What is the best adhesive to use for porcelain tiles onto screed

[ashurst]

We have around 50m2 of 120cm x 20cm porcelain floor tiles to lay onto 75mm screed. I understand the tiles should not be laid for at least a couple of weeks after pouring the screed and using ditra matting or similar would be wise. There will also be wet underfloor heating which we may turn on to help dry the screed faster than normal.

What would be the best adhesive to use. My tiler normally uses powder which sets fast. I remember last year when he laid my marble tiles onto ply after a couple of hours we were walking lightly over it and haven't had any problems.

Thanks in advance

 

[Rick-o]

Hi Ashurst, what sort of screed has been poured? Also you mention about your nirmal tiler, are you doing this floor yourself?

 

[Dumbo]

If you are having a poured screed it may well be some sort of gypsum based screed which even if force dried will take more than a couple of weeks to dry out .

 

[ashurst]

He's my builder who has been working for over 20 years and I am happy with his work from the past, (tiling that is)

The floor screed will be cement and sand (builder knows the grade with small stones etc)

The area where he is tiling is very warm. As triple glazed rooflights and bi-folding doors and a kitchen window. It gets to the late 20s even when the temperature is in the low 20s outside

 

[Ajax123]

He's my builder who has been working for over 20 years and I am happy with his work from the past, (tiling that is)

The floor screed will be cement and sand (builder knows the grade with small stones etc)

The area where he is tiling is very warm. As triple glazed rooflights and bi-folding doors and a kitchen window. It gets to the late 20s even when the temperature is in the low 20s outside

sounds like a recipe for cracking and curling to me...

 

[Flintstone]

You sound a little blasé about the screed drying. It needs to be right. Are you using ditra or not ? How come your asking about about adhesive if a tiler is doing the job, he should know.

 

[ashurst]

Why is it a receipe for curling and cracking and I am asking about which is the best adhesive to use. I thought asking professional tilers would be the way to go. We will use ditra. Not every tiler would do things 100% properly like in all professions but by asking in a forum one would normally get a fair idea of what to use. Or am I totally wrong ?

 

[Flintstone]

it's important that you give all the info in order to get the right answers! Imo if you don't trust the tiler, don't use him!

 

[Flintstone]

If you have a screed put down then crank the heating up in a warm room, it's likely to crack and curl up, best left to dry a bit more naturally, at least for a while

 

[ashurst]

Maybe I should of not mentioned all the bits except for just advice on the best adhesive to use on a sand and cement screed.

 

[Flintstone]

Is that because what your hearing is not what you want to hear ?

 

[Tile Shop]

Maybe I should of not mentioned all the bits except for just advice on the best adhesive to use on a sand and cement screed.

Yeah, then you might have got the wrong advise given to you. Got to say, you seem to have a bit of an attitude for not getting a straight answer. Unless i'm reading it wrong. Understand that tiling is not as straightforward as many think and its the first visual part of the installation you notice when the floor beneath goes belly-up and its not been prepped correctly. Any bag that says tile adhesive will stick to sand and cement. Doesn't mean its right for the overall installation though.

So if you want an honest answer, heres one for you...... and you might not like it. You need to leave your floor 100 days to naturally cure. 1 day per mm for the first 50mm the 2 days per mm for the other 25mm. You also need to commission your underfloor heating for the screed to adjust to the thermal expansion.

After 100 days, the heating has been commissioned and you have checked the relative humidity of the floor and if no cracks appear in the screed, prime it with a suitable acryllic or SBR primer, level it with a flexible levelling compound if required and tile it with an S1 flexi adhesive. If cracks do appear, repair them with a suitable repair morter, and tile as above but this time, incorporate an anti-fracture matting. Cracks or no cracks, you will also need to split the room into two equal size bays and stick an expansion strip down the middle. This is because its a heated area over 40 sqm.

If you're impatient and don't want to wait (which it sounds like the case), you can take a risk tiling direct using an S2 Greenscreed adhesive before the screed has fully cured, or lay a vapour barrier such as ditra matting (preferred option) fitted with an S1 flexi adhesive and use the same adhesive to fit the tiles on top. The expansion strip also needs to split the ditra.

But again, your tiler should know all this, otherwise you shouldn't be letting him near it.

See? Not as easy as asking "what adhesive do i need?" is it........ it all rests on the correct prep.

Examples of the above materials: (i'll stick to BAL as its one of the top brands and easily available but others are available such as Mapei and Tilemaster)

Flexible levelling compound: BAL LEVEL-MAX
Primer: BAL APD or BOND SBR
Anti-Fracture matting: BAL RAPID-MAT
S2 Flexi adhesive: BAL GREENSCREED or SINGLEPART FASTFLEX
S1 Flexi adhesive: BAL SINGLEPART FLEXIBLE (slowset) or BAL RAPIDSET FLEXIBLE FIBRE

Good luck.

 

[Italy]

Yeah, then you might have got the wrong advise given to you. Got to say, you seem to have a bit of an attitude for not getting a straight answer. Unless i'm reading it wrong. Understand that tiling is not as straightforward as many think and its the first visual part of the installation you notice when the floor beneath goes belly-up and its not been prepped correctly. Any bag that says tile adhesive will stick to sand and cement. Doesn't mean its right for the overall installation though.

So if you want an honest answer, heres one for you...... and you might not like it. You need to leave your floor 100 days to naturally cure. 1 day per mm for the first 50mm the 2 days per mm for the other 25mm. You also need to commission your underfloor heating for the screed to adjust to the thermal expansion.

After 100 days, the heating has been commissioned and you have checked the relative humidity of the floor and if no cracks appear in the screed, prime it with a suitable acryllic or SBR primer, level it with a flexible levelling compound if required and tile it with an S1 flexi adhesive. If cracks do appear, repair them with a suitable repair morter, and tile as above but this time, incorporate an anti-fracture matting. Cracks or no cracks, you will also need to split the room into two equal size bays and stick an expansion strip down the middle. This is because its a heated area over 40 sqm.

If you're impatient and don't want to wait (which it sounds like the case), you can take a risk tiling direct using an S2 Greenscreed adhesive before the screed has fully cured, or lay a vapour barrier such as ditra matting (preferred option) fitted with an S1 flexi adhesive and use the same adhesive to fit the tiles on top. The expansion strip also needs to split the ditra.

But again, your tiler should know all this, otherwise you shouldn't be letting him near it.

See? Not as easy as asking "what adhesive do i need?" is it........ it all rests on the correct prep.

Examples of the above materials: (i'll stick to BAL as its one of the top brands and easily available but others are available such as Mapei and Tilemaster)

Flexible levelling compound: BAL LEVEL-MAX
Primer: BAL APD or BOND SBR
Anti-Fracture matting: BAL RAPID-MAT
S2 Flexi adhesive: BAL GREENSCREED or SINGLEPART FASTFLEX
S1 Flexi adhesive: BAL SINGLEPART FLEXIBLE (slowset) or BAL RAPIDSET FLEXIBLE FIBRE

Good luck.

Amen, and peace be with you.

 

[ashurst]

Thank you Paul C for a detailed answer.

 

[Time's Ran Out]

Last year he laid your marble onto plywood and its fine - so no worries here!