Laying new ceramic tiles over old ones

Hi all,

Looking for a little advice as we have had some problems laying new ceramic 30cm floor tiles over old, flat 10cm tiles.

Last Sunday, we ensured that the old floor was clean, grease-free and dry then used a pre-mixed DIY store brand tile adhesive. Trying to 'rough up' the tiles first with a hand-held sander didn't seem to do anything.

We had 4 days of wet, humid weather and there is little natural ventilation in the room we are trying to tile. A week later, the tile adhesive has not gone off at all and we have had to take the tiles up to start again.

Not sure whether the conditions in the weather and room are to blame or the product and / or technique?

We have now bought a powder mix recommended by our local builders' merchants that is meant to be slightly flexible once laid. They claimed that this shouldn't require any 'undercoat', PVA or other preparation before use. We have seen conflicting online advice on this point.

So, any comments or other advice welcome before we try this for a second time!

Thanks in advance


Sorry for the delay, things got away from me a bit...

The powder mix worked finally without any other changes to compensate for the surface below or the humidity conditions in the room.

We believe that it was just a case of needing to pay for a better quality product from a well known manufacturer rather than a DIY store own brand.

Have come across several false economies such as this one during the latest renovation - things like light fittings, plus sockets etc.

So are you going to tell us what you fixed 'em with?

Thanks to all for your replies.

Very pleased to report that the tiles are solidly fixed this morning!

Your two comments "it comes up off the floor completely" and "they are still moving (a bit) nearly 3 times longer than that" would indicate to me that its the substrate thats the problem.

Can you smash the tiles below, or remove them completely?

The product used last time was marked "colle revêtements de sol - carrelage intérieur". The powder mix is labelled as "mortier colle allegé pour carrelage".

The other problem that we are having is that when we use the toothed spreader to get the bedding level, half the time it comes up off the floor completely!

We have started with 8 tiles laid about 40 mins ago. The packaging says that tiles are only repositionable for 15 mins after laying but they are still moving (a bit) nearly 3 times longer than that

Hi Danielle, I would go with Davids suggestion, I am an ex-plasterer, not a tiler but I guess that whats happening is that because you are putting the adhesive onto a non-porous surface (old ceramic tiles) its not actually doing anything different to what its doing in the tub, there is no suction to draw out the moisture in the adhesive, other than of course the bottoms of the new tiles, I bet the adhesive is considerably dryer on the new tile side.

I may be wrong but my guess is that type of adhesive you are using combined with the ceramic surface of your old tiles is the problem.

Good luck, make sure that you get the right adhesive.

Most preparations for laying floor tiles are cementitious that is they are basically cement and a fine sand . They don't set by drying out they set like morter by converting into their original material lime. Are you sure that the tile "adhesive" is for floor tiles or carreaux and not for wall tiles "faience" the adhesive for faience is much more of a glue/adhesive than a bedding/cement compound that you use for floors.

We did it with a powder type, mix it up yourself, adhesive & 7 years on still no problems. They stuck like the proverbial to a blanket. Ours were 450 mm tiles laid on tiny 50 mm in what was a bar so they were filthy. we just cleaned up the old 'uns with soapy water & stuck down the new. No special preparations but it was done in good, warm weather. Good luck.