Sand & Cement vs Liquid screed - which is best? (70mm)

[Great_scot_selfbuild]

I'm getting quotes for both sand & cement and liquid screed floor layer over our UFH.

 

The depth was going to be 75mm, but it turns out my principal designer failed to take into account that the screed needs a layer of self-levelling compound on top before we lay our LVT, so I've been advised by multiple screed companies to allow for at least 5mm as I can always add SL Compound. Therefore, working back from the FFL and 5mm LVT, with 150mm PIR, we'll be needing 70mm of screed.

 

The initial costs I've had back aren't as different as I expected:

 

Area = 130sqm

 

If cost wasn't a deciding factor, what would you choose and why?

[Mr Punter]

I like traditional sand cement screed.  75mm is quite thick for liquid screed.  If you go liquid, use Cemfloor as there is no laitance removal needed.  I have used Sigma Screed in the past and they were very good.

[Nickfromwales]

Use my mate for the dry screed and you can pretty much paint it green and play snooker on it.

 

You won’t need a full bed of SLC, your LVT installers will just use feathering compound wherever necessary (LINK) so less time and complexity and then it’s easier to manage trades.

 

You should only need to do a full layer of SLC if you’re putting LVT down over a concrete slab.
 

A good screeder will give you the result you want, save you time, and money. 

[Great_scot_selfbuild]

2 hours ago, Mr Punter said:

 

I like traditional sand cement screed.

 

Any particular reason?

 

1 hour ago, Nickfromwales said:

your LVT installer

That’ll be us

 

2 hours ago, Mr Punter said:

use Cemfloor as there is no laitance removal needed.

The quote I have is from a recommended cemfloor installer - whilst he said theees no laitance, it does still need keying-in, which is what his £1105 is quoting for. 
 

1 hour ago, Nickfromwales said:

Use my mate for the dry screed

Estimate was iro £4k before laitance removal. 

[Nickfromwales]

6 minutes ago, Great_scot_selfbuild said:

Estimate was iro £4k before laitance removal

There is no laitance with a dry screed?

 

7 minutes ago, Great_scot_selfbuild said:

Any particular reason?

More accuracy, better finish, no follow up to get it ready, generally just better outcome. 
 

Also, it’s not a liquid, so less prep as it doesn’t want to find a gap and disappear down / into it.

 

8 minutes ago, Great_scot_selfbuild said:

That’ll be us

Then make life easy!

 

9 minutes ago, Great_scot_selfbuild said:

whilst he said there’s no laitance, it does still need keying-in, which is what his £1105 is quoting for.

Not sure what that’s all about. Last few cemfloor installs I’ve been on just needed sealing / priming etc. 

[Nickfromwales]

3 hours ago, Great_scot_selfbuild said:

I've been advised by multiple screed companies to allow for at least 5mm as I can always add SL Compound

This only matters at openings, and with a dry screed you can put a line of masking tape and draw a line across it and tell them to screed to that line. 
 

And they will.

 

Then just feather the few places where it needs it, nothings ever perfect, and off to go.

[saveasteading]

1 hour ago, Great_scot_selfbuild said:

does still need keying-in, which is what his £1105 is quoting for. 

I'm confused by that. Any latency in dry screed is deliberately made on the surface for a smooth finish and should be minor.  I can't see why you would have to do much to it.

The main concern would be tamping ripples no worse than on a poured screed.

[Nickfromwales]

41 minutes ago, saveasteading said:

The main concern would be tamping ripples

There’s near zero ‘ripples’ if you lay a dry screed properly, it’s trowelled by hand to float it almost completely flat. 

[saveasteading]

28 minutes ago, Nickfromwales said:

If you lay a dry screed properly

If. 

I believe it is a skill that is fairly rare.

[Great_scot_selfbuild]

1 hour ago, saveasteading said:

I'm confused by that. Any latency in dry screed is deliberately made on the surface for a smooth finish and should be minor.  I can't see why you would have to do much to it.

The main concern would be tamping ripples no worse than on a poured screed.

The reference to keying in was on a Cemflood liquid screed. 
 

The dry screed quote states that they provide the pump - I hadn’t realised that a dry screed would be pumped. Is this normal? (As you can tell, I’ve never seen it done and the only very small amounts of dry mix used so far have just been mixed in the mixer and then used straight away.

[Great_scot_selfbuild]

13 minutes ago, saveasteading said:

If. 

I believe it is a skill that is fairly rare.

This is my concern - by the time I find out they aren’t very good it will be too late. Hence I’m asking for references (some of them have little/no online reviews).

[Nickfromwales]

40 minutes ago, saveasteading said:

If. 

I believe it is a skill that is fairly rare.

My mate (details have been shared with the op btw) did @Russell griffiths place, and I’ve used him for 25 years. 
 

When I say you can paint it green and play snooker on it, I’m not joking. 

[Nickfromwales]

27 minutes ago, Great_scot_selfbuild said:

I’m asking for references

I’ve given you contact details for one of the best screeders you’ll ever meet.

 

Family run business, with dad having passed the baton to his sons.

 

One of their previous projects was an £80m 8-storey mega house for a wealthy chap in London.

 

 

[Russell griffiths]

Edited Friday at 16:11 by Russell griffiths

[Russell griffiths]

Top pic in my previous post was after washing the floor ready to prime it for tiling. 
middle pic was the day after it was laid. 

[Great_scot_selfbuild]

3 hours ago, Nickfromwales said:

I’ve given you contact details for one of the best screeders you’ll ever meet.

 

Family run business, with dad having passed the baton to his sons.

 

One of their previous projects was an £80m 8-storey mega house for a wealthy chap in London.

 

 

Yes - thanks. Just waiting for references from the other quotes.

 

As it is, I think Justin sounds very busy, before considering that at his very rough estimate he’s about £1k more than the other dry screed quotes (of course that is irrelevant if he’s not available).

[Great_scot_selfbuild]

2 hours ago, Russell griffiths said:

Top pic in my previous post was after washing the floor ready to prime it for tiling. 
middle pic was the day after it was laid. 

@Russell griffiths it does indeed look good!

[saveasteading]

11 hours ago, Great_scot_selfbuild said:

with 150mm PIR, we'll be needing 70mm of screed.

Why not increase the insulation? It's much cheaper per m3 than screed and you get better insulation.

 

[Great_scot_selfbuild]

1 hour ago, saveasteading said:

Why not increase the insulation? It's much cheaper per m3 than screed and you get better insulation.

 

1. We’ve already bought the 150mm insulation

2. Thicker screed provides greater thermal mass for retaining the heat from the UFH

[saveasteading]

25mm could be added top or bottom. Gives an overlap too.

Thermal mass is another conversation, but often used to justify over-designed slabs.

 

Eps about  £50/m3   pir £80/m3, grout £400/m3

 

[Bancroft]

Broadening out the topic slightly but when do people think screeding is best sequenced in the overall build?

 

I had in my mind that it would be done early in the process once the main structure was watertight.

 

But, I've seen a number of University of Tube videos where ufh pipe and screed has been laid after first fix electrics and after walls had been plastered.

 

I think the instances I saw were for floors screeded with modern liquid screed, as opposed to the more traditional concrete so there may be a difference with regards to moisture levels.

 

Thoughts?  Pros/Cons? Pooh traps to be avoided?

[JohnMo]

I did concrete over UFH and insulation, it was all done before the walls went up - the external ones.

[Nickfromwales]

25 minutes ago, Bancroft said:

Broadening out the topic slightly but when do people think screeding is best sequenced in the overall build?

 

I had in my mind that it would be done early in the process once the main structure was watertight.

 

But, I've seen a number of University of Tube videos where ufh pipe and screed has been laid after first fix electrics and after walls had been plastered.

 

I think the instances I saw were for floors screeded with modern liquid screed, as opposed to the more traditional concrete so there may be a difference with regards to moisture levels.

 

Thoughts?  Pros/Cons? Pooh traps to be avoided?

Why make it such a pita to airtightness tape etc by screeding so late in the game?

 

Sooner it’s down the sooner it starts drying too. Also nice to be running UFH if working though the winter. Did this on the last one where we boarded and skimmed the plant room very early on, just to get the ASHP in and running.

 

Much nicer site to work on if you’re not freezing and the house doesn’t then have damp / mildew growing on the fresh plasterboards etc. 

[saveasteading]

The job is more in control with a hard floor . The downside would be if you damaged it by impact or scratching s screed, or putting a screw through the ufh pipes.

Drying isn't an issue. It doesn't take long and most of the hardening is chemical.

That all changes if doing it before the weatherproof structure.