As with most jobs, proper preparation is the key to success and is
essential if you want to avoid even the possibility of having to do all
or part of it again! So, do your homework, prepare thoroughly and don’t
rush into anything until you’re sure you know exactly what your plan of
action is and how you’re going to carry it out. This applies just as
much, and possibly even more so, to tiling because the result will
reflect the quality and thoroughness of its preparation.
Here are some of the main things you need to consider before tackling that tiling job you’ve been putting off!
- Probably the most important thing is that the surfaces you’re going to tile should be as flat and even as possible; It doesn’t matter if they’re not smooth. Check with a straight-edge or plumb-bob. If your walls are too uneven, then they will need to be skimmed or even re-plastered if the undulations or unevenness in the wall are greater than the thickness of your tiles. Bonding or renovating plaster should be used. The British Standard for flatness is BS5850 and says that the maximum deviation should not exceed 3mm in 2 meters, although this can be quite difficult to achieve.
- Never correct excessive unevenness or undulations with tile adhesive and always follow the adhesive manufacturer’s instructions because a maximum depth of adhesive will often be stated.
TILING OVER TILES – If you plan to re-tile over existing tiles, remove any cracked or loose tiles and skim over where any are removed. The surface of the tiles should be scored to give a key for the adhesive. Clean and de-grease the tiles thoroughly.
- TILING ONTO NEW PLASTER, PLASTERBOARD, BREEZE OR CONCRETE BLOCK – These surfaces will need to be sealed before you tile, otherwise the moisture in the adhesive will be sucked out and it won’t stick your tiles properly. An acrylic primer is usually the best thing to use, although always check the adhesive manufacturer’s instructions because these will often state which sealant should be used.
- Although PVA (Polyvinyl Acetate) can be used, care should be taken. When you treat a surface with PVA it partly soaks in and partly sits on the surface of the substrate (wall surface), like, say, wallpaper paste. If PVA gets wet it becomes slightly ‘live’ again and although it doesn’t return completely to its liquid state, it does become sticky. When you spread tile adhesive onto the wall, the water in the adhesive makes the PVA ‘live’ and stops the adhesive from penetrating the substrate and gripping properly. This means that the tiles, grout and adhesive are being held to the wall by a thin layer of PVA. Most tile adhesives work by crystallising when they set. Once the adhesive starts to set, crystals form and expand into any imperfections in the substrate surface to create grip. PVA stops this process by creating a barrier between the substrate and the tile adhesive. Primers, however, soak right into the substrate and stop the sponge like “draw “effect but they don’t coat the surface, i.e. they are an impregnator and not a barrier. They also stop a chemical reaction occurring between the cement based adhesive and plaster substrate.