Discuss Tiling onto calcium based screed in the UK Tiling Forum | Tile Advice Forum area at TilersForums.com

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Hi, just after some advice if anyone can help. I’ve just poured the floor on my extension at 110mm thick using Agilia (calcium based).

I am wanting to tile in about 5-6 weeks but after reading a lot on this it has become apparent there will still be moisture in the floor and I should wait for it to dry at 1mm per day.

Of course I don’t want to have a brand new kitchen installed and all my skirting and painted and still have no floor tiles, it seems silly.

What are the implications, if any, of laying porcelain tiles on the floor (600x900mm). They will be on a tilemaster mat and using Kerrakoll Eco A primer with Kerrakoll adhesive. Is it the movement from the drying out process or the actual moisture that is the problem?

No underfloor heating before I get asked.

Thanks in advance
 

Ajax123

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It's the moisture that's the problem. Are you sure its calcium sulphate based? At 110mm it would be far deeper than recommended. There are several agila concrete though that would be that deep.
 
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Why 110mm thick. ? .. wow.

Oh and welcome 👍👍
I don’t actually know I’ve got a builder in to do it, I was a bit surprised too when he told me 110mm.

Thanks!

Any advice on if it’s actually going to cause an issue or if it’s just one of those obligatory manufacturers guidance, as I’d be waiting 220 days to tile it if I followed that… surely nobody waits that long?
 
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It's the moisture that's the problem. Are you sure its calcium sulphate based? At 110mm it would be far deeper than recommended. There are several agila concrete though that would be that deep.
What would the moisture do pop the tiles? I’m pretty sure I haven’t actually asked him exactly which agilia it was as I’ve only really been looking into it today but it was pumped in and it’s flat as a pancake without any tamping so I can only assume so
 
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What would the moisture do pop the tiles? I’m pretty sure I haven’t actually asked him exactly which agilia it was as I’ve only really been looking into it today but it was pumped in and it’s flat as a pancake without any tamping so I can only assume so
You need to find out then we can advise properly.
 
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You need to find out then we can advise properly.
So I’ve found out today it’s MaxiAgilia, after ringing them about 3 times today I finally got through to their technical manager and he’s told me it’s a cement based screed, not anhydrite and it will dry at 1mm per day for floor tiling. It will need the curing agent scraping off the top too and he said it can be forced dry with dehumidifiers. So the question is do I need to wait 110 days or will 45-50 days be enough as that’s when I wanted to do it?
 
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Ajax123

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So I’ve found out today it’s MaxiAgilia, after ringing them about 3 times today I finally got through to their technical manager and he’s told me it’s a cement based screed, not anhydrite and it will dry at 1mm per day for floor tiling. It will need the curing agent scraping off the top too and he said it can be forced dry with dehumidifiers. So the question is do I need to wait 110 days or will 45-50 days be enough as that’s when I wanted to do it?
Its agila concrete then. Just a self compacting concrete so sand of the curing agent and treat like any other concrete. If it's too wet you could use a liquid damp proof membrane
 
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If I used a liquid DPM like blackjack though then surely the screed would never actually dry as there’s nowhere for the moisture to go at that point? Feels like I’m just creating another issue possibly?
 
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Ajax123

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If I used a liquid DPM like blackjack though then surely the screed would never actually dry as there’s nowhere for the moisture to go at that point? Feels like I’m just creating another issue possibly?
That's perhaps because you're not fully familiar with concrete chemistry. Cement will continue to react with water as long as water is present. That uses some water up over time. Liquid dpm technology has also moved forward very considerably since black Jack was the material of choice. They are mostly epoxy or polyurethane. They are vapour check systems which have a low but not zero moisture transmission rate. They allow moisture out at a rate at which the primers and adhesives can cope with it. The concrete will eventually dry out. It'll just take a long time.

There are probably more floor with liquid dpms than not these days. No one wants to wait :)
 
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What would the moisture do pop the tiles? I’m pretty sure I haven’t actually asked him exactly which agilia it was as I’ve only really been looking into it today but it was pumped in and it’s flat as a pancake without any tamping so I can only assume so
The moisture would pop the tiles yes !! That's why noone tiles on fresh concrete , screed etc etc !but if I was this person I would want to know clearly what was pumped in !! I have just read a load of dos and don't about this !and there are alot of don't s !! For starters it should have been tamped at a deep depth and then again at 15mm to 20 mm !! And also expansion joints cut in soon after!! But only for certain size areas !! It sounds like a hydrate screed which is also tempermental!! The depth is fine though !no thinner than 75mm !!
 
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The moisture would pop the tiles yes !! That's why noone tiles on fresh concrete , screed etc etc !but if I was this person I would want to know clearly what was pumped in !! I have just read a load of dos and don't about this !and there are alot of don't s !! For starters it should have been tamped at a deep depth and then again at 15mm to 20 mm !! And also expansion joints cut in soon after!! But only for certain size areas !! It sounds like a hydrate screed which is also tempermental!! The depth is fine though !no thinner than 75mm !!
Its concrete??? hes already confirmed that.It has a curing agent sprayed on during finishing. This needs to be sanded off, along with any other contamination on the surface, before tiling and then treat it like concrete.
 
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Hi, just after some advice if anyone can help. I’ve just poured the floor on my extension at 110mm thick using Agilia (calcium based).

I am wanting to tile in about 5-6 weeks but after reading a lot on this it has become apparent there will still be moisture in the floor and I should wait for it to dry at 1mm per day.

Of course I don’t want to have a brand new kitchen installed and all my skirting and painted and still have no floor tiles, it seems silly.

What are the implications, if any, of laying porcelain tiles on the floor (600x900mm). They will be on a tilemaster mat and using Kerrakoll Eco A primer with Kerrakoll adhesive. Is it the movement from the drying out process or the actual moisture that is the problem?

No underfloor heating before I get asked.

Thanks in advance
 
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sorry to repost ages later in my thread, I did find out it is definitely a sand and cement floor which is why it’s so thick, had to be a minimum of 75mm. It’s been 7 weeks since pouring now and I’m ready to floor tile next week. I have a digital hygrometer on it as well as we speak, it’s been 10 hours, started at 71% and it’s been at 79% for perhaps the last 3 hours so can’t see it going up again now but will check in the morning. What’s everyone opinions as 75% is what I’ve read it should be? Would you risk it being a little higher? I have a dehumidifier so going to get that going 24/7 for the next week after I’ve taken the tester up.

Cheers
 
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Ajax123

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if the crack mat is a moisture stabiliser like ditra youll be fine togo ahead. For info the floor should be 80% to be considered dry but there is an error built into the test regime so has a tolerance of minus 5% hence 75%. for equilibrium you should have two consecurive readings the same 4 hours apart. so based on your tests its not in iequilibrium yet. that could be to do with the changability of the site conditions this time of year.
 
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if the crack mat is a moisture stabiliser like ditra youll be fine togo ahead. For info the floor should be 80% to be considered dry but there is an error built into the test regime so has a tolerance of minus 5% hence 75%. for equilibrium you should have two consecurive readings the same 4 hours apart. so based on your tests its not in iequilibrium yet. that could be to do with the changability of the site conditions this time of year.
Thanks for the info it’s helpful to know, so after 4 hours it was 74% but this morning after 24 hours it was at 83% so my question is will a product like DITRA be able to cope with that if needed at all?
 
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ditra would cope. I would not necessarily trust the hygrometer reading this time of year simply because the temperatures overnight tend to lead to interstitial condensation issues which throws the readings off.
 
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Thanks for the advice, think I’ll go for DITRA or the Kerrakoll equivalent then, what about the adhesive can I still use Kerrakoll biogel or would I need a different adhesive to put the matting on top of? And where would you apply the primer? I think my tiler would know this but just want the advice for my own benefit and peace of mind
 
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