Screed/concrete/dry/wet?

[curlewhouse]

Got my UFH down in the 2 smallest rooms, utility and downstairs WC. Being small rooms I want to do the screeding myself (though may call in the pros for the big rooms). I've got 200mm cellotex, and my pipes and steel mesh in place ready - my "issue" is going in circles about what I should actually put down. Is a normal sand/cement dry screed OK at 100mm thick? All the examples I can find online are thinner than that. (I also intend to add fibres of course) - or would a simple wet concrete mix do the job?  

Edited October 3, 2017 by curlewhouse

[Construction Channel]

Others might know better but i would have thought 100mm of dry screed should be fine. the only issue is it takes a long time to cure properly ( i have heard 2mm/day somewhere but i am happy to be corrected on that)

 

What are you planning to put on top of it?

 

if you are going for lino/karndine/vinyl i would say concrete it as a beginner you should be able to get a relatively decent finish easier and you will have to put some kind of self leveller on it anyway,

 

if you are going for anything with an underlay i would say have a go at screeding, its not as easy as it looks to get it like a bowling green but it is much more controllable and a lot less messy.  one of the hardest parts of screeding is getting the consistency of it right in the first place, after that you can mess about with it for pretty much as long as you like.  

[curlewhouse]

Yes, the quoted drying times are huge, I think you are correct as I had figured it to be about 50 days. I did think maybe to do it to 90 or 95mm and use a self levelling compound on top. We plan to put something like ceramic tiles onto it in the downstairs bathroom and utility room. Stone for the main living area, but I am probably going to get the pros in to do that screed as between it and the smaller sitting room there's about 100m2 to do so well beyond my DIY capabilities to level with any certainty.

Edited October 4, 2017 by curlewhouse

[Declan52]

You can put additives into a screed mix to speed up the drying times.

[Oz07]

Use self compacting Conc not much skill required you will save on labour 

[Nickfromwales]

1 hour ago, curlewhouse said:

Yes, the quoted drying times are huge, I think you are correct as I had figured it to be about 50 days. I did think maybe to do it to 90 or 95mm and use a self levelling compound on top. We plan to put something like ceramic tiles onto it in the downstairs bathroom and utility room. Stone for the main living area, but I am probably going to get the pros in to do that screed as between it and the smaller sitting room there's about 100m2 to do so well beyond my DIY capabilities to level with any certainty.

If you use Ardex A35 instead of cement you can lay ceramic tiles in 4 hours, FACT. 

Just used it and it's outstanding. Only ballache is £35+vat per 25kg bag and you need a pan mixer to mix it. Do not try and use a turn and fall ( regular ) cement mixer.

Can you wait ? If so, just pour a nice wet concrete and tamp it with a timber T bar and leave it 5-10mm shy of where you want it. Finish with leveller or plenty of tile adhesive. 

FWIW, tiling with a green slab can be done in less than a week if you put down a Ditra mat decoupling membrane ? 

[curlewhouse]

Must admit Nick, I have wondered why I can't just pour wet concrete and then use self levelling as you describe - it would seem far simpler, but I presume there's an issue why "dry" screed is used - drying time is still pretty massive, and I've built stuff like sheds or garden walls on top of concrete in far less than the 50 days in theory my dry 100mm screed could take to, er, dry.  Ordered the sharp sand today to do dry screed and have 4 days off work so plan to start on the first room tomorrow ....

Edited October 11, 2017 by curlewhouse