Underfloor heating - constructing the slab

6 Sep 2008
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United Kingdom
Quick question on creating a slab for underfloor heating. I have an existing slab that I have no plans to remove. I'm thinking to:

add 200mm of insulation to it (above the existing slab)
put down some light weight mesh sheets (a142, d49, d98?)
cable tie the heating pipes to the sheets
pour a 50mm liquid screed over it

are there any problems with this approach? thermal expansion rates of the metal vs the screed? depth of screed too shallow? does it weigh enough to effectively compress the insulation and provide a firm base?
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Why the mesh?

The UFH guys just staple the heating pipes direct to the insulation. Our screed guys (E Berry LTD) once advised us that the flo-screeds aren't the best for UFH and that they recommend using sand/cement screed.

Are you using 200mm thick inso' just to gain more height?
Crack resistance, heat spread, something to attach the pipes to, slimmer screed (?)

Are your screeders sand+cement guys, liquid guys or both?

200mm inso to reduce the heat loss from the heated floor into the ground, and because I can afford the height
E Berry ltd obviously has a vested interest in sand/cement screeding.
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