On 28/05/10 21:21, andrew wrote:
Tim Watts wrote:

I have to screed a concrete floor slab. Screed is going over concrete,
not over insulation. Screed depth was supposed to be 60 to 70mm, but
the slab ended up a bit thicker than intended, so in some areas, the
screed will be down to about 40mm thick.
Will a normal dry mix sharp sand / cement be OK at that thickness, or
should I add anything (like SBR etc.) Floor will be tiled.
I was going to use sand / cement in case I need to slightly slope
levels to match floors in two adjoining rooms.
Or should I consider any other type of screed ?
Cheers,
Simon.

I would have though 40mm was OK, but it's getting near the limit.


With or without screed fibres?

Can't answer that for dry screed. However, I've done down to 15mm SBR
screed without fibres with no problems, on small areas (1m x 2m) and
25mm SBR screed over 3x3m areas. I think the SBR bonding is too great to
allow easy cracking.

I've recently had 65^2 of uneven concrete screeded and I know it must be
thin in places as I had 1m^3 left over. even where it tapers of by a door
it hasn't given a problem yet though I fully expect to have to make good
with some epoxy.One chap and a laser level laid the lot in a day without
expansion joints which surprised me a bit.

AJH


--
Tim Watts

Hung parliament? Rather have a hanged parliament.