Advice on laying tiles on problem flooring!

[Rnessbert]

Hi all,
This is my first post and as you will see I am not a tiler and have little knowledge. However I am hoping some of you might be able to help me out with a huge problem i have had over the last 3 years!
Ok so where to start, we moved into a brand new house three years ago, everything was great, we had an amazing porcelain floor from the front door, through the hallway and the whole kitchen. However after approx three months i started noticing the grout cracking and the tiles becoming loose, eventually the building decided to replace aslong as we sourced the tiler and tiles.
I had a couple of tiles come and look at the job, they all seemed to agree the problem was with the type of screed used, this s a self levelling one which was told had a chemical that reacts with normal adhesive hence the movement. An are rep even came in from mapai to advise on the correct primer and adhesive to use. I should add at this point we have a wet underfloor heating system, however we were advised this should not be a problem.
So,we settled on a tiler and started looking for tiles, the ones we liked were White Quartz tiles, i checked with the tiler and he advised no problem they can be used with UFH! So order went in tiles and tiler arrived and floor was layed, it looked fantasic! However after 6 months, i noticed the tiles had started to raise between the kitchen doorway, gradually it got worst and worst, i called the tiler back he said they it was tiles had bowed and probably because they were a resin tile and shouldn't be used with UFH, ok thanks but different to what you told me before! We replaced 6 60mm x 60mm tiles and tried keeping the flooring system turned down, however 6 months later the same patch of floor by the doorway has come up, about 70% of the flor remains solid!
We have now decided we can't live with the floor as is and have decided to replace it one last time! We did think about engineered wood, however this is not even close to the look we are going for so back to tiles! However i want to be 100z% sure that the tiles and laying system is spot on. I have read that a de coupling mat might be worth using, but can't work out if right or not.
Basically I think our story has gone, right tiles wrong adhesive to right adhesive wrong tiles, we just need right adhesive right tiles now!
Any advice gratefully received, i am based in Newport South Wales and will also be looking for a tiler who knows what he is doing to complete this job!
Thanks for listening

 

[Sean SML Tiling]

If its a new floor then the floor should have been commissioned first. Secondly the tiler should of found out what screed and t is so he can make the decision on what adhesive is suitable. Then any decent tiler knows most resin quartz should not be used with ufh. Covering the floor with ditra us a good idea but if there is a latience still on the floor from the screed it needs removing otherwise the ditra will fail.
What screed is it so we can advise u further

 

[The D]

Was the original screed dry when it was tiled ?? Was it sanded ?? Was it vacuumed ?? Was it primed with a suitable primer ?? I am assuming the screed is an anhydrite screed? If it is all the same questions for the second installation. Did anyone test the floor to see if it was dry enough to receive a floor covering? Was you ever told by anyone the steps that need to be followed to make the floor ready to receive a covering?

 

[Stef]

As Deano states above this floor really needs to have a moisture test done on it to make sure it can take the floor coverings.
By the way you have described your floor has failed the 1st time through ettringnite crystals forming between the screed (Calcium Sulphate) & the cement based adhesive.
The second failure could have been prevented if a suitable quartz tile had been used.
You have to make sure that this floor has been sanded to remove the laitance from the surface, if it hasn't then it's going to be baked onto the surface by now.
You can use a cement based adhesive on this screed but it has to be primed properly to form a barrier between the screed & adhesive.

 

[Rnessbert]

Hi all, firstly thank you all for taking time to reply! As you can image having absolutely no idea of tiling and building in general means its all been very confusing and frustrating!

Im not sure i have the exact answers to your queries, however this is what I can add...the screed used was pumped through the window and was self levelling the exact make is unknown as the actual builders are long gone. When we took the original tiles up, it seemed very dry and dusty, chalk like and a beige colour. When the new tiler came out he talked about the option to sand the floor first, but advised this was very messy and time consuming and would not make much difference. He did tell me he put a primer on the floor to stop the chemical reaction with the adhesive.

I guess what I am looking for is confidence that we can have a tiled floor, and if so somebody who actually knows how to do it

i see you are local SML, would you be interested in taking a look? I guess this might now be a scary job considering the history!

thanks again guys for your help

 

[The D]

You will need to remove the tiles and test the floor to see if it is dry. When it is dry you will need to sand the floor to remove the powdery surface and then vacuum to ensure there is no residue. It is most important that the floor is dry and sanded. The primer will depend on the adhesive you use if your tiler uses cement based adhesive it will be best to use an epoxy primer but if he uses an anhydrite adhesive he will need the accompanying primer but in any circumstance the floor must must must be dry.