screed quantities

[Davi]

got thick head on... could someone just confirm if my memory is correct or not. When calc'ing the quantity of sand for screed you ignore the cement as it doesn't increase the volume (by any appreciable amount) and roughly speaking 1 tonne sand = 1 m^3, so to do a floor 3.5m x 2.5m x 0.06m I'll need ~0.5 tonne sand and 5 bags cement - correct?!

now for a bodgeit question - what would the effect of using 3:7 soft:sharp sand mix be, considering the screed is going under a stone and wood floor? bad idea or ok (would mean I wouldn't have to buy anything )

[PGM]

As a quick rough calculation, use the info below.

I would lay a 3:1 sharp sand:cement screed. Sharp sand is easier to lay than fine sharp (leighton buzzard or plastering sand) on the floor and is stronger.

The quantities are:

50kg opc
150kg sand
water to suit
gives approx
90l yield.

Your quantity required is just under 6 of those mixes .

Therefore you need

12 x 25kg cement
36 x25kg sharp sand.

Go to Travis Perkins or Build Center and ask for discount, you should get a decent chunk off the current rip off prices.

Edited to add you can use your sand no problem for that application

Cheers
Paul

Edited by PGM on Tuesday 26th May 21:53

Edited by PGM on Tuesday 26th May 21:58

[V12Les]

3n1?... thats way to strong. 4n1 would be plenty strong enough, even 5n1 would be fine for the OPs use.
Plastering sand is best, even chuck in some grit and the float will glide better, but no building sand.

[Davi]

Cheers chaps

I was going on 4:1 rather than 3:1 after a mate said they had a right mare with the 3:1.

Interesting comment on the plastering sand though - the plasterer ordered a tonne too much and I wondered WTF I'd do with a tonne of plastering sand, only it's plain building sand if you ask me...