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How to tile a mixed suspended and concrete floor
I have a kitchen floor which is just over half suspended and half concrete, over which a layer of 12mm marine ply was put in order to prepare the room for a tiled floor. The ply was screwed to the existing floorboards and it looks like an attempt was made to stick it to the concrete using some sort of adhesive. As the tiling would not be required under the units, the kitchen was subsequently fitted with cabinet feet at max extension and it's only since then that it's become clear that the ply over the concrete is not at all fixed to the concrete and has to be pulled up. Not that it helps a lot, but the concrete end has far fewer fitted units on it.
I feel that the ply needs to simply come up from the concrete and that tiles should be laid directly onto it, and I now wonder if we should have removed the floor boards, added extra battens/noggins and put marine ply in their place in order to have a level wood and concrete base for the tiles. This would have had an added advantage of the floor height only going up by the thickness of the tiles (plus any matting or whatever) rather than by the tiles plus the ply.
With the mixed flooring I've also read about the need for something where they meet to avoid cracked grouting and/or tiles caused by movement.
Any advice gratefully received.
Could you not screw and plug the plywood to the concrete floor-or use frame fixings?
If you still want to take the plywood up, i would just use super flexible tile adhesive, this allows for quite a bit of flexibility and you shouldnt have a problem with it being over two different floor types. However the whole floor space may need a watered down pva mixture to allow the adhesive across the two floor types to allow drying at the same speed and ensure a good adhesion.
In writing this i am assuming the floor is ok to tile straight onto and that the floor boards are in good condition, also the gap between the two different floors is tight. Self leveling compound could be used to get the concrete flat for tiling.
Answered 5th Jan 2012