is formed. The skin, when formed, does not fill that cavity 4 and the remaining space is then taken up by the foamed polymer which adheres to the plasterboard 3. If desired, the inner surface of the plasterboard 3 may be pretreated to promote such adherence.

Figure 2 shows a panel 5 formed in the foregoing manner and the related cross-sectional views forming Figures 3 and 4 show the dense skin 6 and the less dense core 7, as well as the plasterboard sheet 3. In the case of the particular panel 5, which is of generally rectangular shape, the skin 6 extends completely across one broad surface of the panel 5 and across each of the four peripheral edges as is evident from Figures 3 and 4.

A panel produced in the foregoing manner is quite strong but is nevertheless relatively light in weight because of the foamed nature of the core 7. The skin 6 or outer layer of the panel could have any suitable pattern applied by appropriate formation of the mould 1. For example, that skin 6 may be contoured to represent the outline of interlocking tiles as shown by Figure 2. Also, the polymer could include pigments such that the skin 6 has a desired colour or colours.

It is to be understood that plasterboard is mentioned simply as an example material for forming one layer of the composite panel. Other sheet materials could be used for that purpose and the sheet may itself be a composite sheet. For example, the plasterboard may have a facing of galvanized iron sheet over at least part or parts of its inner surface to provide a firm basis for attaching fixing screws or other

devices .

A roofing panel 5 formed in accordance with the invention will usually have a rectangular peripheral shape as shown by Figure 2 and will have a length and width as considered suitable for the intended use of that panel 5. Typically, the length of the panel 5 will be such that it can span from a roof ridge line to an outer periphery of the roof, and the width is such that a plurality of panels 5 may need to be arranged side by side (Figure 3) to form a complete roof section. Such an arrangement will be hereinafter described as an example form of the invention.

The longitudinal side edges 8 and 9 of each roofing panel 5 are preferably arranged so that two adjacent panels 5 are capable of interengagement such as to facilitate formation of a weatherproof seal between them. In the example shown, one longitudinal edge 8 of the panel 5 has a tongue 10 extending therealong and the opposite edge 9 has a groove 11 which is capable of receiving the tongue 10 of an adjacent panel 5 as shown by Figure 3. Each of the edges 8 and 9 is preferably protected by an extension 12 of the main body of skin 6 which forms the outer layer of the panel 5. As shown by Figure 3, each skin extension 12 follows the contour of the respective edge 8 or 9.

In the preferred arrangement shown in Figure 3, the longitudinal edge 8 has a longitudinally extending slot 13 formed therein adjacent the outer surface of the panel 5, which is the surface over which the polymer skin 6 is formed. That slot 13 is arranged to receive a lateral extension or flange 14 of the outer surface skin 6 of an adjacent panel 5 as shown by Figure 3, preferably in such a way that the outer

surfaces of adjacent panels 5 appear to be continuous.

When two roofing panels 5 as described are joined side by side, the tongue 10 of one is located within the groove 11 of the other as shown by Figure 3. Also, the flange 14 of the last mentioned panel 5 intrudes into the longitudinal slot 13 of the first mentioned panel 5, again as shown by Figure 3. A suitable joining and/or sealing compound such as mastic may be included in the slot 13 to fill whatever space is not taken up by the flange 14. Also, a strip 15 of material such as closed cell kiater may be interposed between the two adjacent panel edges 8 and 9 for dust proofing purposes. ^* In the Figure 3 arrangement, one such strip 15 is included both above and below the tongue and groove connection.

The upper or ridge line edge 16 (Figure 4) of the panel 5 may be protected by a further continuation 17 of the outer surface skin 6. As also shown by Figure 4, a connecting rib

18 and 19 may extend transversely across the panel at the upper and lower surfaces respectively ofthe panel 5 at or

-adjacent the ridge line edge 16. The upper rib 18 may be part of the moulded contour of the panel 5, whereas the lower rib

19 could be formed by an inwardly turned edge portion of the skin continuation 17.

In a typical structure as shown by Figure 4, the lower rib 19 sits in or upon a suitable ledge 20 formed by part of a ridge beam 21. A cap section 22 of appropriate form and shape may locate over the upper rib 18 and, if desired, may be secured to that rib 18 or another part of the panel 5 by fixing screws 23 or other fastening means.

Figure 5 shows, in diagrammatic form, part of a building which incorporates roof panels 5 as described above. Figure 6

shows one possible way in which such panels 5 may be connected to a wall 24 of the building. In the arrangement shown, the wall 24 includes or comprises a panel 25 which is formed in a manner similar to that described in connection with the roof panel 5. That is, it includes a core 26, a dense outer skin 27, and an inner layer formed by a rigid sheet 28 of plasterboard or other material. A continuation 29 of the outer skin 27 extends across at least the upper edge 30 of the wall panel 25.

The wall 24 may be composed of one panel 25 or a plurality of such panels connected edge to edge.

In the arrangement shown by Figure 6, a strengthening piece 31 is provided at an upper edge portion of the panel 25 so as to abut against the inside surface of the sheet 28. The strengthening piece 31 may be formed by a length of timber (e.g., plywood) and has openings or recesses (not shown) therein to facilitate keying with the core 26. A similar strengthening piece 32 is provided across the roof panel 5 at a position such that a downwardly projecting part 33 of that piece 32 is exposed and is receivable within a locating recess 34 provided in the wall upper edge 30. Openings (not shown) are provided through the strengthening piece 32 so that the core 26 is not divided into two separate sections.

As shown by Figure 6, the wall and roof panels 25 and 5 can be secured together by fastening screws 35.

The connection shown by Figure 6 may not be appropriate at the end of a gable roof. In such a case, the connection may be arranged as shown by Figures 7 and 8.

Figure 7 shows a gable infill section 36 which is arranged to sit upon the upper edge 37 of a building wall 38.

Both the infill section 36 and the wall 38 can be formed of polymer as previously described so that, as shown in Figure 8, each has a core 39 and 40 respectively, an outer skin 41 and 42 respectively, and an inner rigid sheet 43 and 44 respectively of plasterboard or other suitable material. Also, in each case the respective skin is preferably continued over the edges of the particular panel.

According to the Figure 7 arrangement, the infill section 36 is keyed to the upper edge 37 of the wall 38 through a tongue and groove connection. The tongue ,45 is formed by a section of timber or other suitable material which is secured to the upper edge 37. That attachment may be effected after forming the panel of which the wall 38 is composed. For that purpose, two strengthening pieces 46 and 47 of timber or other suitable material may be provided within the upper edge portion of the wall 38 as moulded. Those pieces 46 and 47 facilitate attachment of the tongue 45 through use of fastening screws 48. The cooperating groove

-may be a preformed recess 49 in a lower edge 50 of the infill section 36.

The infill section 36 can then be secured to the wall 38 by fastening screws 51 as shown in Figure 8. A strengthening piece 52 of timber or other suitable material can be provided within the infill section 36 as shown so as to improve the security of that attachment.

The lower edge of each wall 24 and 38 can be secured to a base 53 in the manner shown by Figure 9. As shown by Figure 9, the lower edge portion of the wall 24 is rigidified by two sections 54- and 55 of timber or other suitable material, and those sections 54 and 55 are encapsulated within the skin 27

of the wall 24. A locating groove 56 is provided within the lower edge 57 of the wall 24. The wall 38 can be similarly constructed.

The base 53 may be formed of concrete, timber, or other suitable material. A locating rib 58 of timber or other suitable material is secured to the base 53 so as to extend along the line of the wall 24, and a similar rib 59 is provided for the wall 38. In the arrangement shown, each locating rib 58 and 59 is a timber stud which is secured by bolts 60 to the concrete base 53. That timber stud 58 or 59 is dimensioned to fit neatly within the locating groove 56 of the relevant wall 24 or 38 and thereby fix the position of that wall on the supporting base 53. The wall 24 or 38 can be secured to the timber stud 58 or 59 respectively by fastening screws 61, or other fastening means extending transversely into both the wall and the stud as shown.

As shown in Figure 9, a flange-like portion 62 may project downwardly from the lower edge 57 so as to overlap the outer edge 63 of the base 53. Such a flange 62 is not usually required for panels which are intended to be used as internal walls of a building.

The outer skin or surface of each wall 24 and 38 may be formed to represent any of a variety of surface finishes. For example, it may have the appearance of bricks, stone, timber, or cement rendering. The outer skin of the wall may also be coloured as required.

A special head section 64 may be used over wall openings such as window and door openings, and such a head section 64 is shown in Figures 7 and 10. The head section 64 can be formed in the same manner as the panels previously described

so as to have a core 65, an outer skin 66 and an inner rigid sheet 67. As seen in Figure 10, the upper edge 68 of the head section 64 is preferably shaped in the same manner as the upper edge 30 of the wall panel 25. The head section 64 locates over a window or door frame 69 and is strengthened to enhance its load bearing qualities. In the example shown, the head section 64 has strengthening pieces 70, 71, 72 and 73 contained therein. Those pieces are preferably moulded in situ and may be formed of timber or other suitable material. Each strengthening piece 70, 71, 72 and 73 preferably extends the full length or width of the section 64 and may have recesses or openings (not shown) into which or through which the core 65 extends.

It is preferred that opposite ends 74 (Figure 7) of the head section 64 are received within respective recesses 75 (Figure 7) provided in the upper edge of the wall 24. The arrangement is such that the head section 64 is supported by the wall 24 rather than the frame 69. Screws 76 or other fastening means can be used to secure the head section 64 to the"wall 24.

Figure 11 illustrates another form of wall panel 77 which is constructed as previously described and has a cap section 78 and 79 encapsulated within its upper and lower edge portions respectively. Each cap section 78 and 79 preferably extends the full width of the panel 77 and may be composed of timber, fibreboard, or other suitable material such as to impart strength to the panel 77 and provide a firm basis for fastening devices.

It will be apparent from the foregoing description that a panel formed in accordance with the invention has numerous

applications. It will be also apparent that use of that panel as a roofing or wall panel enables relatively convenient construction of a roof which is both strong and attractive in appearance.

Various alterations, modifications and/or additions may be introduced into the constructions and arrangements of parts previously described without departing from the spirit or ambit of the invention as defined by the appended claims.