Plyboard on top of old adhesive

**cm0264** · 28-06-2010

Folks - I am a handyman so not an accomplished tiler. A customer has lifted her bathroom tiles but has had problems removing all of the old adhesive from a chipbpoard floor. It is patchy and the majority of the old adhesive is still in place. She says she will have a go removing the rest but I doubt if she will be competely successful.

My question is can I put 6mm plyboard on top of the uneven old adhesive or is this not on. My guess is that it would be fairly stable when nailed on what do you think?

**diamondtiling** · 28-06-2010

6mm ply and nailed is a definate recipe for disaster. You need to be thinking along the lines of 18mm if there is no deflection in the floor. Take up the chipboard and add extra strength with noggins, I would also use 6mm no more ply on top.

**SandyFloor** · 28-06-2010

Yep....fully agree with Diamond. Whatever you do, don't put 6mm on top of old adhesive. I could almost gaurantee that will fail. I wouldn't even do that for Karndean.

**timeless john** · 28-06-2010

The answer is 'fairly stable' is not stable enough!
Any deflection/movement in the chipboard floor (which is moisture sensitive) would transfer through to the tiles.

**Scott** · 28-06-2010

If you do decide to overboard with ply, personally id use 15mm minimum but that depends on the level of deflection if any. Which ever you use it HAS to be screwed down at least every 300mm centres, id do mine at 200mm centres.