Wet room floor issues

[DoNotDisturb]

We had a downstairs wet room installed last year. They used a proforma base thing and small mosaic tiles to get the fall for the drainage. The proforma sits on one beam.

However the grout failed in some of the tiles last month - which they came and patched up. Now another area (which looked absolutely perfect a month ago) is starting to fail.

They are talking about patching it up again but surely this is a symptom of a bigger problem?

I said that the floor mustn't be solid enough and the movement is causing the issue but the builder is saying wet rooms always have non solid floors due to the proforma and that the grout is flexible...

Any ideas what it could be or what I should say? They've agreed to pull up the tiles in the area but I think they're just gonna re lay them which I'm not sure is a long term fix..

Bump

No one? Are you leaving me to the builders who look at me like I'm a crazy woman come on - give me some ammo!!

Wet rooms using proforma trays often fail due to incorrect preparation or installation.
Possible reasons include too much movement of the tray (insufficient support underneath beams & boarding has too much movement) , wrong preparation / insufficient cleaning of surfaces prior to tiling. Wrong/ cheap grout/additive for spacings/situation used. Cheap tray + heavy user - too much flexing.
Here is a tiler asking about the same kind of problems - various solutions suggested.

Wow thanks wonky. You are a guru. Not sure what I was googling but couldn't come up with anything as good as that... Come Monday morning I will be armed with my info. Not sure they'll be happy that I think the floor needs lifting and supporting.

Thanks wonky. Suitably armed with facts they've had up dig up the whole floor to fix the issue

is it a concrete floor or wood?

how did they prepare the floor?

how did you chose the firm that did it?

It's a big hole at the moment. There are three beams which they laid some kind of board on and then the foamy proforma. Then the waterproof membrane and then the tiles.

The problem (in my humble opinion) is that the beams are too wide apart and need braced and then supported from the ground. There's too much movement.

I picked the company as they were a big reputable company who described wet rooms as being part of their speciality. In all fairness they keep coming back to fix it so the big company bit has paid off..

Typically joists will be about seven inches deep and at eighteen inch centres. Ply board will be 18mm for ordinary floors, and 25mm if tiled. There should be noggins to support all joints in the board which go across joists. There should be no unsupported joints. If the boards are screwed down they can be retightened after laying.

Chipboard is a cheap and unsatisfactory flooring material.

There were no noggins. I'm arguing for lots this time. I don't think it was chipboard. It was thicker than that and I think specific for a wet room.

The lack of support I think has caused the grout to fail and the water has got through and the tiles have completely failed. However, what concerns me is that this board and the joints were completely soaked. How can that be when they had the waterproof membrane on top. Even if the tiles and grout failed surely the membrane should have held..!

chipboard is commonly available in 18mm and 25mm. It may have a green coating. It does not have the lines on the edge that ply has. You may be able to see the sawdust that it is made of, in cut edges. There are some special cementitous boards for floors that may get wet and are tiled, but I have not used them. I expect they will be grey and very hard.

If the board was wet then perhaps there was a leak that reduced the integrity of the floor. Some tile adhesive and grout is not waterproof, if you put a used tile in a bucket of water overnight the adhesive goes soft and you can scrape it off. But surely a wet room specialist would not make that mistake.

Thanks pigletjohn. They're back Monday to put it all right having dug up the whole floor. So we'll see..