UFH (wet+concrete) installation efficiency

[Angermayer]

I am building an extension and planned to have UFH on its ground floor. My builder imbeded 15mm pipes under 10cm concrete which was meant to be the total thickness of the floor. Unfortunately as they knocked through to my existing house, it turned out that the new floor is 8cm lower than the old part's floor. Now they suggest puring a further 8cm of concrete to level all up. I am concerned that the UFH will be inefficient with 18cm of concrete over it. Any advice on this please? Thanks. Mike

 

[Ben-gee]

How can they be 8cm out? Didn’t anyone measure down from an existing window or door - what did they do just guess?
As you point out, that will be a huge mass of concrete to heat.

You would probably be better off putting a new run of underfloor pipes on top of this slab, ie within the extra 80mm screed you are adding on top.

I would be worried about their competency if a) they did this c@ck up; b) they didn’t come up with a solution…

 

[ShaunCorbs]

Did they have a design for the ufh route done ?