Advice on limestone floor installation

[Pete.c]

Hi, I am about to start laying a limestone floor, approx area of 80sq mtr. The stone is Sinai pearl antique 600x600 from mrs stone.
It will be layed on a larfarge gyvlon screed 60mm thick with wet ufh, this was poured 7 weeks ago, the heating was commissioned 3weeks ago and gradually bought up to full operating temp, then slowly turned down.
Floor has been sanded to remove laitances.
I was told to seal the floor with Ball p121 sealant, two coats. Adhesive is Gfix Csa flexible white.

The tiles would cover four rooms.Would it be possible to tile right through the doorways without a break, this would mean a longest run of 12 mtrs or will i require expansion joints? If yes, what distance apart would they need to be?
There is 8mm expansion foam layed around all edges of the screed with a 25mm thermal barrier on ext. walls.
Sorry for the long first post, The largest area i have tiled before was 50sqm, but this is my first limestone floor on gyvlon ufh floor.

Cheers

 

[trevortine]

You decoupling this mate?

 

[The Legend; Phil Hobson RIP]

I would put expansion joints in doorways, always a weak point, as above decoupling might be a good idea with limestone.

 

[Diamond Pool Finishers]

as above , but :welcome:to the forum

 

[The Legend; Phil Hobson RIP]

Sorry Pete welcome to TF.

 

[White Room]

Hi and welcome....

 

[m3fitter]

agree on ditra or gmat ( decoupling membranbe ), and expansion joints, you can get colour coded rubber within stainless steel for good aesthtetics. typical companies Schluter, Genesis and local independents
Movement Joints, Expansion Joints And Control Joint Profiles - Schlüter-Systems

 

[Pete.c]

Thanks for the quick replies, looks like ditra or similar is the popular choice.

Is this because of the gyvlon floor or the limestone, or combination of the two?
Would you still use ditra if it was a ceramic tile?

Would expansion in the doorways be enough? I will still have a run of 9mtrs by 7.5mtrs in the kitchen diner, its an L shaped room.

Sorry for all the questions, just wanna get this right, its a lot of limestone.
Cheers.

 

[Ajax123]

Natural stone should be uncoupled. 7 weeks at 60mm even with the heating in the weather conditions we've had recently might not be long enough so do a moisture check first. The natural drying time for this depth would be 12weeks (80 days) in good drying conditions? We have had poor drying conditions in the last few months.

If you must use an acrylic primer go for BAL or Ultra but in my experience epoxy is better with cement adhesive. I would be looking to use a gypsum compatible system to stick the mat down. A vinyl type adhesive might be a better option then your normal flexible adhesive on top. Joints in door hers holds are a must and these should also be in the screed. There should also be joints in the screed between heating zones and where hot meets cold. If these are missing that makes uncoupling even more critical as there is a much higher risk of the screed cracking.

 

[Pete.c]

Thanks Alan,

Would you still use a decoupling mat and expansion joints if it was a standard ceramic/porcelain tile on gyvlon with ufh?

cheers. pete

 

[Ajax123]

Thanks Alan,

Would you still use a decoupling mat and expansion joints if it was a standard ceramic/porcelain tile on gyvlon with ufh?

cheers. pete

generally not unless the screed has become unsound for any reason e.g thermal cracking and such likes. It is only natural stone that is covered within the BS and this is due to it having natural fracture lines whch make it susceptible to cracking under thermal cycling.


With ordinary ceramics or porcs I woudl however recomend the use of a gypsum compatible adhesive rather than a portland cement based one.

 

[Pete.c]

OK thanks Alan, so what make and type of primer and adhesive, would you recommend with the decoupling mat and limestone tiles?

There is only perimeter expansion, so I think this would reduce the effectiveness of any expansion joints in doorways etc?

Cheers.

 

[Ajax123]

Hmmm. So are you proposing not putting movement joints in the tile face? This would be a mistake. Bear in mind you are uncoupling the tiles so the tile face will move ostensibly independently from the screed. As for the adhesive I would recommend a discussion with schluter to see what their current recommendation is. If they will not make a recommendation the speak to f ball and co who supply vinyl adhesives. Not sure which one is most apt.

 

[m3fitter]

Its ooooh sooo technical these days ..lol.. used to be 3/4" ply screwed every 6", PVA, white grout, grey grout, eye joints... rapid set with pva to make it flexible ( or AD1 if you were posh ! ) tub mix for wall tiles, all of your tools used to fit in an old tub mix bucket with your TS40.... ha ha.. the good ol days..
Now TX1200, rectified 1000x330.. acrylic, dukka, ditra.. UFH ( used to be radiators !! ) i'm only 43 ! feels like a different trade to when i started 24 years ago.

 

[bugs183]

You couldn't be more right there m3fitter (except the pva, never used it, always Bal Bond and Admix's), It's become amazingly technical, it's no bad thing and it should be great, but as we all know, the builders and the public have not caught up, so every job is turning into a tile, substrate,cost nightmare!!!

 

[Pete.c]

No, I would put movement joints in, but where, apart from doorways, and at what distance apart?

It is really difficult to find a certain solution, i`ve hunted round on the lafarge site and found this Broken Link Removed.

Also Nicobond Gypfix is 100% compatible, seems like a possible answer.

These both seem to suggest that decoupling is not necessary.

 

[Ajax123]

No, I would put movement joints in, but where, apart from doorways, and at what distance apart?

It is really difficult to find a certain solution, i`ve hunted round on the lafarge site and found this Broken Link Removed.

Also Nicobond Gypfix is 100% compatible, seems like a possible answer.

These both seem to suggest that decoupling is not necessary.

i wrote that....whilst I was still at Gyvlon....

i agree that if you are using non natural tiles like porcs an uncoupling membrane is not required in general but limestone being relatively soft is prone to fracturing due to thermal cycling. There is an argument to say that gypsum screed and gypsum adhesive with limestone on top would mean that all three elements move in a similar manner and to a similar extent but my advice has to reflect the British Standards where they exist as these reflect inspdustry best practice. Simple fact is that if you step outside of British standard and things go wrong you will have no viable defence. British Standard says natural stone then uncouple.

If you use gypfix to stick down the mat make sure you don't prime the screed as it will rely on moisture loss to set fully. Unfortunately you will also find it difficult to get a recommendation to use gypfix from the likes of schluter as they have done no testing. A call directly to nicotine might be helpful.

 

[SJPurdy]

Would expansion in the doorways be enough? I will still have a run of 9mtrs by 7.5mtrs in the kitchen diner, its an L shaped room.


The maximum distance between movement joints on a heated floor should be 8m and the maximum area between movement joiunts should be 40m2; thats a general recommendation of BS. With an L shaped room it may be advisable to break it into 2 rectangles as there will be a stress point at the corner (In my opinion this should have been put into the screed) - I've seen floors where Ditra was used but no movement joint so the tiles were cracking from the corner ouitwards.

If you're going to use Ditra I advise giving their help line a call - they are very friendly and helpfull - have the dimensions of the "L" ready for them to advise on.