Stone Floor Lifting

[Michael Coughlan]

Hi all, I would really appreciate any opinions on the following scenario. Thanks in advance for any help.

House was 20 years old. It had a large hall with carpet on floor (50M2). Carpet was removed and concrete slab was exposed. It was dust free and dry but and reasonably level. Devi underfloor heating cable was installed and a 2 part latex screed poured over it. 2 days later large format marble tiles were installed using ardex flex 5000 white. Tiles were buttered, and fully bedded. 2 and 1/2 years on and several of the tiles are lifting. Hollow sound etc under them. I removed one today very easily using suction cups (after removing any remaining grout). Tile decoupled from adhesive bed easily. Adhesive bed was full ( no voids). The middle of the bed was swollen up in a slight curve which would explain why the tile was rocking on it. I used a kango hammer and removed the adhesive. It was rock hard. 90% of it was still bonded to the levelling compound. However when the compound was removed there was drips of water on the underside and the concrete floor itself was wet.

 

[DHTiling]

Hi and welcome.

Are there any central heating pipes within the floor. ?

 

[Michael Coughlan]

Yes there are central heating pipes in there. And hot water supply pipes I believe.

 

[DHTiling]

Are you losing pressure on your heating system( boiler).. i take it , it is a combi system..?

 

[Michael Coughlan]

It's an older self filling system from a little tank in the attic so not so easy to guage water loss. i could tie up the ball **** I suppose and observe it for a bit. I thought of a heating leak before but there are several tiles lifting in different locations. Even ones in the utility room very far away from the particularly bad ones in the hall.

 

[DHTiling]

If you have water under the tiles then you have either a heating pipe leak or water pipe leak or... some form of damp..

You need to determine what is happening.. BUT a leak would not always blow tiles, so IMO i would eliminate these first..

 

[DHTiling]

You could run the heating as well and see if the wetting is warm water..?.. hard to tell though as we cannot see what you do.

 

[Michael Coughlan]

Moisture content under latex screed is only like a dew. Could it be rising damp? Would that lift the tiles off? If the problem was confined to a single area I would agree with the leaking pipe theory but it is too dispersed for that to make sense.

 

[Ajax123]

20 years old......is there a dpm under the concrete. I think damness explains the failure but you need to explain the dampness before moving forward.

 

[DHTiling]

That is my thoughts with what you have said since OP..

If the damp is blowing the SLC, then this will explain the tiles heaving..

What was the substrate primed with before SLC'ng..?

 

[Michael Coughlan]

I don't know whether there is a dpm installed (I assume there is) and if there is whether it is fully in tact etc. I have studied the areas of the house that are not tiled and there is no obvious dampness apparent. Would a very low level of dampness only become an issue when it's trapped in with the latex and waterproof adhesive?

 

[Michael Coughlan]

No priming was done before the evostik 2 part latex SLC

 

[DHTiling]

The slc and adhesive are water resistant, not water proof, so should allow moisture to rise/escape..through the tile joints but also areas will sweat with rising damp if it is that... hence what you have

It is time to get someone in and get this checked..

 

[Michael Coughlan]

Get someone in to measure moisture content in the concrete slab to confirm the rising damp theory? Are there other things that could be assessed? Should the entire floor have been "tanked" like they did in all of the bathrooms and "seal the dampness down"? Entire ground floor of the house has over 200 meters of marble

 

[CJ]

It does sound like rising damp condensing on the underside of the self levelling compound, causing it to de-bond from the screed.