i wish to use 20cm square thin white glazed ceramic tiles on top of existing glazed tiles. this is on the walls round the bath, over which there is already a shower. the easiest option seems to be using the ready mixed tub of adhesive which also doubles as grout from unibond. will this stick to the underneath tiles ok? will the grout be ok for the shower area or should i use cement based seperate adhesive and grout? most of the wall is already tiled where the old shower cubicle was so i don't have time to hack everything off and render the walls so i just want to tile the bit further out than where the shower cubicle used to be . the existing tiles are on top of old tiles. thanks

bureau you must be crazy to tile over tiles that are already tiled over......disaster waiting to happen IMO

As above, I would say don't tile on top of tiles. Most of all don't use ready mixed addy and grout use cement based.

if you take the old tiles off you don't have to render the wall you could dot and dab plasterboard then tank (waterproof) the plasterboard before tiling

I'm only tiling over one layer of tiles round the edges to extend the existing tiles which are tiled over the same layer of tiles and have been fine and sound for years. i remember seeing on the bal Dvd from topps tiles that it was ok to tile over existing tiles if they were sound. i will give the ready mixed a miss though based on your advice. i have half a bag and bottle of bal fastflex left over from a couple of years ago. it's been in tupperware and is still powdery so should be ok? do i need to prime the underneath glossy tiles with anything? i know a pro would rip everything out and start from scratch here but it's not possible for me to do without creating a massive extra work and cost or to do it before the residents get back in a few days hence the plan to patch it.

what would happen if you tiled on tile, and you then found out that the original tiles were not sound and proceeded to fall off the walls and on to your residents?

NO remove . retile. its the only way. if someone was hurt by tiled falling off . it would be the tiler held to account for this problem!!

I too would re-tile properly.

I'd also give BAL a call to see what the shelf life of that batch of fastflex you have is, because although it may look fine, it's one of their adhesives that's more chemically and you could find a dodgy reaction of something has gone off in the bottle or the bag.

In general, you are safe tiling over tiles once, providing the total weight isn't more than what the substrate can take. In many cases it is too heavy for skimmed plaster, and bigger tiles always go over the weight of even the stronger plasterboard substrate.

Originally Posted by paul flight

NO remove . retile. its the only way. if someone was hurt by tiled falling off . it would be the tiler held to account for this problem!!

But its not a tiler who's doing it!
The advice is - take all existing tiles off.

Originally Posted by bureaucrazy

I'm only tiling over one layer of tiles round the edges to extend the existing tiles which are tiled over the same layer of tiles and have been fine and sound for years. i remember seeing on the bal Dvd from topps tiles that it was ok to tile over existing tiles if they were sound. i will give the ready mixed a miss though based on your advice. i have half a bag and bottle of bal fastflex left over from a couple of years ago. it's been in tupperware and is still powdery so should be ok? do i need to prime the underneath glossy tiles with anything? i know a pro would rip everything out and start from scratch here but it's not possible for me to do without creating a massive extra work and cost or to do it before the residents get back in a few days hence the plan to patch it.

Whatever you do, don't use this....it will be off and won't set. Is this a wind up?

The shelf life of fast flex is 12 months....bin it

As above, tile on tile not a good idea.

Take em all off, sort walls out.
Use tanking system and do it properly.
Do not try and save yourself a few quid taking shortcuts.
DO NOT USE READY MIX ADHESIVE / GROUT, IT IS RUBBISH