Floor Screed

[CHarr]

I'm having trouble finding anyone who can lay a sand/cement floor screed in my extension, so I'm looking at liquid screed (readily available at a day or two's notice from lots of places).

My concrete floor slab is 160mm below DPC and I was going to lay 80mm of Celotex and then conventional screed. I was suprised to see that, say, 120mm EPS is significantly less expensive than 80mm Celotex (but appears to outperform it), meaning that I would only need 40mm screed.

Is there a catch with liquid screed? It's quick to lay, self-levelling and can be walked on after 48 hours. Sand & cement seems to require much more labour to lay and then to be left 7 days to harden. Drying time is much longer too, because of the increased depth. The overall cost seems comparable.

 

[Norcon]

Is there a catch with liquid screed?

Here in the province its nearly three times the price.

 

[CHarr]

Is there a catch with liquid screed?

Here in the province its nearly three times the price.

What would you expect to pay per m2 for either system? The Mrs wanted polished concrete (ha ha).

 

[CHarr]

I have a quote for liquid screed over 34 m2 at 50mm depth (1.7 m3) for £1,106 + VAT (£32.50/m2).

Should I really expect to get 75mm of sand and cement (material & labour) for a third of that? If so, who from?

 

[noseall]

We had a job done recently for a 75mm sand/cement screed over UFH for 54m².

Tot £970 +vat or about £18 p/m.

Tidy bunch of guys and very accurate. All done in less than a day from a cold start.

Flow screeds are not suitable for some applications.

 

[CHarr]

I'm going to have a go at laying my own sand and cement screed in my small conservatory (2m x 3m), see how it goes, and then decide whether I feel able to do the larger kitchen/dining room extension too.

I was going to buy bulk bags of sharp sand and mix at 4:1 with cement, using a hired cement mixer. Should I use plasticiser? I was planning to put the mixer as close as possible to the work area, mix in place and tip out before spreading, tamping and trowling (while another batch was mixing), and then continue, batch by batch, working towards the exit point. Does this sound like a reasonable method. Should I add reinforcing fibres and if so, of what spec.?

If I don't end up with a completely level and smooth surface, I can always use a levelling compound, I suppose.

 

[noseall]

I was going to buy bulk bags of sharp sand and mix at 4:1 with cement, using a hired cement mixer.

Sounds good.

Should I use plasticiser?

No.

Should I add reinforcing fibres and if so, of what spec.?

Just buy a bag of fibres from a builders merchants and chuck a handful in on every mix.

I was planning to put the mixer as close as possible to the work area, mix in place and tip out before spreading, tamping and trowling (while another batch was mixing), and then continue, batch by batch, working towards the exit point. Does this sound like a reasonable method. Should I add reinforcing fibres and if so, of what spec.?

Sounds good to me.

Screeding is hard work but at least the muck affords you plenty of working time.

Do not mix it too wet. If you do mix a wet one spread it about on the bottom. You only need just enough water so that it binds together.

Use 1200mm level and run a screed around the perimeter then fill in using a straight edge. You will need a poly-float and a floor trowel.

 

[CHarr]

Use 1200mm level and run a screed around the perimeter then fill in using a straight edge.

I was going to put in an upstand of insulation around the perimeter and then divide the room into two bays, slightly overfilling one bay with screeding mixture and then placing a suitable straight timber down the middle, tapping it down to get a level front to back & side to side, and then using a straight edge to draw across the two sides before repeating on the other bay, then removing the timber and filling in before floating the whole area smooth.

It sounds like hard work - but then so is earning the money to pay someone else to do it - and no one wants the job!

 

[CHarr]

I'm starting the screeding job tomorrow, having laid the underfloor insulation and taken delivery of all the materials & a hired mixer.

How long will it take before it's OK to walk across the finished floor without risk of damage? I know it takes a while to attain full strength, but I could usefully start putting together a couple of stud partition walls ASAP.