Floating Floor

[TREKKY]

Just been to look at a conservatory, it was built a year ago and the customer says the installers said it has a floating floor. Which as far as I can see is 18mm T&G Weyroc over some sort of polystyrene sheet (about 25mm thick) over concrete. None of which seem to be fixed to the other, just laid one on top of the other with the T&G joints glued. All of the joints stand up by about 7 or 8mm which suggests that either they have swelled or the boards have sagged in the middle into the polystyrene underlay either way it is very wavy (as far as I can see there are no joists under the flooring the whole lot just sits on whatever concrete was laid). The main part of the floor seems reasonably stable but some of the boards do move when walked on and in addition there are several places around the edge where the floor flexes downwards by up to 10 to 20 mm when you stand on it. The customer wants 300X200 porcelain tiles laid on it. Would 12mm ply screwed and glued hold this together without the tiles and or grout breaking up ? Personally I think it wants ripping up and starting again, with new joists to support a 25mm floor. Any ideas would be welcome.

 

[Concept PHT]

To be fair, the polystyrene should be under the concrete with the wooden floor on top of that (obvioulsy with underlay).

My advice is to rip up the T&G boards and drop a screed on top of the polystyrene. Then use flexi materials to finish the job off.

Another option is to take the polystyrene with it too and then re lay it with insulating board and tile as above without the screed. Depends on how high / low the floor will be.

Either way, its going to cost the customer a fair bit to have the job done right

 

[CON5933]

Without seeing it I'd say they've put that down instead of a screed on top of the concrete..
treat it as an unsuitable tiling surface... it could come back to haunt you.
If they've cut corners on that...is there a damp proof membrane under there? you could end up with a call back cos your tiles have gone walkabout around the conservatory.