A reader's General Construction question: Loose ceramic tiles?

Vicky J.   from   Manchester, UK   had this Loose ceramic tiles question.

Bill's answer

Hi Vicky, Tile adhesive takes an hour or so to firm up, and say overnight to get strong enough for the tiles to hold really firm. If they are easily dislodged the day after then you have got something wrong.

• When you say that he painted the plastered walls, I am hoping that he used a proper waterproofing compound, and it is bonded to the plaster OK.
• If he used ordinary paint then that may be the problem.
• On the same thing, I always like to use the same company's products on a particular job. Just to make sure that they are compatible. So if I am using Mapei waterproofing then I use Mapei tile adhesive.
• If he is using a mixture of sand and cement like we used to use in Bolton when I were a lad, then he shouldn't. Cement mortar relies on soaking into and bonding to a porous surface, the plaster.
• In your case the paint is stopping the bond.
• All modern tile adhesives, even the cement based ones have polymer additives that help them to stick to almost anything. (If the tiler is a bit messy and some adhesive is left on the face of a tile, then after a few days it is very hard to shift, and that's to a glass like surface).
• If he is using a modern tile adhesive and some of the tiles are coming loose, then he must be trying to spread too much on the wall at a time. A pro can spread a large area of wall and fix the tiles quickly. The rest of us have to be cautious.
• What happens is that if he is slow placing the tiles the unused adhesive takes on a skin (it starts drying) and that skin stops the bond. So if you spread to much and you can feel a skin, scrape it off and dump it. Don't be tempted to risk it. Mix fresh.
• He has to pull off the bad tiles and refix them, not mixing too much at once and not spreading too big an area that he can't tile quickly.
• Don't do anything that will help the adhesive to skin over quicker than normal. Say having a fan blowing into the room if it is hot weather.
• To find the areas that are not solid, just tap the face of the tiles lightly with something hard, say the handle of a screwdriver.
• The difference between the good ones and the bad ones will be easy to hear. You get a hollow sound from the bad ones. We say that they are "drummy".