EP0265262B1

EP0265262B1 - Improvements relating to building foundation form work

Info

Publication number: EP0265262B1
Application number: EP87309345A
Authority: EP
Inventors: Nicola Leonardis
Original assignee: Individual
Current assignee: Individual
Priority date: 1986-10-23
Filing date: 1987-10-22
Publication date: 1991-10-09
Also published as: DE3773609D1; EP0265262A1; NZ222206A; ATE68222T1; CA1294144C; GR3003552T3

Abstract

A building foundation form work arrangment in which a plurality of boxes (1) are located on a supporting level surface and are kept apart to leave channels (4) between the boxes (1), and spacers (22) engaging respective sides of each of the corners of the boxes (1) so as to hold these in position against substantial lateral dislodgement forces when concrete is poured into the channels (4).

Description

The present invention relates to building foundation form work including a spacer useful in form work, and a method of constructing and using form work for building foundations.
Conventionally, for providing building foundations, trenches are cut into the ground and the concrete is poured into these trenches. The level of the concrete is sometimes above the level of the ground by constraining the flow of concrete above the level of the ground by employing ground form work.
The work involved in cutting the trenches and laying up the form work is extremely labour intensive and thus, expensive, but furthermore, it substantially constrains the style of foundation that is most appropriate for a particular application.
In other words, on many occasions, especially where soil is known to be soft or expansive over different seasons, it would be advantageous to employ an integral slab on which the building would sit, but hitherto the cost of this would be so high as to make it in many cases impractical.
The present invention seeks to reduce the cost of providing a foundation for a building, which foundation will be sufficiently strong to resist substantially expansive soils.
It has previously been known to propose lost form work and also to include rectilinear elements within a foundation form work so that concrete is then poured over these so that they are subsequently incorporated into the foundation. However, the problem has been the cost of providing such elements, which have been previously proposed as being constructed of polystyrene foam.
More recently a cardboard box has been proposed, which has considerably reduced the potential cost of this part of the foundation form work, but there has been a major problem in respect of holding such cardboard boxes in relation to one another, in such a way that the boxes will retain with sufficient integrity, their relative position especially during the pouring thereover of concrete, and secondly such that any means that might be used to hold the boxes in a relative position do not of themselves unreasonably reduce the integrity of any foundation that is subsequently formed. The problem particularly arises due to the inherent constructional characteristics of a cardboard box and the extremely high forces that result when concrete is being poured in a channel on one side of a box where there is no equivalent material on the opposite side of the box. Also, such side pressure will be aggravated by the vibration, conventionally used by concrete pourers, to ensure removal of aids within the foundation being poured.
GB-A- 107699 discloses a spacer of cruciform shape with arms extending from a central supporting boss for spacing apart hollow concrete blocks that are to be incorporated in an overhead floor. The ends of each of the arms of the spacer locate a corner of a block so that each spacer is able to locate four hollow concrete blocks. The spacer is intended to be fastened to shuttering supporting the floor construction through holes in the arms of the spacer. The spacer has extending down to the shuttering a boss so as to provide a support for suspending items such as light fittings from below the floor.
The present invention resides in a spacer for a building foundation wherein a plurality of boxes are located in spaced apart relationship to define channels therebetween, the spacer including diagonal frame members which define a cruciform shape in plan with re-entrant shaped pads at the tips thereof, a first of the re-entrant shaped pads being adapted to engage against adjacent sides at one corner of a first box, whilst at the same time a second of the re-entrant shaped pads is adapted to engage against adjacent sides at one corner of a second box adjacent the first box, characterised in that the spacer is square or rectangular shaped in plan such that the said first and second re-entrant pads lie at corners of the spacer, and the square or rectangular shape of the spacer is formed from at least one additional frame member extending between the said first and second re-entrant shaped pads and providing lateral support therefor, and in that the spacer has an upwardly extending medially positioned part having an upwardly open U-shape slot therein adapted to support and hold a reinforcing rod, and furthermore in that the diagonal frame members and the or each additional frame member each have a lowermost surface which is spaced at such a height above a lowermost edge of the re-entrant pads that concrete can flow freely beneath the said frame members.
Thereby cardboard boxes of the type being discussed can be sufficiently held against lateral pressures when such means engage against respective sides in the vicinity of the corner of the box.
Preferably, the spacer engages against both sides adjoining a corner of each of four adjacent boxes with the corners at a common location.
This accordingly provides substantive resistance to such distortional pressures as previously discussed.
One particular problem that may be associated with locating spacers in the manner described in accordance with the present invention, is that these spacers, in some cases, may aggravate a weakness in the structural strength of the foundation thus poured.
If, for instance, a concrete block is located midway between respective corners of the same box and this is supported on the ground within the channel, and furthermore this block has a width which defines the channel width and is used then as a block to support reinforcing rods, then it is found that this may result in a localised weakening of the concrete where the foundation concrete meets the concrete block material. If this does fracture, while not structurally necessarily dangerous, there may result an access of water which, through capillary action, can reach the steel reinforcing rod or rods.
This can be avoided by ensuring that concrete for the foundation extends to form an integral portion of concrete below the main body of any spacer. This is achieved by providing that each spacer, while having a substantially large outermost engaging surface to bear against the side of a box, nonetheless has frame members which have a lowermost edge which is substantially above the lowermost edge of such outermost engaging surface and, as such, is above any supporting ground level surface.
In this way, a relatively large volume of concrete is allowed to flow and set below such frame members thereby maintaining as much as possible the structural integrity of the concrete.
One further problem that may be experienced, is the fact that in some cases the foundation will be required to be somewhat deeper than might be considered standard, and it has been found uneconomic to provide boxes which has substantially different heights as a range.
It has been proposed that conventional shaped boxes be located one upon the other to provide thereby a double thickness, but the problem has been the same as hitherto experienced, that is, how is the sideways pressure resisted when the foundation is being poured.
In respect of the present invention, it is proposed that there be securing means provided for locating respective corners of the boxes for the box location purposes previously described, wherein one of the boxes is located above the second box, and so defining together, coplanar sides effecting a channel between such sides and other such boxes. Such securing means preferably engage against both sides adjoining a corner of a first box and at the same time against both sides adjoining a corner of a second box where the first box is located above but resting on the second box.
The invention is described further hereinafter, by way of example only, with reference to accompanying drawings, in which:-

Fig.1 is a plan view of one embodiment of a typical building foundation form work arrangement in accordance with the present invention;
Fig.2 illustrates a partly cut-away and partially opened cardboard box in accordance with the embodiments of the present invention;
Fig. 3 illustrates one embodiment of a spacer as incorporated within channels at a crossing over location and where four corners of respective adjacent boxes meet at a common location, in accordance with the present invention;
Fig.4 illustrates another embodiment of a spacer adapted to be used where two corners meet and there is a T-junction of the channels as shown in Fig.1, in accordance with the present invention;
Fig.5 illustrates one embodiment of a spacer, used with one corner of a box, in accordance with the present invention;
Fig.6 illustrates one embodiment of an arrangement for spacing the box elements apart from corner locations;
Fig.7 is a perspective view showing the application of spacers as illustrated in Figs. 4, 5 and 6;
Fig.8 is a plan view in some greater detail of a spacer as in Fig.3 being used in conjunction with reinforcing rods and engaging against the adjacent sides of the corners of four boxes;
Fig.9 is a perspective drawing illustrating the manner in which the form work is used and illustrating the technique for pouring concrete in channels formed between the respective boxes and over the top of these;
Fig.10 illustrates in perspective detail one embodiment of spacers for holding two boxes in adjoining relationship one above the other in combination with a general spacer as in Fig.3;
Fig.11 is a more general view of the apparatus of Fig.10; and
Fig.12 is a perspective view of a spacer used when the boxes are located one above the other as illustrated in Figs.10 and 11.

Referring to the drawings, and in particular to Fig.1, there is shown a plurality of boxes which are supported on level ground and which are surrounded by perimeter form work 2, 3, the boxes 1 and the perimeter form work 2 all being held in spaced apart relationship so as to leave a plurality of channels 4 between the respective sides 5 of the boxes 1 and the perimeter form work 2 and 3.
Each of the boxes 1 in particular as shown in Fig.2 are comprised of cardboard having an external surface coated with an appropriate water repellant material such as a wax, but which otherwise comprise cardboard conventionally reinforced with a corrugated layer within each planar surface, the box 1 including a top 6, a bottom 7 and sides 8, 9, 10 and 11, the sides each defining a flat side and each being arranged to provide in plan, a square shape together with the flat top 6 and the flat bottom 7. Side 10 has been opened out to show a top flap 12, a bottom flap 13 and side flaps 14 and 15. These are folded over so as to lie one against the other and to provide mutual reinforcing therefor for the side of the box thus formed.
In a similar manner, side 11 comprises two flaps one folded over the other, shown particularly at 16 and 17, and likewise side 8 has two flaps 18 and 19.
Internally, the box 1 is reinforced by typical egg-crate type reinforcement which comprises a plurality of transverse members 20 which interlock with crossing members 21 each of the members 20 and 21 being comprised of corrugated strengthened cardboard and each defining a vertical plane extending to immediately below the top 6 and above the bottom 7 so as to provide vertical support for the top 6. In a similar manner, the ends butt against the respective sides and also provide at least some reinforcing strengthening of these sides.
Such reinforcement and strengthening is provided to such an extent that a foundation laying worker can walk on top of the box, and also it is such that the boxes can resist lateral deformation under the relevant stresses involved.
The boxes 1 are located so as to leave channels 4 between the confronting sides thereof, and in accordance with this embodiment there is provided a spacer 22 which in plan view is of square shape but which provides at four symmetrically located corner positions a re-entrant shape shown typically at 23. Each corner contains pads 24a,25a having outermost engaging faces 24 and 25 which will engage against adjacent sides meeting at a corner of a box 1. It is a requisite that there be a relatively significant bearing surface which can engage against an effective area of the side of a cardboard box, and furthermore that this will engage both against an edge at the corner of a box and across the bottom of the box where there is also the bottom 7 which also provides additional reinforcement for the box.
Accordingly, engaging surfaces 24 and 25 are of substantial surface area (each being preferably 55 mms wide and 55 mms high) and are adapted with respect to the remaining parts of the spacer 22 to sit with lowermost edges 26 on the same level surface that is supporting the box 1. There are, in respect of the spacer 22, four such corner positions as shown further at 27, 28 and 29, the pads at each of these being supported in the relative position which provides a re-entrant shape defining the position of four corners of respective adjacent boxes by frame elements 30 and 31. The respective frame elements 30 at the sides of the square are each raised significantly above the ground level and indeed have an upper surface which lies flush with the upper surface 32 of the engaging surface typically at 24.
Midway and extending above such surface level at 32 is an open U-shape 33 which is adapted to receive and support reinforcing rods.
These may be crossing rods and the height of the upwardly open U-shape slots both at 33 and in a centre raised portion at 34, are of sufficient height so as to support first rods in one direction, and then second rods in a crossing direction lying above the first rod.
Such an arrangement is best illustrated in Fig.10, in which the rods are shown at 35 and 36, although the spacer in this case does not have such high sides for its open U-shape slot. The rods fit closely in the width of the slot and therefore secure the spacers collectively tightly together. This securing effect is assisted where the rods cross over and the spacers then become tightly locked together. The diagonal frame members 31 which define a cruciform shape provide for cross bracing, and also because of their general thickness, provide substantial support for such reinforcing rods. The members 31 are raised so as to be significantly above any ground supporting level so as to allow firstly for concrete to pass fully beneath such frame members, and also to ensure an effectively continuous thickness which will effectively resist localised fracturing under stress conditions and therefore resist capillary water egress to the metallic reinforcing rods.
The spacer 37 as illustrated in Fig.4, and also illustrated in Fig.1, is similar to the spacer 22 except that it has one side at 38 adapted to engage against perimeter form work only, thereby leaving only two right-angularly re-entrant shaped pads at 39 and 40, to engage against both sides adjoining a corner of the respective boxes 1. In the same manner, the bottom- most edges, typically at 41 and 42, are adapted to sit on the same level surface that the boxes 1 are adapted to sit on, and the frame elements 43 and 44 are all located well above such ground support to allow for concrete to flow fully beneath these and of such thickness to provide adequate support for openly upward U-shape slots 45 to the side and 46 at the centre.
Fig.5 illustrates a spacer 47 which has the same fundamental elements of the previous spacer, but in this case has only one right-angularly re-entrant pad 48, the remaining outer engaging surfaces at 49 and 50 are adapted to engage against the inner sides of form work such as at 2 and 3 in Fig.1, and to also rest on the lowermost ground level surface so that frame members 50 and 51 are supported well above the ground surface.
In Fig.6 there is illustrated a spacer 52 which does not engage any corners of the boxes but includes two sides 53 and 54 each of the sides being of substantial area so as to provide substantial bearing surface against the sides of a respective box 1 but in each case, frame members 55, 56 and 57 are all located so as to be well above lowermost support level 58 and 59 so that concrete can pass fully, and be continuous below the respective frame members 55, 56 and 57 which in turn provides for reinforcing at such positions at 60, 61 and 62.
The slots 63 and 64 are generally superfluous except for reducing the total quantity of plastic necessary in respect of each of these spacers which are in each case manufactured by injection moulding from an appropriate plastics material such as polypropylene.
In the application of the invention to a foundation, it is conventional to further provide steel fabric 65 which is supported by supports 66 resting on the top 6 of a box 1. As shown in Fig.9, a worker 67 may then safely step on the fabric 65 and support concrete outlet 68 whereby concrete 69 is effectively poured into the various channel shapes 4 and across the upper most surface over the top 6 of the various box elements 1.
In Figs.11 and 12 there is a spacer 70 which acts to maintain the relative spaced relationshp of boxes 1 when located one above the other. This is achieved by having engaging faces 71 and 72 engaging against both sides typically at 73 and 74 of a box 1, and there being a spike 75 and a spike 76 located so as to pierce through the respective top and bottoms at the corner position of the respective boxes 1. These, thereby, positively locate and capture the respective boxes and hold them in a relative position one with respect to the other.
The method of using the elements described is to prepare ground as level, surround this with perimeter form work 2, 3 and then locate sequentially, a variety of spacers as appropriate and then boxes 1 so that these extend fully across the defined area. Boxes of different overall shape and area may be used if the defined area is not appropriately covered by the shapes described.
For parts of a building which are to be higher than others, these can then be provided with a higher foundation part by supporting one box upon the other and joining these in the manner described.
While the spacers have been described as being formed of plastic, these may be made from other compatible materials, such as steel sheet, which may be cut and folded into an appropriate shape.

Claims

A spacer (22) for a form work for a building foundation wherein a plurality of boxes are located in spaced apart relationship to define channels therebetween, the spacer (22) including diagonal frame members (31) which define a cruciform shape in plan with re-entrant shaped pads (24a, 25a) at the tips thereof, a first of the re-entrant shaped pads (24a, 25a) being adapted to engage against adjacent sides at one corner of a first box, whilst at the same time a second of the re-entrant shaped pads is adapted to engage against adjacent sides at one corner of a second box adjacent the first box, characterised in that the spacer (22) is square or rectangular shaped in plan such that the said first and second re-entrant pads lie at corners of the spacer (22), and the square or rectangular shape of the spacer (22) is formed from at least one additional frame member (30) extending between the said first and second re-entrant shaped pads and providing lateral support therefor, and in that the spacer has an upwardly extending medially positioned part having an upwardly open U-shape slot (34) therein adapted to support and hold a reinforcing rod (35, 36), and furthermore in that the diagonal frame members (31) and the or each additional frame member (30) each have a lowermost surface which is spaced at such a height above a lowermost edge (26) of the re-entrant pads that concrete can flow freely beneath the said frame members (30, 31).
A spacer according to claim 1, wherein the spacer (22) of rectangular shape in plan has four re-entrant shaped pads adapted to engage respectively against adjacent sides at one corner of each of four adjacent boxes.
A spacer according to claim 1 or 2, which is moulded from plastics material.
A form work for a building foundation comprising a plurality of boxes (1) located on a supporting level surface and kept apart to leave channels (4) between confronting sides thereof by spacers (22) within the channels (4) between the boxes (1), each of the spacers (22) being constructed in accordance with any preceding claim.
A form work according to claim 4, wherein each of the boxes (1) has vertical reinforcing partitions (20) therewithin.
A form work according to claim 4 or 5, in which the boxes are each formed of cardboard.
A form work according to claims 5 and 6, in which each of the boxes (1) has four sides, a top and a bottom, and the reinforcing partitions (20) comprise planar cardboard strips extending in crossing interlocking relationship and extending from the bottom to the top of the respective box (1), and from one side to the opposite side of the box (1).
A form work according to any of claims 4 to 7, wherein at least one box is located above another box and a joining spacer (71) engages against adjacent sides at a corner of a lowermost of the boxes, and against adjacent sides at the overlaying corner of a second of the boxes which is above said lowermost box.
A form work according to claim 8, wherein the joining spacer (71) includes two spikes (75, 76), a first engaging within one of the superimposed boxes (1) and a second within the other of the superimposed boxes (1) so as to hold the engaging surfaces of the spacers against the respective sides of the respective boxes.
A method of preparing form work for the pouring of a foundation for a building in which a plurality of boxes are located within a boxed area and over a substantially level area of supporting surface and from one another to leave channels (4) between the confronting sides of the boxes (1) and spacers (22) are located within the respective channels (4) such that each spacer engages against adjacent sides at a corner of a first box, and at the same time against adjacent sides at a corner of a second box adjacent the first box, characterised in that each spacer (22) is constructed in accordance with claims 1, 2 or 3, and in that reinforcement rods (35, 36) are laid in the channels (4) so as to rest in the U-shaped slots (34) of the upwardly extending parts of the spacers.
A method of preparing a form work according to claim 10, wherein each of the boxes is comprised of cardboard.