Hi, I want to tile (using mosaic glass tiles) on top of old ceramic tiles. What kind of adhesive will be best? Would you recommend that I try and provide a 'key' on the old ones (by sanding or something like that)? I'd be grateful for any tips.

mapei kerabond T mixed with with the liquid additive would be a good choice for glass over ceramic,i dint advise tile on tile but if you are going that route thats the adhesive id choose

Thanks. Can I buy this in the usual diy chains? Also what do you think about making the surface better by sanding it a bit? No alternative to tiling over - have tried to remove old tiles, but they are on thin board (plaster board, but very thin) and removel leaves great big holes in the wall.

Thanks again for your advice.

how thin is this plasterboard is it 9 mmm?

you would be better just ripping the lot out and re boarding,plasterboard isnt expensive

If your old tiles are not flat neither will your mosaics be...