Reccomendations for construction of solid floor with UFH.

[Tony]

Hello, I have lifted the stone flags in our kitchen and want to re-lay them, with insulation and wet underfloor heating. We have dug the clay out to a depth of 300mm below the finished surface and my intention is to lay 25mm sand, DPM, 25mm sand, 80mm kingspan, fix UFH pipes to surface, screeded over to protect during flag laying ( not sure of depth of screed needed), then a solid bed of sand/cement to lay the flags on, probably one flag at a time. Does this sound like reasonable construction for the floor and has anyone got reccomendations for the UFH, I think 22mm might be prefferable, to raise the temperature quicker. Cheers, Tony.

[John Stumbles]

The UFH article on the DIY wiki has links to maunfacturers' publications on how to do UFH, which should answer most of your questions.

IIRC

[dennis]

You probably need to check building regs. Even if you don't the building inspectors usually offer good advice for nothing.

[The Natural Philosopher]

No. I am fairly sure you need to lay a proper concrete floor first, possibly with rebar, to prevent soil movement from cracking the lot, then go DPM and insulation, then pipes and screed.

I'd say 100mm concrete/rebar, 75mm kingspan and 75mm screed is about right, and then lay stone on top of that.