advice on tiling a bathroom floor

**effery** · 30-03-2011

hi,
Hope you can help.
I had tiles down in the bathroom for about 2 years and the grout cracked and some of the tiles became loose.
having tken up these tiles the builder who layed the ply floor didnt screw it down to the joists, hence the issues I have now.

my question is, I am now left we a ply floor that I have screwed down covered in the old tile adhesive.
Do I need to remove this adhesive before I can do anything, and if so what is the best method.
or can I lay new tiles over the original adhesive,
or can I self level the adhesive to get rid of the ridges and then lay lino. / lay tiles

thanks in advance.

**Stewart** · 30-03-2011

Firstly.... How thick is the ply....?

**effery** · 30-03-2011

I think its 21mm marine ply.

**JRCCR** · 30-03-2011

You could try and remove old adhesive, then if needed self level or replace the ply with new board.

**akinsontiles** · 30-03-2011

You've got a couple of choices like you mentioned. Self levelling over the ply would work but make certain that it has latex mixed into it to provide flexibility and prevent de-bonding. Also if this is an upstairs room I would recommend that you check for cracks and possible leaks as the leveller going onto ceiling below would be a nightmare.

The adhesive may scrape off the ply with a kango breaker or hammer and bolster giving a smooth surface to tile onto.

You will make the job twice as hard as it need be by tiling direct onto old adhesive but if its set solid it shouldn't compromise the bond as adhesive to adhesive will bond.

You must make sure that the ply used is of a suitable grade and thickness to give you the stiffness required over the joists. 12mm for ceramics and 15mm (18mm is closest readily available) for natural stone or porcelains(especially large format). I would recommend that screw fixings are used every 150mm over the whole board to reduce movement.

You could look into debonding membranes over-laid on top of ply once it is fitted properly to further give you the assurance that this won't happen again.

**effery** · 30-03-2011

could you recommend a self levelling product as I think this would be the easiest route to take.

**Aspect Tiling** · 30-03-2011

Another option is to remove old adhesive. Make sure ply is secure with no deflection. Lay 6mm cement board, glued and screwed. Then fix your tiles. This option gives you an ideal substrate to tile to for a long lasting installation.

**akinsontiles** · 30-03-2011

I would be tempted to go witht the fibre plan for this one if it is up stairs as it shouldn't run through to the ceiling below if there are any small holes. Large cracks would need to be filled though first.

So long as it is flexible (has latex in it or added) it will bond to the ply but may need to be primed first.

Check out Mapei's webpage on levellers suited products

regards

Paul

**Rich** · 30-03-2011

Is the ply damaged at all? If there is any sign of damp I would remove the ply all together, replace and then over board with 6mm cement boards.

I wasnt aware that 12mm ply was recommended if you are using ceramics??
Min 18mm BWP for any type of tile to be safe either way.

If this is not an option then have a look at the link atkinson tiles has put up, Mapei is really good stuff