WO2014165913A1

WO2014165913A1 - Slab construction

Info

Publication number: WO2014165913A1
Application number: PCT/AU2014/000387
Authority: WO
Inventors: Brad Frank Golledge; Malcolm Alexander GOLLEDGE; Lyndon Alexander GOLLEDGE
Original assignee: Bfre Pty Ltd As Trustee
Priority date: 2013-04-12
Filing date: 2014-04-10
Publication date: 2014-10-16
Also published as: AU2014252765B2; AU2014252765A1

Abstract

An insulated concrete slab floor (60) construction comprising, spaced piers (20) installed in a building site (100), thermal insulating load bearing packers (44) mounted on the piers (20), a plurality of beams (22) extending between the piers (20) and mounted on top of the packers (44), the beams (22) being connected to form a beam frame (23), a poured concrete support means (30) extending across the beam frame (23), edge insulation means (54) disposed around the perimeter of the beam frame (23), the edge insulation means (54) extending at least to a height of the concrete (60) above the beam frame (23), and concrete (60) disposed over the beam frame (23) and the poured concrete support means (30), and between the edge insulation means (54).

Description

SLAB CONSTRUCTION

Related Applications

[1] This application claims the priority of the following applications, the contents of which are incorporated in full herein by reference:

• Australian Provisional Application No. 2013901262, Title: Insulated slab on ground, R slab, Applicant: BFRE P/L as trustee, Filing Date: 2013-04-12

• Australian Provisional Application No. 2013902163, Title: Improvements in Insulated Slab on Ground R Slab, Applicant: BFRE P/L, Filing Date: 2013-06-16

• Australian Provisional Application No. 2013902255, Title: Beam slab on ground, Applicant: BFRE P/L, Filing Date: 2013-06-20

• Australian Provisional Application No. 2013902756, Title: Further improvements in Insulated Slab on ground R slab, Applicant: BFRE P/L, Filing Date2013-07-25

• Australian Provisional Application No. 2013903228, Title: Edge Support R Slab, Applicant: BFRE PTY LTD, Filing Date: 2013-08-25

Field of the Invention

[2] The present invention relates to an improved building method, and in particular to improvements in design and construction of ground floor concrete slab on ground in Low Rise Residential and Commercial Buildings.

Background of the Invention

[3] Modern building systems involved in the building of residential and commercial buildings are required to be more energy efficient, both in the materials used in the construction and the containment of energy within the building envelop. Generally, roof and wall construction incorporate insulating systems to increase thermal resistance values. In ground floor slab systems however, contact with the ground and exposed edges to the outside may increase energy loss from the building,

[4] Traditionally slab on grounds come in two forms, raft slab and waffle pod. Raft slabs are formed with stiffened edge and internal beams, in most cases the beams are supported by bored piers. Before a concrete slab formwork is installed the ground is levelled and compacted. Bored piers, screw piers and/or pad footing are installed in specific locations to support the concrete floor loading, as well as construction and building materials loading on top of it. The piers are used to reduce the effects of soil movement on the slab. In highly reactive soil conditions, soil movement can cause cracking of the concrete slab and external brickwork. If the reactive soil is moist when the slab is poured, after a while the soil may contract away from the underside of the slab and remains supported only on the piers. In this situation, the slab is fully suspended. When the soil moisture content under the slab increases, the expansion of the soil may heave the slab and lift it from the top of the bored piers. In the latter case, movement in the slab may fail elements of the building structure, and may cause serviceability issues such as difficult to open doors, and cracked cornices and wall plaster.

[5] After the reinforcement bar and mesh is installed, the concrete is poured directly onto a vapour barrier, (usually in the form of a plastic membrane) and is contained within edge boards. The slab is basically in direct contact with the soil and the low thermal resistance of the slab and the soil system is further reduced as the moisture content of the soil increases, and as such is a variable. The edge of the slab is exposed to the external environment as a visual requirement for termite inspection, and there is also an unimpeded thermal pathway to the external brickwork which normally rests upon the rebate in the slab edge. Raft slabs construction is subject to a lot of onsite variables during the concrete pour. These include collapsed soil adjacent the beam excavation, trampled mesh, collapsed or deformed bar chairs supporting the mesh and bar reinforcement, and variable to in some cases no concrete cover to the reinforcement steel.

[6] Waffle pod systems incorporate polystyrene void formers to give a slab height and the spaces between them form a grid of concrete beams integrated with the slab on top when poured. The beam grid and formed edges to the slabs are normally supported on a grid of bored piers. The polystyrene void formers provide low thermal resistance values because of the thin wall thickness of the void former, however the beams formed as a consequence of the spacing left between the void formers are in contact with the ground and with the top of bored piers. The void formers are made in a machine to reduce the polystyrene content and while the sides and top are fully enclosed, the underside is normally composed of system of support ribs moulded into the pod. The pods are lightweight and are difficult to install and hold down on a windy day. In fact, on moderately windy days work installing the pods will stop due to the difficulty in holding them in place after installation. A further deficiency in relation to Occupational Health and Safety in the installation of void formers is in the strength of the top, which is susceptible to collapse due to foot fall impact. The likelihood of foot and leg injury is further increased because the void formers need to be installed with voids between them to provide the form for the concrete ribs. If the need to cut bars arises during the installation process, the bars need to be removed from the pod structures when grinders are used to avoid risk of fire.

[7] Apart from the particular deficiencies described above in all cases the slabs have all or part of the concrete floor in contact with the ground and in particular climatic zones, this can result in up to 30 percent loss in indoor heating through the slab. A characteristic common to traditional slabs is that the strength in the slab relies on internal and external reinforced concrete beams built into them, and due to variables in the placement of reinforcement steel, design slab strengths may not be obtained.

[8] The above conventional arrangements are also labour intensive due to placement and stripping of edge formwork and placement of trench mesh and other reinforcement steel in beams and may use more concrete than planned due to the variability of footing excavation.

[9] When houses are built on sloping sites most builders prefer to prepare the site by a process commonly referred to as cut and fill. The high side of the lands is excavated and this soil is push back into the lower part of the land and compacted. In particular designs the soil in the lower portion of the site may be contained against retaining walls of varying forms or simply left as a batter which is landscaped over. Most designs however in modern housing require the builder to build a retaining wall within the slab edge which extends to the ground level. The slab edge is called drop edge beam construction and can be up to 1500 mm deep. At the bottom of this beam is a rebated edge used to support external brickwork. The construction of the formwork for this edge can be extremely costly and labour intensive, comprising a multitude of timber edge boards stacked on top of each other with propping, extensive bracing and may require significant amounts of reinforcement steel in the design.

[10] The present invention seeks to overcome or substantially ameliorate at least some of the deficiencies of the prior art, or to at least provide an alternative.

[11 ] It is to be understood that, if any prior art information is referred to herein, such reference does not constitute an admission that the information forms part of the common general knowledge in the art, in Australia or any other country.

Summary of the Invention

[12] According to a first aspect, the present invention provides an insulated concrete slab floor construction comprising:

spaced piers installed in a building site;

thermal insulating load bearing packers mounted on the piers;

a plurality of beams extending between the piers and mounted on top of the packers, the beams being connected to form a beam frame;

a poured concrete support means extending across the beam frame;

edge insulation means disposed around the perimeter of the beam frame, the edge insulation means extending at least to a height of the concrete above the beam frame; and concrete disposed over the beam frame and the poured concrete support means, and between the edge insulation means.

[13] In one embodiment, the poured concrete support means are void formers disposed between the beams of the beam frame.

[14] In another embodiment, the poured concrete support means is a decking disposed over and extending across the beam frame.

[15] In another embodiment, the concrete slab floor construction further comprises a vapour barrier extending over the ground and attached to perimeter beams of the beam frame.

[16] In another embodiment, the insulating packers have a minimum height of 20 mm.

[17] In another embodiment, the void formers are made from polystyrene.

[18] In another embodiment, the void formers comprise spaced cavities formed along their bottom surfaces.

[19] In another embodiment, the beam frame extends to a height above the poured concrete support means.

[20] In another embodiment, the concrete slab floor construction further comprises thermal insulating tape covering the tops and exposed edges of the beams.

[21 ] In another embodiment, the concrete slab floor construction further comprises reinforcement mesh disposed within the concrete.

[22] In another embodiment, the edge insulator means comprises edge insulation boards fixed to external surfaces of perimeter beams of the beam frame.

[23] In another embodiment, the edge insulation boards are made from polystyrene.

[24] In another embodiment, the concrete slab floor construction further comprises angle lintels disposed over perimeter piers and fixed through the edge insulation board into the perimeter beam.

[25] In another embodiment, the concrete slab floor construction further comprises a termite reticulation system disposed adjacent perimeter beams of the beam frame.

[26] In another embodiment, the void formers are level with top surfaces of the beam frame.

[27] In another embodiment, the concrete slab floor construction further comprises support blocks disposed midspan between beams of the beam frame for supporting the decking, the support blocks being at least partly compressible to allow ground heaving. [28] In another embodiment, the concrete slab floor construction further comprises lintels disposed to extend along, external to, and spaced parallel to the perimeter beams of the beam frame for supporting an external wall.

[29] In another embodiment, the concrete slab floor construction further comprises spaced wall ties fixed to the perimeter beams, the wall ties extending over the lintel.

[30] In another embodiment, the edge insulation means comprises a slab edge holder fixed to perimeter beams of the beam frame and having a side section extending to the height of the concrete.

[31 ] In another embodiment, the concrete slab floor construction further comprises reflective insulation means disposed below a top surface of the beam frame

[32] In another embodiment, the concrete slab floor construction further comprises a separation membrane disposed over the beam frame and the poured concrete support means, and underneath the concrete.

[33] The present invention also provides a method of forming an insulated concrete slab floor construction, the method comprising:

installing spaced piers in a building site;

mounting thermal insulating load bearing packers on the piers;

mounting a plurality of beams to extend between the piers and on top of the packers; connecting the beams to form a beam frame;

laying a poured concrete support means to extend across the beam frame;

mounting edge insulation means around the perimeter of the beam frame, wherein the edge insulation means extends at least to a height of the concrete to be poured above the beam frame; and

pouring concrete over the beam frame and the poured concrete support means, and between the edge insulation means.

[34] The method preferably further comprises the step of disposing lintels to extend along, external to, and spaced parallel to the perimeter beams of the beam frame for supporting an external wall.

[35] The method preferably comprises the step of disposing a separation membrane over the beam frame and the poured concrete support means prior to pouring of the concrete.

[36] Other aspects of the invention are also disclosed. Brief Description of the Drawings

[37] Notwithstanding any other forms which may fall within the scope of the present invention, preferred embodiments of the present invention will now be described, by way of examples only, with reference to the accompanying drawings in which:

[38] Fig. 1 is a plan view showing an example of bored pier/pad locations on a building site;

[39] Fig. 2 is a plan view showing edge beams and internal beams mounted to the pier/pad locations of Figure 1 ;

[40] Fig. 3 is a plan view showing void formers installed between the internal beams and edge beams of Figure 2;

[41] Fig. 4 (a) is a section view along line A-A of Figure 3, showing an internal beam, an edge beam, a void former, a vapour barrier, load bearing packers, reinforcement mesh and poured concrete, (b) is a section view along line B-B of Figure 3 showing a plumbing pipe penetration and a gap space filled with foam, and (c) is an enlarged view of circled portion C of Figure 2 showing a corner junction;

[42] Fig. 5 is an enlarged view of the corner portion of Figure 4(a) showing a termite proofing reticulation system;

[43] Fig. 6 is a section view of an alternative corner configuration with the void former level with the top of the bearer beams;

[44] Fig. 7 is a section view of a concrete slab floor construction using a metal decking on top of the bearer frame, with supports block at midspan between the internal bearers;

[45] Fig. 8 is a perspective part cut away section view of the concrete floor construction view of Figure 7 showing the internal bearer beams, block supports, metal decking on top of the bearer frame, and the concrete slab;

[46] Fig. 9 is an alternative section view along line A-A of Figure 3, showing a brick veneer construction and a lintel supporting the brick wall;

[47] Fig. 10 is an isometric view showing concrete lintels installed on concrete piers

[48] Fig. 1 1 is a section view along line D-D of Figure 10 showing a concrete lintel installed against an expanded polystyrene (EPS) edge insulation board;

[49] Fig. 12 is an alternative section along line D-D of Figure 10 showing a concrete lintel installed with a metal angle providing a wall cavity; and

[50] Fig 13 is an oblique projection view of an alternative void former having grooves formed along its lower surface. Description of Embodiments

[51 ] It should be noted in the following description that like or the same reference numerals in different embodiments denote the same or similar features.

[52] The present invention in one aspect relates to a concrete slab construction.

[53] Referring to Figures 1 to 4, piers 20, preferably concrete or concrete pads, are installed in a grid arrangement in a building site 100. Other pier systems such as steel screw piers and piling systems may also be used. Piers 20a are installed along the predetermined slab edges 102 and piers 20b are installed between the predetermined slab edges 102 after the site 100 is levelled and compacted. This is carried out using conventional means and practices.

[54] In one aspect of the present invention, the poured in situ concrete beams within and around the perimeter of the slab as would result in a raft slab or waffle pod construction are replaced by structural beams 22, preferably steel beams with appropriate protection against corrosion, or beams made from other material {e.g. wood, plastic) delivered to site. In the preferred form, the beams 22 are galvanised steel tubes rectangular hollow sections (RHS) 150 mm high by 50 mm wide. The rectangular shape provides flat sides to abut and seal against the sides of the polystyrene void formers 30 installed later. In particular designs, the beams 22 and bored piers 20 may be located directly under load bearing walls, rather than designed to work in defined grids. Brackets 42 are installed along the inside face of one pair of opposing edge bearer beams 22a to receive the internal beams 22b, at the spacing related to the centre line of the internal bored piers 20b running perpendicular to the edge beams 22a.

[55] Referring to Figure 4, plastic thermal insulating load bearing packers 44a are installed on all the edge piers 20a for levelling the edge beams 22a (perimeter beams). The packers 44 are made from strong highly thermal resistant material which creates a thermal break between the beam 22 and the concrete pier 20a. The perimeter edge beams 22a are installed on the high strength plastic packers 44 and joined by brackets 42 at the corners. At that time, a check is made to ensure the brackets 44 installed on the opposing pair of edge beams 22a correspond to the line of the internal bored piers 20b between them. Steel screws 43 are used to attach the beams 22 to the brackets 44. As shown, the packers 44 are preferably dimensioned to have the same width as the beam 22 it is supporting, thus supporting the entire lower surface of the beam 22.

[56] Once the edge beams 22a are installed, a vapour barrier 46 is placed over the ground, lapped and taped in the conventional manner, and edges folded upwards and fixed to the inside or outside of the edge beams 22a. Other suitable membrane materials may be used and installed in other configurations that protect the external bearer beams 22a and form a vapour barrier, in such instances where the soil contains acid sulphates, salt and other corrosive components.

[57] Plastic load bearing packers 44b are then located and levelled on the remaining internal bored piers 20b and the internal beams 22b are installed and fixed to the brackets 44 at the opposing edge beams 22a, preferably using class three TEK screws or bolts. The internal beams 22b are normally equi-spaced along the length of the slab 60 to efficiently balance the spanning capacity of the slab 60 on top, the bearer span design capacity, and minimisation of the number of bored piers required to support the building. Preferably, the spacing of the internal beams 22b is maintained at 2500 mm for efficiency of spans and economy of beams 22 and bored piers 20, as well as for the efficient use of solid polystyrene blocks or equivalent void formers installed subsequently. However, other spacing may be used depending on the engineering requirements.

[58] At this stage, the connected beams 22 form a beam frame 23 which is thermally isolated from the ground by the use of the load bearing packers 44, which leaves a small air gap between the underneath of the beams 22 and the plastic membrane covered ground. The air gap addresses the problem with heat loss in conventional slabs, and provides room for the expansion of reactive soils when ground moisture increases.

[59] In highly reactive soils, the heaving of the soil can be accommodated in the bearer design in three ways. The first way is by increasing the depth of the insulating packers 44 supporting the beam frame 23 to the height of the design ground movement so that for example a H2 site with 75 mm ground movement, the insulating packer 44 would be a composite loadbearing structure 75 mm high. Effectively, this means the beam frame 22 would have a 75 mm ground clearance throughout. The second way is to leave the insulating pads at nominal 20 mm deep and dig a trench in the soil directly under the beams 22 to a depth of 55 mm and 50 mm wide minimum prior to installing the vapour barrier 46. This combined with the packer depth, in this same ground movement example results in the ground movements of 75 mm without substantial contact with the bearer beams 22. The third method is to increase the height of the concrete pier pads 20 above the benched site by the desired height less 20 mm for the insulating packer 44 thickness. When the concrete piers 20 are poured, concrete with appropriate slump can be finished 55 mm above the ground level, when the bearer beams 22 are installed on the insulating packer 44 this will result in 75 mm ground clearance between the underside of the bearer beams 22 and the ground for a H2 reactive site. The finished pier height above ground can be adjusted to the design height, and in sites with higher ground movements may require small formwork frames around the pier to achieve the elevated pier pad height. The preferred method for designs on reactive sites is to elevate the bored pier finish height above the benched site. [60] Void formers 30, preferably a nominal 150 mm thick insulating material made from polystyrene, are then installed between the beams 22 (and packers 44) and are pressed tightly into position leaving the top portions of the beams 22 proud of (extending over) the polystyrene void former 30 by the height of the packer 44 used in support of the beam 22. The void formers 30 extend between the side edges of the beams 22 in a tight manner thus substantially avoiding the formation of any cavities between the void formers 30, or between the void formers 30 and the beams 22. The void formers 30 form part of the poured concrete support means for when the concrete is formed to form the slab 60. The poured concrete support means (void formers 30) support the poured concrete. When the concrete hardens to form the slab 60, the majority of the weight of the slab 60 is supported by the beam frame 23.

[61 ] Other materials may be suitable as a void former, including thinner high density polyurethane at the base, combined with stone aggregate fill to level of the top of the beams 22. This can provide higher thermal mass content as well as cost effective use of materials. However, L grade polystyrene appears to offer economy, high thermal resistance and lightweight for installation and is the preferred material.

[62] When the void formers 30 are installed, the top surface is continuous and without voids or holes that may make it unsafe to walk on. The void formers 30 are solid so installers can walk on them without breaking through them.

[63] Referring to Figure 4(b), holes 31 are cut into the void former 30 in the required positions to receive plumbing penetrations 1 10 which are sealed with spray foam 32 after fitment. Point loadings on the slab may be transferred into its footing under the foam 32 by simply cutting a hole in the void former 30 at the location so that concrete may flow into it.

[64] Thermal separation is still achieved by placing load bearing packers 44 on top of the footing and sealing the edges of the holes with spray foam. Preferably, the distance from the top of the beam frame 23 to the top of the polystyrene platform is 30 mm however this may change to suit design considerations, and in a particular design may be used to provide support for the reinforcement mesh which is installed next.

[65] The thermal resistance of the polystyrene void former 30 increases as the density and the cost of the material increases. Commercially available L grade which is the lowest grade and therefore most cost effective, when supplied in nominal 150 mm thick blocks gives a thermal resistance rating R value of approx. 3.5.

[66] Figure 13 shows a preferred feature on the bottom surface of the void former 30 being a regular arrangement of saw tooth grooves 34 with flat sections 35 on the tooth and at its base. The tooth and base formation is regular such that a foam void former 30 may be cut in half and the saw tooth formation 34 produced on each block, providing the same overall height of 150 mm and reducing the actual thickness to 125 mm when a 50 mm deep tooth is cut.

[67] The purpose of the saw tooth grooves feature 34 is to provide sufficient bearing surface to support construction and wet concrete loading, provide less surface contact with the ground to accommodate small discrepancy and irregularities in the flatness of the benched site to aid installation stability. The main benefit of the feature 34 is to compress and allow soil to move into the tooth voids in the event of soil expansion in reactive ground when the slab 60 is in service. This feature will allow the slab 60 and beams 22 to remain on the bored piers under variable soil conditions. The bottom of the feature 34 bears on the ground. When reactive soils expand, instead of placing a lot of pressure on the internal structure of the slab 60 and lifting the slab 60 off the piers 20, the soil extrudes into the teeth void 36 to relieve the pressure. The feature 34 thus provides spaced cavities 36.

[68] To increase the effectiveness of the concrete slab R value, the tops and exposed edge of the beams 22 may be covered with thermal insulating tape 48. However, since the beams 22 are already thermally isolated from the ground and there is no airflow underneath the slab 60, the improvement in thermal resistance value may be marginal.

[69] Reinforcement mesh 50 is then installed on top of the beam frame 23 and void former 30 platform, with bar chairs 52 disposed in conventional ways to support the mesh 50 to achieve the mesh coverage.

[70] Edge insulator boards 54, being a nominally 10 mm thick high density foam board or similar, is then glued and/or fixed to the external surfaces of the edge beams 22a. The edge insulators 54 cover the entire external surfaces of the edge beams 22a and extend upwards to the height of the slab 60 to be formed. The edge insulators 54 are thus disposed around the perimeter of the beam frame 23 and extending at least to a height of the concrete 60 above the beam frame 23. In the slab example described herein, the foam edge insulator 54 extends the height of the edge beam 22a and to the top surface of the slab 60 to be formed. As the edge beam 22a is 150 mm high, and since the slab 60 to be formed will be 100 mm thick, and the beams are raised 30 mm into the slab height by the packer 44a, the edge insulation board will be 220 mm high. The edge insulation board 54 is thus set at the slab height above the edge beam 22a and will contain the wet concrete 17 during the pour.

[71 ] The installation of the polystyrene edge insulator boards 54 provides a thermal break to the external slab edge as well as a lost edge form, which means it does not need to be stripped away after the pour as with conventional slabs. Removable timber edge board or lost galvanised steel angles may likewise be used as edge formwork and the edge insulation boards 54 and angle lintels installed afterwards if required. [72] If the building is brick veneer construction, angle lintels 56 are installed to support the construction of the external brick veneer wall 58, and are placed on top of the perimeter bored piers 20a and abutting the edge insulation board 54 on the edge beam 22a. The engineered angle lintel 56 is fixed through the edge insulation board 54 into the side of the edge beam 22a using a class 3 TEK screw at minimum fixing points. This provides a thermal break between the external brick wall 58 and the slab 60 to be formed.

[73] Referring to Figure 5, a smaller 75 mm x 150 mm angle lintel 56a with suitable clearance above ground may be used to support Hebel™ claddings or similar Autoclaved Aerated Concrete (AAC) cladding systems. When the home is clad framed, the wall frames are placed so that the external claddings finish over the slab edge insulation. The exposed side of the bored pier 20a may be chipped away 21 to allow back fill 130 and pathway slab 132 to conceal it.

[74] When termite proofing is required, a reticulation system 70 may be installed against the edge beam 22a prior to installing the steel lintel 56a or into the ground adjacent the slab edge to manufacturers specification.

[75] All garage slabs, external concrete patios and veranda areas should be thermally broken or disconnected from the main house slab.

[76] The concrete is then poured over the beam frame 23 and poured concrete support means (void formers 30), and finished and there is no stripping of formwork from the main slab. The resulting slab is a fully suspended predominantly one way slab, however the edge beams 22a provide edge slab support for a partial two way slab design. All the concrete in the slab 60 is thermally isolated from the ground and external environment, and its thermal mass can be used to heat the home during the winter time when solar design principles are incorporated into the house design.

[77] Referring to Figure 6, in another form of the present invention, the void former 30 may be dimensioned to be level with the top of the edge beams 22a and internal beams 22b. In this case, the void formers 30 have a nominal height of 170 mm.

[78] Referring to Figures 7 and 8, in highly reactive sites, a metal decking 29 is fixed to extend across the top of the beams 22 as the poured concrete support means, and replaces the void formers 30. Support blocks 39 (preferably polystyrene) are installed midspan between beams 22 when required to support the decking 29 under construction loads, and are designed to collapse or at least partly compress under heave loads from the ground. Mesh 50 is draped over the beams 22 and close to the top surface of the concrete slab 60, and closer to the bottom of the slab 60 at midspan positions. The mesh 50 and concrete 60 is installed on top of the metal decking 29. The decking 29 may simply be lost formwork or composite deck. This method still allows for soil movement as well as high R value insulation of the floor systems. Another feature of using the decking 29 is that drainage pipes can now be installed on top of the ground increasing the fall heights for the drains, and saving work by the drainer. When the decking 29 sags under wet concrete loads, any extra depth of the concrete at the midspan positions increases its resulting flexural strength. Another feature of using metal decking 29 is that excess soil from the piering operation may be now left on site in the voids, where as in conventional waffle pods the soil is removed from the site at the cost of the builder and ultimately the consumer. The support blocks 39 are at least partly compressible to allow ground heaving.

[79] Another means (not shown) for constructing a slab 60 in extreme reactive sites is to suspend the polystyrene void former blocks 60 between the internal beams 22b and be supported mid span on bar chairs. The height of the bar chairs corresponds approximately to the heave height of the reactive soil design plus some. The void formers 30 are supported by metal saddles/brackets installed to the beams 22. The design loading and spacing of the bar chairs will support the construction loading when the soil is dry but will sink when the soil is moist. Alternatively instead of using saddle brackets the whole of the polystyrene infill block may be supported on bar chairs within the design parameters, so that the bar chairs will always collapse into the soil when the soil moistens and expands. It is conceivable that by using appropriate densities of polystyrene void formers 30 that the bar chairs may also be pressed into the polystyrene void formers 30 as well as into the ground when the soil heaves. The air void between the underside of the polystyrene void formers 30 and the ground adds to the systems R value of the formwork system. The preferred thickness of the polystyrene void formers 30 is 150 mm and when installed will be level with the top and underside of the 150 mm high beams 22.

[80] Figure 9 shows an alternative section view along line A-A of Figure 3, showing a brick veneer construction. This alternative construction shows a slab 60, a brick veneer wall 58, edge insulator 54, and a premade reinforced concrete lintel 80 supporting the brick wall 58 to the edge pier 20a.

[81] Figure 10 shows an assembled slab corner with supported concrete lintels 80 spanning between edge piers 20a and showing lintel joins 41. The lintels 80 are disposed to extend along, external to, and spaced parallel to the perimeter beams 22a for supporting an external wall 58.

[82] A benefit of using the pre formed and pre tensioned concrete beam lintels 80 on the perimeter is that the lintel 80 is thermally isolated from the main concrete slab 60, and can be used as edge form when external concrete areas such as veranda, patios and porches are required. These areas are poured directly on the ground (on suitable plastic membranes with specified chaired reinforcement) and because of the present invention can be poured at the same time as the main slab 60. In conventional slab edge systems, timber formwork is present along the edges of the main slab, preventing the external slab on grounds from being poured while it is in place. This means the external slab on grounds are poured at a later time causing more labour costs and delays.

[83] Figure 11 shows wall ties 45 installed along and fixed into the external sides of the edge beams 22a at specified spacings, the wall ties 45 extending over the lintel 80. Subsequently installed brick wall 58 connects to the wall ties 45 with mortar. When the first course of brick is laid, the mortar will bond the wall ties 45 in place, restraining the brick work and lintel 80 against lateral movement.

[84] In another alternate shown in Figure 12, a metal angle 49 is screw fixed to the top surface of the edge beam 22a and the edge insulator 54 is omitted . A plastic water vapour membrane 47 extends from under the slab beam frame 23 and is wrapped over the outside of edge beam 22a and fixed/taped against the metal angle 49. The metal angle 49 is typically galvanised and has one side section 51 the height of the concrete 60 and a base wide enough to enable fixing to the edge beam 22a, and to provide adequate structural support to resist lateral wet concrete loading during the pour. The metal angle 49 thus forms a slab edge holder means. The concrete lintel 80 is installed adjacent to the plastic wrapped edge beam 22a to the specified overall wall thickness and a cavity 71 is formed between the edge beam 22a and the edge of the concrete lintel 80. Wall ties 45 are installed along the outside face of edge beam 22a and are subsequently locked into the wall and concrete lintel assembly by mortar during the bricklaying process.

[85] Other alternatives and modifications to the present system are also possible.

[86] In one alternative form, the present invention includes an insulation means being an insulation board nominally 10 mm thick. The insulation board comprises reflective foil insulation each side bonded to a polystyrene sheet. The insulation board is installed nominally 80 mm below the top of the beams 22, resting on saddle brackets fitted to the beams 22, and spanning between the beams 22. The insulation board can be supported on plastic bar chairs at nominal centres or polystyrene support blocks. The resulting insulation board provides nominal insulation benefits from heat flow in air, however its primary benefit is to reflect back radiant heat from the underside of the slab. When installed with appropriate air gaps and appropriately sealed, and with a totally sealed sub floor void , high thermal resistance values for the slab can be achieved. [87] Results from analysis carried out on this slab, systems R values ( thermal resistance ) for this floor combination of materials is R 6.5 for heat loss from the inside to the ground in the winter time, and R4.2 for the heat gain from the ground in the summer time. R= 6.5 is over 4 times greater than any other ground floor slab system available in the market place. Where foil board is used, a separate vapour barrier may not be required saving further costs in the slab construction.

[88] In another form of the present invention, thermal insulation may be obtained by using a combination of a thinner polystyrene slab which has nominal dimensions 120 mm thick by 1200 mm wide by 2500 mm long and air gap and a reflective foil membrane resting on or near the ground with the reflective foils upwards. To maintain the top of polystyrene slab level with the top of the beams 22, polystyrene support blocks as described before, can be sized and installed to support the construction loading for the slab and to accommodate vertical ground heaving in reactive sites and progressively collapse when certain heave loading is reached.

[89] The reflective foil installed on or near the ground when properly taped can also act as a vapour barrier, providing further economy, and is fully effective in reflecting heat an air gap needs to exist between the underside of the polystyrene slab and the foil.

[90] To keep the concrete 60 from bonding to the polystyrene blocks 30 during the pour (if required), a plastic membrane is installed over the top of the beams 22 and polystyrene blocks 30 and all the joints taped. The added advantage is that it insures that water from the wet concrete pour doesn't discolour the reflective foil film and lose its efficacy in reflecting heat. In recycling the floor system, the concrete slab portion 60 can be removed from the top of the floor frame 23. leaving the structural frame 23 and other components re-useable as they will be free of any contact with wet concrete during the pour. In this arrangement, total system R values of 6.9 have been gained for the winter heat flow out, and R = 5 for summer heat flow in, both values substantially higher than any other ground floor slab systems in the market.

[91 ] For brick veneer construction, angle lintels, or other lintel systems made of reinforced or pre tensioned concrete, or reinforced concrete (as in conventional strip footing) and pre made composites of other suitable materials can be used. In the preferred form of the present invention, pre-tensioned concrete lintels 80 available in standard sizes 1 10 mm wide x 80 mm high, and 1 10 mm wide x 170 mm high are placed on top of the perimeter bored piers 20a and abut the edge insulation board 54 on the edge beam 22. The dead load of the concrete lintel 80 offers further lateral support to the edge insulation board 54, reducing the number of fixings to install them. [92] When Hebel or AAC panels are used, the concrete lintels 80 are installed in a similar way and may be dowelled at each end into the concrete edge pier 20a instead of tied into the edge beams 22a with wall ties 45.

[93] The present invention provides a number of advantages.

[94] The present slab construction comprises a grid of structural beams that are already designed to support the design loads of the building as well as the weight of the slab and other design loadings on the cured slab. The concrete slab sits on top of the beams and is planar and of uniform thickness throughout, so its thickness to its underside does not vary as with traditional domestic slabs, where the underside of the slab forms into beam valleys.

[95] In the present invention, the building loads are designed into the beam structure before the concrete floor slab is poured. In contrast, in the prior art, the design loadings are formed after the slab is poured, and as long as 28 days after the concrete has developed its strength.

[96] The present slab construction comprises a structure which is completely insulated from the ground and from lateral sides of the slab. The structural beams are insulated from the ground by loadbearing support packers which are installed between the underside of the structural beams and the footing piers.

[97] The external loadbearing wall perimeter (the internal brick wall of cavity brick construction, and the timber wall of brick veneer construction sits on) is insulated by edge form in the cavity.

[98] The present invention also provides various means to fill the voids between the beams, including polystyrene, soil from the site excavations, or metal decking, reflective foil, solid hi density polystyrene blocks or any combination thereof.

[99] When another plastic membrane is installed above the void formers prior to pouring the concrete, the concrete does not bond to the polystyrene void formers which will allow easy recycling of the concrete slab as well as re use of the materials under the slab. In contrast, in waffle pod slab systems, the pods are mixed up with the concrete and therefore creates a mess, as well as it cannot be recycled, and in raft slabs where the beams are much larger, it requires very large equipment to break the slabs up.

[100] The components of the present system, such as the steel beams, and the concrete beams lintels around the perimeter, as well as the polystyrene void formers can be reused, and the concrete slab can be peeled off the support frame and recycled into road base.

[101 ] The installed structural steel frame provides positive and predetermined slab dimensions in the installation process using the cut to length beams, there is less chance the overall slab dimensions will be incorrect. [102] The particular arrangement of beams around the perimeter enables the easy separation and insulation of the slab edge from the external brick veneer walls support, a source of a lot of energy loss in traditional slabs, due to the integral step down rebate.

[103] Another benefit of the present invention is that there is no need to have sub floor ventilation, as the slab edge board (edge insulation board 58) completely encloses the small spaces underneath the beams. As such, there is less likelihood of condensation, or corrosion by oxidation, as the environment will be devoid of oxygen due to limited corrosion of the zinc, if any moisture remains at the time of installation.

[104] Another benefit is that the amount of concrete needed for the pour is predictable and easy to quantify, as it is a uniform slab thickness across the extent of the floor. It is also efficiently employed, being used to create a uniform slab, rather than used to fill voids in a slab due to hasty and inefficient excavations of beams, and placement of waffles pods. The present invention will simply require a measure of the slab area by the slab thickness with a small percentage for screed variation, of say 2%.

[105] Another advantage is that the edges of the slab and where the steel beams are located, can receive load sooner than the prior art.

[106] Another benefit is the increased energy efficiently rating provided to the home, approx. 30 % more efficient than a traditional slab on ground.

[107] The structural support beams are themselves insulated from the footings/piers, for greater thermal efficiency.

[108] Whilst preferred embodiments of the present invention have been described, it will be apparent to skilled persons that modifications can be made to the embodiments described.

[109] For example, instead of grooves formed in the lower surface of the void formers, other spaced cavity formations can be formed such as spaced circular or other shaped cavities.

Claims

1. An insulated concrete slab floor construction comprising:

spaced piers installed in a building site;

thermal insulating load bearing packers mounted on the piers;

a poured concrete support means extending across the beam frame;

edge insulation means disposed around the perimeter of the beam frame, the edge insulation means extending at least to a height of the concrete above the beam frame; and

concrete disposed over the beam frame and the poured concrete support means, and between the edge insulation means.

2. The concrete slab floor construction of claim 1 wherein the poured concrete support means are void formers disposed between the beams of the beam frame.

3. The concrete slab floor construction of claim 1 wherein the poured concrete support means is a decking disposed over and extending across the beam frame.

4. The concrete slab floor construction of claim 1 further comprising a vapour barrier extending over the ground and attached to perimeter beams of the beam frame.

5. The concrete slab floor construction of claim 1 wherein the insulating packers have a minimum height of 20 mm.

6. The concrete slab floor construction of claim 2 wherein the void formers are made from polystyrene.

7. The concrete slab floor construction of claim 6 wherein the void formers comprise spaced cavities formed along their bottom surfaces.

8. The concrete slab floor construction of claim 2 wherein the beam frame extends to a height above the poured concrete support means.

9. The concrete slab floor construction of claim 8 further comprising thermal insulating tape covering the tops and exposed edges of the beams.

10. The concrete slab floor construction of claim 1 further comprising reinforcement mesh disposed within the concrete.

1 1 . The concrete slab floor construction of claim 1 wherein the edge insulator means comprises edge insulation boards fixed to external surfaces of perimeter beams of the beam frame.

12. The concrete slab floor construction of claim 1 1 wherein the edge insulation boards are made from polystyrene.

13. The concrete slab floor construction of claim 1 1 further comprising angle lintels disposed over perimeter piers and fixed through the edge insulation board into the perimeter beam.

14. The concrete slab floor construction of claim 1 further comprising a termite reticulation system disposed adjacent perimeter beams of the beam frame.

15. The concrete slab floor construction of claim 2 wherein the void formers are level with top surfaces of the beam frame.

16. The concrete slab floor construction of claim 3 further comprising support blocks disposed midspan between beams of the beam frame for supporting the decking, the support blocks being at least partly compressible to allow ground heaving.

17. The concrete slab floor construction of claim 1 further comprising lintels disposed to extend along, external to, and spaced parallel to the perimeter beams of the beam frame for supporting an external wall.

18. The concrete slab floor construction of claim 17 further comprising spaced wall ties fixed to the perimeter beams, the wall ties extending over the lintel.

19. The concrete slab floor construction of claim 1 wherein the edge insulation means comprises a slab edge holder fixed to perimeter beams of the beam frame and having a side section extending to the height of the concrete.

20. The concrete slab floor construction of claim 1 further comprising reflective insulation means disposed below a top surface of the beam frame

21 . The concrete slab floor construction of claim 1 further comprising a separation membrane disposed over the beam frame and the poured concrete support means, and underneath the concrete.

22. A method of forming an insulated concrete slab floor construction, the method comprising:

installing spaced piers in a building site;

mounting thermal insulating load bearing packers on the piers; mounting a plurality of beams to extend between the piers and on top of the packers; connecting the beams to form a beam frame;

laying a poured concrete support means to extend across the beam frame;

23. The method of claim 22 further comprising the step of disposing lintels to extend along, external to, and spaced parallel to the perimeter beams of the beam frame for supporting an external wall.

24. The method of claim 22 comprising the step of disposing a separation membrane over the beam frame and the poured concrete support means prior to pouring of the concrete.