Slate Floor onto ply

[Sammy85]

Hi

We're coming to the final stages of our build, externals were done by builder and internals have been DIY except for plastering.

Im now looking to lay a slate floor in an opus pattern in our kitchen and would really appreciate some advice on the best course of action.

We have underfloor heating set in screed, with ply over. The ply is nailed and screwed down as best as we can into the batons that are between the areas of screed, but the ply has some flex in it in places and we cant screw down any more than it already is as we may hit the pipes under it. The units etc are all in, so lifting boards to glue down wont be easy and we were told when the ply was laid that gluing probably wouldnt work as the screed is a sandy mixture.

I should say that ive had two tilers round to look at the job as i felt at little out of my depth on this job - one has said he can do it no problem. The other said he didnt want the job, that slate would stick but the grout would probably crack with the movement. I have to say i dont think the movement under foot is as bad as he made out and i would have expected the weight of the slate to dampen the movement a little, but im no expert (hense why im here looking for some advice).

Any advise on what we need to do prep wise and what adhesives and grout would be best are greatly appreciated.

Im still thinking this needs a professional but im now concerned about making sure any tiler that does take on the job does it right and that i know what should be being done.

Thankyou in advance.
Sam

 

[Gazzer]

Not a job I would take on.

 

[Time's Ran Out]

Don't understand the logic of having plywood over the screed and nailed into battens between pipes:yikes:

Not one I'd consider in the present preparation. The 2nd tiler may have just done you a favour - sometimes you have to walk away from work.
Options:
Take the ply up, re screed and fix direct.
Take the ply up, fix Wedi board to original screed and fix direct.

Good luck.

 

[kilty55]

hi there,personally i wouldnt touch it

if you can see flex in the ply floor then it will have a risk attached that it will fail,also why nail and screw ply over the top of a screeded floor with batons whos advice have you taken on this

 

[Sammy85]

The screed is a dry mix. Batons with insulation board between, UFH pipes on that then 25mm dry mix on top. Its a heat diffuser and has no structural strength, therefore we were told to board over with 12mm ply, then finish up with our chosen flooring (they knew we were going for slate tiles).

Its only when we've got to the point of having all finished but the floor that its come to light that there is too much flex. :-(

 

[Gazzer]

12mm is too thin anyway. 15mm is BS and in real life its 18mm due to availability. If there is any flex the slate will crack at some point.

 

[Ian]

Crikey, the ply is 12mm, if it had been 25mm you might have stood a chance. Sorry to hear of this predicament, the only way to do a proper job that will last, is to get back down to the screed and start again.

 

[flaggy]

no thanks for me ,,,,,sorry

 

[andyb1]

can see it all ending in tears, who gave you that advice to start with!:mad2:

 

[Sammy85]

Thankyou to everyone who has taken the time to reply.

I know the situation is far from ideal (understatement) but we are now at a point where we're stuck with what we have. The kitchen is fully installed and there is no way we can the ply up.

Theoretically - IF we managed to screw the boards down more and removed much of the flex, what prep would we need to do to the ply before tiling and what adhesives and grouts are recommended, im assuming flex ones, but does anyone recommend a specific brand?

I understand that none of you would recommend going on with the tiling, but right now I dont see any way of going forward but to make the best job of the ply we can and then give the tiling a shot.

 

[Martyn Leeds]

Vinyl or laminate for me.
Might not be as good as the slate you want - but at least you won't be ripping it all up again in six months time