Tiles keep lifting!!!!

[drexall11]

Hi eveyone,
i'm putting big floor tiles on my bathroom floor, have screwed down plywood and using unibond flexi adhesive. But a few have not stuck and the grout we have used (brown to match tiles) is starting to crack . What are we doing wrong as this is starting to bug us , if anyone can help would be much appreciated. thanks

[ultimatehandyman]

How thick was the plywood?

Did you seal the plywood first?

[drexall11]

Hi, Thanks for you reply,
the ply is 12mm thick and we didnt pva ply as the instructions on adhesive said not to!!
Have we done something wrong?

[ultimatehandyman]

The ply wood is definately WBP ply isn't it?

[drexall11]

Hi, thanks for your reply .
We bought ply from wickes and dont think it is wbp!!!
do we need to treat the ply before relaying the tiles?

[ultimatehandyman]

I'm not 100% certain that the ply is the cause of them lifting, but it certainly will not be helping.


You might have to replace the plywood, or overboard it again with some WBP plywood.

Does it recommend any kind of primer at all on the adhesive instructions?

If it does, then you might get away with priming the plywood, but not with PVA of course.

[bathstyle]

What tiles are you fitting? (material)

I believe that your problem here is the adhesive.

Go for something like Bal rapidset flexible or Toppfix rapidset flexible (from topps tiles)

Grout with Bal superflex wide joint grout.

The sub floor should be screwed down before overboarding, overboarding Ply should be screwed at approx. 150mm centres

[drexall11]

hi,
the tiles are porcelain, had a look at primer and flexi additive today.
but unibond adisive that were using and flexi additive both say dont use primer!!!
so not sure what to do next?

[bathstyle]

See my post above, that would be my next step, it's been tried and tested for over 20 years