Expanded polystyrene tiles, which provide decorative covering for the ceiling, reduce condensation and cut down sound transmission, are suitable for any room in the house. In addition they help reduce heat loss; although a polystyrene tiled ceiling should not normally be regarded as a substitute for loft insulation, it makes a useful barrier in flat-roofed houses or extensions where other forms of insulation are difficult to install.
Following assertions that expanded polystyrene tiles were a fire risk, a series of tests were carried out by the Home Office, the Joint Fire Research Organisation and the Rubber and Plastics Research Association. They concluded polystyrene did not represent a significant fire hazard, was difficult to ignite and there was no rapid spread of flame.
The fire resistance of tiles is governed by the flammability of any covering material, paint being the normal covering. For this reason the tiles must not be covered with gloss paint; only emulsion or a fire-retardant paint should be used. Most tiles are now produced with a fire-retardant additive in line with current safety requirements.
Types of tile
Polystyrene tiles are widely available in sizes of 300 and 600mm sq (12 and 24in sq), although 9in sq tiles can sometimes be found. If you use the largest size, you will have fewer tiles to fit; but you will probably find the smaller ones more convenient if you have an awkwardly shaped ceiling. Plain, patterned or textured tiles are available.
A tiled ceiling can be finished off round the perimeter with expanded polystyrene cove, which makes a neat finish and covers up any imperfect cutting on edge tiles. Cove comes in lengths of 1-2m (or 3-6ft) and is butt-joined; external or internal mitre pieces are available to fit corners. Estimating quantity Some manufacturers supply a quantity table which tells you at a glance how many tiles will be needed for a given area. For example, a room 2.44m (8ft) wide and 2.74m (9ft) long will need seventy-five 300mm tiles or twenty 600mm tiles. Alternatively work out the ceiling area in sq m and multiply this by 11.2 for 300mm sq tiles or 2.8 for 600mm sq tiles. If you are using 9in sq tiles, work out the ceiling area in sq ft and multiply by 1.8.
To find the best starting point for tiling, use drawing pins or small panel pins to fix string lines from the centre edge of each wall along the width and length of the ceiling. Mark with chalk the point where the lines cross, using coloured chalk if the ceiling is white; this will be the centre point. If this does not leave equal size part tiles at each edge, adjust one or both string lines, as necessary, until the correct balance is found.
It is not essential to leave equal size tiles at the perimeter — it merely gives the ceiling a more balanced look. If preferred, you can leave full tiles along the edges of the two walls most prominent from the doorway and cut tiles to fit the remaining area on the other two walls.
Fluorescent light fittings can cause problems if they do not lie parallel to the tiles or if they lie in a position which will entail cutting narrow strips of tiles to fit round them. You may have to reposition the starting lines to facilitate fitting.
Remove dirt, grease, old paper or loose paint and distemper. Old gloss paint, provided it is sound, should be rubbed down with glasspaper to provide a key for the adhesive. If you are tiling a new or bare ceiling, check with the tile manufacturer’s instructions since you may be recommended to coat the ceiling with size first, as for wallpapering. Finally, fill any cracks with cellulose filler.
Only expanded polystyrene tile adhesives should be used since the Home Office recommends an all-over spread adhesive; these are readily available under different trade names from the same outlets as the tiles. Always check the instructions on the pack to make sure your ceiling surface is suitable for the adhesive. Don’t use an adhesive with a solvent base such as cellulose, which would dissolve the tiles and make them highly inflammable.
Applying adhesive Using an old paint brush, apply the adhesive liberally to the entire surface of the back of each tile. Don’t use the old ‘five-blob’ method (one in each corner and one in the middle) since this does not ensure total adhesion; in a fire the tile would drop off the ceiling, whereas coating the entire surface will prevent this.
Fixing the tiles
Fix each tile in place as soon as you have spread the adhesive on the back. Place the first four tiles in the right-angles formed by the lines marked on the ceiling. Thereafter work outwards to the walls, closely following the chalked lines and making sure the edges of all tiles are closely aligned. It is not necessary to force together the edges to make a tight butt joint — a very fine gap will ensure a neat appearance.
Polystyrene is easily damaged, so avoid pressing the tiles with your fingers when fixing them in place. Cut a piece of hardboard or plywood the same size as the tile and use this to hold each tile in place until the adhesive has set; since the tile is very light this should take only 15 to 30 seconds. Nevertheless it can still be tiring to stand witti arms stretched and you may find it easier to support the tile by nailing the board to a broom handle.
Edge tiles When all the full tiles have been fixed in position, prepare the edge tiles. To mark the cutting line, place a loose tile over the last full tile; if there is a pattern, make sure it is running the right way. Place another tile over the first one, but with its edge butted up against the wall, and mark lightly in pencil where the rear edge of the top tile touches the one below it. Take down both tiles and cut the marked one along the pencil line; the cut tile should fit neatly into the space left at the edge, with the cut edge butted against the wall.
The tiles can be cut with a hot wire-cutter (which is a purpose-made tool); if you do not want to go to the expense of buying one, a sharp trimming knife will do the job just as well. Lay the tile — decorative face uppermost — on a flat surface. Place a metal straight-edge along the cutting line, press down on it and cut firmly through the tile in one action. Shapes You may need to cut a variety of shapes to fit round obstacles and fittings. Use a square of card the same size as the tile as a template and cut it to the required shape. Transfer the shape outline in pencil to the tile and cut. To fit tiles round ceiling light roses, cut out a circle of the correct diameter and slip the tile over the fitting. Usually the diameter of the rose is largest at the ceiling surface; but if it is not, you will have to divide the tile in two, cut a semi-circle from each piece and fit the two pieces round the fitting. Cut tiles in the same way if the rose lies along the joint line of two or more tiles. Finishing If you want, you can finish off the edges with cove, using a recommended adhesive. Clean the tiles where necessary by wiping lightly with a cloth moistened with a mild detergent. Remember if you want to paint the tiles, use emulsion or a fire-retardant finish — don’t use gloss paint.