Most flexible floor tile adhesive for limestone with UFH?

[Kenco]

Hi all,

I had 120m2 of 610x406x12mm laid by cowboys in 2009, halfway through the job, I found they had switched to non-flexible grout to save money! Not an easy one to resolve as I had sourced the limestone, so would have been difficult to make the rip it up again, as I think they would have just walked! Cut a long story short, we fell out over it, they finished the job by adding a flexible additive to the remaining bags of adhesive they had sourced & promised me it would be ok, I delayed payment for 6 months, but then paid them in full. Surprise surprise, sound 35 tiles have cracked over the years.

Hairline cracks in the screeded (with piped UFH) subfloor migrating to the tiles, and yes I wish I had used decoupling membrane, relying in the professionals and all that…

I intend to chop the damaged tiles out and use Most flexible floor tile adhesive for limestone with UFH on the market. I have chopped one tile out (just to check) and the subfloor is solid, just a tiny hairline crack.

Can anyone recommend the most flexible adhesive in this situation?

I know I’m running the risk of reoccurrence, but cannot stomach the cost of ripping up 120m2 & relaying. Must be a £20k+ job minimum after removing & refitting kitchen, skirtings, architraves etc etc…

 

[Dave]

Hi all,

I had 120m2 of 610x406x12mm laid by cowboys in 2009, halfway through the job, I found they had switched to non-flexible grout to save money! Not an easy one to resolve as I had sourced the limestone, so would have been difficult to make the rip it up again, as I think they would have just walked! Cut a long story short, we fell out over it, they finished the job by adding a flexible additive to the remaining bags of adhesive they had sourced & promised me it would be ok, I delayed payment for 6 months, but then paid them in full. Surprise surprise, sound 35 tiles have cracked over the years.

Hairline cracks in the screeded (with piped UFH) subfloor migrating to the tiles, and yes I wish I had used decoupling membrane, relying in the professionals and all that…

I intend to chop the damaged tiles out and use Most flexible floor tile adhesive for limestone with UFH on the market. I have chopped one tile out (just to check) and the subfloor is solid, just a tiny hairline crack.

Can anyone recommend the most flexible adhesive in this situation?

I know I’m running the risk of reoccurrence, but cannot stomach the cost of ripping up 120m2 & relaying. Must be a £20k+ job minimum after removing & refitting kitchen, skirtings, architraves etc etc…

Hi. No flexible adhesive will stop the tiles cracking. If the subfloor cracks , then these will crack the tiles as well. I always use an uncoupling mat. No ifs or buts.
You could use one of the thinner mats so not to affect the finished tile height when you do the repairs

 

[Kenco]

Hi Dave, thanks for the advice, I bought some DITRA uncoupling mat a while back with this in mind. Not sure I have enough room to install it though, around 5mm?

What are your thoughts on this?

 

[Kenco]

Would Mapelastic CI be a viable alternative to provide crack isolation?

 

[Dave]

Hi Dave, thanks for the advice, I bought some DITRA uncoupling mat a while back with this in mind. Not sure I have enough room to install it though, around 5mm?

What are your thoughts on this?

Just depends if you have enough depth.

 

[deepakkumar]

Sounds like you've had quite a journey with that install — really sorry to hear about the issues. Unfortunately, skipping on the right products early on (like flexible grout and a decoupling membrane) often leads to exactly what you’re seeing now, especially with UFH systems in play.

Good to hear the subfloor is still solid despite the hairline cracks. For your repair, I’d definitely recommend going with a highly flexible S2-rated adhesive — they’re specifically designed to handle substrate movement and temperature changes from underfloor heating.

A couple of solid options to look into:

• Tile Adhesive Gold-501 – Excellent flexibility and bond strength, very reliable for limestone and UFH.
• Tile Adhesive PLATINUM-901 – Another top performer, especially for natural stone and heated screeds.
• Tile Adhesive SILVER-101 – A great combination for flexibility, particularly when decoupling isn’t an option.

Also, since you're doing spot repairs, make sure the back of each replacement tile is fully buttered, and the adhesive covers 100% to avoid voids that can lead to cracking again.

Best of luck with the repairs — sounds like you’re tackling it the right way now!