Anhydrite+Ditra+Porcelain - Mapei Primer or not / Keraquick with or without Latex Plus

[Eminem]

Hello Everyone! First time writing here. 😅Contemplating the horrendous prospect of installing underfloor heating in a fully inhabited house with furniture and belongings now in the garden I have read a ton of posts on this forum and you’ve been a marvellous help. So, a zillion thanks ahead of this request dear competent tradesmen! I am truly grateful that there are good men like you who bother to support your colleagues in the industry and share all you know enthusiastically and so freely. I’m not doing this job myself but in a remote area of Spain with little UFH knowhow IMHO it’s best to be fully informed. Here’s what I am doing:-

• Removed old floor to approx. 7cm leaving level and fairly even concrete substrate, polyspan beneath
• Castellated wet pipe UFH fed by solar collector panel and Vaillant heat pump shortly to be installed
• Paris Slim Anhydrite self-levelling to be laid over UFH, laitance to be sanded and vacuumed accordingly by me no doubt!
• commissioning of UFH and correct drying to be observed before applying further layers
• Mapei Eco Prim T diluted coat 1 part primer 2 parts water and, once dry, a further a neat coat (YES/NO?)
• Mapei Keraquick S1 (with latex plus YES/NO?)
• Ditra 25 matting, already ordered, no going back now!
• Gypsum based tile adhesive preferred by builder but forum seems to favour flexible cement based (?)
• Porcelain tiles to go on top preferably without any grout at all at it will ruin the design somewhat but if it’s necessary I will have to leave spaces. The idea of the anhydrite, and DITRA was I wouldn’t have to separate. (What's your take on that?)

So I have three main questions:-

1) I understand it is a bad idea to use the primer as the moisture from the Keraquick needs somewhere to disperse. I’m happy to take that off the distributor’s invoice and go direct onto the anhydrite without priming at all. (Dave DHTiling’s / Ajax 123 advice) If the Keraquick sticks well what’s the problem? However I have jut read that AD Ceramics says to “Prime, then prime again until no more soaks in. Stick down ditra matting will Mapei keraquick and latex additive…”

2) Do I need to use the Latex Plus in the Keraquick S1? I don’t think the distributor has the Rapid Set Flexible version nor the S2 version but I can ask.(Also, it’s going to be hot here soon and I’m not sure a rapid set anything is a good idea.)
If I can avoid the Latex Plus I’d be happy. These 10k tubs cost about 75 euros each and seeing as I will need at least 6 we’re talking 400 GBP. Anyfix is not available where I live so a Mapei product seems to be the only option.

3) Finally, the top layer before the Porcelain tiles; will a flexible (S2?) cement-based adhesive be better than a gypsum one? There’s only the Ditra underneath it.

Again, I am so grateful if any of you have the time to answer anything at all.

All the best, Em

 

[Wraiththe]

Just curious, why don't you call Mapei? Their tech support is terrific. Post back what they said.

 

[Ajax123]

I wouldn't recommend using keraquick on anhydrite withoutva primer. Keraquick is cement based so wont stick well without.

 

[Eminem]

Dear All,

I wrote the below post intending to use Kerakoll products. There might be something useful in there so I am posting it anyway. However, since writing it I have decided to try and ship some Anhyfix from UK to Spain and I will message LKAB about this. Regards

Progressing with tile anhydrite adhesive Ditra conundrum. Thanks for your suggestion Wraiththe, I did speak to Mapei in the UK - 0044 121 508 6970 Martin was helpful. He wryly commented anhydrite was a favourite of theirs NOT!:-
1) screed needs to be dry till 0.02% carbide bomb test available from Mapei UK at least, maybe Spain would supply
2) Once dry & commissioned & laitance mechanically abraded can use Eco Prim T at 1:2 or 1:3 with a 2nd coat of same
3) Keraquick S1 adhesive needs the Latex Plus and no other Mapei product would give that flexibility. If they were to do a spec for this project it would specify the latex as absolutely essential to give the layer of adhesive enough scope for absorbing movement from the underlying UFH and screed.

However, the above option would cost me over 800€ for a 40m floor with almost half the cost being the latex. So, I then turned to Kerakoll whose H40 Gel is, I understand, similar to your UK version H40 No limits. The Gel is a C2 type adhesive and thus eminently suitable for a UFH application where the adhesive will be heating up and cooling down continually over many years. He said a primer was essential whether an adhesive was “anhydrite compatible” or not. He said that anhydrite is a material which needs priming because it’s soft and a primer gives it stability.

Due to Anyfix, your real gypsum-based adhesive, not being available here I checked out our Spanish versions of “gypsum compatible” adhesives, one in particular, the Gecol Yeso Porcelanico although Puma do a version (Pegoland Professional Flex Elite and similar) and found out that although they are Gypsum compatible they’re still cement-based products. The Kerakoll rep told me that this type of adhesive had been adapted with ingredients that prevent the reaction between the adhesive and the anhydrite. The technical rep for Gecol said that no primer was needed. However, Miguel from Kerakoll said all anhydrite floors need a primer and I felt more comfortable with his assurances than with those from Gecol. Kerakoll’s Primer A (similar to Eco A) is their primer which needs the first coast diluted 1 to 1 and a second coat neat according to their tech spec.

Finally, I spoke to Ditra. At first the rep said that they couldn’t guarantee a product they hadn’t tested and it was down to the adhesive manufacturer to say what their product could stick to! He had another tech person from their Madrid office call me and he said that for the adhesive to stick to the Ditra 25 it had to comply with the Spanish regulation for sticking tiles so Kerakoll H40 would be great.

I´m going with the Kerakoll H40 now as the price difference is substantial. However, I have toyed with the idea of replacing the Kerakoll primer with an Epoxy. I haven’t resolved the doubt as to whether it’s best to use epoxy from a different manufacturer or the recommended Kerakoll Primer A made by the same manufacturer as my adhesive.

What a palaver!

All the best, Em

 

[Eminem]

I wouldn't recommend using keraquick on anhydrite withoutva primer. Keraquick is cement based so wont stick well without.

Hi Mr Jackson,
Could you ship 8 sacs of Anhyfix to Spain? Could I call you to discuss this? All the best

 

[Ajax123]

I think you are very much over thinking it. And getting very confused about manufacturers and suppliers. LKAB do not make or sell Anhyfix. Anhyfix is a tile adhesive made by Tilemaster. Tile master is owned by Kerakoll.

Moisture testing with Carbide bomb needs to give 0.5% moisture not 0.02%.

Priming is to stop suction not to "stabilise a soft surface". if the surface is soft it is not right.

Unfortunately to answer your direct question, can I ship 8 bags of Anhyfix to Spain the answer has to be no because it is not one of our products. You would need to speak to Tilemaster, who make it.

 

[Eminem]

I think you are very much over thinking it. And getting very confused about manufacturers and suppliers. LKAB do not make or sell Anhyfix. Anhyfix is a tile adhesive made by Tilemaster. Tile master is owned by Kerakoll.

Moisture testing with Carbide bomb needs to give 0.5% moisture not 0.02%.

Priming is to stop suction not to "stabilise a soft surface". if the surface is soft it is not right.

Unfortunately to answer your direct question, can I ship 8 bags of Anhyfix to Spain the answer has to be no because it is not one of our products. You would need to speak to Tilemaster, who make it.

Hi, I appreciate your clarification. No, I didn't know Tile Master was owned by Kerakoll. I have had to think sideways as there are less products here and they are different. I am keen to be 100% sure the floor doesn't fail and some of the manufacturers to me don't seem to be genuine. They won't be there if things go wrong whatever they have said on the telephone. All the best and thanks again for your comments.

 

[Ajax123]

No problem. Good luck

 

[Ricochet]

Hi Em I have just read this thread and I am sure you will have completed the project by now, but I would be interested to know how it worked out.
I wondered why you wanted to use an anhydrite screed, as it seems to have created many issues with the choice of adhesive?

Like the guy at Mapei I have never been a fan of Anhydrite, I did a similar project to yours here in Italy and I used a cementitious self levelling screed, using a product by Fassa Bortolo SA500. I tiled directly onto this using Keracoll H40 no limits, which seems to be the go to specification here.
I also wanted to avoid using Dita from a heat transfer point of view, whilst I couldn't find any data on this it seems to me that introducing a layer of plastic and decoupling must interfere with the heat transfer. Anyway mine has been down for two years now with no problems and is working very well.

 

[Ajax123]

Hi Em I have just read this thread and I am sure you will have completed the project by now, but I would be interested to know how it worked out.
I wondered why you wanted to use an anhydrite screed, as it seems to have created many issues with the choice of adhesive?

Like the guy at Mapei I have never been a fan of Anhydrite, I did a similar project to yours here in Italy and I used a cementitious self levelling screed, using a product by Fassa Bortolo SA500. I tiled directly onto this using Keracoll H40 no limits, which seems to be the go to specification here.
I also wanted to avoid using Dita from a heat transfer point of view, whilst I couldn't find any data on this it seems to me that introducing a layer of plastic and decoupling must interfere with the heat transfer. Anyway mine has been down for two years now with no problems and is working very well.

I presume that you are not a fan of anhydrite simply because you dont know enough about it and its benefits. H40 no limits would be equalyy suitable for use with anhydrite. Im not sure what anhydrite screed is available in Italy though.

 

[Ricochet]

Hi Alan
You're welcome to presume of course, I guess the tech guy at Mapei is equally uninformed?

 

[Ajax123]

Hi Alan
You're welcome to presume of course, I guess the tech guy at Mapei is equally uninformed?

It would be innaproprate for me to comment on the technical guy at Mapei. I have run training sessions for them in the past in the UK but not for some considerable time. They dont have gypsum based adhesives in the UK so are a bit scuppered for choice so they are not generally my primary recomendation over here. I dont know what they have in Italy. I do know that Kerakoll and Mapei in Italy are very much arch rivals so I would have thought they would have similar materials.

I also find that often people over specify for anhydrite in the misuided beleif that more is better. I find that simply using appropriate materials is the cheapest and easiest way forward.

 

[Ricochet]

Hi Alan

I am disappointed that you consider it appropriate to afford greater courtesy to the guy at Mapei than you do myself, maybe time for you to revisit that LKAB code of conduct, who knows I could have been a potential customer.

Having worked all my life in the UK construction industry, mostly with national main contractors, I have a very good eye for detail and specification. I have also witnessed some spectacular failures in the early days of Calcium Sulphate / Anhydrite screeds, failures that cost a lot of money, time and disruption and we all know that consequential losses are never recoverable. Those experiences stay with you Alan.
I have no doubt that these products have evolved and improved, but I also note that Anhydrite screed producers / contractors always want to compare their product to traditional sand and cement screeds rather than self-levelling cementitious screeds, telling perhaps.

Gypsum has its place, my career started as a plasterer, but I am not convinced that floors are its optimum application, not least because of its love of moisture. From the knowledge and experience that I have and the research that I did, I chose a cementitious self-levelling screed for the following reasons:

Cost

Speed of laying

Quality of finish, flatness and level

Speed of drying / foot traffic

Thermal performance with UFH

Strength

No laitance

COSHH implications

No sanding required (although I did choose to hand sand)

Choice of adhesive / cost of adhesive

No priming required

No requirement for decoupling

Moisture resistance

Recycled content

End of life disposal implications

I have no doubt that in my case, a pumped self-levelling cementitious screed was the best choice, that is my opinion, an informed and impartial opinion.
I would urge anyone to consider its use carefully, I believe it is available in the UK from companies like Tarmac Topflow, Mincrete Cemfloor, EasyFlow, Longfloor. These are the names I found from a quick google.

Ciao

 

[Ajax123]

Hmmm… I’m not sure what about my reply you found discourteous. My apologies if you were offended. There was no intention to do so.

 

[Kevbos]

Hi, I appreciate your clarification. No, I didn't know Tile Master was owned by Kerakoll. I have had to think sideways as there are less products here and they are different. I am keen to be 100% sure the floor doesn't fail and some of the manufacturers to me don't seem to be genuine. They won't be there if things go wrong whatever they have said on the telephone. All the best and thanks again for your comments.

I was on a job at London Bridge many years ago when anhydrate first stated to be used !! We tiled 3 floors of flats !to recommended guides !! We then had to go back and take it all up !! Mapei were used to find problem ! They did ! Laytenance needed taking off ! Floor needed a newly invented primer then a matting !ditra or equivalent ! Stuck with mapei keraflex and the previously mentioned additive !! There is no way ever that anhydrate should not be primed !! I would go with mapei as I have never had problem since that job in 2005 !