Fixing Polystyrene Tiles and Coving
A quick, neat way of redecorating
Polystyrene tiles provide an effective method of covering cracked or discoloured ceilings. Do not use them where there is any risk of their becoming overheated (near fireplaces or abovewater heaters).
They should never be painted with gloss paint as this constitutes a fire risk. Remove any already gloss-painted and, if a finish is required, use emulsion paint.
Most ceiling tiles measure 305 x 305 x 9 mm (12 x 12 x in), but 610 x 610 mm (2 x 2 ft) and 229 x 229 mm (9 x 9 in) sizes are also available and some are only 6 mm (a in) thick.
Specialare sold for fixing polystyrene tiles, but not all are suitable for every surface to be covered. Before buying any particular , consult the dealer on its suitability for the surface on which it is to be used.
Preparing the surface
Make good cracked ceilings and remove and replace any loose plaster. Hair-line cracks need no attention. Remove distemper with water and sponge. Wash emulsion paint. Rub over gloss paint with glasspaper or a wire brush to provide a good key for the. Remove any traces of grease with a liquid detergent. If the grease is thick, use Flash or liquid Ajax.
On really rough ceilings, remove all the existing plaster and laths, then face the joists with standard or medium, and fix the tiles to that.
Draw lines dividing ceiling in half along the length and the width. Measure lines AB and AC, and count the number of whole tiles that will go along each line.
If the space left over is 152 mm (6 in) or more (ie. at least half a tile), you can fix the tiles from the marked line. If it is less than 152 mm, you would end up with a narrow, unsightly row of tiles near the wall, so mark a new line 152 mm From the centre line and work from that.
If there is a central light fitting, cut the corners of the four centre tiles with a sharp trimming knife to fit snugly round the rose, using a conveniently sized cup as a guide.
If the rose is offset, or the centre lines do not intersect at this point, adjust one of the centre lines so that the rose comes between rows of tiles. Cut semicircles in adjacent tiles to fit round it.
If the ceiling has a tubular light fitting, arrange its centre line to fall between two rows of tiles. You may have to re-align the fitting, because it should at least lie parallel to these rows.
All tiles which butt on to the fitting will have to be cut to fit round it snugly.
Following recommendations by fire authorities, polystyrene tiles should be fixed with an even coat of adhesive to exclude air pockets behind them. Spread a 1.5 mm in) thick layer of adhesive in one of the right angles formed by the centre lines and over an, area large enough to take about nine tiles. Firm the tiles with a flat block to avoid making finger dents.
Fix tiles in the remaining three angles, to form a square at the centre, and continue tiling outwards. If there is a large central obstruction, the ceiling can be tiled in two separate sections.
Check constantly that the tiles fit closely together and run in straight lines.
To mark border tiles for cutting, place a ‘dry’ tile over the last fixed tile. Hold a third tile as shown, one edge against the wall, and mark with a pencil where it overlaps the ‘dry’ tile. The part of the tile that remains uncovered will fit the border exactly when cut.
Polystyrene coving, available in several sizes, is fixed with the same adhesive as tiles . Fix the corner mitres first — they can be bought pre-cut. Cove improves the decorative effect and conceals narrow borders.