Laying large limestone tiles over UFH

[Schoolrunmum]

Hello all,
We had a wet self levelling screed floor pumped into our kitchen back in October. UF Heating has been running well since. Just ordered 900x600 limestone tiles and need advice on prep before laying them. We have been told various things, conflicting too. Do I need to seal/prime the floor? Do I need a decoupling membrane? Do I use a fast or slow drying adhesive? Do I use a flexi adhesive?
Thanks in advance!

 

[Ajax123]

I assume when you say pumped self levelling screed you mean something like Gypsol. If so...

Turn off the underfloor heating for 48 hours and carry out moisture test to make sure its dry. sand and vac the floor to remove any loose friable laitance or other contamination. Prime it using an acrylic primer and stick an uncoupling membrane down using a gypsum based adhesive. then stick your tiles to this using a flexible adhesive suitable for the application and grout with a flexible grout. clean off and seal tiles once adhesive and grout are fully dried.

the gypsum adhesive is a medium rapid setting with a pot life perhaps 40 minutes to 1 hour. on top of the uncoupling membrane rapid set or standard set is largely a matter of personal choice.

 

[Schoolrunmum]

I assume when you say pumped self levelling screed you mean something like Gypsol. If so...

Turn off the underfloor heating for 48 hours and carry out moisture test to make sure its dry. sand and vac the floor to remove any loose friable laitance or other contamination. Prime it using an acrylic primer and stick an uncoupling membrane down using a gypsum based adhesive. then stick your tiles to this using a flexible adhesive suitable for the application and grout with a flexible grout. clean off and seal tiles once adhesive and grout are fully dried.

the gypsum adhesive is a medium rapid setting with a pot life perhaps 40 minutes to 1 hour. on top of the uncoupling membrane rapid set or standard set is largely a matter of personal choice.

The guys that laid it tell me its TS40 by Gypsol, if that helps..oh, and the tiles are being delivered tomorrow, but will have to stay outside till we lay them. Snow forecast here tomorrow, is cold likely to crack them or anything?? Also, can anyone recommend an acrylic primer?

 

[Time's Ran Out]

Use a primer recommended to go with your adhesive.
Outside fine - keep off floor and covered.

 

[Schoolrunmum]

Its appears Gypsol don't make a TS 40 ! Apparently, it's Gypsol Classic...

 

[Time's Ran Out]

You are getting the limestone laid professionally?

 

[Ajax123]

The guys that laid it tell me its TS40 by Gypsol, if that helps..oh, and the tiles are being delivered tomorrow, but will have to stay outside till we lay them. Snow forecast here tomorrow, is cold likely to crack them or anything?? Also, can anyone recommend an acrylic primer?

that's interesting as TS40 is not a mix. there is TS20 and TS15 but no TS40??? how deep is it? is it on insulation?? Who Laid it??

 

[Schoolrunmum]

that's interesting as TS40 is not a mix. there is TS20 and TS15 but no TS40??? how deep is it? is it on insulation?? Who Laid it??

Hi Alan, apparently it's Classic...laid by Southern Screed..it's 50mm on Kingspan 80mm approx with wet UFH x

 

[widler]

If you can get tilemaster use there matting along with anylfix to fit it and depending on the colour of limestone use either grey or white s1 tilemaster addy .
Id personally use standard set to fix the tiles .
Screed need sanding , vacing and priming using tm primer (if you can get it, if not use which ever addy you can get hold of)

 

[widler]

Are you doing it yourself in between the school run or is a tiler fixing the stone

 

[Schoolrunmum]

I'll have a go at most things, but we have so many jobs to do we are getting a tiler in, but we have had 2 quotes, and both advised different things....

 

[Time's Ran Out]

Tell us what was advised for an opinion.
Have they been recommended and have you seen their work .

 

[Ajax123]

Hi Alan, apparently it's Classic...laid by Southern Screed..it's 50mm on Kingspan 80mm approx with wet UFH x

that's fine. I know they don't make a TS40 cos I work there... Classic is just the normal all purpose screed so treat as per advice above.

 

[Schoolrunmum]

that's fine. I know they don't make a TS40 cos I work there... Classic is just the normal all purpose screed so treat as per advice above.

Thanks all, we have been told variously to use fast drying adhesive, then slow drying, flexi and non flexi, and a decoupler...confuzzled!

 

[widler]

Go with the one who says flex and decoupler.make sure they sand ,vac and prime though , gotta be done on anyldrite

 

[Ajax123]

with ufh it must be flexi as you will get differential thermal expansion and contraction and uncoupling is a specific recomendation of the british stone federation. i agree with widler... go with the one who says flexi and uncoupling as he at least sounds like he knows what he is talking about. slow or standard set means you would not be able to traffic the tiles or grout them for at least 24 hours. i dont do much tiling myself and then only for myself but even so i prefer rapid set

 

[Schoolrunmum]

with ufh it must be flexi as you will get differential thermal expansion and contraction and uncoupling is a specific recomendation of the british stone federation. i agree with widler... go with the one who says flexi and uncoupling as he at least sounds like he knows what he is talking about. slow or standard set means you would not be able to traffic the tiles or grout them for at least 24 hours. i dont do much tiling myself and then only for myself but even so i prefer rapid set

Thank you all for the input-last question, I have been told I need to seal floor with a polymer primer...can anyone recommend one? A google search comes up with a Wickes own brand one- wickes Primer and Admixture, a copolymer based on n-butyl acrylate and styrene, and a BAL APD acrylic primer. Are either of these suitable?

 

[widler]

Which ever adhesive you are using use the same make primer , so if you are using bal use the bal primer