Screeding new extension floor

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Hi guys

Start of next year i will be putting in my finished floor in our new extension, as it stand we got it water tight late last night with the glazing.

We have our sub concrete floor in, and there will be a 1200g dpm, then 100mm insulation, then another dpm and finally 65-70mm screed. Size is 4m x 4m

Couple questions i have is, i plan to screed myself with help, sand and cement based. How long at best do you think before it could be tiled? I have seen it can be months. I have a mixer already so no hire cost.

Other option is i get someone in to pump it in liquid as this goes off quicker, but i have been stung badly by traders so having trust issues that they will get it level.

Im thinking its my own house i do take more pride, but do i let this one go or not.

Also, the sub floor is damp because the skylight was only fitted this week, so do i need the concrete to dry out or will i be safe to asume dpm will hold up.

Thanks for the help!
 
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Have you got a DPM under the concrete?

I looked at doing the screed myself, but whimped out and had it poured (30 sqm), it's excellent, but a bit dearer than doing it manually... it's very flat, and don't think I could have got it that good by doing it manuallly. I suspect it will be too costly for a floor that size.

You should wait for the subfloor to dry before proceeding really, that said I'm sure many builders don't, they can't be waiting a month for a floor to dry.
Have you go access to a dehumidifier, you could lob that on to aid drying.

I left a month for mine concrete floor and probably nearly 6 weeks for the screed layer that is around 65/70mm thick. Through Chrimstmas I'm starting the tiling next.

Are you putting UFH in? I can recommend it, I'm a convert.

My plasterer was saying 3 sand 1 cement mix for the screed if doing manually.

Good luck, keep us updated.

Merry Christmas.
 
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Hey pal, thanks for the reply! Merry christmas!

Yes i will be using a dehumidifier as the walls could do with a dry out too.

Well, i had thought about ufh, but i would need to dig up the old kitchen floor, and also was not sure as we may lino it or laminate with the composite stuff.

Theres no dpm under concrete, the slab is quite far down and its going to be built back up to existing old kitchen floor height. Architect who did plans advised two dpm's as he said something to do with celotex attacks concrete or something like that i cant recall!
 
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We have had a re-think over all this. I have talked myself into digging our old kitchen floor up, and having the whole floor screeded as one pumped. I didnt think screeding with sand and cement was so hard but after searching on here, seems most people hated doing it.

Also the ufh is on the cards. Been looking at the jg speedfit kit. I worked out how much i would spend on designer rads, the kit pretty much cost the same!
 
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Good effort, it will be worth it.
especially with tiles.

Will you be doing The work yourself or having it fitted?
I did my own, surprisingly straightforward.

Good luck.
 
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We have had a re-think over all this. I have talked myself into digging our old kitchen floor up, and having the whole floor screeded as one pumped. I didnt think screeding with sand and cement was so hard but after searching on here, seems most people hated doing it.

Also the ufh is on the cards. Been looking at the jg speedfit kit. I worked out how much i would spend on designer rads, the kit pretty much cost the same!

Don't do it yourself, it's skilled work.

I used to use a company with a screed pump, they would do your floor in half a day.

Don't forget perimeter expansion foam

For underfloor heating Id recommend mapei top cem, better thermal conduction for UFH and dry for tiling in 2 days.

Never fit underfloor heating in existing floors, always in new with 100mm celetex below it.
 
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Hey guys.

I wont be doing the screeding, but i will be doing the new slab in the existing part of the house. (The bit i gotta dig up). Theres not much of this extension i havnt done myself, but i do agree i have no idea on how to use screeding pumps etc.

As for the ufh, thanks for the heads up. I will fit this myself, i have done a fair amount of my own plumbing so far so id give it a bash!

So i will be digging up the old floor, 100mm pad, dpm, 100mm celotex, dpm + ufu then il get someone who does the screeding. This will match the specs of my new build.

Hopefully that will cut the costs. Any ideas what i could be looking to pay (midlands)? About 25sqm in total
 
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Wasn’t talking about screeding, just the ufh, sorry wasn’t clear.
 
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Around £500 for the screed and pump/operative around £300.

For some strange reason, you can’t buy the screed yourself (ready mix) the pump dudes have to organise it.

will be done in under 2 hours.
 
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Sounds like a plan then. Thanks. I will post some pictures in here once done!
 
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I was originally planning on using a liquid screed as part of the floor replacement in our living room, with wet ufh aswell.

However when the guy came round to measure up etc, he said that they're preferring to lay sand and cement based screeds with a chemical additive called Retanol Extreme. Benefits were that it reduced the thickness to that of a liquid based screed, and was dry in less than a week, versus the 6+ weeks required for a liquid screed...

Also, when I used Wunda for our ufh kit. Found the company really good to work with, responsive and the design service was really good. And priced out pretty well against the rest...
Being a designed system, had a bit more backup if had questions etc...
 
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Thats interesting. I thought liquid screeds generally set a lot faster. Theres two companys im going to call in the new year. Il ask them what they use before i take anyone on. Il take a look into wunda too, thanks!
 
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Thats interesting. I thought liquid screeds generally set a lot faster. Theres two companys im going to call in the new year. Il ask them what they use before i take anyone on. Il take a look into wunda too, thanks!

So my understanding with wet screed is that they dry at the rate of 1mm per day on average... So a 50mm screed would need approx 50 days to dry...
You can obviously speed that process up using heaters etc, but that increases the risk of cracking...
 
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I would like to expand a little on this question guys. Slightly off topic but here goes.

So i had a chat with a couple of companys about the screed. The one bloke basically said that, having the extra work/screed done on the old kitchen sise will only add another £100-150 to the bill.

As he put it, hes there already in terms of day rate, and i would of already paid the pump cost. Hes come in at £900 for 27sqm.

Thats to level it and do the laying.

The other questions on my mind,

i need put down a new 100mm concrete pad. Now generally i go pumped, but its 1.2 cubed so im tempted with getting my mixer out. Got a belle 150 to hand. Bad idea? It will cost about £100 as i have ballast left over

Not sure if they could get the pump pipes in, it would have to go 20m down my drive, around two corners then back on itself through the house

This will be around £350/400

I could have it shooted onto some dpc poly on my drive, not sure how long i would get to play with it?
 
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Faced the same thoughts, mixing it myself.
I eventually bought it ready mixed, from memory £300, 100mm x 30sqm.
The mixer was one of those volumetric ones, (Not the drum mixer type) that mixes it onsite and you pay by your usage.

the two concrete chaps helped barrow it all in and I made 3 of us, and within 40 mins it was all in.

it’s a lot of work, and yes you could mix it, but it too much shovelling aggregate around.

The ready mixed way took a lot of work out of the job, same with pumped screed, yes a bit more expensive, but rare for me to say, worth it.

Things I had overlooked that were time consuming we’re getting hardcore level with pegs in the ground, building a level perimeter brick border (Dry) in the building So I had something to level the wooden screeds around on To get the concrete Base flat.
Perimeter foam expansion blah blah blah.

I’m a bit further ahead of you, I’ve Just put the decoupling mat down, and was thinking of tiling but with the ufh turn off, I think it will be too cold

fire any more questions through.

HNY.
 
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