WO2021043778A1

WO2021043778A1 - A building raft foundation system

Info

Publication number: WO2021043778A1
Application number: PCT/EP2020/074373
Authority: WO
Inventors: Paul GLAVIN
Original assignee: Glavloc Build Systems Limited
Priority date: 2019-09-02
Filing date: 2020-09-01
Publication date: 2021-03-11

Abstract

A raft foundation apparatus has modules (2 - 8) each having a body of insulation material, the body having a dovetail socket (21) which allows it to be connected to another module by a bridging lock (10) with opposed dovetails. A raft foundation of desired configuration can be assembled on site by inter-connecting the modules according to the architectural design. The modules may, in various examples, have raised platforms (22, 31, 41, 61, 71, 81) which provide greater surface area for contact with poured concrete and hence addition structural strength.

Description

“A Building Raft Foundation System”

Introduction

The invention relates to construction of a building foundation, especially a raft foundation.

A raft foundation is a type of foundation which spreads the load over a large portion or all of the full building area. It is particularly beneficial where the underlying ground is relatively soft.

WO2014196878A1 describes a method and apparatus for forming a formwork for a ribbed or waffle concrete slab.

EP1970504A1 describes a foundation for an electrical transformer station, wherein the foundation is assembled from a plurality of cuboid modules fixed to each other and forming a solid and static foundation.

W00214608A1 describes a sub-base layer for use in construction, with a plurality of connected substantially cuboid modules each having spaced-apart, substantially parallel top and bottom walls joined by a peripheral sidewall defining an enclosed volume.

W02004106641A1 describes an insulating shuttering element, in particular for producing a building floor plate shuttering and to a method for producing said shuttering.

US2009123230 describes a process for the production of a frame for a construction adapted to float.

AU727681B describes a formwork module for use in the construction of a waffle slab foundation.

Objectives of the invention are to provide for construction of a raft foundation in an improved manner which requires less labour and provides excellent insulation. Other objectives are to achieve some or more of: improved dimensional accuracy, less time on site for construction of the raft foundation, reduction in the extent of concrete required, better predictability of structural properties, better thermal insulation between building ground-level floor and the ground,

Summary of the Invention In various aspects we describe a raft foundation apparatus as set out in appended claims 1 to 18, a raft foundation constructed using the apparatus as set out in claim 19, and a method of constructing a raft foundation as set out in claims 20 to 27.

We describe a raft foundation apparatus comprising a plurality of modules each having a body of at least some insulation material and locking means to engage the modules together in an arrangement to form a raft foundation. The engagement is lateral, in a generally horizontal plane in use.

Preferably, the locking means comprise male and female lock components. Optionally, the male lock components include a dovetail, and the female lock portion comprises a dovetail socket in the module body.

Preferably, the locking means include discrete locks which engage and bridge across modules. Preferably, at least some of the discrete locks comprises opposed dovetails.

Preferably, at least some of the module bodies are of foam material.

Preferably, at least some module bodies each has one or more raised platform. Preferably, at least some of the module bodies have a raised rim ridge.

Preferably, at least some of the modules and/or locks comprise an adjustment member, the vertical position of which is adjustable relative to the remainder of the component. Optionally, the adjustment member includes a bolt. Preferably, the adjustment member is of foam material.

Preferably, at least some of the adjustment members comprise a top slot configured to act as a seat for a rebar. Rebar seats may be provided elsewhere in the module, for example as a groove in a raised platform of a module. Preferably, at least some modules have a through hole. Preferably, the apparatus further comprises plugs for insertion into said through holes. Preferably, said plugs have a different density than that of the module bodies.

We also describe a raft foundation whenever constructed using an apparatus of any example described herein.

We also describe a method of constructing a raft foundation comprising the steps of engaging a plurality of the modules to form a base on the ground and pouring concrete over the modules up to a level of rims of the modules and/or formwork around the modules.

Preferably, at least some of the modules comprise an adjustment member, the vertical position of which is adjustable relative to the remainder of the module, and the method includes adjusting level of at least one module by adjustment of level of the adjustment member relative to the module body.

Preferably, at least some modules have vertical through holes, and the method includes pouring concrete into said through holes and/or inserting insulation blocks into said holes.

Preferably, the method comprises providing lateral formwork with struts engaging in recesses in laterally-facing surfaces of edge modules.

Preferably, the method comprises the steps of rotating the adjustment members to align rebar seats on top surfaces of said members and placing rebars on the modules in said seats before pouring the concrete.

Preferably, at least some modules have raised platforms and rebars are placed on the modules in spaces between the platforms before pouring the concrete.

Detailed Description of the Invention

The invention will be more clearly understood from the following description of some embodiments thereof, given by way of example only with reference to the accompanying drawings, in which: Fig. 1 is a plan view of a raft foundation ready for pouring of floor concrete, and Fig. 2 is a perspective view;

Figs. 3 to 9 are perspective views of components of a system used for constructing the raft foundations, as follows:

Fig. 3, a dovetail lock,

Fig. 4, a four-unit module,

Fig. 5, a two-unit edge module,

Fig. 6, a single-unit internal module,

Fig. 7, a single-unit edge module,

Fig. 8, a three-unit module with an internal comer, and Fig. 9, a single-unit corner module;

Fig. 10 shows a module for the edge of a foundation; and

Fig. 11 shows the assembly of a module at the edge of a foundation, with particular detail of how shuttering is done and external concrete ties in with the edge modules to integrate the surrounding concrete with the foundation.

Referring to Figs. 1 to 3 a raft foundation 1 comprises a number of insulating foam modules 1, 2, 3, 4, 6, 7 and 8 arranged to interconnect together in the horizontal plane by separate dovetail locks 10. Concrete Is poured on site over the assembled modules to a depth which varies, typically between 100mm and 200mm depending on the profile of the top surfaces of the modules.

Each lock 10 has a body of insulating foam material, in this case EPS 300™, moulded into a pair of opposed dovetails 13, with a V-shaped surface on each side defining the dovetails. Each module is also of EPS material, in one example EPS 200™, which is foundation-grade polystyrene

There is an adjustment bolt 15 of harder foam material engaged vertically in the body of the lock 10. The bolt 15 has a top slot 11. The bolt 15 is for adjustment of position above ground so that the foundation modules are level on the site. As described in more detail below, the components 15 are used throughout the foundation, most modules having at least one bolt 15. As shown in Fig. 1 a temporary formwork 50 may be provided, with an elongate block 51 and stmts 52 in an ICF (insulated concrete formwork) -like arrangement. The stmts 52 engage in indents of the module rims. This formwork allows constmction of a surrounding border such as a secondary ring beam or a stone or concrete plinth, of for example 40 mm width. Concrete is poured into the space between the block 51 and the modules, around the stmts 52.

Referring to Fig. 4 the module 2 is referred to as a four-unit module (Fig. 4) having a foam body 20 forming on each of its four sides two dovetail sockets 21. In this specification the number of squares defined by a dovetail socket defines the number of “units”, l x l being one unit and 2 x 2 (as in module 2) being four units.

The module 2 has a main body and four integral raised platforms 22 to provide additional bulk of insulation and also provide more surface area (top and side surfaces of the platform) for engaging poured concrete. Moreover, the pattern of platforms 22 provides spaces between each other for convenient placement of reinforcing bars (“rebars”) before pouring of the concrete. The slots 11 at the tops of the adjustment bolts 15 also can be aligned to act as seats for rebars, as shown in Fig. 1.

The module 3, shown in Fig. 5, has a body 30 defining four dovetail sockets 21, two narrow raised platforms 31, and four sets of four adjustment bolts 15. This module has a raised rim 32 along one edge, to define a foundation edge. The top surface of the rim 32 is the upper level for concrete, in use.

The module 4 is a single-unit module, shown in Fig. 6, with four dovetail sockets 21 and a single raised platform 41.

The module 6 is also single unit, as shown in Fig. 7, with three dovetail sockets 21, a single narrow platform 61, and two series of four adjustment bolts 15. There is an edge rim 62.

The module 7 is a three-unit module, shown in Fig. 8, with six dovetail sockets 21 formed in a foam body 70. There are narrow platforms 71 and 72, and an L-shaped platform 73 to provide additional strength at a corner diagonally opposed to a corner indent 75 with a rim 76. There are four series of four adjustment bolts 15, and two additional single bolts. The module 8 is a single-unit comer module, shown in Fig. 9. It has a foam body 80 with two dovetail sockets 21, two sets of four adjustment bolts 15, a single small platform 81, and a rim 82 forming an external comer.

Some of the modules have vertical through holes:

35, in the module 3;

65, in the module 6;

77, 78, and 79 in the module 7; and 85, in the module 8.

These allow the architect to choose to insert a foam block into the opening. The choice of insert block is made on the basis of the desired extent additional insulation, and possibly additional strength compared to the remainder of the module if the infill block is of a high-density foam. This allows excellent versatility. In some circumstances, an opening may be left open, with concrete free to pour through. This is however in general not preferred as it causes a degree of cold-bridging to the ground underneath.

Referring to Figs. 10(a), (b) and (c), in another embodiment a module 100 is shown. The module 100 has a main body 101, a raised rim 102 along two edges and a raised platform 103. As in previous embodiments, the raised platform 103 provides additional bulk of insulation and also provides more surface area for engaging poured concrete. A socket 104 and a bolt 105 are configured to engage with each other to provide height adjustment. In use, the bolt 105 is rotated in the socket 104 in such a way as to provide customisable height to the module 100. This allows achievement of a level foundation without need for much levelling of the ground underneath.

The raised rims 102 have a non-planar exterior surface with recesses which widen inwardly from the outer surface, and in this case in the form of dovetail sockets 106. There are also “internal” dovetail sockets 107 to provide a locking mechanism with other modules, as per the previous embodiments.

Referring to Fig. 11 the module 100 is shown at the edge of a foundation, alongside which a plinth suitable for use as a base for an exterior leaf of a wall to reside on is formed. In this example, formwork 110 and 115 is assembled alongside the module 100 via spacers 111 and 116, also shown in Fig. 10. The formwork 110 and 115 are joined at right angles for concrete shuttering. The spacers abut against the exterior surfaces of the modules to provide a volume of space between the modules 100 and the planar surfaces 110 and 115. Concrete 120 is then poured into the space and allowed to cure to form a suitable frame around the raft foundation to bear an external wall leaf. In this example, the external dovetails 106 provide excellent locking of the concrete 120 to the modules, achieving excellent structural integrity once the formwork is removed.

It will be appreciated that the invention provides for excellent levels of thermal insulation in a raft foundation, as well as very quick and convenient construction on site. Once the modules are interconnected according to the desired pattern they may be easily adjusted vertically by rotation of the adjustment bolts 15. Because of the extent of factory off-site manufacturing, there is excellent accuracy, to the mm-level of tolerance. Because of the per-module height adjustment potential, there is less requirement for the underlying ground to be perfectly level. Also, there is excellent thermal insulation with avoidance of cold-bridging between the concrete deck and the underlying ground. The volume of concrete can be chosen at the design stage by choice of module rim heights. This is typically in the range of 100mm to 200mm. This allows the volume of concrete to be only in the range of about 15% to 30% of the overall raft foundation volume, thereby achieving a requirement for use of less concrete and consequent environmental advantages.

Also, there is excellent versatility in choice of the extent of steel reinforcing, by choice of the distribution and number of re-bars between the module platforms.

It will be appreciated that the invention provides a raft foundation apparatus with modules (2 - 8) each having a body of insulation material, the body having one or more dovetail socket (21) which advantageously allows it to be connected to another module by a bridging lock (10) with opposed dovetails. A raft foundation of any desired configuration can be assembled on site by inter connecting the modules according to the architectural design. The modules may, in various examples, have raised platforms (22, 31, 41, 61, 71, 81) of any suitable shape which provide greater surface area for contact with poured concrete and hence addition structural strength.

The invention is not limited to the embodiments described but may be varied in construction and detail. For example, the modules may have any suitable combination of sockets, rims, apertures, and platforms to suit the building design. It is envisaged that the modules may have male and female locks which are integral with the module bodies, rather than having discrete locks. Whether or not there are discrete locks, the manner of interconnection may have male and female configurations other than dovetails and dovetail sockets. Any interlock arrangement which provides engaging surfaces facing at least partially in the direction between the modules may be used. It is preferable that the interlock be by way of one module moving from out-of-plane to in plane, and/or a discrete lock moving from out-of-plane to in-plane with respect to the modules.

Rebar seats may be provided elsewhere in the module, for example as a groove in a raised platform of a module. Alternatively, spaces between raised platforms may act as rebar seats in other arrangements. Also, the foam which is used may have a higher density than EPS 200 or EPS 300, and there may be different densities for different components. For example, the inserts 15 and/or any inserts in the apertures 35, 65, 77, 78, and 85 may be of a different density than the main body of the module.

Claims

1. A raft foundation apparatus comprising a plurality of modules (1-8) each having a body (20) of insulation material and locking means (10, 21) to engage the modules together in an arrangement to form a raft foundation (1).

2. A raft foundation apparatus as claimed in claim 1, wherein the locking means comprise male and female lock components (21, 13).

3. A raft foundation apparatus as claimed in claim 2, wherein the male lock components (10) include a dovetail (13), and the female lock portion comprises a dovetail socket (21) in the module body.

4. A raft foundation apparatus as claimed in any preceding claim, wherein the locking means include discrete locks (10) which engage and bridge across modules.

5. A raft foundation apparatus as claimed in claim 4, wherein at least some of the discrete locks comprises opposed dovetails (13).

6. A raft foundation apparatus as claimed in any preceding claim, wherein at least some of the module bodies (20, 40, 60) are of foam material.

7. A raft foundation apparatus as claimed in any preceding claim, wherein at least some module bodies each has one or more raised platform (22).

8. A raft foundation apparatus as claimed in any preceding claim, wherein at least some of the module bodies have a raised rim ridge (32).

9. A raft foundation apparatus as claimed in any preceding claim, wherein at least some of the modules and/or locks comprise an adjustment member (15), the vertical position of which is adjustable relative to the remainder of the component.

10. A raft foundation apparatus as claimed in claim 9, wherein the adjustment member is a bolt (15, 105)) for engagement with a socket (104).

11. A raft foundation apparatus as claimed in claims 9 or 10, wherein the adjustment member (105, 105) is of foam material.

12. A raft foundation apparatus as claimed in any of claims 9 to 11, wherein at least some of the adjustment members comprise a top slot (11) configured to act as a seat for a rebar.

13. A raft foundation apparatus as claimed in any preceding claim, wherein at least some modules have a through hole (35, 65).

14. A raft foundation apparatus as claimed in claim 13, further comprising plugs for selective insertion into said through holes.

15. A raft foundation apparatus as claimed in claim 14, wherein said plugs have a different density than that of the module bodies.

16. A raft foundation apparatus as claimed in any preceding claim, wherein at least one module has a non-planar laterally-facing external surface (106) on a rim.

17. A raft foundation apparatus as claimed in claim 16, wherein the non-planar external surface comprises at least some recesses (106).

18. A raft foundation apparatus as claimed in claim 17, wherein the recesses widen inwardly to form dovetails (106).

19. A raft foundation whenever constructed using an apparatus of any preceding claim.

20. A method of constructing a raft foundation comprising the steps of engaging a plurality of modules of an apparatus of any preceding claim to form a base on the ground and pouring concrete over the modules up to a level of rims of the modules and/in a space between formwork around the modules and edge module laterally facing surfaces.

21. A method as claimed in claim 20, wherein at least some of the modules comprise an adjustment member (15, 105), the vertical position of which is adjustable relative to the remainder of the module, and the method includes adjusting level of at least one module by adjustment of level of the adjustment member relative to the module body.

22. A method as claimed in claims 20 or 21, wherein at least some modules have vertical through holes (35, 65), and the method includes pouring concrete into said through holes and/or inserting insulation blocks into said holes.

23. A method as claimed in any of claims 20 to 22, comprising providing lateral formwork (50) with struts engaging in recesses in laterally facing surfaces of edge modules.

24. A method of any of claims 21 to 23, comprising the steps of rotating the adjustment members (15) to align rebar seats on top surfaces of said members, and placing rebars on the modules in said seats before pouring the concrete.

25. A method of any of claims 20 to 24, wherein at least some modules have raised platforms (22) and rebars are placed on the modules in spaces between the platforms before pouring the concrete.

26. A method of any of claims 20 to 25, wherein a laterally-facing external surface of at least one module is non-planar (106) for enhanced locking with concrete (120), and concrete is poured into a space between formwork and said laterally-facing external surface.

27. A method as claimed in claim 26, wherein the concrete flows into dovetail recesses (106) in said external surfaces.