The Natural Philosopher wrote:
Sadly wrote:
gaffar wrote:
Apologies, slightly long post.

Recently had a new bathroom as part of new extension, floor is green
backed chipboard, which was then tiled over. A week ago I was in there
and heard a loud crack, 1 tile had cracked, over the course of the next
couple of days 3 others the same.

If its a cheap shoddily built contract laid floor, you have a
problem. You may take a chance, bit you may decide to rip it up and lay
e.g. ply instead in LARGE sheest - or even a single sheet...or do the floor
properly in chip GLUED together.

Or plywoood over standard floorboards.

- now the tiles Use substantial floor grade tiles Not 4mm thick. 6-8mm thick.!!"

Good god yes, use as thick a tile as you can get away with. Mine are
about 8-9mm.
My floor has started to move ever so slightly under the tile recently,
as I wasn't generous enough with the flexible adhesive. The ply is
fixed very securely to the subfloor though, and the tiles aren't
showing any sign of breaking yet. They're also very large, which is
helping spread the load.

- now the cement..at least 6mm of flexible cement is mandatory to absorb
any slight movement. That at least is likely to mean cracking grout only,
not cracking tiles. Try and arrange it so lines in the underlying floor do
not lie along grout lines.

I've used wood floor tiling adhesive. Be generous !

So get your substrate right, and don't skimp on the tiles and cement, and
make sure you have no leaks and you will have success.

Check.

Cheers

Paul.