First problem in 10 years....

[Old Mod]

There's a lot said about decouplers but I have never seen the need on a concrete screed. Thoughts?

Well it would depend in what context you're referring to.
As an antifracture membrane or as a vapour barrier for fast tracking green screeds?
Either way, I think it's worth starting another thread as this is way

 

[J Sid]

would this problem have happened if a Schluter type uncoupling membrane was used, imho NO

 

[J Sid]

beat me to it marc

 

[Scott]

Schulter won't recommend it on a green screed with ufh either. Heating has to be commissioned before laying, they used to say it's OK but not anymore