The important thing about preparing walls for tiling is that they should be true and flat and that their surface should be good enough for tiles to stick permanently. That means that you will have to strip off any wallpaper, fill any depressions or holes with general purpose interior filler and remove flaking paint.
If you are tiling over an old tiled wall make sure that you check that the old tiles are firmly fixed. If you find any loose ones remove them carefully, clean off their backs and refix them with new adhesive. Use a tile cutter to score the surface of the old tiles to give a key for the adhesive. It’s a good idea with painted or stripped or plaster surfaces to give them a coat of stabilizing solution after sanding them down with coarse abrasive paper.
TIP: Test a painted wall by sticking long – lengths of sticky tape to four or five sections. Rub them down then pull them off quickly. If any paint comes off with the tape you will need to remove all the paint.
If the wall is in terrible condition when you have got back to a sound surface, you have the option of re-plastering or lining the wall with new plasterboard — or one of the manmade boards such as chipboard or block-board or ply. If you are using a timber board don’t use a thickness of less than 12mm for ceramic tiles — anything thinner will eventually sag and loosen the tiles.
In wet areas such as shower compartments, the best backing is waterproof ply or exterior grade ply. Don’t use chipboard or blockboard — they will swell if they get wet. Remember in wet situations that you must use waterproof adhesive and grout — not water resistant.
With the surface of the wall prepared, plan the pattern of the tiles. Start by making a measuring rod from a long batten. Mark it off in divisions of one tile not forgetting to allow for the thicknes’s of the grouting gap between each tile.
To mark the measuring rod accurately, lay a row of tiles on the floor, inserting spacer cards if they have no lugs or ire not universal tiles. Mark off the rod directly from the tiles.
The most common — and glaring — mistake some people make when they tile a wall is to start from the bottom against a skirting or edge of a bath. The chances are that neither are truly horizontal with the result that the subsequent rows of tiles lean off at an angle. The only way to guarantee a perfect arrangement of tiles is to start against a level batten.
Draw a line on the wall marking the top of the area you want to tile — this may be at the ceiling. Use the rod to measure down to the bottom — the floor or skirting board or the edge of a bath. The chances are that this will show you that you will have to use cut tiles in one row. This row should be at the bottom, but if you are tiling the complete height of a wall and discover that the ceiling is uneven or slopes at a slight angle, you may have to cut an additional row of tiles to fit. Whatever the case, always draw a level line at the top and measure down from it.
Mark the position of the bottom of the last row of full tiles using another line on the wall. Check that it is level and straight. Nail a batten the same length as the wall along this. This is the support for the first row.
Normally you will find the width of the wall doesn’t coincide with the module of the tiles either and you will have to run cut tiles up the sides as well. If you have internal angles at each end it looks best if you run a row of cut tiles up each side. Try to make them even on either side. If you have an external angle you should use full tiles at the corner and use cut tiles at the other end.
When you have decided about the positioning of cut tiles, mark off the fixed batten into tile wide divisions. Draw a line up the wall marking the last row of full tiles and fix another batten to the wall aligned on this vertical mark. Check that it is vertical with a spirit level and make sure that it is at right angles to the bottom horizontal batten. Once you have marked up and fixed the battens you are ready to start tiling.