tiling over old tiles!

[Joystick]

Usual story, take old tiles off to find original tiles underneath!

I tile about 8 / 10 bathrooms / wetrooms a year but i have never tilled over old tiles!! I always remove and skim / TBB before tiling. In this case, there is no other option other than tile over the original tiles! Long story but that is the fact!

While taking the top tiles off and adhesive off, I noticed that it appeared that the original tiles had been painted with a thick PVA solution before that top tiling job was done.

My question is:

what prep to do on the old tiles? I will probably be using weber waterproof tile adhesive but as i said, I have never tiled over old tiles before!

Pro help appreciated!

 

[tpt]

its probably a slurry coat of something like pva and cement or acrylic and cement. it'll be to aid adhesion to existing tiles.

whilst using a slurry coat is good it doesnt help if the old tiles come off the wall. tiling on tile does work (yes i know some pros hate doing it) but its becoming less practical these days as tile sizes and weights get bigger.

if the old tiles are solid, and your using small tiles then you may get away with it, check with the addy manufacturer to see what they suggest, most push for an acrylic\cement slurry coat to be applied and left to dry.

if the new tiles are large, thick things then dont do it

 

[Karis]

Unless there is no real option I would never advise tile on tile, it’s a bit of a bodge really! It is, however, possible but on walls you will also have to consider the weight of the new tiles + the weight that is already on there. If it’s plaster under the tiles, it has a max weight limit of 20 kg/sqm including addy/grout & this could be a problem with the combined weight, even more so if the new tiles are large format which can easily exceed the weight limit on their own.

Standard PVA is not suitable as a tile primer, it can give adhesion problems & remains water soluble, if used in a wet area it can re-emulsify & your tiles could end up on the floor. Hopefully what you have is a previous bonding primer but if it is PVA (test with water), I’d advise you get it off, then prime with an SBR primer/cement slurry mix or a proprietary bonding primer and fix the new tiles with a Rapidset addy.

You may have problems with initial adhesion & need to support the tiles till the adhesive “grabs” which will make the whole job rather time consuming.