Whichever type of ceiling tile is to be fitted, setting out is the most important factor and, as with ceramic wall tiles, the object of the exercise is to have cut tiles of equal width all round the perimeter of the ceiling.
Polystyrene tiles
With polystyrene tiles, begin tiling at the centre of the ceiling. The first job is to find the centre point by linking opposite corners of the walls with string lines. The intersection marks the centre of the room. Obviously, an allowance has to be made for non-rectangular rooms. Next, estimate how many whole tiles will fit in each row across the ceiling; if the border is ridiculously narrow, better results will be achieved either by fitting coving round the edge of the room to hide the gap, or if this is impossible, by fixing one tile over the centre point instead of four abutting it.
To stick the tiles in place, coat the backs completely with adhesive, and then simply press them into position. They should not be stuck up with blobs of adhesive on the backs as this could increase the flame spread hazard. Once all the whole tiles are in place, work round the perimeter of the room cutting and fitting the border pieces. A polystyrene tiled ceiling can be painted with emulsion paint, but gloss, or any other oil-based paint, must never be used.
Fibre tiles
When using tongued-and-grooved fibre tiles, either stick them to the ceiling with panel adhesive (usually used for fixing panels of wallboard to walls) or staple them into place. In either case, start fixing the tiles in one corner of the room, rather than at the centre, so that the interlocking edges can be assembled correctly. This means that the width of the border tiles must be worked out and the ceiling marked exactly where the first row of full tiles comes.
When stapling the tiles, first pin slim sawn softwood battens to the ceiling at right-angles to the joists to provide fixing grounds for the staples they will not hold in plaster or plasterboard. To do this determine the joist spacing, and mark the ceiling at each joist position. Pin up the first two battens at right-angles to the joists, spaced at just the right distance to allow staples to be driven through the tongues of the tiles into the battens. Fix the first row of tiles to the battens with the grooved edges towards the corner of the room, driving the staples through the exposed tongues. Then cover the tongue of one tile with the groove of the next, and so on, to give a secret fixing. With one row completed, add the next row of battens, fix the next row of tiles and carry on in this fashion until all but the last two sides of border tiles are in position.
Cut border pieces and slip them into position before stapling through them into the battens. Finish oil” the ceiling by pinning quadrant beading all round the perimeter, driving the nails into the battens.
Illuminated ceilings
These come complete with detailed fixing instructions, but the basic principle is the same in all cases. First draw a true horizontal line round the room at the level where the illuminated ceiling is to be installed. Then fix the wall support battens along this line, using masonry nails.
Next, install the required number of fluorescent fittings on the existing ceiling. Cut the T-shapcd support battens to length and rest them in place across the room, from one wall batten to the one on the opposite wall. Finally, drop the ceiling panels into place.
Cornice and coving
This is simply stuck into place using the appropriate type of adhesive. Where pre-formed corners are available, fix these first, and then add full and cut lengths of the cornice or coving to complete each wall. Where mitres have to be cut, fix full lengths from each corner out towards the centre of the wall, and then fill in with butt-jointed lengths to complete the run.
