Discuss New screed down - trying to figure tiling out approach! in the Tiling over Electric Underfloor Heating area at TilersForums.com

GrayD

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Hi all,

I'm new to the forum but have read many posts over the past year as I have created and tiled a wet room and also created and tiled a bathroom in my house that we are renovating. I've also tiled our utility room too. Thanks for all the tips & tricks I learned!

So, I'm ok with tiling walls and simple floors (they get better each time!) but I'm no expert by any stretch. I have all the relevant tools, etc but haven't ever tiled on a new screed floor.

So, here's the background: (bear with me!)

We had a wet UFH system (ProWarm) laid under a 45mm flow screed and the 45m2 floor has been down now since 29th March - nearly 7 weeks. UFH hasn't been turned on. The screed company that laid the floor had to change their material provider last minute because the other one messed up their schedule or something. I'm 90% sure the screed is not anhydrite but I am not 100% sure... There looks like there could be something that looks 'like' calcification on the surface but it's not all over and really only in a few patches here and there. I didn't order anhydrite but I can't be sure what's been laid. Here's the reason why...

The floor company who laid it down created a 4-5mm difference between two areas (thermal break between heated and non-heated floor areas) by not setting it out properly I guess but I only saw this after I trimmed the Celotex thermal break to floor level between the two areas.

They are refusing to deal with the issue so we have fell out now because to me they should sand back the higher area as they knew I was tiling the whole floor across the thermal break. It's only a small area that's too high - 3m2 max so no big deal for them. The upshot is that they aren't coming back to me on whether the floor is or is not anhydrite.

So, I am going to treat it as if it is anhydrite just to be 100% sure we don't get a failure. I'm also going belt & braces on it because I don't want any issues at all.

What I am thinking is as follows, please do tell me if I am wrong, have chosen the wrong product(s) or there's anything I have missed or just not thought about - thanks!

Porcelain tiles on the floor:
1. prep the floor by getting rid of any points, etc and then sweep & hoover it
2. prime the floor a couple of times with Mapei Eco Prim Grip
3. lay down a Durabase CI membrane across the whole area - wall to wall and over thermal break -
4. use Mapei Kerquick adhesive (or better to use Kerakoll Biogel maybe?)
5. use Mapei Ultra Colour Plus grout

Seems so simple when I have written now (!) but I want to be certain I am going about this in the right way.

Thanks in advance for any pointers, appreciated.

Ps. any clues on how to stick down the Durbase would be appreciated too - Kerquick with Latext Plus? Not sure.
 

Localtiler

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First thing, determine if the floor is cement or anhydrite. Post photos and take it from there, no point guessing !
 

hmtiling

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Sand the screed so you can see aggregate. Commission the heating. Test for moisture and make sure it's below 75% relative humidity. Do this with heating off for 48hrs. Barrier prime. You can then fix matting and tiles with most c2's and all s1's. I'd use a rapid C2 suitable for ufh for the membrane then a standard s1 for the tiles. Good luck
 

LEE MAC

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As above and you also need to honour the joint in the two floors.
 
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GrayD

GrayD

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First thing, determine if the floor is cement or anhydrite. Post photos and take it from there, no point guessing !
Thanks for the reply. I have taken some pics just now, see what you think. Cheers.

IMG_1189.JPG IMG_1190.JPG IMG_1191.JPG
 
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GrayD

GrayD

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Sand the screed so you can see aggregate. Commission the heating. Test for moisture and make sure it's below 75% relative humidity. Do this with heating off for 48hrs. Barrier prime. You can then fix matting and tiles with most c2's and all s1's. I'd use a rapid C2 suitable for ufh for the membrane then a standard s1 for the tiles. Good luck
Appreciate the advice, thank you.

I'll look up some C2 and some S1 to use.
 
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GrayD

GrayD

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As above and you also need to honour the joint in the two floors.
Cheers Lee Mac. When you say 'honour the joint' can you tell me what you mean by this? I think I have a clue but just want to check! Thanks.
 

Localtiler

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Can't be certain from those photos but it does have a hefty layer of laitance on there which needs removing
 

jcrtiling

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Hi all,

I'm new to the forum but have read many posts over the past year as I have created and tiled a wet room and also created and tiled a bathroom in my house that we are renovating. I've also tiled our utility room too. Thanks for all the tips & tricks I learned!

So, I'm ok with tiling walls and simple floors (they get better each time!) but I'm no expert by any stretch. I have all the relevant tools, etc but haven't ever tiled on a new screed floor.

So, here's the background: (bear with me!)

We had a wet UFH system (ProWarm) laid under a 45mm flow screed and the 45m2 floor has been down now since 29th March - nearly 7 weeks. UFH hasn't been turned on. The screed company that laid the floor had to change their material provider last minute because the other one messed up their schedule or something. I'm 90% sure the screed is not anhydrite but I am not 100% sure... There looks like there could be something that looks 'like' calcification on the surface but it's not all over and really only in a few patches here and there. I didn't order anhydrite but I can't be sure what's been laid. Here's the reason why...

The floor company who laid it down created a 4-5mm difference between two areas (thermal break between heated and non-heated floor areas) by not setting it out properly I guess but I only saw this after I trimmed the Celotex thermal break to floor level between the two areas.

They are refusing to deal with the issue so we have fell out now because to me they should sand back the higher area as they knew I was tiling the whole floor across the thermal break. It's only a small area that's too high - 3m2 max so no big deal for them. The upshot is that they aren't coming back to me on whether the floor is or is not anhydrite.

So, I am going to treat it as if it is anhydrite just to be 100% sure we don't get a failure. I'm also going belt & braces on it because I don't want any issues at all.

What I am thinking is as follows, please do tell me if I am wrong, have chosen the wrong product(s) or there's anything I have missed or just not thought about - thanks!

Porcelain tiles on the floor:
1. prep the floor by getting rid of any points, etc and then sweep & hoover it
2. prime the floor a couple of times with Mapei Eco Prim Grip
3. lay down a Durabase CI membrane across the whole area - wall to wall and over thermal break -
4. use Mapei Kerquick adhesive (or better to use Kerakoll Biogel maybe?)
5. use Mapei Ultra Colour Plus grout

Seems so simple when I have written now (!) but I want to be certain I am going about this in the right way.

Thanks in advance for any pointers, appreciated.

Ps. any clues on how to stick down the Durbase would be appreciated too - Kerquick with Latext Plus? Not sure.
Have you paid them .
 

Glynn

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I am thinking anhydrite. It just doesn't look the right colour for sand/cement and the surface seems to have a slight sheen. It also seems as flat as a billiard table. You can do a simple test with PH paper that will give an indication of the screed type and it should indicate green or purple but the best way to find out is from the people who supplied it (Humble pie?), and it won't matter which screed it is it can still be tiled but with different prep needed. HMTiling's advice is good.
 

antonio

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mapei eco primer grip,
not appropriate, it is used to lay other tiles on top of the tiles.
you need a mapei primer like primer g or similar
 

Pauly tiler

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Hi, If it was a flow screed the laitance should have and or will still have to be mechanically removed. To my knowledge there is no such thing as laitance free flow screeds, just reduced laitance. I would then use a suitable primer for flow screeds, (Gyvlon – Truflow – High Flow – Cem Flo, are just a few) they are variations on a theme really. You need to prime them well as they all react badly to water/damp. As you are rightly using a stress membrane I would use a quality adhesive like Ardex AF200 plus to install the matting to the primed screed. After that you can pretty much treat it as a standard heated screed floor to be tiled, don't skimp on adhesive, C2 S1 grade at a minimum.
Please please please cycle the floor up and down with the UFH to stabilise it and remove any remaining moisture before you install the membrane, as I say, these floors react badly with moisture especially when its trapped below the stress membrane.
You can find details of the cycle procedure online.
I hope it helps.
Pauly
 

hmtiling

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Hi, If it was a flow screed the laitance should have and or will still have to be mechanically removed. To my knowledge there is no such thing as laitance free flow screeds, just reduced laitance. I would then use a suitable primer for flow screeds, (Gyvlon – Truflow – High Flow – Cem Flo, are just a few) they are variations on a theme really. You need to prime them well as they all react badly to water/damp. As you are rightly using a stress membrane I would use a quality adhesive like Ardex AF200 plus to install the matting to the primed screed. After that you can pretty much treat it as a standard heated screed floor to be tiled, don't skimp on adhesive, C2 S1 grade at a minimum.
Please please please cycle the floor up and down with the UFH to stabilise it and remove any remaining moisture before you install the membrane, as I say, these floors react badly with moisture especially when its trapped below the stress membrane.
You can find details of the cycle procedure online.
I hope it helps.
Pauly
If using ditra or durabase s1 would be the maximum not minimum
 

Pauly tiler

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Noted HMT, it was the C2 I was referring to, should have left the S1 out of the line.

Cheers
 

LEE MAC

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Cheers Lee Mac. When you say 'honour the joint' can you tell me what you mean by this? I think I have a clue but just want to check! Thanks.
The joint between the two areas of floor must be continued upwards right through the membrane and tiles. Ideally but not critically you will able to set the tiles out so as a full tile falls on this joint and then instead of grouting this joint fill it instead with a colour matched silicone from the same brand as your grout.
 

Ajax123

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Its cement based screed. Still needs sanding and moisture testing. UFH needs to be commissioned and run and screed needs priming etc etc
 

Ajax123

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Its cement based screed. Still needs sanding and moisture testing. UFH needs to be commissioned and run and screed needs priming etc etc
 

widler

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It looks like cement based to me as well, colour looks wrong for analshite .
One word though , flexbone :)
 

hmtiling

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I've seen my first 2 anhydrite screeds ober the last 2 weeks. They are awful! Loads of laitence and all over the place for level. They're completely different to the alpha hemi ones which I normally get. The anhydrite are a cheaper island company. Get what you pay for as always
 

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