On 28 July, 02:10, John Rumm wrote:
Tim S wrote:
The aim is to put celotex on top then screed to 60-70mm - so 2nd question -
is any of this likley to matter that much? My default opinion is to wash
some dilute PVA over the top to firm up the surface then proceed as
planned. There is mesh in the slab and it's 100mm thick on a well packed
base so I can't actually see it going anywhere.

Opinions? Shame because I'd got it *very* level

Given this is a sub floor I can't see it being a problem. Very little
point pressure will be placed on it through the celotex. You will also
find it gains in strength with time.

--
Cheers,

John.

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Tim
My recent concrete laying exercises have 'always' tended to end up
with such a problem. In fact the workshop floor was laid from the end
of a batch on a concrete lorry (conveniently shot through the hedge
from the roadside) but it was a pretty wet batch and that, with the
slight drizzle that started as we levelled it, meant that there was
'loose' water on the surface once it was level and covered.

That was about a year ago and it set perfectly hard - maybe a little
loose dust but the surface is OK and is not showing any signs of
breaking up with machinery on it.

Rob