The present invention relates to a spacer for spacing apart two substantially parallel surfaces . The spacer of the present invention has been developed especially for use in spacing reinforcing mesh away from a building wall when a plastered wall finish is being applied, and will be described with particular reference to this application. However, it will be appreciated that the spacer of the present invention could in fact be used in a wide variety of applications where it is necessary to rapidly and reliably space apart two parallel surfaces. Background Art Many buildings are constructed with an exterior finish of plaster over the walls. In general, this finish is achieved by securing an approved type of backing board over the wall framing, placing a layer of building paper or equivalent over the backing board, and then supporting a sheet of reinforcing mesh over the entire wall surface to be plastered and applying a plaster finish, so that the reinforcing mesh is embedded in the plaster. In a variant of this type of finish, an existing weatherboard or pre-cladded building has a sheet of reinforcing mesh supported over the surface to be plaster finished and, as with the previously described method, the plaster is applied over the surface so that the reinforcing mesh is embedded in the plaster.

For a plaster finish of this type to be satisfactory, it is important that the reinforcing mesh is thoroughly embedded in the plaster:- if the plaster is simply applied as a layer over the top of the reinforcing mesh, the plaster is not sufficiently reinforced, and may flake or crumble with time. To ensure that the mesh is

properly embedded in the plaster, it is necessary to space the reinforcing mesh away from the building paper or the existing wall. However, this is very difficult to achieve: - at present, the most common method of spacing the mesh out from the supporting surface is to use small blocks of plywood secured to the backing board or to the existing wall at spaced positions across the width and along the length of the wall . These spacers are time consuming to secure in position, and also tend to disrupt the final plaster finish of the wall.

Another method of spacing the reinforcing mesh which has been experimented with is to crinkle the reinforcing mesh before use, but this is difficult to achieve and has not proved at all satisfactory in use. Because of the difficulty of obtaining adequate spacing of the mesh, many builders simply do not attempt to space the mesh out from the wall at all, with the result that the application of the plaster tends to press the reinforcing mesh back towards the wall and the mesh is not adequately embedded in the plaster.

US patents 5 287 673 and 5 481 843 (Kreikemeier) both disclose a reinforcing mesh of plastics material which incorporates spacer portions as part of the mesh. The spacer portions contact the underlying wall and space the mesh away from the wall during plastering. However, the mesh disclosed in these patents is very much more expensive than conventional building mesh. Disclosure of Invention

It is an object of the present invention to provide a spacer which can be applied to a building wall quickly and easily and which provides satisfactory and cost- effective support to the sheet of reinforcing mesh so that when the plaster is applied, the mesh is held away from the building paper/backing board or existing wall

surface and is adequately embedded in the plaster.

The present invention provides a spacer comprising an elongated length of material formed into a repeating, compact configuration which is extensible when tension is applied thereto, said configuration being such that said spacer when extended has a predetermined length, depth, and width.

Preferably, said compact configuration is a helical coil or a zig-zag shape. However, a wide variety of different configurations may be used e.g. an elliptical coil, a helical coil, a zig-zag, a zig-zag with flats formed on the apices, and a square wave-form shape, all are suitable. The configuration used must be capable of resting securely on the surface to be plastered, without twisting out of place when plaster is applied, and also must be capable of even extension when tension is applied.

The present invention further provides a method of applying a plaster finish to a wall surface including the steps of: -

(a) providing a plurality of spacers described above;

(b) securing a first spacer at one end to or adjacent the area to be plastered, and applying tension to said spacer to extend said spacer across the area to be plastered and such that said extended spacer has a predetermined depth;

(c) securing the other end of said spacer at or adjacent the area to be plastered, thereby maintaining the spacer in its extended state;

(d) repeating steps (b) and (c) with each of the remaining spacers, adjacent spacers being spaced apart by predetermined distances;

(e) applying a plaster finish over said spacers

such that said plurality of spacers are embedded within said plaster.

Alternatively, reinforcing mesh is stretched over said spacers before step (e) , and the plaster is applied over both the spacers and the mesh.

Preferably, the plaster is a fibre reinforced plaster.

It will be appreciated that the plurality of spacers may be arranged in any desired manner and as used herein the term 'across' includes arranging the spacers such that each spacer extends at a desired angle, or is substantially horizontal or vertical, or combination thereof. Further, the spacers may be weaved or over-laid to form a cross-hatched arrangement. The spacer may be made of any suitable material; it is envisaged that for the coiled spacer, low tensile galvanised wire will be the most suitable material, but it is possible that alternative types of wire or coils of plastics material also could be used. For the zig-zag spacer, it is envisaged that galvanised sheet steel would be suitable.

The depth of the unstretched spacer will vary according to the material used for the spacer and the amount by which the spacer is extended to cover the necessary length; it will be appreciated that the final depth of the stretched spacer is the distance by which the reinforcing mesh is spaced away from the supporting surface underneath.

The ends of the spacers can be secured in position by nailing or by stapling or any other suitable means, and the ends of the spacer may be provided with hooks or rings to assist in securing. The spacer may be sold in precut lengths to suit average wall heights but it is also envisaged that the spacer could be supplied as a

very long continuous length which a builder would simply cut to length as required.

Brief Description of Drawings

By way of example only, two preferred embodiments of the present invention are described in detail with reference to the drawings, in which:-

Fig. 1 shows a diagrammatic longitudinal section through a wall constructed using a first embodiment of the spacer of the present invention; Fig. 2 shows a side view of a spacer of Fig. 1, unextended; and

Fig. 3 shows a side view of a second embodiment of the spacer of the present invention, as extended.

Mode for Carrying Out the Invention Referring to Figs 1 and 2 of the drawings, the wall

2 of the building includes a top plate 3 and bottom plate

4 with associated conventional framing (not shown) all of which support a backing board 5 which is covered by a layer of building paper 6 in known manner. A plurality of spaced apart spacers 7 hold a sheet of reinforcing mesh 8 a pre-determined distance (typically about 8mm) away from the building paper 6.

It will be appreciated that, instead of a backing board 5 and building paper 6, the layers so indicated could simply be the existing wall of a house made of, for example, weatherboard or similar cladding material.

Each spacer 7 is secured in place by nailing its upper end into the top plate 3 , stretching the spacer and then nailing its lower end into the bottom plate 4. Each spacer 7 is substantially vertical and a series of spacers is evenly spaced across the width of the wall. The spacing between the spacers can vary, depending upon the overall width of the wall, the weight of the reinforcing mesh to be used, and the type of

plaster to be used.

Typical spacings are:- if the studs are spaced at 600mm centres, the spacers are spaced at 300mm centres i.e. one spacer over each stud and one spacer between each adjacent pair of studs. If the studs are at 400m centres, the spacers are also spaced at 400mm centres, with one spacer over each stud.

Fig. 2 shows a spacer 7 before application to the wall:- spacer 7 is simply a continuous helical coil of wire, formed with a loop 9 at each end to facilitate securing the coil in place. Alternatively, the loop 9 may be replaced by hooks or the ends of the spacer left plain.

The diameter of the helical coil of the spacer must be such that when the spacer is extended into position as shown in Fig. 1, the overall depth of the coil equals the required distance between the backing board 5 and building paper 6 and the reinforcing mesh 8. It will be appreciated that the stretched diameter of the coil can be adjusted on site if necessary simply by increasing or decreasing the tension on the coil.

One suitable material for forming the spacers has been found to be 2mm diameter low tensile galvanised wire coiled into helical coil with an 18mm inside diameter. This wire is not appreciably resilient and when the coil is extended, it remains so.

Once the spacers 7 and the reinforcing mesh 8 are secured over the backing board and building paper 6, a layer of plaster (not shown) is applied in known manner such that both the reinforcing mesh 8 and spacers 7 are embedded in the plaster.

Optionally, the reinforcing mesh 8 may incorporate the spacers wherein each spacer 7 is secured across the reinforcing mesh 8 whereby each respective coil is

extended and adjacent spacers are spaced apart by a predetermined distance. Once the reinforcing mesh 8 incorporating the spacers 7 is secured over the backing board and building paper 6, a layer of plaster (not shown) is applied as hereinbefore described.

It will be appreciated that the spacer of the present invention is easy and quick to secure and can be secured very accurately in place without difficulty.

Referring to Fig. 3, a second embodiment of the present invention comprises a strip 10 of sheet material (e.g. galvanised steel) bent into a zig-zag shape.

The zig-zag has each peak 11 and each trough 12 'squared off to form a flat 13, 14, respectively, so that in use the spacer lies with one set of flats 13 against the wall and the other set of flats 14 in contact with the mesh. It would be possible to form the spacer without the flats 13, 14, but this design would not be as stable.

In a further application of the present invention, the spacer of the present invention is used as a means of reinforcing and bonding plaster in place, and may be used for this purpose with or without a reinforcing mesh.

In this application, the spacer is made and is secured in position as described above:- the spacers, extended, are secured vertically down the height of the area to be plastered, with the spacers spaced apart across the wall. The plaster may be applied directly over the spacers, without using reinforcing mesh and the presence of the spacers themselves are sufficient to key the plaster effectively to the wall. It is believed that this method would be particularly effective with the stronger fibre reinforced plasters, but it is possible that the method would be also be effective for ordinary plasters.

The above described method may be used over any of the existing surfaces which are normally plastered and may also be used over an assembly of polystyrene blocks, in constructions of the type where polystyrene blocks are assembled to form a wall and are then plastered over to give a permanent weatherproof finish.

Whilst the present invention has been described and depicted with the spacers extended in a substantially vertical orientation, it will be appreciated that each spacer may be secured across the area to be plastered, or alternatively incorporated in the reinforcing mesh, in any desired position. For example, some or all the spacers may be secured at any desired angle, or extend substantially horizontal or vertical or any combination thereof. Further, the spacers may be weaved or overlaid to form a cross-hatched arrangement.