Uneven plywood flooring over fitted kitchen

The problem is your builder has fixed the tiles direct to the 18 mm ply ,I would suggest you use a self leveling compound over the ply but you must prime the ply,then the slc should have be covered with an uncoupling matt in my opinion the best is Schluter ditra then tile onto this it would be a far better and quicker than screeding.

Seen this to many times before. Your first port of call should be the builder, if its been down only 9 months he should be putting it right. First the wooden joists should be fixed to the concrete, then the ply, should have be 22mm, 18mm should be ok but need to be screwed every 300mm. Prime the ply and use a self leveling compound suitable for ply to level the floor. The floor should not have any bounce in it if done properly. Then, as been said, use a uncoupling membrane, I only use Ditra-25. The floor is now ready to tile. The tiler should use a suitable adhesive for the chosen tile and the tile back should be 'back buttered' to improve the bond. This all should be able to be done without removing the kitchen, just the kick plinths and appliances. You will find the finished floor height will be about 4 to 5 mm higher than it is now if the same time thickness is used, so check there is still clearance under work tops if you have any free standing appliances.

I would not have a problem using 18mm ply as long as, like said before, it is securely fixed every 300mm. I would then prime both sides of ply with a neat SBR and then use a flexible tile adhesive or an Ardex glue to apply Ditra mat, and then tile on top of that. I would only level over the ply if the area is running that far out of flatness, rather than level, unless a completely level floor is wanting to be achieved, I would agree with the previous comment that you would not need to remove all the kitchen units to rectify the problem.

Hi There, The best option would be to carefully cut out the 18mm ply boards with a sonic cutter to the areas that are tiled and therefore leaving the kitchen in place. Tiling onto wooden ply sheets is always a risk and very good preparation is needed for it to be successful. In this instance i would recommend a floor sheeting product from Hardie Backer which is 22mm thick, is structurally tested for floors, fully water proof, will not flex, shrink or move once fitted. You will not need to self level and you can tile directly to the sheets with a rapid set flexible adhesive. Topps Tiles have just released a fibre adhesive product which is excellent for adding more strength to areas affected by movements and flexibility.