On 07/04/2018 15:01, wrote:
On Saturday, 7 April 2018 14:52:07 UTC+1, Mathew Newton wrote:

Thanks everyone for the input; there seems to be a slight preference for insulation-over-slab and the potential for this feeling slightly warmer underfoot appeals. Points noted regarding the potential downsides though.

I went for insulation below the slab as I thought insulation with just screed over would be a bit "wobbly" with a spinning washing machine on it (wait for someone to say should-a bought a Miele). This option just seems more solid to me.

With ours being a lounge I am assuming that loadings should be fairly static and spread out. It will be certainly something I'll make sure are factored into the design.

Speaking of design, or rather considerations for installation, I note from the Kingspan brochure (https://www.kingspan.com/irl/en-ie/p...-tf70-brochure, page 8 specifically) that insulation-above-slab requires the slab to have dried out completely before insulation boards are laid. That sounds reasonable, but it also says that this will typically take 1 day per mm. With a 100mm slab that means 100 days which seems rather a long pause in an installation?!

yet another reason to insulate under.


NT

But you still need to wait 100 days before putting down any sort of wood
flooring, unless you use 2nd dpc.

My 1976 house has solid internal walls (3 inch cinder blocks). On the
ground floor these have a line of thin bricks on the slab, then a
bitumen dpc, which would have been just above the screed, but hidden
by the skirting board, then the internal wall.

I think this was to stop moisture from the slab and screed wicking
up the internal walls and damaging the plaster and paintwork.