Tiling onto self-leveller

[Coastaltrades]

I've just had the whole ground floor of a house we are working on levelled with a pump in liquid screed. It's an anhydrite so we are going to grind it & prime it to remove surface latency.

I'm risk-averse when it comes to tiling, and usually always use decoupling membranes but we do not have the height in the doorways to add anything extra as it's right on the limit of over-trimming standard doors.

I'm interested to know if people think tiling straight onto a primed leveller is ok? The subfloor is floorboard with joists at no more than 350mm centres. Leveller is approx 15mm thick.

 

[ciego21]

Hi coastal I'm new to the forum but I've been tiling in the UK just north of London for 27 years.
Tile master and bal both do a thin uncoupling membrane.
Only about 1 mm thick. So height increase is minimal.
I put it through doorways on unheated screeds to try and minimise the risk of cracking cutting round door linings.
You don't say if there is ufh.
No ufh just prep the floor as you described and tile.
Laying tiles on floors with ufh even if it's been commissioned and run for a while can still sometimes cause issues.

 

[Coastaltrades]

Hi coastal I'm new to the forum but I've been tiling in the UK just north of London for 27 years.
Tile master and bal both do a thin uncoupling membrane.
Only about 1 mm thick. So height increase is minimal.
I put it through doorways on unheated screeds to try and minimise the risk of cracking cutting round door linings.
You don't say if there is ufh.
No ufh just prep the floor as you described and tile.
Laying tiles on floors with ufh even if it's been commissioned and run for a while can still sometimes cause issues.

Thank you for this, to confirm there is no UFH and the only threshold is also levelled through into the next room.

 

[ciego21]

A layer of thin crackmat through the door.
If you can't set out for a grout joint through door way then put a crack joint or expansion joint in the floor under the door.

 

[Coastaltrades]

I'm definitely going to look into the 1mm decoupler. Just out of interest, what is the reason to be especially concerned about the doorway? Before we installed a liner this would have just formed part of the hallway so the subfloor and leveller are continuous.

 

[ciego21]

Any kind of corner cuts even small massively weaken the tile.
I stopped using a wet cutter for these cuts because of the over run on the underside of the tile. Some guys now drill a small hole and then cut to it. All time.
I use an angle grinder now. Round off the corner to try and prevent a fracture. Screed (cement screeds) often cracks through door ways. Screeds are just a floor covering to take finished floor coverings. They have no real strength when it comes to lateral movement.
Liquid screeds are new to me. Don't really know what the benefits are. Cos they can take a long time to dry before you can lay a covering that sticks to them .
I would check the liquid screed for moisture content before doing anything.

 

[ciego21]

I've recently done a floor for a builder I work for at his own house.
Tried to upload some pictures but it just kept saying can't support blah blah blah. (I'm not very tech minded)
He had 1200 x200 plank laid herringbone but wanted it to run through all doorways without expansion joints or crack joints as I call them. Which I did. So I put the bal mat through the door ways first extending out about 800mm either side of the doorway.
Just to hopefully eliminate any cracking. Might not happen screed been down for 15 years maybe.
All door ways no cracking bar one into his office . Little crack in the screed through the doorway.
It took about half hour to lay it in 4 doorways.
It's just an extra bit of security.

 

[Bishbashbosh]

A lot of the chat has been about gypsum based flow screeds. My question is, what about cement based flow screeds. Do you still prime, ( I assume so ) does it need decoupling Matt/ cloth. What type of adhesive. I have a 100sqm floor to lay for my son, and obviously don’t want to get it wrong. He is having limestone tiles.

 

[Ajax123]

A lot of the chat has been about gypsum based flow screeds. My question is, what about cement based flow screeds. Do you still prime, ( I assume so ) does it need decoupling Matt/ cloth. What type of adhesive. I have a 100sqm floor to lay for my son, and obviously don’t want to get it wrong. He is having limestone tiles.

All the same rules apply to cement based liquid screeds that are in place for anhydrite/gypsum screeds. The only exception I guess is that you can use a cement based adhesive. ALL screeds should be dried, sanded, vaccuumed, heating comissioned and primed before tiling. uncoupling depends on the tile type more than the screed type but bear in mind that gypsum is MUCH MUCH less likley to crack than cement so i would say its more useful on cement. All natural stone tiles should be uncoupled regardless of screed type.

 

[Bishbbashbosh]

All the same rules apply to cement based liquid screeds that are in place for anhydrite/gypsum screeds. The only exception I guess is that you can use a cement based adhesive. ALL screeds should be dried, sanded, vaccuumed, heating comissioned and primed before tiling. uncoupling depends on the tile type more than the screed type but bear in mind that gypsum is MUCH MUCH less likley to crack than cement so i would say its more useful on cement. All natural stone tiles should be uncoupled regardless of screed type.

cheers ajax123