Causes of cracked limestone tiles with UFH

[diamondtiling]

thanks for responses so far - answers to peckers questions:

1 why was the heating not turned on and commisioned with the screed down before tiling?
I'll be asking the builder/tiler but he was pushing to get the job finished quicker.
2 is there expansion joints in the screed around the perimeter of the room?
Yes there is supposed to be - I believe there is a 25mm polystyrene border
3 is there expansion joints for the tiles around the perimeter of the room?
Yes for 2 also
4 why was there not a de-coupling membrane used, was one suggested?
Not suggested. I only came across this type of thing when googling for background information.
5 The exact adhesive and grout used?
Unfortunately I do not know this - on te invoice it just says flexible. Manufacturer was Weber and Stonell were who we bought it all off.

The heating in the screed. I will suggest the method you have proposed for removing individual tiles.

The sentence in bold letters above may have been the start of your problems. Screed dries at 1mm per day at the correct temperature, when it was laid it should have been covered whilst it gained maximum strength, with the cold weather we have had lately drying times take longer.
I have just finished a Sandstone floor that was on a 70mm screed that also had wet UFH in the screed, the screed was allowed to dry for nearly 3 months.

Can you post some pictures?

 

[Gazzer]

10m is a long run...too long IMO for tiles without an expansion joint.
As the guys have said, the heating should have been commisioned before tiling by bringing it up to full heat over a period of days.
Again as mentioned Limestone and indeed again IMO natural stones should have a decoupling membrane added for extra safety.
And lastly the floor was not allowed time to dry before tiling even at 6 weeks !

 

[jasonh15]

Here is a picture
Consensus seems to be screed cracking is the problem here due to poor implementation of it (lack of drying time and failure to run up the UFH for a period before laying tiles). Rather than poor or non flexible adhesive.

Still difficult to explain why one third of the room remains unaffected and coincidentally that is where the different screed was used.

 

[jay]

Still difficult to explain why one third of the room remains unaffected and coincidentally that is where the different screed was used.

do you mean screed as in sub floor or screed as in tile adh

 

[Gazzer]

Still difficult to explain why one third of the room remains unaffected and coincidentally that is where the different screed was used.

There proving that not all adhesives are the same but the point being that either adhesive companies would specify the drying period as the same as we have stated.

 

[doug boardley]

the picture imo, shows that there's a stress crack in the screed

 

[jasonh15]

do you mean screed as in sub floor or screed as in tile adh

sorry I meant different adhesive not different screed - the screed was laid in one go.

Also after the tiles were laid the heating was not turned on for at least a couple of months and then only turned up in small increments over about 6 weeks.

 

[Gazzer]

do you mean screed as in sub floor or screed as in tile adh

sorry I meant different adhesive not different screed - the screed was laid in one go.

Also after the tiles were laid the heating was not turned on for at least a couple of months and then only turned up in small increments over about 6 weeks.

The heating in the screed should have been fired up to max temp BEFORE laying of tiles . It should be then lowered until its off and then wait 2 days before laying tiles.

 

[Ajax123]

Sorry Guys only just seen this one. Loks fairly straight forward. Peckers has hit most of the nails on th head in his poss as have most of the rest so my input is probably not really needed. However I will give it anyway but not till tommorrow cos I playing snooker again tonight......wish me luck:hurray:

just to start off though. Polystyrene is not a suitable edging material for screeds. It should have been a minimum 5mm compressible etherfoam type edge strip. The polystyrene is to prevet thermal briging to the structure. The screed should have been jointed into bays which reflect the underfloor heating zones and if on zone there shoudl have been expasnion releif joints at around 15m2 intervals. Also joints through any door thresholds were required. Th underflor heating MUST be comissioned prior to tiing. The effect of comissioning it acts to releive stresses within the screed. If there are stresses and the screed cracks and your tiles are on top the tiles will also crack. I would hazard a gues that if you take some tiles up th screed will almost certainly be cracked.

 

[Ajax123]

This is unlikely in my opinion to be an issue with the adhesive