WO2005042854A1 - Foundations and bases for buildings - Google Patents

Abstract

A “slab-on-grade” monolithic concrete floor (100) with foundation for a building is described. The slab includes internal reinforcing (101) and thermal insulation (102, 012A) . The slab is compatible with unstable ground (108) including expanded clays and frost heave. Thermal insulation (102, 102 A) comprises a low-density form of a plastics foam such as expanded polystyrene foam. The system and procedure for erection is compatible with a franchised management system and together result in minimised “lost time”.

Description

FOUNDATIONS AND BASES FOR BUILDINGS

TECHNICAL FIELD

This invention relates to construction, and in particular, though not solely, to construction of foundations of buildings having concrete slab floors (such as the "slab-on-grade" type), including a means for thermal insulation. BACKGROUND ART

The foundation of a building should be a stable, fixed structure capable of supporting the weight of the building and its contents for many years. The foundation relies on the underlying soil or other material, and in some circumstances the underlying soil is not capable of serving as a reliable base. Frost heave, and expansive clay soils present problems. One method to overcome this distortion of the surface of the ground comprises allowing heat to leak into the ground under and surrounding the foundations (preferably beneath an apron of insulation) so that the ground beneath is prevented from freezing. That apron is a non-loadbearing insulation layer extending outwards for several feet (about 1 metre) from a shallow foundation in order to keep building heat within the foundation area and prevent frost heave. Another approach, for colder areas, is to prevent permafrost from melting. Approximately 1.5 million foundations including frost protection measures have been constructed in Scandinavia. A further measure is to provide a layer having "give" between the substantially rigid slab and the potentially movable substrate.

Monolithic concrete slab foundations/floors have become acceptable in recent years - in particular the type of base or foundation that is placed on or slightly above the soil surface (known as "slab-on-grade") there is usually no cellar or basement in such designs. The inventors have developed a version of a "raft floor" with included voids in the foundation or base, yet having sufficient inherent strength to sit upon ground which may subsequently move, for which some antecedents exist in patent specifications such as:

US 2881501 Raney describing an improved cardboard box for forming a void, and providing internal reinforcing beams in a slab floor, but it should be noted that these boxes have never found much favour. US 3763750 Bokvist et al (using pellets of burnt expanded clay beneath) and US 3956859 Ingestrom (sides) relate to insulation for slab-on-grade foundations. US5934036 Gallagher describes expanded polystyrene foam blocks and polystyrene beam supports. US 5924251 Julia describes a perimeter trench that can be joined to internal trenches dug into the soil in order to create beams cast in situ, with reinforcing as required. The trench system has been tried in New Zealand but (a) breaks down on rainy days and (b) does not easily permit use of a waterproof membrane.

In relation to US4694625 Gregory (describing use of pilings extending up from within the ground into monolithic horizontal beams), the inventor has two forms of concrete pad system. One uses pre-cast thick disks of concrete produced to a relevant Standard. Each one is placed at the bottom of a hole in contact with good ground and each one includes a vertical central aperture for a large nail or other fastener to be driven through the aperture into a vertical wood post or pile which when installed reaches upward to make contact with a floor/foundation structure. The hole is normally filled in with soil. The top of the pile is cut so that a series of such piles provide a flat surface. The other form also uses concrete pads and usually concrete risers which reach upward to make contact with the underneath of a concrete floor slab.

A raft floor may not need any of the above supports. It may sit directly on the soil (usually above a mandated water barrier made of an impermeable membrane) which may in turn be placed upon a layer of compacted hard fill, sand, or gravel. The inventor has also created a range of wire stirrups for use with monolithic poured floors including substantial void-forming structures, the sides of which delineate a matrix of steel-reinforced beams criss-crossing the foundation, beneath the floor and above the surface of the ground. The total consumption of concrete is reduced for a given stiffness and some insulating properties are provided if the void-forming structures (covered above with concrete and reinforcing mesh) hold low-density plastic foam. They are usually polystyrene foam blocks but alternatives include cardboard boxes. The wire stirrups hang across the spaces between the void- forming structures. The stirrups define the width of each resulting rib and also support reinforcing bars of steel (for tensile reinforcement) at a suitable height above the base, and position within the channel until surrounding concrete has been poured and has set around the reinforcing. Another type of stirrup supports reinforcing around the outer perimeter of a slab floor. The stirrups also minimise tying the reinforcing bars together with wire that is otherwise required. Many problems are met when constructing a foundation for a building: soil stability over the long term, disposal of removed soil, establishing secure foundations, providing a strong, reliable base on which a building may be constructed, and carrying out the construction in an expedient manner

To provide an improved and cost-effective foundation or base for a building, or at least to provide the public with a useful choice.

All references, including any patents or patent applications, cited in this specification are hereby incorporated by reference. No admission is made that any reference constitutes prior art. The discussion of the reference states what their authors assert, and the applicants reserve the right to challenge the accuracy and pertiency of the cited documents. It will be clearly understood that, although a number of prior art publications are referred to herein, this reference does not constitute an admission that any of these documents forms parts of the common general knowledge in the art, in New Zealand or in any other country.

It is acknowledged that the term 'comprise' may, under varying jurisdictions, be attributed with either an exclusive or an inclusive meaning. For the purpose of this specification, and unless otherwise noted, the term 'comprise' shall have an inclusive meaning - i.e. that it will be taken to mean an inclusion of not only the listed components it directly references, but also other non-specified components or elements. This rationale will also be used when the term 'comprised' or 'comprising' is used in relation to one or more steps in a method or process.

It is therefore an object of the present invention to provide a method of a construction of a foundation, and/or a foundation which will go at least some way towards addressing the foregoing problems or which will at least provide the industry and/or public with a useful choice. Further aspects and advantages of the present invention will become apparent from the ensuing description which is given by way of example only.

DISCLOSURE OF INVENTION

In a first broad aspect this invention provides a strong, monolithic foundation or base for a building of the raft floor type, wherein the mass of the raft rests upon a layer of thermal insulation so that heat exchange between the foundation or base is minimised, in order to conserve heat within the building and so that underlying permafrost is not weakened.

In a related aspect the thermal insulation comprises a creep-resistant, non- degradable material having a controlled amount of resilience so that deformation of the ground beneath the foundation or base may be taken up by deformation of the thermal insulation.

A preferred thermal insulation is a high-density polystyrene foam, of at least 18 kg/cubic metre density, used at sheets of about 50 mm (2 inches) thickness.

In a second broad aspect, the monolithic foundation previously described in this section permits simplification of the management of construction. Preferably a given site can be inspected, the soil can be tested, the mode of foundation support can be designed, the plan can be drawn, and a schedule of materials and "instructions for use" can be generated so that the workers on the site do not need any particular training or responsibility.

Preferably a plurality of sites can be managed together, so that temporary shortfalls in one area are overcome by supplying materials or labour units from another area.

In a related aspect the management is supplied in the form of a franchised business.

In another aspect, the present invention may broadly consist in: a floor for a building or base of a building, which includes a substantially monolithic foundation which rests upon a layer of thermal insulation characterised in that, the thermal insulation layer is configured to minimise heat exchange between the foundation in order to conserve heat within the building and any underlying permafrost remains substantially un-weakened.

Preferably, the thermal insulation includes a creep-resistant, substantially non- biodegradable material having a controlled amount of resilience so that deformation of the ground beneath the foundation may be absorbed by deformation of the thermal insulation layer.

Preferably, the thermal insulation is a high-density foam of at least 18kg.m -3 Preferably, the high-density foam is substantially 38 mm or more in the longitudinal, or thickness, dimension.

Preferably, the high-density foam is an expanded polystyrene.

Preferably, the foundation is formed as a raft-or beam-type construction.

Preferably, a water impermeable membrane separates the foundation and thermal insulation layer.

Preferably, the thermal insulation layer is coated with a protective coating.

Preferably, the protective coating is a fire-retardant, bug-retardant or fungus- retardant.

In another aspect, the present invention may broadly consist in; A method of forming a floor for a building or base of a building comprising the steps of: i. distributing a thermally insulating layer upon at least the area to be occupied by a substantially monolithic foundation, and ii. placing or forming the substantially monolithic foundation upon the thermally insulating layer.

Preferably, the area upon which the thermally insulating layer is to be distributed is prepared to provide a substantially flat and stable base.

Preferably, crushed rock is distributed over the area prior to distribution of the thermally insulating layer. Preferably, a water impermeable membrane is placed over the thermally insulating layer, separating the foundation from the insulating layer.

Preferably, piles are inserted into the area with their tops substantially flush with the plane of the underneath of the foundation.

Preferably, when the foundation is formed by pouring a curable material upon the water impermeable layer, prior to pouring the curable material a matrix or system of channel forming structures are located upon the water impermeable layer so as to form a series of channels, after pouring, which become internal beams once the material has cured. Preferably, the matrix or system of channels created is formed by the arrangement of high-density foam.

Preferably, the high-density foam is an expanded polystyrene foam.

Preferably, reinforcing mesh or rods are used within the foundation to enhance the strength characteristics of the foundation. Preferably, spacing means are used to ensure the channel forming structures maintain their arranged location, and where mesh is used, supporting means are used to hold the mesh in place, within the channels formed.

Preferably, the rods lie centrally within the channels and are located at least 50mm from a surface of the foundation. Preferably, the channels are intersected by spacers, or stirrups, and engage with the reinforcing mesh and/or rods held in place by the supporting means.

Preferably, the thermal insulation layer is coated with a protective coating.

Preferably, the protective coating is fire-retardant, bug-retardant or fungus-retardant.

Preferably, supporting means are plastic chairs which have beveled edges. Preferably, the plastic chairs have one or more plastic tongues extending away from the chair which are adapted to engage with the mesh or rods.

In another aspect, the present invention may broadly consist in; a method of co-ordinating a construction process characterised by the steps;

(i) identifying at least one local franchisor and at least one on-site franchisee, and

(ii) providing the said at least one on-site franchisee with information pertaining to a plurality of specific tasks to be formed according to a unified schedule for said constructions process, and iii) co-ordinating the performance of said plurality of specified tasks in parallel by a number of sub-contractors of said at least one on-site franchisee, and iv) supplying corrective information to said at least one local franchisor from said at least one on-site franchisee. Preferably, the method further includes an additional preliminary step of identifying at least one regional franchisor.

Preferably, the method further includes an additional preliminary step of identifying at least one national franchisor.

Preferably, at least one local franchisor supplies training information to said at least one on-site franchisee with respect to the specific tasks of the construction process to be completed.

Preferably, at least one on-site franchisee pays royalty fees to said at least one local franchisor.

Preferably, an on-site franchisee co-ordinates the performance of specific tasks by a number of sub-contractors over a plurality of construction-sites.

Preferably, the performance of said specified tasks by an on-site franchisee's subcontractors is linked to a system of checks and monitoring.

"Slab-on-grade" relates to a monolithic, usually reinforced, concrete slab forming a foundation for a building and lying on top of, or slightly inset into, the soil surface (the grade).

A "raft floor" is, as we use it, a term for an existing type of reinforced concrete structure, shaped to include reinforcing beams and voids wherever possible, that has sufficient internal strength to sit upon a variously prepared soil or other ground surface, serve as a ground-level floor, and support the weight of the remainder of a house on its back, without failure even if part of the surface below has given way. The raft floor has a typical thickness of 350 mm. It typically includes voids which may be made of expanded polystyrene foam blocks, or cardboard boxes, which are left in place. It is a type of slab-on-grade foundation. One building code relevant to concrete raft floors is Australian standard No AS2870; Residential foundations. "Reactive soils" relates to any type of unreliable substrate upon which a foundation slab is to be placed. This term particularly relates to expansive clays (such as those including bentonite), also sand and sandy soils and peat. For the purposes of the invention the term also relates to situations where it is suspected that there are layers of peat beneath apparently satisfactory strata, and soils affected by frost heave, or soils which are already frozen when encountered. Methods for dealing with reactive soils also apply to man-made situations such as presence of old fill and poorly compacted soils, The construction process may involve re-shaping a slope and generating fill which can most conveniently be buried beneath the slab.

BRIEF DESCRIPTION OF DRAWINGS

Fig 1 : is a diagram showing an internal portion of a raft floor in cross section on good ground; Fig 2: is a diagram showing a raft floor in cross section on poor ground, with a support pile reaching down to good ground;

Fig 3: shows a perimeter of the raft floor, in cross section, with an optional pile; and

Fig 4: is an outline of inter-relationships between franchise holders. BEST MODES FOR CARRYING OUT THE INVENTION

EXAMPLE 1

In a first aspect of the invention, a novel technique for providing thermal insulation for a "slab-on-grade" foundation for a building is provided, and is in relation to conductive losses from the building through the foundation. See Canadian national building codes (Model National Energy Code of Canada for Buildings (1997).

This aspect sets out to retain heat within a building, typically in order to prevent permafrost from thawing or to at least make the building more thermally efficient. Loss of heat to the ground may be undesirable, or unacceptable, on account of building laws or regulations imposed by a local authority. The inventors have realised that a dense grade of expanded polystyrene foam (EPS) can be used in the form of a layer comprised of a sheet in the range of 1.5 to 3 inches thick and usually substantially 2 inches (50 mm) thick. The material provides effective thermal insulation, as well as providing a layer which can be distorted under sufficient pressure to provide "give" in the event that frost heave or expanded clay causes movement, so that the rigid slab is exposed to less strain or distortional forces.

The foam is deposited over at least the entire area to be occupied by the raft floor (or foundation), lying below, that is underneath, the damp protection course (DPC), waterproof/impermeable membrane and below the concrete to be poured later. An overlap of about a metre all round the perimeter of the foundation may assist in further insulative properties - and can later be covered by soil (see fig 3).

A preferred dense foam is available as "Polyfoam" in New Zealand (also known as geotechnical foam). It is an expanded polystyrene foam (EPS) having a raised density of from 15 kg/m³ (0.94 lb per cubic foot) the "standard" grade), through the hard grade, 28 kg/m³ (1.75 lb per cubic foot), to the "very hard" grade with a density of from 36-54 kg/m³ (2.25 to 3.37 lb per cubic foot). Despite lying in contact with ground water, this type of material has been shown to take up only about 5% by weight of water after one year's exposure to soil moisture. Deformation in relation to loads over time has been well documented as the material has been used in highway engineering applications. The EPS material can also be used to fill voids in the surface of the site.

Typical R values (m².k/W) are, for a 50 mm thick layer, 1.32 to 1.47. It is noted that polystyrene foam is approved in Canada for "below grade" insulation applications.

In use according to a further aspect of the invention, the EPS is provided as about 50 mm thick sheets rather than as granules or solids. Typically manufacturers cast a large block of EPS and then slice it with hot wire cutters in order to obtain the required sheets and thickness. Remote areas such as in the north of Canada may benefit by use of on the spot portable EPS foam makers which heat and casts pods and sheets from foamable polystyrene granules, rather than the logistics and cost of transporting the light, bulky material over a great or uneconomic distances.

During construction of a slab-on-grade floor, the steps relating to construction of the foundation slab include: conventional site preparation in order to provide a flat, stable (as far as possible) base. Optionally, piles are inserted into the ground with their tops flush with the plane of the underneath of the slab. Also as an optional step, a pad of crushed rock can be laid or placed over the area.

Distribution of a layer of EPS sheets (as previously described in this section) over at least the area to be occupied by the slab, then the EPS sheets are covered with a conventional impermeable membrane, placing a matrix or pattern or arrangement of void-forming structures (also typically comprised of EPS) over the mesh so as to form a pattern of channels that will (after pouring of concrete or another curable material) become internal beams. The voids are connected across the channels by spacers (also referred to as stirrups), and also including means to support reinforcing rods or bars along the channels so that the rods lie centrally (and advantageously more than about 50 mm into the mass of the concrete). The rods can be placed and tied in place and placed above the reinforcing mesh over the voids. The rods or bars are supported on "bar stool" spacers so that the mesh lies within the floor surface. In construction of the floor or foundation or base, there can also be the provision of a level-controlled perimeter surround with boxing, shutters, bricks or blocks, so that the foundation is ready to receive a single pour of concrete. After concrete is delivered, poured, distributed, agitated, levelled, and cured as necessary, the concrete slab is then ready to support the remainder of the building, to be constructed on top. Different types of stirrups can be used around the perimeter, and a wide variety of stirrups exist for different purposes within raft floors. Of course, dependent upon the construction materials, the type of stirrup will be chosen accordingly.

Services such as plumbing and under-floor heating may optionally be distributed within the floor prior to pouring the concrete.

Referring to Figures 1 and 2, which illustrate a construction of the aspects described above, noting that some components are shown separated from each other, for the purpose of these illustrations only - they would in-use be in firm contact. In Figure 1, 100 is the upper surface of a concrete floor. 101 (repeated) is a series of sections through a layer of reinforcing mesh within the concrete floor, which overlies voids such as polystyrene foam (EPS) blocks 102, 102A, herein also termed as "pods". Typical pod dimensions can be 4 feet long by 4 feet wide by 8-12 inches in thickness. Thickness of the pods used should generally be consistent for a given site construction. Pods can be cut to size as necessary, for example with a wood saw, if the building plan requires.

The two pods in Figure 1 are separated by an internal strengthening beam 103 comprising a "trench" or channel between the arranged pods, which will be filled with concrete that forms part of the monolithic slab. Within the beam channel or trench lies one (or more) substantially longitudinal reinforcing rods or bars 105, supported above the base of the concrete by stirrups 104 (made of bent 1/8 inch steel wire on a computer-controlled bender) that also serve to maintain horizontal separation and positioning of the voids in the period between installation of the components of the foundation and subsequent pouring and setting of the concrete or curable material. A layer of waterproof or impermeable (DPC) membrane 106 lies beneath the pods. This layer lies on top of the high-density EPS sheet 107 (which serves as a thermally insulating layer or barrier).

In Figure 1 we have assumed that a flattened (scraped or compacted) layer of good ground 108 lies immediately below the thermal barrier and the top surface 109 is substantially planar or flat - the entire height of which may be about 350 mm (about 12-16 inches).

Figure 2 shows how the system is altered in the event that the material 201 below the thermal barrier 107 is not solid or fully supportive. Piles 203, with their fastened (205) feet 204 made of pre-cast or cured concrete are placed in holes cut down to underlying good ground 202 at intervals and support either the perimeter of the floor (Figure 3) or internal beams (Figure 2). The exact intervals, like other dimensional details, are prescribed by engineering analysis based on test strengths, soil tests, loadings, depth to good ground, experience, and governing Standards.

Note that all piles are also covered on their top surfaces by a layer of EPS sheet (as shown above the pile 203 in Figure 2) although it must be realised that the loading here is greater. For that reason the piles may be capped with the hardest grade of EPS available.

Figure 3 shows a preferred finish for the perimeter in which a ring of blocks 301 surrounds an edge beam 303, which contains (in this example) two reinforcing steel rods 305 (although other known configurations such as a cage of 4 rods may be used). A variant stirrup 304 supports the rods within the beam until the concrete has set. For thermal and dampness barriers, the impermeable membrane 106 and the dense EPS sheet 107 are bent, folded and glued up against the exterior of the blocks 301. A pile 203 is shown supporting the edge beam. This is of indeterminate length, depending on the depth to good (stable) ground under the soil at the site.

Figure 3 also shows an example "bar stool" wire stirrup 306 that is placed at intervals in order to support the reinforcing mesh 101 at a suitable height within the floor.

In combination, the above improvements advantageously provide:-

(1 ) A raft-like foundation, capable of riding out, or able to withstand a certain amount of, soil movement just as a marine oil rig, also supported on piles, rides the ocean waves. (2) Frost heave or expansive clay movement tends to preferentially deforms the EPS layer rather than cracking or breaking the concrete slab initially.

(3) Ability to overcome potentially poorly compacted fill or base support materials on a site; the construction team can bypass the problem simply by drilling holes through it, rather than either compacting the fill, replacing it, or carting it away. (4) The entire raft-like foundation is ideally thermally insulated from the soil beneath, thereby allowing a saving of heat and energy whether or not under-floor heat generation means is used. In addition the preferred EPS pods provide substantial thermal insulation.

EXAMPLE 2 In a further aspect, there is provided a business method for streamlining the construction of a "raft floor". In housing construction, money can be saved by (a) optimised use of materials and time, (b) saving time by procedures which are less dependent on weather, supplies, or skilled manpower, and (c) by continuous monitoring and quality control so that processes run to completion without interruption. A raft floor according to Example 1 uses more concrete and steel than a prior-art slab-on-grade foundation.

Even without advanced management, the floor can be completed more quickly and this reduces the final cost. Some of the saving occurs at the stage of placing steel reinforcing. Some of the saving occurs in relation to site preparation because of use of the raft principle, and/or because a pile-supported foundation allows construction on top of less firm ground (the detailed procedure for any site having been dictated by analysis and subsequent structural or geotechnical design by an engineer on the basis of soil tests). Fill or excess materials generated on site can even be covered by the foundation, saving on its removal and cost of disposal. Site tidiness and organisation helps considerably in saving time and costs. A thick sand "mattress" or layer is not required with the present invention system.

Construction of a building upon a foundation of this type generally involves four groups of steps (which may apply to a single site or an area having thousands of sites): (1) Site acquisition, and

(2) house plan preparation. (3) On-site soil testing,

(4) consequent engineering, and

(5) raft floor specifications.

(6) Setting out the surveyed foundation shape upon the site,

(7) site preparation, and (8) foundation construction.

(9) Concreting, pouring, distributing, levelling, and curing the concrete, then removing the boxing, all so that

(10) the remainder of the house can be constructed on top.

"Site acquisition" refers to the process of acquiring land for development, and "House plan preparation" refers to the process of preparing plans suitable for the intended use of the building (usually a dwelling). These two steps are outside the scope of this invention except that a developer should have checked the soil suitability before obtaining the rights to the site.

"On-site soil testing" refers to inspection, by a duly qualified person, of the soil and rock beneath each individual site, looking for any weakness likely to compromise load-bearing properties, such as the presence of peat, wet ground, mobile/expansive clay, old fill, and the like. In a large development this process can be hastened by complementing a general report with specific reports.

"Foundation engineering" refers to a process in which an experienced engineer uses knowledge of the soil under the position of the building to be constructed (taking the actual plans into account) in order to generate specifications for preparing the site for use (if possible), such as the depth to which piles must be sunk to reach solid ground, or whether underlying metal fill can be used (and if so how much, what type, and how it is compacted) and generates schedules of materials required. In the present invention this work can be facilitated by a computer-assisted process within a specialist office.

The specifications will instruct that ground should be levelled and compacted so that it can receive the heavy raft floor. If the ground had a slope, the soil removed from one part may be placed under the other part so that the overall site is level. That removed and replaced soil will not be inherently stable, though it may lie upon weight-bearing ground. In that case piles (Figures 2 and 3) may be used. The replaced soil is used on the site so that less material has to be carted by road transport to another place. Consuming "waste" soil beneath the foundation has the advantage of keeping the site tidy. "Raft floor engineering" refers to a process in which an engineer uses particular knowledge of the building to be constructed in order to specify dimensions, concrete thickness and type, reinforcing (position, type, quantities), and any included plumbing or other items to be included with the floor, and generates schedules of materials required. In the present invention this work can be facilitated by a computer-assisted process within a specialist office, making use of experienced engineers. The process can print out detailed schedules of requirements for the particular site and place automatic orders for supplies.

"Setting out the site" means laying down the surveyed foundation shape upon the ground exactly where it is intended to be located. This process may have to allow for disruption of the site during subsequent excavation and levelling. Standard surveying techniques, or use of GPS or Galileo satellite co-ordinates (optionally supplemented with a fixed local transmitter) allow this to be done to millimetre accuracy. The specialised equipment involved may be provided and used more effectively under a franchised system according to the invention. "Site preparation" includes levelling, excavation and/or filling (if required), intermediate layer of metal (crushed rock) if required and its compacting. Often a small power excavator - a digger or a backhoe - would be used, and a powered compactor would be used. The system is capable of use on sloping ground where some of the soil may be cut away and then used (or disposed of) as backfill under the slab.

"Foundation construction" includes all work that is required to form the slab floor prior to pouring the concrete; such as installing pile foundations (if required), placement of thermal insulation (see Example 1 and Figures 1 to 3) placement of damp course, placement of void-forming materials, placement of stirrups, placement and tying of reinforcing, and placement of boxing, shutters, or blockwork for surrounding and containing the concrete. In addition, placement of wiring, plumbing or other services (such as under-floor heating) to be embedded would be carried out by the relevant subcontractor or qualified employee of the franchised company. "Foundation concrete work" refers to pouring, distributing, levelling, and curing the concrete, then removing the boxing, all so that the remainder of the house can be constructed on top.

It will be appreciated that steps 1 and 2, and (if conditions are consistent) steps 3, 4 and 5 may be dealt with in bulk by a developer in a development-wide manner by handling site data in a remote office, but the remainder of the steps are carried out, more or less in the sequence as given, by suitably supervised labourers on each site. Step 5 could be done remotely. One problem with the present system is that many of the individual actions in steps 6-9 have in the past been carried out by separate self- employed labour units (block-layers, concreters, steel riggers, back-hoe operators, and frequently one labour unit cannot start work if a pre-requisite part of the job has not been completed. The restricting factor may be the weather, shortage of supplies, or shortage of labour. Some of the on-site tasks (such as laying of concrete blocks or bricks) may be relatively small (despite being essential to the project) so it is hardly worth the while of an self-employed block layer to travel about in order provide the service.

This example provides an improved management system including all aspects (such as from number 3 to number 9 in the list above) as an integrated system. The management system typically comprises a franchised or otherwise licensed business that has the capability to contract to sell a developer a ready-to-continue foundation/floor slab with built-in quality control and properly engineered performance, according to the specifications and/or plans supplied, so that a developer can leave this work to the experts. The franchisor may in turn be controlled by a regional or national business. (See Figure 4). The local franchisor may be a concrete supply company, if only because the value of the concrete in a raft floor according to the invention is relatively large. Figure 4 shows a typical layout, where the downward arrows represent the usual support given in a franchise including the movement of knowledge and training manuals, and the upward arrows show the flow of corrective information arising from carrying out the specified tasks, as well as the usual franchise and royalty fees. It may be that engineering work is carried out within one of the higher levels above the on-site franchising level, so that economies of scale, and previous experience are used. Knowledge includes:

1. Know how and experience, some of which is made available within individual engineering specifications for particular sites. 2. Training, information and support for the franchise holder, so that the holder can formulate effective contracts, co-ordination of site work, inter-relationships of sites, manage or alleviate local problems such as supply shortages and weather conditions, and provide quality control for employees. (This is apart from the usual business support, getup, co-operative advertising, and the like). 3. Training for employees, so that an unskilled person may acquire the capability to competently perform all steps (except those restricted by specific trades certificates such as for plumbing and electrical work).

Multi-skilled labourers are thereby trained for a relatively limited range of tasks, coupled with a system of checks and monitoring. For example, the foreman of each site would prepare a daily report for faxing back to his employers. Any problems will become apparent to management. As a result, the specifically trained, multi-skilled labourers, with their foreman, follow a unified schedule or programme. Because the subcontractor equivalents are already present, delays with consequent waste of money are reduced to the unavoidable minimum. In any case, delays are reduced by means of the use of raft floors (as herein defined) which comprises a different style of construction from the concrete slab floor typically in use now.

This scheme has the result of ensuring that a given site will be finished sooner because there is no waiting for a series of sub-contractors. Tasks will be completed without errors. The order of tasks can be altered in accordance with constraints such as a shortage of concrete one day, and bad weather another day. (Within a site, most jobs must be done in a sequence, where completion of one job is usually a strict prerequisite for starting the next, but where several adjacent sites are progressing in parallel, there is more freedom to undertake jobs without the same prerequisites. The allocation of people depends in part on the duration of each aspect of the work and the relative time taken, dependent on whether it is labour- intensive or machine-intensive. For example there may be one digger/bobcat operator to every four manual workers.

The set of components described in relation to Example 1 also simplify construction in that a given site can be inspected, the soil can be tested, the mode of foundation support can be designed, the plan can be drawn, and a schedule of materials and "instructions for use" can be generated so that the workers on the site do not need a high level of training or responsibility. Inspection prior to pouring, as by a building inspector, is easy to do and the use of stirrups and ties should ensure that reinforcing stays in position during pouring. The saving in labour and in management of the soil reduce the total cost of construction, yet the physical and thermal performance of the resulting structure is enhanced.

VARIATIONS

The piles, the dense grade of EPS sheeting, and possibly the polystyrene blocks could be used with a timber floor such as one of the suspended type held on piles.

Where construction is proceeding in environments of less than about 12°C (about 50°F) the chemical reactions involved in the curing of concrete are slowed. If necessary, the concrete slab can be heated temporarily during a curing process, This may be done by passing high currents (such as from an arc welding transformer) through temporary electrical connections to metal reinforcing materials, so that ohmic heating takes place. Otherwise, buried pipes carrying hot water can be used, or warm water can be sprayed on the block during curing. Preferably the slab is covered above with a thermally insulating layer during the curing period, so that heat within the slab becomes evenly distributed and the power used is conserved. The insulating layer might be, for example, a thermal barrier 107 that is intended for use on the next site.

COMMERCIAL BENEFITS or ADVANTAGES

The raft floor as herein described is a convenient process for creating a monolithic slab-on-grade foundation. The device and process are suitable for use in cold climates.

The invention cheaply provides a thermally insulated raft floor or "slab-on-grade" foundation made resistant to frost heave by (a) thermal insulation, (b) use of piles optionally provided with feet, and (c) some "give" built into the deformable thermal insulation (the sheets of geotechnical grade EPS or "Polyrock"), as well as the intrinsic strength of the internally reinforced slab.

This type of floor is suitable for use with relatively mobile substrates, such as expandable clays (bentonites and the like), frost heave, poorly compacted sites, and sites including old fill. The cost involved in remedying such sites is avoided.

The management scheme of the invention provides further cost savings in terms of minimising materials and labour required, over the cost savings inherent in use of a raft floor. The invention replaces a variety of uncoordinated contracting services that are required on a site with a much reduced number, so that better integration of workers with the job, better interlacing of one type of job with another, and better optimised use of materials is provided. Given that 5000 homes a day are completed in the USA, the savings in the cost of housing can be considerable. The invention provides better quality control over the provision of foundations (whether a concrete slab (raft) floor or a timber floor, by prescribing the components and procedures to be used. Also, load-bearing concrete pads under piles are procured, so that work at the site does not need to be held up while curing takes place.

Where multiple sites are being constructed as part of a large development, the daily allocation of tasks can be juggled in order to avoid consequences of forecasted or actual bad weather, or shortages of supplies. The process described herein is not susceptible to bad weather, unlike equivalents where polystyrene pods are replaced by cardboard boxes for example, or where trenches dug into the ground must remain water-free and must hold their shape. The flooring system of the present invention can include a facility to insert metal lifting irons into the floor design to enable the concrete floors for the trailer park homes to be manufactured and lifted into position, removing the requirement for on- site construction. This facility will benefit the tight cost and time constraints on producing low budget homes. For example, pre-cast concrete flooring slabs or bases or foundations can be manufactured off-site and then move into place according to any such need.

The manufacturing of and use of an on-site prefabrication pad for the flooring can help reduce or remove the requirement for trucking costs and limitations relating to access of vehicles loaded with pre-cast flooring. For example, the present invention and system described above can allow an existing trailer home to be lifted by mobile crane and the flooring to be positioned upon the ground and trailer home to be replaced back into position within 1 day. This is not possible with current US building techniques, and for the first time the quality, warmth and stability of the mobile home will be improved. This can result in an improved lifestyle, health and cost of the trailer home owner.

In various embodiments of the present invention, the flooring system has the facility to install services ducts electrical, plumbing etc, at the time of manufacture. This allows the sub-trades to return and disconnect and re-connect the services at whatever time, without the time constraints of traditional flooring systems having to have all sub trades on-site concurrently.

Due to the component nature or system of assembly, the flooring system can allow the floor slab and manufactured home to be re-located at a later date if required. The pods can have a protective sealant or coating applied to the outer layer of the Waffle Pod; this sealant is fire-retardant, bug-retardant and fungus retardant.

The protective sealing on the pod can also protect the edges of the pod against damage enabling the installer to walk and work over the Waffle Pod without the edges chipping and maintaining the structural integrity of the pod. The pod can also be manufactured of an environmentally friendly material if necessary.

The plastic chairs are usually positioned under the steel sheet mesh or reinforcing bars or rods. These chairs hold the mesh or reinforcing in the desired position, with the correct spacing between the pod and the top layer of the concrete (when poured) being substantially maintained.

The plastic chairs can also be specially designed with a bevelled or rounded edge on the bottom of the chair (the surface contacting the pod), to facilitate the chair rolling into place easily and/or without damaging an EPS pod.

The top of the chair can also have plastic tongues which extend and which allow the chair to be attached to the steel mesh or reinforcing at the desired positions, with the mesh lying flat on the pods, prior to the concrete being poured. This allows installers/contractors to walk safely and easily over the flooring without being obstructed by the steel mesh, improving safety and reducing damage to the pods.

Once the concrete pouring has commenced, the mesh can be lifted with a special hook, automatically rolling or helping to position the chairs into the desired position or location, at the required height with minimal physical effort.

This feature can help to reduce the time required and the physical demand in tying the mesh or reinforcing materials in place. The flooring system can also dramatically reduce on-site injury, failure rates, insurance requirements and costs and labour required compared to a traditional concrete flooring systems. The flooring system can also use spacers with a variety of design and components not limited to wire but including plastic and plastic hybrids and mixes produced by injection molding or similar systems. The spacers can be hung on the top of the pods as necessary.

The flooring system can also incorporate steel mesh sheets of, for example, a size of 20 ft x 7 ft steel (or other reinforcing material) mesh.

Plastic sheets (for example) can form the DPC membrane and can be laid underneath the pods over substantially the building foot print. Overlapping joints are taped along their full length to produce a full moisture egress barrier over the whole building footprint. The DPC membrane can also be constructed or laid so that it runs up the formwork/boxing faces around the footprint where the foundation is to be laid to prevent any moisture entering the floor. This will produce a final product resistant to rising damp. This is not a component used in the traditional US flooring systems. The resistance to rising damp is significant because homes with this problem and the resultant fungus formed in the house results in the building being deemed uninhabitable and condemned.

Finally, it will be understood that the scope of this invention as described and/or illustrated herein is not limited to the specified embodiments. Those of skill will appreciate that various modifications, additions, known equivalents, and substitutions are possible without departing from the scope and spirit of the invention as set forth.

Aspects of the present invention have been described by way of example only and it should be appreciated that modifications and additions may be made thereto without departing from the scope thereof as defined in the appended claims.

Claims

THE CLAIMS DEFINING THE INVENTION ARE:

1. A floor for a building or base of a building, which includes a substantially monolithic foundation which rests upon a layer of thermal insulation characterised in that, the thermal insulation layer is configured to minimise heat exchange between the foundation in order to conserve heat within the building and any underlying permafrost remains substantially un-weakened.

2. A floor as claimed in claim 1 , wherein the thermal insulation includes a creep- resistant, substantially non-biodegradable material having a controlled amount of resilience so that deformation of the ground beneath the foundation may be absorbed by deformation of the thermal insulation layer.

3. A floor as claimed in claim 1 or claim 2, wherein the thermal insulation is a high-density foam of at least 18kg.m^"3.

4. A floor as claimed in claim 3, wherein the high-density foam is substantially 38 mm or more in the longitudinal, or thickness, dimension.

5. A floor as claimed claim 3 or claim 4, wherein the high-density foam is an expanded polystyrene.

6. A floor as claimed in any one of the preceding claims, wherein the foundation is formed as a raft-or beam-type construction.

7. A floor as claimed in any one of the preceding claims, wherein a water impermeable membrane separates the foundation and thermal insulation layer.

8. A floor as claimed in any one of the preceding claims, wherein the thermal insulation layer is coated with a protective coating.

9. A floor as claimed in claim 8, wherein the protective coating is a fire-retardant, bug-retardant or fungus-retardant.

10. A method of forming a floor for a building or base of a building comprising the steps of: iii. distributing a thermally insulating layer upon at least the area to be occupied by a substantially monolithic foundation, and iv. placing or forming the substantially monolithic foundation upon the thermally insulating layer.

11. A method as claimed in claim 10, wherein prior to step (i) the area upon which the thermally insulating layer is to be distributed is prepared to provide a substantially flat and stable base.

12. A method as claimed in claim 10 or claim 11 , wherein crushed rock is distributed over the area prior to distribution of the thermally insulating layer.

13. A method as claimed in any one of claims 10 to 12, wherein a water impermeable membrane is placed over the thermally insulating layer, separating the foundation from the insulating layer.

14. A method as claimed in any one of claims 10 to 13, wherein piles are inserted into the area with their tops substantially flush with the plane of the underneath of the foundation.

15. A method as claimed in claim 13 or claim 14, wherein when the foundation is formed by pouring a curable material upon the water impermeable layer, prior to pouring the curable material a matrix or system of channel forming structures are located upon the water impermeable layer so as to form a series of channels, after pouring, which become internal beams once the material has cured.

16. A method as claimed in claim 15, wherein the matrix or system of channels created is formed by the arrangement of high-density foam.

17. A method as claimed in claim 16, wherein the high-density foam is an expanded polystyrene foam.

18. A method as claimed in any one of claims 10 to 17, wherein reinforcing mesh or rods are used within the foundation to enhance the strength characteristics of the foundation.

19. A method as claimed in any one of claims 15 to 18, wherein spacing means are used to ensure the channel forming structures maintain their arranged location, and where mesh is used, supporting means are used to hold the mesh in place, within the channels formed.

20. A method as claimed in claim 19, wherein the rods lie centrally within the channels and are located at least 50mm from a surface of the foundation.

21. A method as claimed in any one of claims 15 to 18, wherein the channels are intersected by spacers, or stirrups, and engage with the reinforcing mesh and/or rods held in place by the supporting means.

22. A method as claimed in any one of claims 8 to 19, wherein the thermal insulation layer is coated with a protective coating.

23. A method as claimed in claim 22, wherein the protective coating is fire- retardant, bug-retardant or fungus-retardant.

24. A method as claimed in claim 19, wherein the supporting means are plastic chairs which have beveled edges.

25. A method as claimed in claim 19 or 24, wherein the plastic chairs have one or more plastic tongues extending away from the chair which are adapted to engage with the mesh or rods.

26. A method of co-ordinating a construction process characterised by the steps of;

(i) identifying at least one local franchisor and at least one on-site franchisee, and

(ii) providing the on-site franchisee with information pertaining to a plurality of specific tasks to be formed according to a unified schedule for the constructions process, and iii) co-ordinating the performance of the plurality of specified tasks in parallel by a number of sub-contractors of the on-site franchisee, and iv) supplying corrective information to the local franchisor from said on-site franchisee.

27. A method of co-ordinating a construction process as claimed in claim 26, further characterised by the additional preliminary step of identifying at least one regional franchisor.

28. A method of co-ordinating a construction process as claimed in claim 26 or claim 27, further characterised by the additional preliminary step of identifying at least one national franchisor.

29. A method of co-ordinating a construction process as claimed in any one of claims 26 to 28, wherein said at least one local franchisor supplies training information to said at least one on-site franchisee with respect to the specific tasks of the construction process to be completed.

30. A method of co-ordinating a construction process as claimed in any one of claims 26 to 29, wherein said at least one on-site franchisee pays royalty fees to said at least one local franchisor.

31. A method of co-ordinating a construction process as claimed in any one of claims 26 to 30, wherein an on-site franchisee co-ordinates the performance of specific tasks by a number of sub-contractors over a plurality of construction-sites.

32. A method of co-ordinating a construction process as claimed in any one of claims 26 to 31, wherein the performance of said specified tasks by an on-site franchisee's sub-contractors is linked to a system of checks and monitoring.

33. A method of co-ordinating a construction process substantially as hereinbefore described and as illustrated with reference to any one of the accompanying drawings.

34. A floor substantially as hereinbefore described and as illustrated with reference to any one of the accompanying drawings.

35. A method substantially as hereinbefore described and as illustrated with reference to any one of the accompanying drawings.

36. A floor constructed according to any one of claims 8 to 19.