Slate tiles on screed floor with UFH - tiles not sticking

[dvinchik]

can anyone give as some advice.

We forgot to turn off UFH when starting the job , and the adhesive hasn't adherred to the tiles - it has adherred to the floor and is a real pain to get off the floor. We have now turned UFH off - does that sound a reason for it not adhering?

We're using a 10mm notched trowel and flexi adhesive. The tiles are honed green slate.

Can anyone give us any tips on pitfalls to avoid when embarking on this kind of tiling?

 

[Gazzer]

Did you clean residue from the slate betore fixing ?

 

[dvinchik]

thanks, ....no, didn't clean it 1st time round - have done this time tho...as did occur to us that might be a problem too...

 

[diamondtiling]

Leave the adhesive on the floor and just cover it with a self leveller (flexible), you should have brought your heating up to maximum slowly and then back down before tiling.

 

[dvinchik]

Leave the adhesive on the floor and just cover it with a self leveller (flexible), you should have brought your heating up to maximum slowly and then back down before tiling.

we've already scraped it all off now ... and not all the tiles were loose so adding anymore height to the adhesive would have meant the tiles would then be uneven.

Our heating has been on for a couple of years now, and we turned it off this morning. I'm guessing we then turn it up gradualyl again once we've finished tiling.

 

[Gazzer]

we've already scraped it all off now ... and not all the tiles were loose so adding anymore height to the adhesive would have meant the tiles would then be uneven.

Our heating has been on for a couple of years now, and we turned it off this morning. I'm guessing we then turn it up gradualyl again once we've finished tiling.

Yes but wait 2 weeks before turning it on to allow the adhesive and grout to fully set.

 

[dvinchik]

Yes but wait 2 weeks before turning it on to allow the adhesive and grout to fully set.

brrrrrr... it'll be a chilly couple of weeks for us then

 

[White Room]

Put a rug on the floor for the time being

 

[DHTiling]

Is the slate hand split or calibrated..?.. best to back skim to aid the adhesion..

 

[dvinchik]

Is the slate hand split or calibrated..?.. best to back skim to aid the adhesion..

they are calibrated, and again today some are not stuck despite the heating being turned off. We've wiped the back of the tiles to remove the dustyness on them - is there anythign we should be treating them with?

 

[dvinchik]

Did you clean residue from the slate betore fixing ?

We wiped them with a damp cloth - is there anything we should be using to remove the residue? We've woken this morning and already we are able to lift some off the adhesive - they've been down about 12 hours. Would you expect to be able to lift them?

 

[jay]

whats your adhesive i know you said flex but what exactly thanks

 

[dvinchik]

adhesive is stone fix s1 rapid/flex adhesive

Am dreading lifting all the tiles that laid yesterday and having to start all over again! The ones that are hollow we've lifted and there is condensation on the under side of the tiles - would you expect that? We've sealed the scredd with stone fix acrylic primer.

Any help will veyr gratefully be recieved

 

[jay]

right can you walk me through the whole thing starting with the ufh was done at least two years ago
when was the slate laid
how long was it down before probs
what type of sealer was used if any
was slate dry when laying
the slate is it slate or limestone

thanks

 

[dvinchik]

ufh heating was installed at same time as screed, it's a wet system, about 2 1/2 years ago. It's been in use since. Since then we've had a screed floor as the floorsurface in our kitchen, having a toddler has pushed us into getting slates down - lack of funds however has meant we're doing it ourselves rather than getting an expert in.
We started laying the slate at the beginning of the week.
1. cleaned floor, measured, checked levels, drew grid, worked out where to start etc
2. primed floor with acrylic primer diluted to right strength for screed floor.
3. put down bed of adhesive, combed and put tiles down.
4. 12 hours later checked to see if adherred and slates (rio verde brazilian honed 400x400x10 slates) lifted, some sounded hollow which was ones initially checked.
5. scraped up all adhesive off floor - it had adherred to floor ok.
6. tiles needed no cleaning as had not adherred.
7. turned off underfloor heating completely, as previously had just turned it down to 15deg.
8. next day, pt down bed of adhesive combed it, put down wiped (after suggestion that need to wipe off residue) tiles.
9. last tile down at 6pm, checked adhesion about half hour laid and tile came up with adhesive on it, re-laid that tile. At 8.30 am tapped tiles to check again and found a hollow one, tried to lift and it came away nearly clean. Adhesive attached to floor tho.
10. 9am rang adhesive manufacturers Stone Fix, who advised we were trying to lift them far too early as takes 28 days for it to fully cure, and a child could lift it after 12 hours.... doh!!!! but did advise we buttered them to help with adhesion, and to mix leave to settle for a couple of mins and then re-mix adhesive to maximise adhesive qualities.
5. will continue with rest of tiling, buttering and extra mizing and leave for at least a couple of days before checking adhesion again....