Tiling over chipboard floor

[Paul Giverin]

I'm just about to tile my bathroom floor. I'm going to be using fairly large tiles (408x408mm) and I'm conscious of the risk of the tiles cracking if there is any flexing of the chipboard.

I was planning to use a plastic substrate matting that the guy in the tiling shop recommended but the other day I had the plasterer in to do some work in the bathroom and he reckoned I'd be better off gluing and screwing sheets of 12mm plywood to the chipboard and laying the tiles on top with a flexible adhesive. I must admit it sounds like good advice although I'm a bit worried about raising the height of the floor too much.

Any advice appreciated.

[noelogara]

chipboard on the floor of a bathroom is dodgy at the best of times because a leaking joint will go unnoticed until the bath falls through the soggy chipboard. tiling is short term cover. the chipboard just soaks up water and if you cover it, it will never dry but rot more.

[Paul Giverin]

In message , [e-mail] writes

The entire first floor is chipboard. Its been like that since it was built 20 years ago. I believe its pretty much standard these days. I don't have any problems with leaky joints and I'm not covering up any damp chipboard. The floor will be waterproof once it is tiled.

[JoeJoe]

Tiled floors of kitchen, utility room and two bathrooms - all had chipboard floors, and I nailed 6mm ply on top (nail every 10cm or so, and make sure there is no movement in the chipboard first. I know that most experts here recommend 12 or 18mm ply, but this was done on the advice of a very good friend who does this for a living (self employed). According to him he had done this for nearly ten years and has yet to be asked back to a job (and I fully trust him). Just make sure you use Wide Gap Flexible Adhesive (Topps Tiles do them and I am sure many others).

Hope this helps.

[Mike Dodd]

Conversely, I didn't use any ply, in a 1st floor bathroom / chipboard floor. 2 days later it all came up to be replaced with spare laminate I had in the attic.

[The Natural Philosopher]

Got chipboard in all upstairs bathrooms. Tiled direct. No probs with a THICK bed of flexible cement. Unless yu have a long term leak and non waterproof grout.

Doesn;t destroy the chip, but it swells enough to crack the tiles off.