This invention relates to methods of applying coatings to wall surfaces and to apparatus for use therewith .

A method of applying a decorative finish to a wall surface is known from EP-A-0160315 in which a moulding frame of foamed polyethylene is adhered to a prepared wall surface, the adhesive being initially covered by paper peelable from one surface of the frame. An acrylic resin is then sprayed completely over the frame and onto the prepared wall surface. When the sprayed resin is partially dry, a second cover paper adhered to the upper frame surface is removed to leave the frame boundaries clear of resin . When the resin is completely dry, the foamed polyethylene frame is removed to leave the required decorative finish . A transparent paint may be applied to the exposed surfaces of the moulded resin .

EP-A-0106165 discloses a method of applying relief plastering in which a network sheet of lands of moisture-resistant material is applied by adhesive to a surface. Plaster is applied to the surface covered by the network which is subsequently pulled off the surface to expose a required pattern .

In practice, it has been found to be extremely difficult to remove a vertically or substantially vertically-sided single wall frame as exemplified by EP-A-0160315 without disturbing the desired contours of the decorative

pattern to be achieved . Furthermore, the dual requirements of rigidity and lightness cannot easily be achieved with such single wall frames . Also, the use of adhesive to attach a moulding frame to a dry wall whose surface is unlikely to be entirely smooth and flat is unsatisfactory .

The present invention sets out to provide a method of and apparatus for applying to an interior or exterior wall a coating which has the appearance of inter alia a brick, block, stone or flint wall with or without a rough cast or textured finish using a grid which has the required rigidity and strength lacking in the structures discussed above. Additionally, use of the apparatus does not require the use of adhesive.

More particularly, the present invention provides a method of applying to an upstanding wall a surface coating , the method comprising the sequential steps of placing on to a cement rendering on a wall surface a twin-walled open-sided grid to create in the rendering a pattern representative of the peripheries of a plurality of adjoining bricks, stones, flints or the like, projecting on to the rendered wall surface with the grid in place a particulate material with sufficient force to cause the particles to become embedded in or adhere to the render, and removing the grid from the wall surface, the upstanding twin-walls of the grid being inclined to the vertical and diverging to define a taper to assist removal of the grid from the coated wall surface .

The render is preferably wet or semi-dry when the grid is placed in or onto its surface, the grid walls being pushed into the wet or semi-dry render .

The particulate material may be grit or sand based and may include a dye and a bonding and/or sealing agent.

The spacings between the brick, stone, flint or the like impressions may subsequently be pointed using a conventional sand/cement mix .

The sand-based material may be sprayed through the grid on to the rendered wall surface in the form of a slurry comprising a mixture of sand , cement and a liquid (e. g . water) with or without the presence of a dye to impart colour to the slurry and/or a PVA bonding agent from a pneumatically operated gun or the like to produce a rough cast finish to the treated wall . Additional particles may be applied to the surface coating to create, for example, a textured appearance .

In another aspect the invention provides apparatus for applying to a cement rendered surface of an upstanding wall a coating, the apparatus comprising a twin-walled grid whose upstanding walls are inclined to the vertical and diverge one from the other to define a taper and which is open on at least one of its sides and is shaped to define the peripheries of a plurality of bricks , slates , flints or the like bordered by partial peripheries of a number of adjoining bricks , stones, flints or the like.

The grid is preferably produced from a plastics material whose thickness is, typically , between 1 mm and 3mm .

The grid may be produced by a vacuum forming process . Alternatively, it may be injection moulded . One or more surfaces of the grid may be treated with a release agent, a wax or a low friction coating such as Teflon (Registered Trade Mark) .

The apparatus may also include a particulate material and means for projecting this particulate material on to the rendered wall surface through the grid whereby material particles become embedded in the rendered surface between the grid partitions .

One side of the grid may be closed by a backing sheet which may be removable. The inner surface of the backing sheet may include indentations or projections to create a textured finish to the render over

which the grid is positioned .

The invention will now be described by way of example only with reference to the accompanying diagrammatic drawings in which :-

Figure 1 is a plan view from above of apparatus in accordance with the invention ;

Figure 2 is a side view of the apparatus shown in Figure 1 ;

Figures 3 and 4 are side views of alternative apparatus in accordance with the invention ;

Figures 5 and 6 are perspective views of further apparatus in accordance with the invention;

Figures 7 and 8 are perspective views of further apparatus in accordance with the invention ;

Figures 9 and 10 are also perspective views of alternative apparatus in accordance with the invention ; and

Figures 11 to 14 are perspective views of further apparatus in accordance with the invention .

The apparatus illustrated in Figures 1 and 2 comprises an open-sided twin-walled grid 1 produced from a rigid or semi-rigid material such as plastics or a fibrous material . Each wall 2 of the grid comprises a pair of sides 3 upstanding from a base 4 which are inclined to the vertical and diverge away from one another to define a taper 5 therebetween . As shown , the walls 2 together define the contours of three brick courses and parts of the contours of bricks which will lie alongside, above or below the

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courses defined by the grid . Other grid sizes encompassing less or more than three brick courses could , of course, be employed . The base 4 may be formed with discrete apertures through which render or mortar may pass . The grid contouπ ^' llustrated in the drawing is merely exemplary of grid used to create in a rendered wall surface the appearance of a brick wall . Other grid contours could , of course, be adopted to replicate, for example, a regular or random stone or block wall finish or a flint wall finish . In each case the grid comprises a plurality of closed shapes bordered by open shapes in the manner shown in the drawing .

The grid is designed to be placed on to a cement rendered wall surface with the closed bases of the walls 2 protruding into the wet render to create the impression of brick or other courses . The tapering walls ensure that the render completely fills the spaces defined by the walls . That is to say, as the inclined walls are pushed into the wet or semi-dry render, the render is urged into intimate contact with the grid walls. Other grids which might be identical or similar to that illustrated may also be placed into the rendered surface with the open partitions in line to create the contours of further brick courses . The outer surfaces of the grid may be patterned or textured to create a complementary pattern or texture in the contacting render.

The plastics or fibrous material from which the grid is produced ensure that the weight of the grid is such that it remains in place when pushed into the render and does not move downwardly under gravity . The twin-walled construction ensures that the relatively light weight grids have the required rigidity which enables them to be removed from the rendered surface with minimal disturbance of the impression created in the render. The taper 5 assists in the removal process and is necessary to achieve the required minimal disturbance of the render on removal of the grid . The taper also assists stacking of grids before use .

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Twin-walled grids having differently shaped bases to those of the grid shown in Figures 1 and 2 are illustrated in Figures 3 and 4. In Figure 3, the base 6 is stepped and in Figure 4 the base 7 is partially inclined . Alternatively, the grid base may be triangular, chamfered , curvilinear, semi circular, even or uneven to produce any one of a selection of mortar joints in the render . Apertures formed in the grid base 4 assist pinning of the grid to a semi-dry or dry render .

On occasions, it is necessary to link the grids 1 together or to construct specially sized and dimensioned grids to fill small or irregular spaces or to achieve special effects . Thus, single elongate twin-walled grid strips 8 as shown in Figure 5 may be provided and cut to shape as required . Thus, one side wall 9 may be formed with a tapered cut-out 11 to receive the side walls 3 of a twin-walled grid or other strip. Also, as shown in Figure 6 the strip 8 may define a carrier for a spirit level 12 set, for example, in mastic .

When applying a decorative finish around a curved or bowed surface, a series of notches can cut into the grid walls 3 to enable the grids to follow the curve or bow .

Twin-walled strips 8 may be used in combination with a twin-walled linking grid 14 as shown in Figure 7 to create specially sized or shaped grids . Thus , the grid lengths 15 locate within side-by-side strips 8 with the grid cross-piece 16 passing into and through tapered cut-outs 11 of the strips 8.

In Figure 8, strips 8 are shown to lin k with a corner piece 17.

As will be seen from Figures 9 and 10, the grids 1 can be used in association with formers 18 having protruding sections 19 joined by webs 20 to create decorative effects on walls . As shown , the formers 18 are

produced as mesh cages, preferably of plastics, joined by galvanised wire or plastic clips and connected to side pieces 21 which can be secured to an appropriate wall surface by pins or nails . Other materials for the cages can be employed . The cages are formed to create any desired decorative feature and may be f lled with afiller material such as foamed polyethylene. A barrier gasket may be placed inside the mesh cage to create an even walled void between the mesh and a preformed liner of plastics or card. The open cavity defined between the liner and the mesh cage may then be filled with a material such as an expanded foam. Reinforced holes 22 may be provided in the cage faces for ease of filling .

Once a cage is pinned to a wall , render material is forced, trowelled or pumped through the reinforced holes 22 to fill the cage and any exposed cage surface is covered with further render material . After trowelling , the grid 1 is placed over the rendered cage in the manner discussed above.

In any one of the discussed arrangements, with the grid or grids in place particulate material is projected on to the rendered surfaces between the grid partitions to create a pleasing aesthetic appearance to the surfaces . If the required surface finish is that of a brick wall , the particulate material may be sand-based to which a suitable dye has been mixed appropriate to the required wall finish . A water-resistant or repellant sealant such as a PVA-based bonding agent may be added to the sand-based material to enhance its performance. A textured effect may be created in the rendered surfaces to simulate different species of bricks, stone etc.

The particulate material may be projected on to the wall surface in a number of ways . Thus, it may be thrown by hand or by shovel on to the rendered wall or may be propelled on to the wall surface by, for example, a pneumatic gun or a machine known as a TYROL machine. Where a grit blast gun is employed , one operating at a pressure of 80 to 120 psi would

be appropriate. The gun would normally be connected to a compressor able to generate 150 psi .

Alternatively, the particulate material may be sprayed on to a rendered surface in the form of a slurry mix comprising sand , cement, a colour dye, water and a PVA agent. Slurry may be sprayed using a pneumatic gun to ensure that it is effectively embedded into the render and to produce on the surface a rough cast effect with random freckling if this is required .

Masking shields may be provided to mask areas and deflect projected material away from, for example, windows gutter, paintwork and earlier coatings .

After spraying , the grid is removed from the wall surface and the spaces between the brick impressions may then be pointed using a conventional sand/cement mix or left as open joints . Coloured grit may be projected onto the brick impressions to improve the aesthetic appearance of the coating . Colouring may also be effected by spraying the previously sprayed material with a pigmented cementitious slurry coating either before removal of the grid . Because of its rigidity and twin-walled construction , the grid can readily be removed from the rendered and sprayed material with minimal interference of the decorative effect produced by the grid .

The required colouring , sealing , bonding and texturing materials may be included in the render, the grid then simply being impressed into the wet render to create the required pattern . One or more of the following can be admixed with the base render or slurry :-

a pigment, bonding agent, water-proof material , thixotropic pumping aid , suspension agent, reinforcing agent, fibres , insulation , sealer, oxide, resin , acrylic, polymer, particulate

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of various grades, minerals and crushed materials such as brick, stone, rock or slate.

One side of the grid may be closed by a backing sheet whose inner surface is raised or indented to produce on the wet render a textured or patterned surface. The backing sheet may be permanently or temporarily attached to the grid . A grid with a backing sheet may also be used to mask selected coated surfaces from other such surfaces during selective painting , for example.

A comb may be applied to the coating to achieve a desired effect.

As mentioned previously, the grid may be interlinked to other grids or strips by conventional connecting devices . Grids may include hinged sections for corners and individual grids comprising a single or half brick or other shape may be provided . Also, the individual pieces of the grid may be detached from its neighbouring pieces by providing weakened zones

When the coating is to be applied to an upstanding wood or metal surface, an expanded metal mesh or sheet (EML) may be secured to the surface before rendering .

The apparatus described may be used to apply a decorative coating to precast or sectional buildings where movements between the section panels and joints is inevitable. If rendering is applied directly to such section panels in the manner discussed above, cracks would appear in the render as movements occur . To overcome this problem, a floating secondary wall as illustrated in Figures 11 to 14 is employed . The secondary wall provides an intervening wall surface between the precast or section panels of a building and the rendered decorative coating which prevents cracking in the event of relative panel movements .

As shown in Figure 11 , positioned between precast or section panels 25 and a corrugated sheet 26 lined with fibrous material 27 is a floating coupling 28 comprising a layer 29 of a flexible material such as rubber, neoprene, foam, sponge or a vulcanized material bordered by and secured to metal plates 30. The sheet 26 is shown in greater detail in Figure 12. Threaded studs or spikes 31 pass through the coupling 28, these passing through the corrugated sheet 26 and being fastened by nuts, wire or the like. The studs or spikes 31 are welded to the metal plates 30 to enable the coupling to act as an independent suspension coupling . The couplings may be of linear construction as shown in Figure 13 or circular as shown in Figure 14. The corrugated sheet 26 may comprise an expanded metal lathe insulation board or the like and provides a keying surface for a render into which is subsequently impressed one or more grids as described above.

It will be appreciated that the foregoing is merely exemplary of a method and apparatus in accordance with the invention and that modifications can readily be made thereto without departing from the true scope of the invention .