Patent Publication Number: US-2010107536-A1

Title: Thermo tech mark ii limited

Description:
BACKGROUND OF THE INVENTION 
     1. Field of Invention 
     This invention relates to pre-formed or pre-cast building panels and methods of manufacturing these panels. The invention also relates to building panels that are pre-cast using an improved casting bed. 
     This invention also relates to an improved apparatus for fastening pre-formed building panels together, and a method of fastening building panels in place using the improved apparatus. 
     This invention also relates to an improved method of casting other building elements into a pre-formed building panel. 
     2. Description of the Prior Art 
     Pre-casting structural elements such as wall or floor panels is a method used to form prefabricated building elements that is well-known in the construction art. Prefabricated wall panels are typically cast either at a location other than the building site or sites where they are to be used, with the sections then delivered to sites as required, or they are cast on-site. When formed (and if necessary transported to the required location), they are assembled to form part of an overall structure, such as a house. 
     The pre-forming method of construction can help overcome logistical disadvantages in building construction. Building timescales can be reduced, workflow on site can be improved, and reliance on on-site construction is removed or reduced. 
     The forming techniques used to create these panels have become increasingly sophisticated since their introduction. Panels can be formed that include integral wire mesh or metal reinforcing bars to strengthen the structure. Panels can be formed that include hooks or eyes to facilitate transport or connection of the panel to the building structure. Lightweight inserts such as foam or polystyrene can be used to help shape and form these panels. 
     U.S. Pat. No. 5,313,753 discloses a prefabricated panel and a method of forming the panel. An outer frame  54  is created from pre-formed elements, and is used to define the outer boundary of the panel. Preformed and pre-sized elements, appropriate for use with this specific size and shape of outer frame  54 , are placed within the perimeter of this frame—e.g. service channels  20 , polystyrene blocks  16 , reinforcing rods  64 . These elements are fitted within the frame in a predetermined manner so that there are no gaps between the elements. This creates a base within the outer frame. Concrete is then added, filling the frame and covering this ‘base’. Once the concrete has set, the completed panel is ready for use and can be transported to a building site. The studs created using the method disclosed in U.S. Pat. No. 5,313,753 are formed as part of the concrete pour, and run essentially the full depth of the panel. The construction disclosed leaves no airgaps or air channels, and elements such as cable runs  48  have to be factored in during the pre-forming process. This removes a degree of flexibility from the construction. The manner in which the mix of elements is added and arranged in the outer mould framework can also tend to work against flexibility and modularity. The polystyrene blocks  16  are a standard depth, and run from the mould surface to the required height. If a different thickness of concrete panel is required, a different set of blocks of a different size must be used. 
     U.S. Pat. No. 4,751,803 discloses a panel forming method and a panel thus formed that allows a greater degree of flexibility. Pre-formed beams or framing members  16  form an outer framework, with support members  18  located within the framework at the base and supporting concrete studs  20  to form a ‘skeleton’. The outer framework and inner stud pattern can be varied in size and overall shape. The studs  20  include upwardly facing fasteners  24 . Once the framework is laid in place, a rigid insulation sheet  26  is laid over the top of the framework and held in position by impaling it on these fasteners. A wire mesh is then laid over the top of the insulation sheet, with the fasteners protruding upwards through the mesh. Steel rebar is also inserted. The finished panel is created by pouring concrete over and through the mesh and the sheet. The studs and the framework are held in place by the fasteners, which become embedded in the concrete panel after the poured concrete has set. 
     In the panel created using the method of U.S. Pat. No. 4,751,803, there is some contact between the fresh poured concrete and the edge sections of the frame. However, the main structural contact between the pre-formed studs and the fresh concrete pour that forms the flat concrete panel is via the fasteners. As described above, the studs and the newly poured concrete are separated by the plastic sheet or panel, and are only connected via the fasteners. While this configuration has the advantage of constructional flexibility, the final product may not be suitable for some applications, for example where structural strength is required between the panel and the studs. 
     It should also be noted that the method described in U.S. Pat. No. 4,751,803 is what is known in the construction art as a ‘double pour’ method. That is, the studs  20  are formed separately from a ‘first pour’ of concrete, prior to being laid out in the grid pattern shown in  FIG. 1  of U.S. Pat. No. 4,751,803. The fresh concrete pour over the top of the grid is the ‘second pour’ that forms the flat concrete panel. It should also be noted that the concrete studs  20  of U.S. Pat. No. 4,751,803 (those formed in the first pour) need to be formed with all the necessary fasteners already in place, and with apertures for wiring or other items formed into each of the studs  20  during this first pout, or subsequently machined in. As two pours are required, time and complexity is added to the panel forming method. Also, as the studs  20  are formed from concrete, they are heavy. If not formed on site, the studs need to be stored and then transported to the forming site. Storing and transporting heavy concrete studs adds to the complexity of the building logistics, and usually requires additional storage space. 
     Furthermore, it should be noted that the studs  20  are formed with strips  22  located on what will in use be the inner facing side of the wall panel. This arrangement can limit the options that are available for attachment of inner drywall panels (drywall is also commonly known as gypsum board, plasterboard, and GIB™ board, depending on the country). The material (e.g. wood) used to form the strips  22 , and their thickness, will at least partly dictate the panel attachment mechanism. 
     Also, it should be noted that the final construction of the panel of U.S. Pat. No. 4,751,803 includes support members  18  bounding the panel. This arrangement adds complexity and weight to the final construction. 
     A further difficulty that can arise when casting concrete panels is mitring the lip correctly. When casting, one (or more) walls of the mould can be angled, usually at 45 degrees, so that the edge face of the finalised panel is angled. This angled edge face can be butted up against a similarly formed angled edge face to create a mitred 90 degree corner. If the mould is formed with what will be the outer face of the panel towards the forming surface or floor, it can be difficult to correctly form these corners, as one wall of the mould will be required to be angled inwards. As concrete is poured, it can tend to cavitate (cause cavities) against the inner face of the wall of the mould. This means that this face of the panel, once removed from the mould, will not be smooth or perfectly formed. 
     Another difficulty that can arise with the forming methods known in the art is rotational lifting of the panels. That is, lifting the panels from the flat, horizontal alignment into a vertical alignment. The standard panel forming method is, for the sake of simplicity, to form the panel horizontally, usually by pouring wet concrete into a flat and wide container. In use, wall panels are aligned vertically, and the finalised panel will need to be rotated and lifted out of the casting bed into a vertical orientation. Because the forces exerted on the panels when they are lifted are generally greater than those they will experience in daily use, It is usually necessary to overdesign them. That is, a panel must be designed to withstand the stresses it will experience as it is rotated and lifted from a horizontal position to a vertical position. These stresses are greater than those it will experience once in position. This problem can be exacerbated by prior art bed casting apparatus and methods, where additional suction forces must be overcome as the wall panel is lifted from a horizontal position in/on the casting bed, into a vertical, ‘use’ position. 
     An additional difficulty that can be experienced when building structures using prefabricated elements such as building panels is the difficulty of correctly aligning these elements and fastening them together. It is standard practice in the building industry to cast a number of apertures into the top edge of a building panel—for example, the top edge of a ground floor external wall panel. These could also be machined into the top edge post-casting. A number of complimentary fastening elements are set into the lower edge of a first floor panel, extending downwards. The first floor panel is hoisted into position above the ground floor panel, and manoeuvred into position so that the downwardly extending fastening elements locate into the apertures. Usually, the apertures are filled with chemset or a similar fastening chemical. The chemset bonds the fasteners into the lower panel, binding the top and bottom panels together. It can be seen that the tolerance range in the location of the apertures, and the location of the fasteners, is critical. If the location of the apertures or the fasteners is not correct, the upper and lower panels will not correctly align. Rectifying this can be expensive and time-consuming. 
     A third difficulty with using pre-cast construction elements is that of forming windows and doors into wall panels during the panel forming process. Windows usually have an upper head and a lower sill, which extend horizontally backwards (i.e. into the room) from a vertical frame, which passes through the concrete panel. The frame holds the glass pane of the window in place. Apart from this, windows are generally not standard structures. Therefore, the builder must either maintain a large library of various window sizes, or custom make every window mould. The most commonly used prior art forming method is to build a wooden mould, pour the concrete, remove the mould and then insert the window frame and glass. 
     It can be seen that there exists a need in the construction industry for a simplified method of creating pre-cast sections with integral studs, where the studs are not formed in a separate pour. Also, there exists a need for a panel forming method and a panel which has studs that can be easily formed, stored and transported, and where the studs allow for the use of a greater variety or increased range of e.g. drywall fasteners, which can be easily added after to panel is formed. Also, where the studs can be easily machined post-casting, for example to add holes for cable conduits, etc. Also, where the panel can be formed face-up, with mitred corners. 
     There also exists a need in the construction industry for a simplified method and construction for fastening a panel in place, for example to fasten the panel to another panel, decreasing the reliance on correct manufacturing tolerances in two separate elements. 
     There is also a need in the construction industry for a method of casting elements such as windows and doors in place in wall panels, in their final form. This method would decrease or remove the need for additional post-casting and post-transporting work. 
     SUMMARY OF THE INVENTION 
     In a first aspect, the invention consists in a building panel, comprising: 
     a concrete portion, having an inner surface and an outer face, 
     a plurality of insert blocks embedded in said concrete portion to form said inner surface along with part of said concrete portion, said inner surface being substantially planar, 
     a planar plastic panel covering said planar inner surface, 
     a plurality of spacing members located against the outer face of said plastic panel, each of said spacing members including at least one fastening member that protrudes through said plastic panel and into said concrete portion, such that said fastening members are embedded in said concrete portion. 
     Preferably said fastening members are embedded in said concrete section, between said insert blocks. 
     Preferably said plastic panel is a polystyrene panel having a minimum thickness of 20 mm. 
     Preferably said insert blocks are positioned in parallel block rows along said plastic panel and are sized to reach from one edge of said plastic panel to the opposite edge. 
     Preferably said spacing members are elongate members positioned parallel to one another, spaced apart along said panel to form parallel spacer rows, said elongate members having an outer surface parallel to the plane of said plastic sheet and spaced from said outer face of said plastic panel. 
     Preferably said parallel block rows is from 400 mm to 600 mm on centre, and the distance between said parallel spacer rows is from 400 mm to 600 mm on centre. 
     Preferably said outer surface is spaced a distance of between 25 mm and 45 mm from said outer face of said plastic panel. 
     Preferably said elongate members are U-channel beams, one side wall of said U-channel abutting said sheet, said side walls having a height of 35 mm, said base of said U-channel having a width of 65 mm. 
     Preferably said fasteners protruding beyond said plastic sheet is at least half the total length of said fastener. 
     Preferably said fastening members are each between 60 mm and 80 mm long, and the number of said fastening members per elongate member is at least 5. 
     Preferably said insert blocks are formed from foamed polystyrene. 
     Preferably said insert blocks are formed as hollow constructs. 
     Preferably said hollow constructs are filled with an insulation material such as mineral wool, natural wool or polyester wool. 
     Preferably said insert blocks has a height of at least 40 mm. 
     Preferably said insert blocks have angled side walls, the face of each of said blocks that contributes to said inner surface being broader than the corresponding opposite face, said base having a width of between 400 mm and 550 mm, said top having a width of between 350 and 500 mm. 
     Preferably said spacing elements are positioned such that said parallel block rows are interspersed between said parallel spacers. 
     Preferably said building panel also includes a plurality of rebar elements embedded in said concrete section. 
     Preferably said building panel is aligned at an angle to said inner face. 
     Preferably said angle is chosen, and said end is shaped, to allow said end to interlock with a mutually complimentary formed end of a second one of said building panels placed adjacent said first panel. 
     Preferably said angle is 45 degrees. 
     Preferably said building panel includes at least one corner connector partially embedded in said concrete portion, with part of said corner connector extending from said concrete portion to enable connection of said building panel to an adjacent building panel of similar construction. 
     Preferably said building panel is shaped to allow said edge to interlock with a mutually complimentary formed edge of a second one of said building panels placed adjacent said first panel, said interlocking forming a cavity between said interlocking panels suitable for insertion of one edge of a wall stud. 
     In a second aspect, the invention consists in a method of forming a concrete building panel comprising the steps of 
     forming an enclosed-perimeter outer framework, 
     positioning at least one spacing member within said outer framework, each of said spacing member or members including at least one fastening member extending upwards, 
     placing a planar plastic panel within said frame over the top of said spacing members, with the upper portion of said fastening members protruding through the upper surface of said plastic panel, said plastic panel sized to fit within said outer framework, 
     positioning a plurality of insert blocks on said plastic panel, 
     pouring concrete into said frame to cover said plastic panel, said fastening members, and said insert blocks. 
     Preferably said method includes the step of removing said outer framework once said concrete has solidified. 
     Preferably said method includes the step of inserting a plurality of reinforcing elements within said outer framework after said insert blocks are positioned on said plastic panel, and before said concrete is poured. 
     Preferably said method also includes the step of positioning a corner connector element in said outer framework before said concrete is poured, in such a manner that at least part of said corner connector element protruding from said building panel. 
     Preferably said blocks are sized and positioned such that the space between at least one end of each of said blocks and the wall of said frame is between 50 mm and 400 mm. 
     In a third aspect, the invention consists in a casting bed for the creation of at least one building panel, comprising: 
     a plurality of beam members, arranged in substantially parallel rows, 
     a plurality of mould sections, connected to one another to form at least one enclosed-perimeter mould, 
     a clamping mechanism adapted to clamp said enclosed perimeter mould onto the top of said beam members, said beam members adapted to receive clamping mechanism. 
     Preferably said beam members are I-section beams, the upper part of said beam members adapted to receive said clamping mechanism. 
     Preferably said beam members have a length between 50 m to 150 m, with the outer ones of said beam members spaced apart between 2 m and 3 m. 
     Preferably said bed includes at least four of said beam members arranged in parallel, and arranged at equally spaced intervals. 
     Preferably said bed includes at least four of said beam members arranged in parallel, and the inner ones of said beam members are spaced at intervals of between 200 mm and 2000 mm from the outer ones of said beam members. 
     Preferably said mould sections are elongate framework members that can be bolted together to form said mould. 
     Preferably said mould sections are shaped so that when cast, said building panel will have shaped edges. 
     Preferably said mould section are adapted such that at least one of said mould sections can be angled from the vertical when attached to the others of said mould sections, so that when cast, at least one edge of said building panel will be at an angle. 
     In a fourth aspect the invention consists in a building panel, comprising: 
     a concrete portion, having an inner face, an outer face, and an enclosing boundary portion around the perimeter of said inner face, 
     a rigid planar plastic sheet having an outer face, and an opposed inner face fitting against and sized with said concrete portion inner face, 
     a plurality of spacing studs located against said outer face of said plastic panel, each of said spacing studs including at least one fastening member that protrudes through said plastic panel and into said concrete portion, such that said fastening members are embedded in said concrete portion. 
     Preferably said boundary portion has four sides, the first, second and third of said sides having a substantially flat inner face, said first and second sides parallel, said building panel also including parallel spacer blocks located against said flat inner faces of said first and second sides, said spacer blocks the same width as said faces, and a timber top plate, one face of said timber top plate located against the inner face of the fourth side of said boundary portion, said timber top plate sized to cover said fourth side. 
     Preferably said building panel includes steel mesh and rebar elements embedded within said concrete portion. 
     Preferably said concrete has a compressive strength of approximately 40 MPa. 
     Preferably said parallel spacer blocks run the full length of said building panel, and said 
     Preferably said building panel includes a service channel located against, and running the length of, said one face of said timber top plate. 
     Preferably said timber top plate has a profile width of between 130 and 150 mm, and a profile depth of between 35 mm and 55 mm, and said parallel spacer blocks each have a profile width of between 130 mm and 170 mm and a profile depth of between 23 mm and 70 mm, said spacer blocks being the same length as the sides of said building panel. 
     Preferably said building panel includes a plurality of bolts, protruding from said inner faces of said boundary portion and embedded in said spacer blocks. 
     Preferably said bolts are 130 mm M12 bolts embedded in said spacer blocks to a depth 5 mm less than the depth of said spacer blocks. 
     Preferably said building panel also includes a plurality of screws, passing through said timber top plate and said service channel, and into said concrete. 
     Preferably said building panel is between 180 and 220 mm, and said plastic sheet has a thickness of between 25 mm and 60 mm, and the length of said fasteners is 75 mm. 
     Preferably said spacer blocks, the inner face of said timber top plate and the inner portion of said spacing studs all lie in substantially the same plane. 
     Preferably said service channel is formed from a u-channel section attached to said timber top plate, with the open face of said channel facing said top plate. 
     Preferably said service channel is a USG ceiling batten with a depth of 23 mm and a base width of 37 mm. 
     Preferably said building panel also includes a perpendicular spacer block located against and fully covering the third side of said boundary portion, perpendicular to said parallel spacer blocks and parallel to said timber top plate, said perpendicular spacer block the same length as the closest, parallel edge said plastic sheet, and the same width as the adjacent flat inner face. 
     Preferably said perpendicular spacer block has a profile width of between 60 mm and 110 mm and a profile depth of between 30 mm and 50 mm. 
     Preferably said building panel are perpendicular to said panel outer face, except for the edge face which is adjacent one of said parallel spacing blocks, which is angled inwards towards said spacing studs and said plastic panel. 
     Preferably said inwards angle is 45 degrees. 
     Preferably said spacing studs are steel U-channels, aligned so that one side of said channel abuts said plastic panel, the outer ones of said spacing studs arranged to form a closed perimeter inner framework around the edges of said outer face of said planar plastic panel, the bases of the channels that form said closed perimeter aligned to face outwards from said inner framework towards said enclosing boundary portion. 
     Preferably said spacing studs have a width across the base of said u-channel of between 50 mm and 100 mm. 
     Preferably said spacing studs have a width across the base of said u-channel of 64 mtn, said building panel having an overall width of 200 mm, such that the thickness of concrete from said concrete portion inner face to said panel inner face is 86 mm. 
     Preferably said spacing studs have a width across the base of said u-channel of 51 mtn, and said plastic sheet has a thickness of 30 mm, said building panel having an overall width of 200 mm, such that the thickness of concrete from said concrete portion inner face to said panel inner face is 119 mm. 
     Preferably said spacing members have a width across the base of said u-channel of 90 mm, and said plastic sheet has a thickness of 50 mm, said building panel having an overall width of 200 mm, such that the thickness of concrete from said concrete portion inner face to said panel inner face is 60 mm. 
     Preferably said U-beams are filled with polystyrene. 
     Preferably said spacing members are closed sections, having a depth of 23 mm, and said plastic sheet has a thickness of 25 mm, said building panel having an overall width of 200 mm, such that the thickness of concrete from said concrete portion inner face to said panel inner face is 151 mm. 
     Preferably said closed sections are formed from USG ceiling battens, the top of the channel of said battens including a plate which closes said channel. 
     Preferably said building panel are perpendicular to said panel outer face, except for that edge face which is adjacent one of said parallel spacing blocks, which is angled inwards towards said spacing studs and said plastic panel. 
     Preferably said inwards angle is 45 degrees. 
     Preferably said spacing members have a width across the base of said u-channel of 90 mm, and said plastic sheet has a thickness of 50 mm, said building panel having an overall width of 200 mm, such that the thickness of concrete from said concrete portion inner face to said panel inner face is 60 mm, all the edge faces of said building panel substantially perpendicular to said panel inner face. 
     Preferably said U-beams are filled with polystyrene. 
     Preferably said building panel includes at least one intertenancy spacer on said building panel outer face, held in place by fasteners protruding downwards into said concrete. 
     Preferably said panel includes at least two and preferably three intertenancy spacers, arranged in parallel and running substantially from the top to the bottom of the building panel. 
     Preferably said spacing studs lies in a plane between 8 mm and 12 mm further towards said outer face of said building panel than said inner faces of said spacer blocks and said inner face of said timber top plate. 
     Preferably said building panel also includes at least one embedded wall panel fastener, said panel fastener comprising a hollow fastening tube and a main body, said main body embedded in said concrete panel, said fastening tube passing through one side of said boundary portion. 
     Preferably said at least one fastening tube is sized and aligned to pass through that side of said boundary portion adjacent to said perpendicular spacer block. 
     Preferably said main body is an elongate member bent to form a panel portion and a connection portion, said panel portion embedded between said inner face and said outer face of said concrete portion, said connection portion passing between and connecting said panel portion and said fastening tube. 
     Preferably said wall panel also includes a portal, passing through said concrete portion and said planar plastic sheet, said portal comprising: 
     an open-ended box frame, the inner edges of said box frame planar with inner side, 
     a portal frame element, the inner part of said frame element adjacent the outer edges of said box frame, the outer part of said frame element embedded in said concrete portion. 
     Preferably said box frame and said portal frame element is surrounded by polystyrene blocks. 
     Preferably said polystyrene blocks and said portal frame element are surrounded by a PVC barrier sheet arranged such that said concrete and said frame are not in direct contact. 
     In a fifth aspect, the invention consists in a method of forming a concrete building panel comprising the steps of: 
     1) forming an enclosed-perimeter rectangular outer framework, 
     2) positioning a plurality of spacing studs within said outer framework and spaced from said outer framework, each of said spacing members including a plurality of fastening members extending upwards, 
     3) placing a planar plastic panel within said frame over the top of said inner framework, the upper portion of said fastening members protruding through the upper surface of said plastic panel, said planar plastic panel sized and shaped to substantially match the size and shape of said inner framework, 
     4) pouring concrete into said frame to cover said plastic panel and said fastening members, and fill said outer framework to the required depth, 
     5) removing said outer framework once said concrete has cured. 
     Preferably said spacing studs are arranged to form an inner framework with a rectangular and closed perimeter. 
     Preferably said method also includes the steps of placing plastic spacer blocks and a timber top plate in the space between said inner framework and said outer framework before said concrete is poured, said timber top plate having the same length as one side of said inner framework, the width of said top plate the same as the distance between adjacent parallel walls of said inner framework and said outer framework, said plastic spacer blocks arranged to fill at least the gap between the ends of said timber top plate and said outer framework and the space between said inner framework and the outer framework on the sides perpendicular to said top plate. 
     Preferably said method includes the step of attaching a channel section to said top plate to form a service channel, said channel section running the length of said timber top plate. 
     Preferably said method also includes the step of placing at least one spacing stud inside said inner closed perimeter as part of said inner framework. 
     Preferably said method includes the step of embedding bolts in said spacer blocks, aligned upwards. 
     Preferably said bolts are embedded in said spacer blocks in such a manner that the lower ends of said bolts are a minimum distance of  5 mm from the lower face of said spacer blocks. 
     Preferably said spacer blocks and the lower face of said top plate are emplaced so that they lie in the same plane as the lower edge of said inner framework. 
     Preferably said method includes the step of placing shims underneath said spacing studs before said concrete is poured in order to space the plane in which said lower sides of said spacing studs lies upwards in relation to the plane which the lower edge of said outer framework and said spacer blocks lie. 
     Preferably said shims are between 8 mm and 12 mm. 
     Preferably said method also includes the step of emplacing at least one intertenancy fastener on the upper face of said concrete by pressing attached anchors into said concrete before it sets. 
     Preferably said method also includes the steps of: 
     1) assembling a rectangular box frame from a portal head panel, a portal sill panel and two portal wall panels, said head panel and said sill panel located on opposite sides, and connected by said wall-panels, the dimensions of said box frame matched with the inner part of a separately preassembled portal frame element, said box frame open at both ends, 
     2) attaching polystyrene blocks to the outer surfaces of said head, sill and wall panels, the upper edges of said polystyrene blocks overlapping one end of said rectangular box, 
     3) attaching a PVC barrier sheet to the outer faces of said polystyrene blocks, the lower edge of said barrier sheet substantially aligned with the lower edges of said polystyrene blocks, the upper portion of said barrier sheet overlapping the upper edges of said polystyrene blocks, 
     4) placing said box, blocks and sheet inside said inner framework, so that said polystyrene blocks face upwards, 
     5) attaching a plastic barrier block to the outer part of said preassembled portal frame element, said barrier block matching the dimensions of the outer part of said preassembled frame element, the outer face of said barrier block offset from the inner face, 
     6) emplacing said portal frame element so that said inner part rests on the upper edges of said box frame, said polystyrene blocks overlapping the sides of said frame element, 
     7) attaching said upper portion of said PVC barrier sheet around said bather block and said frame to form a seal, 
     8) removing said bather block once said concrete has been poured and has cured. 
     In a sixth aspect the invention consists in a wall panel fastener, comprising: 
     a hollow fastening tube, 
     a main body comprising a rod bent to form a panel portion and a connection portion, the connection portion end of said rod attached to the side of said fastening tube, said panel portion spaced from said fastening tube, said panel portion aligned substantially parallel to said fastening tube. 
     Preferably said fastening tube to said connection portion is between 60 mm and 200 mm, and said fastening tube is between 30 mm and 250 mm in length. 
     Preferably said perpendicular distance is between 90 mm and 110 mm, and said fastening tube is 90 mm in length. 
     Preferably said fastening tube is formed from a 90 mm length of NB20 galvanised pipe, and said main body is formed from D10 rio rod. 
     Preferably said wall panel fasteners embedded within it in such a manner that said at least one fastening tube passes through a first side wall of said first panel, to a separate building element, said first preformed wall panel positioned so that said first side wall is adjacent an outer surface of said separate building element, said method comprising the steps of: 
     1) using said fastening tube as a drill bit guide and drilling a hole in said separate building element, 
     2) filling said hole and said fastening tube with a chemical anchor, 
     3) inserting a bolt in said tube, said bolt fitted with a washer and nut at the outer end to act as a flange on the end of said tube, said bolt sized so that the lower end of said bolt will be within said hole when said outer end is resting on the end of said tube. 
     Preferably said step of drilling said hole is carried out so that said hole is substantially the same depth as the length of said tube, and said bolt is chosen to be between 120-150% the length of said tube. 
     Preferably said tube is 90 mm long, said hole is 80 mm deep, and said bolt is a 120 mm M12 bolt. 
     Preferably said separate building element is a second preformed building panel. 
     In a seventh aspect the invention consists in a method of using the wall panel fastener as claimed in any one of claims  88  to  91  to connect a first preformed wall panel that has at least one of said wall panel fasteners embedded within it in such a manner that said at least one fastening tube passes through a first side wall of said first panel, to a separate building element, said first preformed wall panel positioned so that said first side wall is adjacent an outer surface of said separate building element, said method comprising the steps of: 
     1) using said fastening tube as a drill bit guide and drilling a hole in said separate building element, 
     2) filling said hole and said fastening tube with a chemical anchor, 
     3) inserting a bolt in said tube, said bolt fitted with a washer and nut at the outer end to act as a flange on the end of said tube, said bolt sized so that the lower end of said bolt will be within said hole when said outer end is resting on the end of said tube. 
     Preferably said step of sealing said PVC sheet is achieved by taping said sheet to said barrier block. 
     Preferably said method includes the step of emplacing a number of stud elements around said box frame, before said building panel is moulded. 
     Preferably said method includes the step of pre-cutting said barrier block with an angled rebate before it is attached to the outer part of said frame. 
     Preferably said rebate is 5 degrees. 
     In an eighth aspect the invention consists in a method of casting portal elements into a building panel, comprising the steps of: 
     1) assembling a rectangular box frame, open at both ends, from a portal head panel, a portal sill panel and two portal wall panels, said head panel and said sill panel located on opposite sides, and connected by said wall panels, the dimensions of said box frame matched with the inner part of a preassembled portal frame element, 
     2) attaching polystyrene blocks to the outer surfaces of said head, sill and wall panels, the upper edges of said polystyrene blocks overlapping one end of said rectangular box, 
     3) attaching a PVC barrier sheet to the outer faces of said polystyrene blocks, the lower edge of said barrier sheet substantially aligned with the lower edges of said polystyrene blocks, the upper portion of said barrier sheet overlapping the upper edges of said polystyrene blocks, 
     4) placing said box, blocks and sheet in a building panel mould, so that said polystyrene blocks face upwards, 
     5) attaching a pre-cut plastic barrier block to the outer part of said frame element, said barrier block matching the dimensions of the outer part of said preassembled frame element, the outer face of said barrier block offset from the inner face, 
     6) emplacing said frame element so that said inner part rests on the upper edges of said box frame, said polystyrene blocks overlapping the sides of said frame element, 
     7) attaching said upper portion of said PVC barrier sheet around said barrier block and said frame to form a seal, 
     8) moulding said building panel around said box frame and said frame element, 
     9) removing said barrier block. 
     This invention may also be said broadly to consist in the parts, elements and features referred to or indicated in the specification of the application, individually or collectively, and any or all combinations of any two or more of said parts, elements or features, and where specific integers are mentioned herein which have known equivalents in the art to which this invention relates, such known equivalents are deemed to be incorporated herein as if individually set forth. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       Preferred forms of the present invention will now be described with reference to the accompanying drawings in which; 
         FIGS. 1   a  and  1   b  show top and side views of a ‘standard’-designated embodiment of the wall panel of the present invention. 
         FIGS. 2   a  and  2   b  show top and side views of an ‘extra’-designated embodiment of the wall panel of the present invention. 
         FIGS. 3   a  and  3   b  show top and side views of a ‘heavy-duty’-designated embodiment of the wall panel of the present invention. 
         FIGS. 4   a  and  4   b  show top and side views of an ‘extra-heavy-duty’-designated embodiment of the wall panel of the present invention. 
         FIG. 5  shows a side view of an ‘intertenancy’-designated embodiment of the wall panel of the present invention. 
         FIG. 6  shows detail of the wall panel fastening device of the present invention. 
         FIG. 7   a  shows the wall panel fastening device of panel  6  in use, connecting a ground floor wall panel to a foundation plate. 
         FIG. 7   b  shows the wall panel fastening device of panel  6  in use, connecting a second floor wall panel to a first floor panel located underneath. 
         FIG. 8  shows a perspective view from one end of a prior art ceiling batten manufactured by USG, which is used as part of the construction of several of the preferred embodiments of wall panel. 
         FIG. 9  is a cross-sectional side view of a typical window frame including a window sill and window head, formed using the method and apparatus of the present invention. 
         FIG. 10  is a cross-sectional side view of the standard wall panel including a window, showing detail of a window frame, sill and head formed using the method and apparatus of the present invention. 
         FIG. 11  is a cross-sectional side view of the extra wall panel including a window, showing detail of a window frame, sill and head formed using the method and apparatus of the present invention. 
         FIG. 12  is a cross-sectional side view of the heavy duty wall panel including a window, showing detail of a window frame, sill and head formed using the method and apparatus of the present invention. 
         FIG. 13  is a cross-sectional side view of the extra heavy duty wall panel including a window, showing detail of a window frame, sill and head formed using the method and apparatus of the present invention. 
         FIG. 14  shows a top cross-sectional view of two panels connected at their edges to form a mitred corner. 
         FIG. 15  shows an example of a standard wall panel with cast-in windows and doors. 
         FIG. 16  shows an example of how a horizontally aligned element such as a floor panel can be attached to a vertically-aligned wall panel of the type shown in any of  FIGS. 1 to 5 , by showing a floor panel connected to an extra wall panel, the extra wall panel having a standard wall panel emplaced above it. 
         FIG. 17  shows a perspective view of an example partial mould layout that can be adapted to produce the panels of  FIGS. 1 to 5 . 
         FIG. 18  shows an isometric view of an outer framework used to form a construction panel, having outer walls and spacers positioned within the perimeter of the framework, the spacers having vertically aligned fasteners. 
         FIG. 19  shows an isometric view of the framework and spacers of  FIG. 18 , with a high density polystyrene sheet in position over the top of the spacers, the fasteners protruding through the sheet, and polystyrene blocks positioned on top of the sheet leaving a network of channels between adjacent blocks. 
         FIG. 20  shows an isometric view of the framework of  FIGS. 18 and 19 , with rebar elements added within the outer frame, and the front facing wall not shown for clarity. 
         FIG. 21  shows the framework of  FIG. 20 , with concrete being poured into the framework to form the construction panel. 
         FIG. 22  shows an exploded view of the construction panel and outer framework. 
         FIG. 23  shows a cutaway side view of the finished construction panel of the preferred embodiment. 
         FIG. 24  shows adjacent ends of two construction panels, connected via a pair of corner connector units partially embedded in each panel. 
         FIG. 25   a  shows adjacent ends of two construction panels used as floor panels, each having an edge that is shaped so as to interlock with the edge of an adjacent panel, the panels located over a floor joist, with one of the panels bolted to the floor joist. 
         FIG. 25   b  shows adjacent ends of two construction panels used as wall panels, each having an edge that is shaped so as to interlock with the edge of an adjacent panel, the shaped edge also allowing the panels to interlock around the end of a horizontal wall stud. 
         FIG. 26  shows an end view of a casting bed for creating the construction panels of  FIGS. 18 to 25 . 
     
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     While the invention is susceptible to embodiment in different forms, specific embodiments are shown in the drawings, and described in detail. The present disclosure is to be considered an exemplification of the principles of the invention, and is not intended to limit the invention to that as illustrated and described herein. 
     There are three main aspects to the invention, which are described in detail below: Firstly, improved panel casting methods will be described. Also, the structure of the panels formed by this method. 
     Secondly, an improved panel construction for fastening pre-cast panels to other panels, foundation slabs, or similar will be described, and the method by which this improved construction can be formed. 
     Thirdly, an improved method of casting elements such as windows and doors into a pre-formed panel during the panel forming process will be described. 
     Pre-Formed Panel Casting 
     The panel forming methods of the present invention can be used to form panels of a variety of different configurations. A first forming method and the panel created using this method will be described first, with reference to  FIGS. 18 to 26 . Then a second general forming method will be described, and five different preferred embodiments of panel configuration which can be formed using the second general forming method, will be described below, with reference to  FIGS. 1 to 5 , and  8 . 
     The construction of the panel of the first forming method, and the method of construction, will be described in tandem below. 
     The general construction method can be broadly outlined as follows: Firstly, an outer frame  5001  of the required overall perimeter size is created using pre-cast or pre-formed outer or side walls  5002 ,  5003 . The side walls are connected together in such a manner that there are no gaps in the perimeter. That is, the outer frame  5001  forms an enclosed perimeter around an inner space. It is usual for this framework  5001  to be created on a factory or warehouse floor or similar. The floor must be reasonably level (that is, substantially horizontal), but does not have to be a completely flat or clean surface. The outer frame  5001  forms the sides of a mould. In the preferred embodiment, the walls  5002 ,  5003  are used only to form the mould, and do not become part of the final panel. However, other embodiments not specifically described herein may use the side walls as part of the finalised panel. The side walls  5002 ,  5003  can be of different lengths and sizes, depending on the overall final size of panel required. Next, spacing elements or spacers  5004  are added. These lie inside the outer frame  5001 . In the preferred embodiment, the spacers  5004  are steel U-channel beams, placed on their sides within the outer frame  5001  (that is, turned through 90 degrees) so that one side of the beam lies flat on the floor or forming surface, and the open part of the U faces sideways. In the preferred embodiment, the base portion of the ‘U’ (which is vertical and defines the height of the spacer element when the channel is positioned on its side for use) is 65 mm, and each of the side walls is 35 mm in length. In the preferred embodiment, the spacers  5004  are laid in parallel rows at intervals of approximately 60 mm centre to centre (on centre), with the ends of each spacer  5004  contacting or close to the inner surface of one of the side walls  5002 ,  5003  of the outer frame  5001 . It should be understood that alternative arrangements are possible. For example, more complex ‘hash’-type arrangements could be created, rather than simple parallel rows. Alternatively, custom spacers of a required shape (e.g. circular, rectangular, oval etc) could be used. It should also be noted that constructions where window or door frames are moulded into the panel  5012  during this creation phase are possible, and a preferred method by which this casting process can be carried out will be described in detail below. If window frames or door frames are moulded into the panel  5012 , the spacers  5004  are arranged and spaced accordingly. 
     The upper sides of each of these spacer elements  5004  are fitted with fastening members or fasteners  5005 , spaced along the upper side. These fasteners  5005  face substantially vertically upwards. The fasteners  5005  are steel pins or similar, riveted or otherwise connected to the upper side of each channel. In the preferred embodiment, these are approximately 70 mm high (or long), and are spaced at intervals along each of the spacers  5004 . In the preferred embodiment, there are five or six of the fasteners  5005  spaced at regular intervals along each of the spacing members  5004 . 
     In the finalised panel  5012 , the steel channel spacer beams  5004  form lightweight inner studs that protrude from the inner surface of the finished panel  5012 . The panels  5012  can either be used as house wall panels, with the outer surface forming part of the outer wall of a house, or alternatively, these panels can form floor panels, with the outer surface forming the internal floor of the house. The inner studs or spacers  5004  can be used to attach gib board or similar internal finishing material to the panel  5012 , to form the inner wall of a house. The spacers  5004  of the preferred embodiment also have other uses. For example they can be used to route cables between the outer wall (the panel  5012 ) and the inner wall (the gib board) of a house. 
     Once the U-beam spacers  5004  have been emplaced in the outer frame  5001 , a heavy duty plastic panel or planar sheet  5006  of plastics material is positioned over the spacers  5004 . This sheet  5006  fills the outer frame  5001 , and is sized such that it exactly fills the inner space of the outer frame  5001 . It should be noted that exactly in this context means that there is a close enough fit between the edges of the sheet  5006  and the walls  5002 ,  5003  to ensure that wet concrete will not leak through between the two. In the preferred embodiment, the sheet  5006  is 25 mm thick polystyrene. The thickness of the sheet  5006  ensures that it is robust and heavy-duty, and will not bend, break or otherwise deform when carrying a heavy weight of wet concrete during the panel forming process. 
     The sheet  5006  is impaled on the fasteners  5005 , with approximately half the overall length of the fasteners  5005  protruding through the upper surface of the sheet  5006 . 
     When ‘inner surface’ and ‘outer surface’ of the sheet  5006  for the first forming method are referred to, these have the following meanings: the inner surface of sheet  5006  is the upwardly facing surface during the forming process (it is ‘internal’ or ‘inside’ the finished block  5012 ), and the outer surface of the sheet  6  faces downwards during forming, with the spacers  4  abutting the outer surface. It should be noted that for the concrete block formed by this method, the outer face is the face that will form part of the external building wall when it is in use, and the inner surface of the concrete block or concrete portion of the panel is inside in use. 
     Once the sheet  5006  is in place, polystyrene blocks  5008  are placed on the sheet  5006 . In the preferred embodiment, these are elongate, generally rectangular blocks, having sides  5010  that slope inwards when the blocks are viewed end-on (so that the base, positioned on the sheet  5006 , is wider than the topmost face of the block). The preferred height of each block is 50 mm, with a base of 500 mm and a top surface having a width of 450 mm in the preferred embodiment. It should be noted that this is the preferred form, which gives an appropriate mix of insulation and strength. If required, the dimensions of the blocks  5008  can be altered. For example, the base could have a width of between 350 mm and 550 mm, with the top surface tapering in from this base as appropriate. It should also be noted that the block  5008  does not have to be tapered at all if this is preferred. 
     In the preferred embodiment, the blocks  5008  are positioned so that they lie in parallel rows, between the parallel rows formed by the fasteners  5005  protruding through the sheet  5006 . It is preferred that the gap between the ends of each of the blocks  5008  and the side walls is in the region of 200 mm. However, this gap can be altered as required. The blocks  5008  are spaced from one another in rows. It can be seen that elongate trenches are formed between adjacent ones of the blocks  5008 . These form stud channels, so that when concrete is poured into the outer frame  5001  in the final panel forming step, the concrete that fills the trenches or stud channels forms concrete studs  5011  which are an integral part of the finished panel  5012 . That part of the concrete studs  5011  contacting the sheet  5006 , together with the bases of the polystyrene blocks  5008 , form a planar inner face that abuts the sheet  5006 . 
     It should be noted that other embodiments are possible. For example, the polystyrene blocks  5008  could be held in place by co-locating or impaling these with the fasteners  5005 . However, the preferred embodiment has the advantage that the spacing elements  5004  are co-located with the concrete studs  5011 . This provides a visual indication of the location of the concrete studs  5011  to a builder or other worker viewing the finished panel. 
     Before the final step of pouring concrete is carried out, other desirable elements can be added as required. For example, rebars  5013 , wire strengthening grids or similar can be emplaced inside the outer frame  5001 , over and around the polystyrene blocks  5008 . The preferred embodiment includes reinforcing elements or rebars  5013  laid within the outer frame  5001 . In the preferred embodiment, these are parallel with, and located directly above the spacers  5004 . The rebars  5013  are also positioned so as to be located at or around the same height as the upper surface of the polystyrene blocks  5008 . 
     As shown in  FIG. 23 , the outer frame  5001  can be formed with at least one of the side walls at an angle from the vertical. A panel  5012  having this feature can be useful in certain constructions. For example, if two adjacent blocks have complimentary angled faces (for example each face angled at 45 degrees), these can be connected to form the corner of a house wall, as shown in  FIG. 24 . 
     As shown in  FIGS. 25   a  and  25   b , the corners can be moulded into other shapes if required.  FIG. 25   a  shows two adjacent panels  5012 , where the adjacent edges have been shaped so that the adjacent panels interlock over a floor stud  5100 . A bolt  5101  in the floor stud is used to attach at least one of the panels to the stud  5100 . 
       FIG. 25   b  shows a similar interlocking arrangement, where the mutual edges of two adjacent panels have been shaped to allow the panels to interlock, and also so that the panels can interlock with a wall joist  5200  or similar, so that the wall joist  5200  becomes partially embedded in, and supported by, the wall formed by the panels. 
     In order to aid with this connection process, other elements can be added when forming the inner frame  5007 , as required. For example, a corner connector. Before the concrete is poured, the corner connector is positioned over the polystyrene blocks  5008  and rebars  5013 . A part of this corner connector protrudes from the side of the outer frame  5001 , so that after the concrete is poured, it protrudes from the edge of the panel  5012 . This connector can be angled at e.g. 45 degrees, so as to fit flush with a similar connector on an adjacent panel, with for example apertures (not shown) passing through the exposed part to allow the use of bolts (not shown) or similar to connect adjacent panels  5012 . 
     As noted above, other elements can also be added as required—for example door or window framing elements. If a panel with this mix of elements is required, the polystyrene blocks  5008  and other insert elements are shaped appropriately, for example, being shorter elements to fit around the door and window framing elements. 
     Once the required mix of elements is in place within the outer framework  5001 , the final step of pouring concrete into the framework  5001  to form the panel  5012  takes place. Concrete is poured over the top of the polythene sheet  5006 , the polystyrene blocks  5008 , and any other additional, optional elements which are present, such as the rebars  5013  or the connectors  5014 . In the preferred embodiment, the total depth of concrete poured should be about double the height of each of the polystyrene blocks  5008 . The poured concrete has a flat upper surface, which forms the outer or outwards facing surface of the wall panel  5012  once it has hardened. 
     Once this concrete has dried and hardened sufficiently, the outer framework  5001  can be removed and the panel  5012  is ready for use and transport as required. 
     For the first preferred forming method, a casting bed  5300  can be used to create multiple panels of the type described above. The casting bed  5300  allows the creation of multiple moulds, with concrete poured into these multiple moulds either simultaneously or sequentially, to create a plurality of panels. Multiple moulds allows a number of panels of different construction to be created simultaneously. The casting bed is described below. 
     Casting Bed 
     The preferred embodiment of casting bed is shown from one end in  FIG. 26 . Four I-beams  5301  are laid in parallel. The beams  5301  can be as long as is required. For example, if a large number of panels  5012  are required (requiring a large number of moulds), the I-beams could be 100 meters in length, with a number of moulds spaced along the length of the beams  5301 . Sections of the outer framework  5001  are placed on these I-beams and bolted together to form as many separate moulds as are required. It can be seen that the spacing between the two outer I-beams  5301   a will dictate the dimensions of one edge (e.g. the width) of the panel  5012 . In the preferred embodiment, the two outer beams  5301   a  are spaced apart approximately 2770 mm (measured from the vertical part of each beam), to form a panel  5012  or set of panels  5012  of this width (less 2× the wall thickness of the outer frame  5001  on each side). The two inner I-beams  5301   b  are placed inside the two outer I-beams  5301   a,  spaced parallel and equidistant between the outer beams  5301   a.  Sections of outer framework  5001  are laid parallel to and crossways to the I-beams  5301  to form the moulds, the I-beams  5301  providing a stable platform for the outer framework sections. It should be noted that in the embodiment described above, the outer walls of the frame  5001  are placed on the outer two of the I beams  5301 . However if required, one or both of the walls of the frame  5001  could be moved in to one of the inner I beams. It should also be noted that the spacing of the inner I beams can be altered if required. 
     Once the concrete has been poured into the moulds and allowed to solidify, the outer framework sections can be unbolted and removed. 
     This arrangement has the advantage of allowing several concrete pours to take place either simultaneously or sequentially (pouring into each sub-frame in turn) without requiring a break in construction to reposition elements or create another, separate outer frame. 
     Second General Forming/Casting Method 
     The second general forming/casting method is similar to the first method described above. A number of elements are assembled to form an open-topped mould, into which concrete is poured to form a panel  2000 . The panel  2000  formed in the mould is aligned horizontally, and after the concrete is cured, the panel is lifted and rotated through 90 degrees so that it is vertical, ready for use. 
     To form the outer perimeter or outer framework of the mould, a pair of perpendicular bracing members are laid out parallel to one another, on an appropriate surface. This can be any flat, clean surface, and is usually a surface such as a factory or warehouse floor, or similar. A pair of parallel bracing members are connected to the perpendicular bracing members so that the connected perpendicular and parallel members form the outer walls of a hollow structure. In the preferred embodiment, the members are aligned vertically, and one of the parallel bracing members, member  6 , is attached to the perpendicular bracing members so that it is angled outwards at 45 degrees (the bottom edge being further in towards the centre of the structure than the top edge). The bracing member  6  could be angled at any required angle between vertical and horizontal. However, the preferred embodiment of a 45 degree angle produces cast concrete panels that can easily be butted together with other similar panels to form 90 degree corners, without complicating building logistics. It can be seen that the width of the panel will depend on the depth of concrete pout, and therefore the width of the members. A minimum panel depth (width in use) of 200 mm is preferred, and the members are sized accordingly. 
     As described above, the parallel bracing members interlock with the perpendicular bracing members to form the closed outer perimeter of the mould. In the preferred embodiment, the ends of all the bracing members are interlocked. However, any of the members could overhang the connected members, as long as they are all connected to form a closed structure overall. In the preferred embodiment, the mould is rectangular, so that a rectangular building panel  2000  will be formed once concrete is poured. The 200 mm minimum height of the closed structure formed by the bracing members allows a minimum width of building panel formed in the mould to be 200 mm. That is, once concrete is poured, the panel will be 200 mm wide (or deep). It could of course be made wider by pouring a greater depth of concrete. 
     Polystyrene spacer blocks  7 ,  8 ,  9  are laid out against two of the sides of the rectangular mould, so that their outer edges are flush with the inner surfaces of the bracing members  3 ,  4 ,  5 ,  6 . These polystyrene blocks are arranged parallel to one another—parallel spacer blocks  7  and  8 —on opposite sides of the mould. It is preferred that blocks  7  and  8  run the full length of the inside of the mould, with their first ends fitted snugly against the inner face of member  3 , and their second ends fitted snugly against the inner face of member  4 . However, if required, the blocks  7 ,  8  could run from the inner face of one of the members and stop short of the inner face of the opposite member. In some embodiments, a perpendicular spacer block  9  is fitted perpendicular to blocks  7 ,  8 , with each end of block  9  sized and shaped to fit snugly between the adjacent first ends of blocks  7 ,  8 , so that spacer blocks are arranged around three sides of the mould. A timber top plate  10  is laid along the fourth side of the mould, with its outer edge against the inner surface of the adjacent perpendicular bracing member  4 , and the ends of the timber top plate  10  fitting between the adjacent second ends of the blocks  7 ,  8 . The timber top plate  10  is aligned parallel to polystyrene block  9  on the other side of the mould. The polystyrene blocks  7 ,  8 ,  9  and the timber top plate  10  form a hollow rectangle or square inside the perimeter of the mould. If polystyrene block  9  is not present, the polystyrene blocks  7 ,  8  and the timber top plate  10  form a U-shape in plan. It is preferred that the ends of the timber top plate  10  lie between the second ends of the blocks  7 ,  8 . That is, the timber top plate  10  does not run the full width of the mould, although this is not a critical feature of the construction. If block  9  is not present, when the concrete is poured, it is poured directly onto the flat surface at that point. 
     Each of the parallel polystyrene blocks  7 ,  8  are 50 mm thick (depth), and have a width of 150 mm. The perpendicular block  9  is 39 mm thick (depth), and has a width of 90 mm. The timber top plate  10  has a thickness (depth) of 45 mm, and a width of 145 mm. 
     A 23 mm service channel or service conduit  20  is placed on top of the timber top plate  10 . The conduit forms a channel on top of the timber top plate  10 . In the preferred embodiment, a ceiling batten manufactured by USG, and well-known in the construction industry, is used. This is emplaced with the open side facing towards the timber top plate  10 . The profile of the preferred USG ceiling batten is shown in  FIG. 8 . The preferred form of ceiling batten used has a depth of 23 mm, and the flat base has a width of 37 mm. It is preferred that the conduit  20  is nailed to the plate  10  to hold it in position. The service channel  20  runs the length (end to end) of the timber top plate  10 . 
     Outer spacing studs,  1   a,    1   b,    1   c,    1   d  are placed in the mould, around the perimeter of the hollow rectangle formed by the polystyrene blocks  7 ,  8 ,  9  and the timber top plate  10 , so that the lower portions of the studs  1   a - d  lie against the flat surface (e.g. factory floor). The studs can also be shimmed so that the lower surface lies 10 mm above the flat surface of the factory floor. If a window is cast into the panel, this allows a window jamb to be set on the factory floor, and GIB™ board or drywall can be inserted into the jamb. On other style windows, the jamb may lie flush with the drywall or pass below the drywall. In the preferred embodiment, the studs  1  are square U-channel metal beams, with the base of the U-channel aligned vertically. The upwards-facing side or surface of the U-channel includes a number of fastening elements or fasteners  2 . In the preferred embodiment, these are vertically aligned elongate metal elements, fastened at intervals along the length of the upper face of the stud  1 . The spacing studs can be quickly and easily created from standard U-beam sections, attaching the fasteners to one side of the U-beam by pin spotting or instant welding, or any other suitable attachment method. There is no need to cast these fasteners into a concrete stud. 
     In the most preferred embodiments, the four outer spacing studs  1   a - 1   d  form a closed perimeter around the outside of the hollow square, and face inwards as described above. The vertically aligned ‘base’ of each of the outer U-channels  1   a - 1   d  is aligned with, and flush against, the inner edge of the adjacent polystyrene block—blocks  7 ,  8 , and  9 , and the timber top plate  10 . Alternatives to this arrangement shall be described in more detail in the ‘extra heavy duty’ section below. 
     In the preferred embodiment, due to the 45 degree angle of member  6 , the polystyrene block  8  has its outer face or side cut at an angle of 45 degrees so that it will fit flush against the inner face of the parallel bracing member  6 . In the preferred embodiments, the width of block  7  is 150 mm, and the width of the upper (or wider) face of the angle-cut block  8  is 150 mm. 
     Fastening bolts  90  are inserted towards each end of each of the blocks  7 ,  8 , protruding upwards from the blocks  7 ,  8 . The lower ends of the bolts  90  pass through the polystyrene to a point where the ends are 5 mm shallower or 5 mm less depth than the lowest point on the studs  1 . 
     The upper ends of the fastening bolts  90  protrude upwards from the upper face of the polystyrene blocks  7 ,  8 . In the preferred embodiments, the bolts  90  are 130 M12 studs. The function of these bolts  90  shall be described in greater detail below. 
     The timber top plate  10  includes vertically aligned anchor screws  11 , protruding upwards, one at each end, passing through the full depth of the top plate  10 , and the service conduit  20 . 
     One or more central studs  1   c  is added in parallel with the studs  1   a  and  1   e,  running the length/height of the hollow rectangle between the studs  1   b  and  1   d,  against the timber top panel  10  and the polystyrene block  9 . 
     An example of a mould with elements similar to those described above arranged inside the perimeter is shown in  FIG. 17 . The example mould is shown with two of the outer side walls or bracing members not present, so that details of the inner layout can be seen. It should also be noted that the elements which are arranged inside the mould are not shown in their correct proportions or dimensions, and the layout shown is for example purposes only, and does not correspond to any of the specific layout examples described below, which are used to produce the preferred embodiments of wall panels. 
     A plastic or polystyrene sheet  12  is laid over the top of the studs  1   a - 1   e.  The sheet  10  is sized so that it just covers the studs  1 . That is, it is the same size and dimensions as the hollow rectangle in the centre of the mould. The two ends of the sheet  10  that face towards the parallel bracing members  7 ,  8  are flush with the vertical portions of the outer studs  1   a - 1   d  to form a continuous vertical surface. The polystyrene sheet  12  is 50 mm thick in most of the preferred embodiments. However, it is thinner in some alternative embodiments, as will be described in detail below. 
     When ‘inner surface’ and ‘outer surface’ of the polystyrene sheet  12  for the second forming method are referred to, these have the following meanings: the inner surface of sheet  12  is the upwardly facing surface during the forming process (it is ‘internal’ or ‘inside’ the finished concrete panel), and the outer surface of the sheet  12  faces downwards during forming It should be noted that as for the first forming method, the outer face of the blocks formed is the face that will form part of the external wall or surface of the building wall it is in use, and the inner surface of the concrete block or concrete portion of the panel is inside in use. 
     A steel mesh and reinforcing bars can be added to the mould, arranged so that they are spaced above the polystyrene sheet, but below an upper pour level of concrete when this is added to the mould. That is, so that they will be embedded in the concrete once it is poured. 
     Once this mix of elements has been assembled, concrete is poured into the framework over the top of all the elements within the mould. Where required, other elements can be added to the wet concrete from above as will be described in further detail below. Once the concrete has set or cured, the bracing members  3 ,  4 ,  5 ,  6  are removed. The general wall panel  2000  is now ready to be lifted into the vertical position and moved to wherever it is needed. 
     It can be seen that there will be a concrete ‘overhang’ around the perimeter of the panel  2000  formed as described above. That is, the central part of the concrete panel over the top of the polystyrene sheet  12  will be less thick than the edge portions. This overhang forms a boundary portion or edge wall that runs around the perimeter of the panel. As the panel is rectangular, there will be four sides to the perimeter portion. Each of the four sides will have a flat inner face, and these faces will be at different depths through the panel, as the timber top plate and polystyrene blocks  7 ,  8 ,  9  are different thicknesses or depths. The flat inner face on each side will be the same width as the spacer or top plate to which it is adjacent. The parallel spacer blocks will lie against first and second sides on opposite sides of the panel—parallel to one another. The timber top plate will lie against the forth side, and in the embodiment where the perpendicular spacer block is used, this will lie against the third side. When aligned for use, the concrete portion of the building panel  2000  will have an inner face, surrounded by the boundary portion, and a smooth outer face. The inner face of the concrete portion will be adjacent to the inner face of the polystyrene sheet, which fully covers the inner face of the concrete portion. The inner side of the building panel will be planar, with the inner faces of the spacer blocks, the timber top plate and the inner side of the spacer studs all lying in the same plane, unless the spacing studs are shimmed as described above. 
     It should be noted that some of the dimensions of certain elements have been specified above—for example widths and depths of certain elements have been specified, but the lengths have not. Standardised widths and depths allows elongate items to be sourced and cut to length as required—for example, an elongate length of polystyrene having a 50 mm×150 mm cross section. The lengths of the items can be varied as required to produce panels of the required overall size. That is, the required length for a specific layout can be cut from a source piece of standard width and depth. Also, using studs formed from steel channels allows flexibility in the layout and dimensioning of the wall panels, and keeps the overall weight of the panel down. 
     As at least one side or end of the panel can be produced at an angle—e.g. a 45 degree angle—the corners of the panels can be connected together at 90 degrees to form mitred corners. An example of two standard panels  100  with a 90 degree mitred corner is shown in  FIG. 14 . To connect the two panels in this manner, the 45 degree angled corners are brought together so that the faces of the panels  100   a  and  100   b  are aligned at 90 degrees. The bolts  90   a  and  90   b  are embedded in the polystyrene during the forming process—panels  107   a  and  107   b,  and before the panels  100   a  and  100   b  can be connected, the polystyrene around the ends of the bolts is scraped and cut away. A right angle bracket  190  is placed in the corner, with the heads of the bolts  90   a  and  90   b  protruding through apertures in the bracket  190 . In the preferred embodiment, the bracket is a 100×100×6 mm RSA. Nuts  191   a and  191   b  are threaded onto the bolts  90   a  and  90   b  to hold the bracket  190  in place, and to hold the panels  100   a  and  100   b  together. Drywall boards  192  are added to finish the internal faces of the room. The bolts  90  can also be used to attach horizontally aligned elements to the vertically aligned wall panels. For example, flooring panels. An example of this connection is shown in  FIG. 16 , where a horizontally-aligned floor panel  3000  is connected to a vertically aligned ‘extra’ panel  200 , which has a vertically aligned ‘standard’ panel  100  connected to its upper edge. The panel  3000  is connected to the panel  200  by means of bolts  90  passing through apertures in an angle-bracket  3001  which is connected to the floor panel  3000 , the bolts  90  and bracket  3001  held in place by nuts. 
     The mould internal elements formed as described above can be assembled and then transported with the elements in place to e.g. a building site, with the outer frame of the mould formed, and concrete poured, on site. For example, the mould internal elements can be assembled in one country, and then shipped in shipping containers to another country where the concrete is poured. The internal elements of the mould are the spacing studs, the polystyrene elements, and the timber top plate. The outer framework could also be included in the shipped elements, if required. 
     Specific embodiments of the panels of the invention shall now be described with reference to  FIGS. 1-5 . The five panel embodiments described below are designated as ‘standard’, extra’, ‘heavy-duty’, ‘extra-heavy-duty’, and ‘intertenancy’. 
     Standard Panel 
     The standard wall panels  100  are intended for the construction of single storey buildings, and the top floor of multi storey buildings. The standard panels  100  can also be used as external cladding (non-structural and non-weight bearing) e.g. on a high rise. A plan view of a standard panel  100  is shown in  FIG. 1  (during manufacture of the panel, this would be a cross-sectional side view). 
     In the standard wall panels, there are three parallel U-section studs  101   a,    101   c  and  101   e,  arranged in parallel so that when the panel  100  is in use, they will be aligned vertically. Each of these is a steel channel having a 90 mm width. The U-sections of the outer two studs  101   a  and  101   e  face inwards, and these are completely filled with polystyrene  150 . The polystyrene  150  is held in place in place by the upper edges or lips of the U-beam, which are angled inwards. The polystyrene  150  can be added to the U-beam before the lips are angled inwards, or a length can be pushed in from one end. The central U-section  101   c  is empty. Two further studs  101   b,    101   d  are arranged perpendicular to studs  101   a,    101   c,    1010   e,  across the ends of the studs  101   a,    101   c,    1010   e.  Studs  101   b  and  101   d  are also filled with polystyrene  150 . 
     A polystyrene sheet  112  is located above the studs  101  and is held in position by the fasteners  102  on the studs  101 . The polystyrene sheet  112  has a standard thickness of 50 mm as described above. 
     The fasteners  102  are 75 mm long/high. 
     The parallel polystyrene blocks  107 ,  108  have a standard thickness of 50 mm as described above. 
     The timber top plate  110  has a width of 145 mm along its length, and a thickness of 45 mm, as described above. 
     The polystyrene block  109  has a width of 90 mm, and a thickness of 39 mm, as described above. 
     As described above, steel mesh and reinforcing bars are also added. 
     Once these elements are arranged in the mould, concrete  170  is poured so that the panel has an overall depth (or width in use) of 200 mm. It is preferred that concrete with a compressive strength of 40 MPA is used in the standard panel  100 . It can be seen that the depth of the concrete over the polystyrene sheet  112  will be 60 mm. 
     Extra Panel 
     The extra wall panel  200  shown in  FIG. 2  is constructed in a very similar manner to the standard wall panel, but it is intended to be used in situations where a greater thickness of concrete is needed. That is, where a greater degree of structural strength is required. For example, the ground floor of a two storey building, the second floor of a three-storey building, and single storey buildings in increased risk building zones such as coastal areas or areas of greater seismic activity. 
     The timber top plate  210 , parallel polystyrene blocks  207 ,  208 , and the polystyrene block  209  are as used in the standard panel  100 . The polystyrene sheet  212  is also the same, with a thickness of 50 mm. 
     The studs  201   a - 201   e  are 64 mm width steel channels. 
     The fasteners  202  are 75 mm long/high. 
     The polystyrene  250  in the channels of the studs  201  does not completely fill the channels. It fills the upper third of the channel when they are aligned for the pour (outer third when the panel is aligned for use). These polystyrene lengths  250  are glued in place in the channels. 
     Concrete  270  is poured to create an overall panel width of 200 mm, as in the standard panel  100 . However, as the studs are 64 mm, and not 90 mm, the concrete depth over the polystyrene sheet  212  is greater than that of the standard panel and is 86 mm. It is preferred that concrete with a compressive strength of 40 MPA is used in the extra panel  200 . The finished extra panel  200  is thicker and stronger than the standard panel  100 . 
     Heavy Duty Panel 
     The construction of the heavy duty panel  300  is similar to the standard and extra constructions described above. The heavy duty panel  300  is intended for use in constructing the first floor of a three storey building, or the wall of a commercial building, or as an over-engineering option (that is, the heavy duty panel  300  can be used in situation where a standard panel  100  or an extra panel  200  would probably be sufficient, but the risk is minimised by using the heavy duty panel  300 ). As before, the concrete is poured to create an overall panel depth of 200 mm. 
     The constructional differences are as follows: 
     The steel channels used for the studs  301   a,    301   b,    301   c  are 51 mm wide, and a thinner polystyrene sheet  312  is used, having a thickness of 30 mm. As the studs  301  are shorter, and the polythene sheet  312  is thinner, the depth of concrete  370  over the polystyrene sheet  312  is greater at 119 mm. It is preferred that concrete with a compressive strength of 40 MPA is used in the heavy duty panel  200 . The finished heavy duty panel  200  is thicker and stronger than the extra panel  200  and the standard panel  100 . 
     It should also be noted that no polystyrene is included inside the channels of the studs  301 . 
     Extra Heavy Duty Panel 
     The construction of the extra heavy duty panel  400  is very similar to the panels  100 ,  200 ,  300  described above. 
     The extra heavy duty panel is intended to be used to form basement walls, or retaining walls, or the lowest floor of a multi-storey building. 
     The constructional differences are as follows: 
     The studs  401  are formed from trapezoid or box profile pipe USG battens, the same as are used to form the service conduits. The depth (height) of the studs is 23 mm. The thickness of the polystyrene sheet  412  is 25 mm. The studs are arranged in parallel rows, and do not form a closed perimeter. 
     Also, the perpendicular spacer block  9  is removed or not emplaced at all, so the concrete on that side of the panel, when poured, reaches all the way to the flat surface or floor. 
     Concrete  470  having a compressive strength of 40 MPA is poured to form a panel  400  having an overall width of 200 mm as before. The thickness of the concrete  470  over the polystyrene sheet  412  is 151 mm. 
     Due to the dimensions of the studs  401 , the polystyrene sheet  412  and the spacer blocks, the lower (or inner) edges of the polystyrene sheet overlap with the outer or upper edges of the spacer blocks and the timber top plate. 
     Intertenancy 
     Intertenancy walls are used to divide up internal spaces within multi-occupancy buildings, and are used where a greater degree of strength is required than can be provided by a frame and drywall arrangement. There may be other considerations that dictate the use of a concrete intertenancy wall, for example sound damping between apartments or similar. Also, concrete intertenancy walls provide a better fire barrier than walls constructed from other materials—e.g. wooden framing and drywall. 
     Intertenancy panels  500  can be constructed using the method described above. They are formed from the same mix of elements as the standard panel  100 . However, intertenancy panels  500  do not generally have one side face angled at 45 degrees, as their ends are generally connected perpendicular to the inner face of an external wall. Therefore, support member  6  is aligned vertically when forming the mould, and not at 45 degrees, so that both ends of the panel  500  are squared off. 
     It should also be noted that the outer face of the panels  100 - 400  is formed from the upper surface of the poured concrete. As this is intended as the outer face when the panel is emplaced as part of a building, an unfinished concrete surface is acceptable. However, occupants generally prefer drywall for internal walls. Also, the space between the concrete wall and the internal drywall can be used to run cables or similar. Therefore, when forming the intertenancy panel  500 , once the wet concrete has been poured, spacers are pressed into the concrete before it sets. In the preferred embodiment, the intertenancy spacers  560  are USG ceiling battens, the same as those used to form the service conduits, and are emplaced with the open side facing towards the wet concrete, with anchors  561  protruding downwards into the concrete. When the intertenancy panel is emplaced, the spacers  560  are used to fasten up drywall panels in a similar manner to the studs  1 , the studs  1  and the spacers  560  allowing drywall to be added to both sides of an internal wall. The flat base of the USG channel provides a flat surface suitable to screw drywall boards onto. 
     In all the embodiments described above, the wall panel is standardised at 2.4 m (interior drywall measurement) with an overall height of 2.545 m. 
     If extra height is required—e.g. for a 2.7 m high wall (interior drywall measurement), the building panel has an overall height of 2.845 high. This wall is formed by using the same steel track frame to form the spacer studs as is used for the 2.4 m, but an additional 300 mm high rectangle of steel track and stud is added between the top of the 2.4 m steel track spacing studs, and the timber top plate. A 50 mm polystyrene sheet and reinforcing is also added on top of this rectangle, just like the regular wall (the size of the spacing studs and polystyrene sheet depends on the size of wall required). The additional rectangle is screwed to the bottom of the timber top plate prior to either concrete pouring or shipping. If the wall is shipped, this is done in two parts—a 2400 mm bottom section and a 445 mm top section. On arrival, the 445 mm rectangle/top plate/reinforcing assembly is screwed to the top of the 2400 mm bottom stud assembly, and the concrete poured to form the panel. 
     Pre-Cast Panel Fastening 
     The apparatus for fastening pre-formed building panels together, and the method of fastening building panels in place using the improved apparatus, will now be described with reference to  FIGS. 6 and 7 . 
     As has been described in the prior art section, wall panels are normally formed with a number of apertures cast into the top edge of a building panel—for example, the top edge of a ground floor external wall panel (these could also be machined into the top edge post-casting). A number of complimentary fastening elements are set into the lower edge of e.g. a first floor panel, extending downwards. As described, the tolerance ranges in this prior art fastening method are critical, as the embedded fastening elements and the apertures must align. 
     The fastening apparatus of the present invention removes the need for elements to be cast into the building panels within a tolerance range, so that they align with another set of elements in a separate panel. 
     A preferred embodiment of wall panel fastening device  600  is shown in  FIG. 6 . The fastening device  600  has a main body  601  and a connected fastening tube  602 . The main body  601  is formed from D10 rio rod, bent through  90  degrees partway along its length to form a panel portion  603  and a connection portion  604 . The fastening tube  602  is formed from a 90 mm length of NB20 galvanised pipe, so that the ends can be aligned with the edges of the panel  9  (90 mm width in the preferred embodiment). The fastening tube  602  is connected (by welding or similar) to the connection portion end  605 , approximately halfway along the length of the outside of the fastening tube  602 , so that the fastening tube  602  is aligned parallel to the panel portion  603 . In the preferred embodiment, the connection portion  604  is approximately 104 mm long, from the end  605  to the centre line of the panel portion  603  (perpendicular distance from the side of the fastening tube  602  to the centreline of the panel portion  603 ). The length of the wall panel portion  603  can be adjusted to suit the stud height when the fastening device  600  is emplaced. 
     In use, a number of the fastening devices  600  are cast into panels—e.g. panels  100 ,  200 ,  300 , etc. The fastening devices  600  are aligned so that when they are emplaced in the mould, each of the outer ends  606  ate located against the adjacent support member that forms the wall of the mould, with the side of the fastening tube  602  resting on top of the panel  9 . Wall panel portion  603  is located above and parallel with the top surface of the polystyrene sheet  12 . When the concrete is poured, the depth of the concrete ensures that the wall panel portion  603  is fully submerged and embedded. 
     When the supporting members that form the mould are removed, the outer end  606  is flush with the lower edge of the wall panel and the inner end can be accessed from the inwards-facing part of the wall panel. The fastening tube  602  passes all the way through the lower edge wall of the wall panel. That is, the lower part of the boundary portion, edge wall or perimeter portion that runs around the perimeter of the panel. In use, the wall panel is lifted into position, for example a standard wall panel  100  is lifted into position on the foundation slab  1000  of a bungalow, as shown in  FIG. 7   a . The outer face of the wall panel  100  is aligned as required with the foundation slab. As the outer ends  606  of the embedded fastening tubes  602  are flush with the lower edge, there is no need to pre-form apertures in the foundation slab, and the need for pre-formed apertures to match up with protruding members on the lower edge of the building panel  100  is removed. To attach the building panel  100  to the foundation slab, a user (e.g. a construction worker) moves to the inside face of the building panel  100 , once it has been positioned. The user, equipped with a masonry drill, locates the drill bit into the inner end of the fastening tube  600 , using it as a guide for the drill bit, and drills downwards to create a hole  620  in the foundation slab (which will be aligned with the fastening tube  602 ). The depth of the hole  620  is approximately the same as the length of the fastening tube  602 —90 mm. The hole depth should be sufficient that there is some overlap with the reinforcing mesh and bar in the panel. The hole  620  and the fastening tube  606  are filled with a chemical anchor  630  such as Ramset™ chemset capsules. An M12 bolt  618  is then pressed into the top of the fastening tube  606 , down into the hole  620 , activating the chemset capsules. The top end of the bolt has a nut  617  and washer  619  pre-fitted to act as a flange, with the washer resting in position on the top of the tube  606 , keeping the bolt  618  in position until the chemset is solid. It is preferred that the body of the bolt is at least 120 mm long, so that there is at least a 120 mm embedment. 
     A similar fastening arrangement is shown in  FIG. 7   b , where the lower edge of a second floor building panel (e.g. a standard panel  100 ) is positioned on the top edge of a first floor building panel (e.g. an extra panel  200 ). The drilling and positioning of the bolt  618  and chemset  630  are the same as described above with reference to  FIG. 7   a . The cross-section of extra panel  200  also shows the steel mesh  240  and reinforcing bars  250  that are added to the mould before the concrete is poured, to add strength to the structure. 
     The panel attachment method and apparatus used when attaching panels  100 ,  200 ,  300 ,  400 ,  500  to each other or to other elements is very similar to that outlined above with reference to  FIGS. 7   a  and  7   b.    
     Casting Elements into a Panel during the Panel Forming Process 
     The method and structure by which elements such as complete window assemblies and door assemblies can be cast into a building panel during the panel forming process shall now be described with particular reference to  FIG. 9 . Assemblies such as window assemblies or door assemblies can generally be referred to as portal elements. Preferred embodiments of the standard panel  100 , extra panel  200 , heavy duty panel  300  and extra heavy duty panel  400 , including cast-in windows formed using the method described, are shown as cross-sectional side views in  FIGS. 10-13 . 
     In the preferred embodiment(s), the casting method is used to cast windows, with the window glass already in place, directly into a wall panel of the type(s) described above, during the wall panel casting process. 
     A cross-section of the general wall panel  2000  is shown in  FIG. 9 . The wall panel  2000  with the window cast in, is formed in the same overall manner as the general panel casting method. That is, a number of elements as required to form the finished product are added to a mould framework formed from outer parallel and perpendicular members  3 ,  4 ,  5 ,  6 . Elements are added inside this outer framework, around the edges—e.g. blocks  7 ,  8 ,  9 , timber top plate  10 , studs  1 , etc. The window will be located reasonably centrally, so it will not interfere with any of these elements located close to the edges. 
     To form the finished window, firstly an open-ended rectangular box is formed from the wooden window framing elements. As shown in  FIG. 9 , the window has an upper wooden head panel  801 , and a lower wooden sill panel  802 , both arranged so that when the panel is aligned for use, they will be horizontal. The head  801  and the sill  802  are connected by vertical timber side wall panel portions (not shown) to form the rectangular box. The size of the rectangular box frame will be dictated by the required size of the window. Windows can come in standard sizes, but are normally custom-tailored depending on the builder&#39;s or end-user&#39;s requirements. Before the timber frame sill, head and sides are cut to length, the size of the window frame element needs to be known. This information determines the size of the rectangular frame, which is matched with the window frame or door frame (frame elements). The emplacement of the window frame  805  will be described in detail below. 
     Once the rectangular box is formed, by gluing or nailing the timber head  801 , sill  802  and sides together,  10 mm polystyrene window blocks  804  are then glued to the outer sides or surfaces of the head  801 , sill  802  and timber wall sections. The width of the window blocks  804 , and their location, is such that they do not reach all the way to the inner or lower edges of the head  801 , sill  802  and side walls. The lower edges of the polystyrene blocks  804  are located about halfway down the head  801  and sill  802 . 
     A PVC barrier sheet  803  is then glued in place on the outside of the blocks  804 , with the lower edge of the sheet  803  aligned with the lower edge of the blocks  804  (although this alignment is not strictly necessary for the forming method). Alternatively, the sheet  803  can be added to the blocks before they are glued to the wooden frame. The PVC sheet  803  is sized so that it can overhang the top of the polystyrene blocks  804  by approximately the same length again as the blocks  804 . 
     This assembly—the head  801 , sill  802  and side walls, plus the polystyrene blocks  804  and the barrier sheet  803  is placed where required in the mould. 
     A set of inner studs  1   b  are then arranged around the outside of each of the head  801 , sill  802 , and the timber window frame side walls. The studs  1   b  face outwards, with their bases pressed up against the PVC barrier  803  on the outer face of the window blocks  804 . The studs  1   b  are sized and preformed to fit the known size of window frame for that particular panel type and window size. 
     The polystyrene sheet  12  is then pressed down onto the fasteners  2  protruding upwards from the studs  1 . The polystyrene sheet  12  has a central aperture pre-cut into it so that it will fit snugly against the outer sides of the polystyrene window blocks  804 . This can easily be achieved if the window frame dimensions are known, by adding 10 mm to each of the sides to give the overall dimensions of the aperture. The blocks  804  are sized so that when the polystyrene sheet is in place, they stand slightly proud of the top surface of the polystyrene sheet  12 . 
     The preformed or preassembled window frame  805  has a barrier block  807  added to it before it is emplaced. The barrier block  807  is exactly cut to size, to fit the individual frame. This is achieved in the preferred embodiment by placing the frame onto a 30 mm thick sheet of polystyrene while the frame  805  is still separate from all the other items, so that the outer edges of the frame  805  are on the surface of the polystyrene. The outline of the frame  805  is then marked onto the polystyrene. The polystyrene is then cut to shape, with a −5 degree negative rebate, so that the inner face  808  and the outer face  809  of the barrier block  807  are offset from one another. That is, the upper and lower (‘in use’ alignment) sides  810  and  811  of the barrier block  807  are angled downwards at an offset of 5 degrees from horizontal, as shown in  FIG. 9 . The barrier block  807  is taped (e.g. using duct tape or similar) to the outer part of the frame  805 . Duct tape is also added to the frame around all the exposed portions. 
     The preformed or preassembled window frame  805 , including glass  806 , and with the barrier block  807  taped in place, is then inserted into the central space formed by the four window blocks  804  (two side blocks, and an upper block and a lower block). In the example embodiment shown, the window frame  805  is an extruded aluminium frame produced by Fairview windows. As can be seen in  FIG. 9 , the frame  805  is narrower on the inner part than the outer part (inner and outer referring to ‘in use’ alignment), with a lip  850  resting on the perimeter formed by the polystyrene blocks  804 , and the inner part—the lower or inner edge  860 —resting on the upper (outer) edge of the timber portions. It can be seen that the polystyrene window blocks surround the intersection where the lower edge of the window frame  805  rests on the upper edge of the box frame formed from the timber portions. Once the frame  805  is in place, the ‘spare’ portion of the PVC sheet  803  is then folded up to help shield the frame  805  from concrete slurry or similar during the pour. 
     The concrete  70  is then poured into the mould to form the panel  2000 , flowing over the top of the sheet  12 , and around the emplaced frame  805 . The PVC sheet  803  acts as a barrier to stop the concrete slurry touching the frame. The barrier block  807  stops the concrete slurry flowing across the top of the frame. 
     Once the concrete has cured, the barrier block  807  can be cut out from the panel, and a panel with a window, including glass, cast in place, has been formed. 
     Door frames can be cast into the panels in the same manner. 
     An example of a standard panel  100  adapted to include cast-in windows and doors is shown in  FIG. 15 . The adaption of the pattern of the internal studs  1   c  can clearly be seen.