How do I prepare a mixed floor for ceramic tiles?

catt_2

I want to have ceramic floor tiles in my kitchen diner.

The diner has a concrete floor and the kitchen is part tiles on concrete and part wooden floorboards. The levels are very slightly different.

The levels could be made equal by liquid screed but my builder is also suggesting laying plywood boards on top of the lot and screwing them down firmly to prevent movement to the proposed new floor because there are floorboards.

The tiles I want are 8mm thick and ply would be 18mm so my new floor would have a step down of about 30mm to my hallway.

I'd rather have it flat. Could the floorboards in the kitchen just be taken up and replaced with the plywood boards? That would keep much the same level.

Would appreciate any advice on this. The tiles I've chosen are 300mm square.

Bungarm2001

My OH always puts 18mm (minimum) ply over floorboards to stabilise the floor before laying ceramic tile. Any thinner and there is a risk that the tiles will eventually crack or lift due to the flexing of the floor, even if you use flexi tile adhesive.

If you replaced the existing floorboards with the 18mm ply only, you will still get movement/flexing, so as far as my OH is concerned, it's not a good idea. You need the thickness of the boards plus the thickness of the ply for maximum stability.

We did much the same thing in one house..levelled the concrete part then plyed the whole thing. We ended up with a step also. Can't actually remember what we did to minimise it though...:o

weekendwarrior

You can do as you suggest, but really you need to use 25mm WBP plywood- see here- http://www.ultimatehandyman.co.uk/tiling/tiling_wooden_floors.htm

If you specify 18mm and then the builder does the job and the tiles start to lift he will blame you because you specified it.

catt_2

Thank you both. You have been very helpful.