Jon Weaver wrote:

"Christian McArdle" wrote in message .net...

My problem is that the current 'slab' height means that it will
be impossible to raise the floor by any more than 100mm.. So,
If I have to add 50mm of insulation and 75mm of screed, the only
physically way possible would be to lower the slab by 25mm, and
as you will imagine, this impossible.

Well, 25mm of insulation would be infinitely better than none. That would
allow 75mm of screed.

Christian.


Interesting.. I just spoke to my local(ish) supplier of insulation and
they can supply 40mm boards.. This will give me 60mm of screed, and if
I follow the next posters advise of using chicken wire as re-enforcing
material, its should give me a base which is still strong enough.

With regards to installation, is it as simple as cutting it to shape
and placing it on the floor (ontop of the DPC) before they lay the
screed? Should it go right upto the wall, or should I leave a gap??

I was surprised how much the insulation costs though (£16+vat for
1.2x24m boards).. I will make some enquiries over the next few days.


Make sure you are gettng polystrne foam - blue or pink generally - not
Cleotex. That price sounds about right for a 5 pack of 4x2 shhets.

Just slap it down, and you may, if its a huge area, want to lay some up
the sides of the screed as well to allow for expansion, but it shouldn't
be necessary on normal installations.




Thanks for your advice, I will see what I can find before the builder
returns on Saturday.

Jon