Omri wrote:

Sand / cement dry screed needs to be about 1" to 11/2" thick. mix damp sand
with cement and voila. Use a float to work it quite easily into a lovely
flat finish. No good as a thin layer, eventually it will lift.

It's suggested by Newheat at a depth of 15 mm as a heat diffuser instead
of their optional aluminium spreader plates that go around the pipe.

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