Background to the Invention The applicant is aware that presently void formers, in the form of a cardboard box, with or without a wax coating, are used in the construction of foundations of buildings. For the rest, the building industry use wooden and/or steel shuttering to form voids and or receptacles for casting a settable composition on or in to form a slab having a desired configuration.

The applicant believes that the above prior art methods have many draw backs, amongst which are included ; the single use aspect of the cardboard void formers, the cost and effort required to put up wooden and steel shuttering, and the difficulty in achieving uniform spacing of shuttering and/or void formers to define the beams of a slab. Other problems include, for example, the difficulty in forming void formers for long span constructions such as bridges and the effort and cost required to provide a framework for casting columns and pillars and/or the base portions for columns and pillars.

One typical construction method uses steel void formers configured to define a grid of channels into which a settable composition may be cast and over which further settable composition is cast to form a slab having a reduced weight, and thus using less settable composition. One problem with such a construction method is that the steel void formers need to be positioned on a steel construction to form a platform and define the channels, and once the slab has set, these must be removed, which procedure has labour implications. The problem of removing the void formers from the set slab may be mitigated by the pre-coating of the settable composition facing side of the void formers with a releasing composition, such as an oil.

Summary of the Invention Thus, according to a first aspect of the invention, there is provided a void former having a chamber defined by one or more sidewall and at least one spacer extending laterally from the chamber for spacing the chamber of the void former from adjacent objects.

Typically the spacer spaces the chambers of adjacent void formers from each other thereby to provide a series of channels for casting a settable composition into when forming a slab and/or beams for a stab.

The spacer may comprise one or more flap portion extendable outwardly from the chamber of the void former.

The dimensions of the spacer may be selected to, in use, provide a channel width of suitable dimensions for the slab being cast.

The void former may be provided with a reinforcing insert to reinforce the void former against compression.

The reinforcing insert may be an egg-crating type insert comprising a cardboard, wood, plastics or other suitable rigid material grid.

The invention extends to a spacer accessory for a void former configured to be used with a void former.

The spacer accessory may be in the form of a collar having laterally extending spacer portions provided thereon, the collar being sized and dimensioned complementarily to the void former size and dimensions.

The invention extends further to a method of spacing void formers using a spacer as set out above, the method comprising the arranging of void formers with the spacers in close proximity or in contact with an adjacent void former or object.

According to a second aspect of the invention, there is provided a removable cover for a void former having a chamber, the cover being adapted to from a barrier between the void former and a settable composition to be cast over the void former.

The cover may be in the form of a hood sized and dimensioned complementarily to the void former to be covered.

The cover may be sized and dimensioned such that a single cover covers a plurality of void formers.

The cover may be made of a material substantially impervious to the settable composition.

The cover may be made of a material substantially impervious to water.

The cover may have one or more spacer regions for spacing the chambers of adjacent void formers to, in use, form a channel between void formers.

The spacer regions may be peripherally located on the cover.

Where the cover is sized and dimensioned to cover a plurality of void formers, the one or more spacer regions may located internally on the cover, for example, by stiffened zones on a sheet.

The peripheral region of the cover may be sized and dimensioned to cover a spacer of the void former.

Typically the cover is made from a water tolerant material, such as wax coated cardboard, plastic, masonite, plastics sheeting, plastic coated cardboard, laminates, treated wood, or the like.

The cover may be reusable or single use.

The spacer regions may be in the form of flaps extending laterally from the cover.

According to a third aspect of the invention, there is provided a void former having a chamber defined by side walls and at least one end wall, wherein at least the end wall is provided with a suitable rigid water tolerant surface.

The end wall may be made entirely of a plastics material, masonite, wood, or any suitable sufficiently rigid water tolerant material, or it may be a layered or laminated material including a plastics, masonite, wood, or any suitable sufficiently rigid water tolerant material layer.

The void former chamber may be open at one end. Typically, the void former chamber has a retaining formation provided on the open end for retaining a reinforcing insert in the void former chamber.

Typically, the sidewalls are also made of the same material as the end wall.

The void former may be provided with a spacer extending laterally from the chamber for spacing the chamber of the void former from adjacent objects, substantially as described above.

The void former may be substantially parallelipipedal, typically having rectangular and/or trapezoidal sides.

In a useful embodiment, the sidewatts of the void former are trapezoidal and the or each end wall is rectangular.

The invention extends to a re-usable void former which can be recovered from a construction and re-used.

The void former may have a second end wall adapted to, in use, permit heaving soils to expand into the void former.

Typically, the second wall is adapted to use in heaving soil conditions by providing it with an apertured zone, a weakened zone and/or a water weakenable zone through which soil may expand into the void former.

According to a further aspect of the invention there is provided a method of constructing a settable composition stab, the method including the steps of : - supporting void formers in a desired configuration such that the void formers define a plurality of channels for receiving a settable composition ; - covering the void formers with void former covers or hoods ; - casting a settable composition into at least the channels ; - removing the void formers once the settable composition has set ; and - optionally, removing the void former covers or hoods.

The casting step may include casting the settable composition over the void formers to form a slab having projecting beam portions, coffer fashion.

The removed void former covers or hoods may be reused or disposed of.

According to a further aspect of the invention, there is provided a void former for use in the construction of long span slabs, the void former being elongate and having a polygonal cross-sectional profile.

Typically the void former is octagonal in cross-section.

The octagonal cross-section may be obtained by two trapezoidal box void formers sandwiching a rectangular box void former. A reinforcing grid may be provided in the void former.

According to yet a further aspect of the invention, there is provided a frame or receptacle for use in casting a column from a settable composition.

The frame or receptacle may be in the form of a cardboard box having one or more cardboard layers to provide sufficient rigidity.

Typically, the frame or receptacle is used in casting a column base portion.

The invention extends to a method of casting a column from a settable composition, the method including the steps of : - placing a frame or receptacle made from a lightweight material such as cardboard, plastics, masonite, or laminate, on a previously excavated and cast foot portion ; - optionally, inserting steel reinforcing elements into the frame or receptacle ; and - casting a settable composition into the receptacle.

The method may include the prior step of assembling the frame or receptacle from a sheet of the lightweight material.

The frame or receptacle may be left in situ and, for example, decorated, or it may be removed from the set settable composition.

Description of the Drawings The invention will now be described, by way of non-limiting example only, with reference to the accompanying diagrammatic drawings.

In the drawings, Figure 1 shows, in three dimensional schematic representation, a void former, broadly in accordance with the invention ; Figure 2 shows, in three dimensional schematic representation, a reinforcing insert for a void former, broadly in accordance with the invention ; Figure 3 shows, in three dimensional schematic representation, a top and bottom for a void former, broadly in accordance with the invention ; Figure 4 shows, in three dimensional schematic representation, a spacer accessory for use with a void former ; Figure 5 shows, in three dimensional schematic representation, another embodiment of a void former in accordance with the invention ; Figure 6 shows, in three dimensional schematic representation, a reinforcing insert for the void former of Figure 5 ; Figure 7 shows, in three dimensional schematic representation, a trapezoidal void former ; Figure 8 shows, in three dimensional schematic representation, a reinforcing insert for the trapezoidal void former of Figure 7 ; Figure 9 shows, in three dimensional schematic representation, a cover or hood for the trapezoidal void former of Figures 7 and 8 ;

Figure 10 shows, in three dimensional schematic representation, a plurality of covered void formers as shown in Figures 7 to 9, configured to form channels for receiving a settable composition in the construction of a slab ; Figure 11 shows, in three dimensional schematic representation, a polygonal elongate void former for use in construction long span slabs ; Figure 12 shows, in three dimensional schematic representation, a reinforcing insert for the void former of Figure 1. 1 ; and Figure 13 shows, in three dimensional schematic representation, a frame or receptacle for casting a column or pillar.

Figures 1 shows one embodiment of a void former 10, having a chamber 11 defined by four sidewalls 12,13, 14,15, and spacer 16 extending laterally from the sidewalls 12,13, 14,15 for spacing the chamber 11 of the void former 10 from adjacent objects (not shown).

In use (see Figure 10 for a similar arrangement of a different embodiment of void former 10), the spacer 16 spaces the chambers 11 of adjacent void formers 10 from each other thereby to provide a series of channels for casting a settable composition into when forming a slab and/or beams for a slab.

The spacer 16 comprises four flap portions 18,19, 20,21 extendable outwardly from the chamber 11 of the void former 10.

The dimensions of the spacer may be selected to, in use, provide a channel width of suitable dimensions for the slab being cast.

In Figures 2 and 3 is shown a void former 10 provided with a reinforcing insert, in the form of a so called egg-crate or grid 22 to reinforce the void former 10 against compression. The egg-crating 22 comprising a cardboard (or wood, plastics or other suitable rigid material) grid.

Figure 4 shows a spacer accessory 30 for a void former configured to be used with a conventional void former as shown in Figures 2 and 3.

The spacer accessory 30 is in the form of an angle section of cardboard (or plastics coated cardboard) having a laterally extending spacer portion 32 provided thereon, the spacer accessory 30 being sized and dimensioned complementarily to the void former size and dimensions with which it is to be used.

An alternative embodiment of the void former 10 is shown in Figures 5 and 6 in which a void former 40 is assemble from an outer channel portion 42 having spacer portions or flaps 44,46. An oppositely directed inner channel portion 48 co-operates with the outer channel portion 42 to form a chamber 49 of the void former 40. A reinforcing inner part 47 is recevable within the chamber 49 of the void former 40 to inhibit compression of the void former 40 in use.

Figure 10 shows a method of spacing void formers 10 (or similar) using a spacer accessory 30 or a void former having a spacer 16, as set out above, the method comprising the arranging of void formers 10 with the spacers 16 in close proximity or in contact with an adjacent void former 10 or object.

Figure 7 shows a void former 50, the sidewalls 52, 53, 54, 55 of which are trapezoidal and the end wall 56 is rectangular define a chamber 57. The end wall 56 and sidewalls 52,53, 54,55 being made from plastic i. e. providing a suitable rigid water tolerant surface Thus void former 50 can be recovered from a construction and re-used.

Figure 9 shows a removable cover or hood 60 for a void former 50 having a chamber 57, the cover or hood 60 being sized and dimensioned complementarily to a void former chamber 57 to be covered and, in this embodiment, having a peripheral region 62 for spacing the chambers 57 of adjacent void formers to, in use, form channels 66 between the void formers 50.

Typically the cover is made from a water tolerant material, such as wax coated cardboard, plastic, masonite, plastics sheeting, or the like and may be removed for re-use.

Figure 10 illustrates a number of void formers 50 covered with a number of covers 60 to provide a template for a slab (not shown).

Figures 11 and 12 show a void former 70 for use in the construction of long span slabs, the void former 70 being elongate and having a octagonal (polygonal) cross-sectional profile.

The octagonal cross-section may be obtained by two trapezoidal void formers 50 sandwiching a rectangular box void former 10 between them. A reinforcing grid 72 is provided in the void former 70. This type of octagonal void former 70 can be used in the place of currently used round cylindrical void formers which are cumbersome and expensive.

Figure 13 shows a frame 80 or receptacle for use in casting a column (not shown) from a settable composition.

The frame 80 is in the form of a cardboard box having two cardboard layers 82,84 to provide sufficient rigidity.

Typically, the frame or receptacle is used in casting a column base portion.

The frame 80 is assemble from a sheet 86 of corrugated cardboard.