Random cracks in Limestone Floor tiles

[CamR]

All,

I have a specific issue that would benefit from knowledgeable, 3rd party advice

We have just had a new limestone floor fitted on to a newly laid concrete floor with wet UFH

So far we have found 21 cracked tiles, they are random throughout the tiled area which is a lounge, dining room, kitchen, approx 45m2

The UFH temp is set at a steady 18 degrees

The tiles have been laid with flexible adhesive and NOT dot & dab

I do not know how the heating was applied after the tiles were laid because we are not in the property and the builders managed that bit.

Both Tiler and builder reckon they have laid similar floors with no problems in the past and are trying to get me to talk to the stone tile supplier.

My initial searches on the forum suggest that expansion gaps and de-coupling membranes should have been used but I am no expert and I may be jumping on a bandwagon trying to find a cause.

I would appreciate some comments that I could share with the builder/tiler

Thanks in advance

CamR

 

[White Room]

Hi and welcome....decoupling membrane should have been used...

 

[DHTiling]

Was the screed heating commissioned prior to tiling. ?

 

[Ajax123]

Newly laid concrete floor....what sort of concrete?? Are we talking sand gravel and cement or are we talking screed. Was it cured, was it dry, was the underfloor heating comissioned, lots of possible issues. I agree uncoupling membrane should have been used but several other steps should have been followed as well.

 

[CamR]

Was the screed heating commissioned prior to tiling. ?

I believe so, the builders used to sit on the floor and have their bait because it was nice and warm

 

[Andy Allen]

was the heating bought up to temp slowly and in stages..

 

[CamR]

Newly laid concrete floor....what sort of concrete?? Are we talking sand gravel and cement or are we talking screed. Was it cured, was it dry, was the underfloor heating comissioned, lots of possible issues. I agree uncoupling membrane should have been used but several other steps should have been followed as well.

Thanks for the response, is it possible to jot down the steps that should have been followed so that I can then ask the relevant questions of the builder/tiler?

CamR

 

[Ajax123]

If your floor makeup is traditional ground borne floating concrete then
Sub base laid and blinded with sand
Sub base overlaid with minimum 1200 gauge polythene DPM
Insulation laid with minimum 8mm compressible edging strip at perimeters and abutments
Minimum 500 gauge polythene slip membrane laid and all joints lapped and taped
Suitable joint formers placed to rom bay sizes no more than 15m2 (NHBC chapter 8.3) with additional joints across for thresholds and between heating zones
Underfloor heting pipes laid and secured
Underfloor heating pipes filled with water an pressurised to minimum 6bar or the maximum system pressure whichever is the lower
Concrete laid and cured under a membrane for seven days following installation
Pipe pressure reduced after 24 hours
Curing membrane removed and concert allowed to dry for sufficient time (1mm per day dying rate)
Minimum 28 days following laying concrete heating switched on at ambient.
After three days temperature increased by maximum 5 degrees per day up to maximum temperature
After three days reverse this process then switch off for three days.
Carry out suitable moisture test to Determine if concrete is dry enough to tile to
If not dry, leave for longer
If dry, clean the surface of the concrete ideally by sanding to remove laitance, lime bloom, construction dirt and debris and the vaccuum thoroughly

Your concrete is now ready to lay lies to so I shall ask the tilers to take over......

 

[Houston]

It might be the quality/grade of stone

 

[bugs183]

Are the cracks running in lines on several tiles, and do you have any cracks across or near to doorways, if so this would indicate the screed is cracking underneath.
Or if the tiles are only on random tiles, it could be bad fixing.
To be fair the use of ditra on underfloor heated floors is a relatively new thing, so many tilers who are not up to speed with recent developments so it doesn't mean they are inexperienced or bad tilers.