40m2 cracked tiles laid on 18mm WBP - wet underfloor heating

[amuiphoto]

Hi All,

My kitchen extension was completed around a year and a half ago and has developed a major problem with the 600x600x15mm basalt (volcanic natural stone) tiles. The tiles are laid on 18mm WBP ply using Mapei Keraquick adhesive and there is NO ditra matting.
There is wet underfloor heating throughout, and the problem which has arisen is that the tiles on the ply joints have cracked which means you can see the outline of all of the 2400x1200 ply boards.
The builder isnt interested in fixing it as no decoupling layer was specified by the architect. The architect blames the builder for not switching on the underfloor heating before tiling and allowing the boards to dry out. Hence I'm left with this rather expensive problem.
My question is, should i remove only the cracked tiles, attempt to remove the adhesive and replace the cracked tiles? Or remove the whole lot and re-tile the whole area? Bearing in mind I have a flush finish with the sliding glass doors and the outside decking so if I relaid the whole floor and used 15mm tiles plus Ditra and didn't remove all of the adhesive I'd finish up high with the sliding doors and the decking.
If I did replace only the broken tiles which are in view, ie the cheaper option are there any adhesives I can use which will allow an amount of flex, for example a latex based adhesive?
Any suggestions would be greatly appreciated!
Cheers
Angus.

 

[iwaters]

Surley it is not upto the archtiect to specify a decoupling layer. That should be the call of the person who laid the tile.

There could be any number of issues. If the back and edges of the plywood wasn't sealed when laid it could be absorbing mositure and expanding. The edges of the plywood may be butted together with no expansion gap and so might be expanding and buckling. The might not be enough support at the plywood edges (were noggins added between the joists?). Its possible that there is just to much movement in the floor.

Lastly a de-coupling membrance should have been used.

Whatever the actual cause is whoever laid the tiles is responsible and should fix it. I think the only way you are going to get a proper result is to re-tile the lot. Trying to remove flexible adhesive from plywood is a ngihtmare of a job.

I don't think any flexible adhesive is going to be able to cope with the amoutn of movement.