Tiles not bonded to floor properly

[help_me_please]

We are having some issues with our newly laid tiles. Within several weeks of being laid, we noticed some hollow and 'popping' sounds on the tiles in high traffic areas and the grout started to crack. We are getting conflicting answers about what the issue could be from our contractor.

Can you please tell me if the process below looks correct?

1. UFH heating channels grinded into concrete and wet UFH pipes laid
2. Floor was then levelled with Dunlop LX40 self-leveller
3. Floor was left to dry for approx. 6 weeks and moisture test showed over 97% dry
4. Heating system commissioned and tested prior to tiling (as far as I am aware, the heating system remained on low heat during tiling and was not fully switched off again)
5. Floor primed using acrylic primer
6. Large format porcelain tiles laid using solid bed flexible cement-based adhesive

The tiler noted that the floor seemed 'soft' prior to tiling but the contractor said this was not an issue and to proceed.

After we reported the issue, one of the tiles was lifted to investigate. The adhesive was sticking to the tile but not the floor. There seemed to be a thin layer attached to the bottom of the adhesive which seems to be where the bond with the floor was broken, but it is not clear what this material was (primer?) - it was sent to lab to investigate but does not seem to have given any conclusive results. There were also some white deposits on top of the floor that looked like salts or other minerals.

Anyone spot anything that could help us identify what the issue could be? The tiles have been down around 3 months now and we are concerned this will become bigger issue in future.

 

[Slippery]

(as far as I am aware, the heating system remained on low heat during tiling and was not fully switched off again)

That's my prime suspect!!

 

[help_me_please]

That's my prime suspect!!

Thanks - we did ask about this and the contractor doesn't feel this is the issue but we are not sure. Their comment was that the advice to leave heat off only applies if the heat had been cranked too high and low heat would not impact the curing of the adhesive.


What is the recommended time to leave heat off after tiling?

 

[Ajax123]

97% dry?? What does this mean?

 

[help_me_please]

97% dry?? What does this mean?

I'm not sure, they said that they did the moisture test and reading came back at 97%. Does this sound correct?

 

[Ajax123]

No it sounds extraordinarily incorrect. The floor should be dry to below 75% to be suitable for covering. 97% is far too damp

 

[help_me_please]

No it sounds extraordinarily incorrect. The floor should be dry to below 75% to be suitable for covering. 97% is far too damp

Hmm, ok will try to get more information from them, I had taken that to mean there was only 3% moisture level left, but that doesn't seem to line up with the ranges that should be expected.
The floor did not feel damp to the touch - would this match tiler saying it felt 'soft'?

 

[Tiberiu]

Could be the laitance hasn't been mechanically removed prior to tiling.
Laitance is a weak, easily-crumbled layer on the surface of concrete, consisting of cement and fine aggregates that rise to the surface when too much water is added.

 

[Thompson65]

I think there are several issues here, for example, moisture of the floor, the softness of the floor (the tiler noted that the floor felt "soft" before the tile was laid, which may indicate that the concrete base is not strong enough to support the weight of the tile. This could cause the tile to move and shift, which led to pops and cracking of the solution), poor floor preparation, and quality of glue.

White deposits on the top of the floor can be efflorescence, which is a common problem on tiled floors where moisture is present. This occurs when salts and other minerals in the concrete or subfloor are dissolved by water and then deposited on the surface as the water evaporates. Efflorescence can be removed with a weak acid solution, but it is important to address the underlying moisture problem to prevent a recurrence.

 

[David John]

I think there are several issues here, for example, moisture of the floor, the softness of the floor (the tiler noted that the floor felt "soft" before the tile was laid, which may indicate that the concrete base is not strong enough to support the weight of the tile. This could cause the tile to move and shift, which led to pops and cracking of the solution), poor floor preparation, and quality of glue.

White deposits on the top of the floor can be efflorescence, which is a common problem on tiled floors where moisture is present. This occurs when salts and other minerals in the concrete or subfloor are dissolved by water and then deposited on the surface as the water evaporates. Efflorescence can be removed with a weak acid solution, but it is important to address the underlying moisture problem to prevent a recurrence.

I also think these could be the reason.