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Chat Area => General Discussion Area => Topic started by: Sir Tigger KC on 04 September 2012, 13:34:33

Title: I'm laying a concrete floor.....
Post by: Sir Tigger KC on 04 September 2012, 13:34:33
I've got a good base of concrete down and just have to lay the screed on top, which I was planning on doing tomorrow.  Trouble is while sweeping it today I noticed that the concrete still seems a bit damp... :-\

Should I wait a few more days for it to dry out properly or will it be OK to lay the screed as is?  ???

I've never done this before and it's a bit of a learning curve!!  ::) Thanks!!  :y
Title: Re: I'm laying a concrete floor.....
Post by: RobG on 04 September 2012, 13:38:42
You should allow one week per cm thickness of concrete, up to 4 cm. Allow twice as much time for the remaining thickness more than 4 cm. In other words, for a thickness of 6 cm, you must allow minimum (4 x 1) + (2 x 2) = 8 weeks drying time. For concrete thicker than 6 cm, allow 4 weeks drying time per additional cm.
Don`t forget a membrane must be laid between the sub-floor concrete and the screed.
Title: Re: I'm laying a concrete floor.....
Post by: ozzycat on 04 September 2012, 14:22:02
you dont have to lay a membrane between the base and the sceed the screed is only a self leveling top coat
the building co iwas plant eng never laid one under the screed but did between the substrait  &base coat of concrete
Title: Re: I'm laying a concrete floor.....
Post by: cem_devecioglu on 04 September 2012, 14:46:24
You should allow one week per cm thickness of concrete, up to 4 cm. Allow twice as much time for the remaining thickness more than 4 cm. In other words, for a thickness of 6 cm, you must allow minimum (4 x 1) + (2 x 2) = 8 weeks drying time. For concrete thicker than 6 cm, allow 4 weeks drying time per additional cm.
Don`t forget a membrane must be laid between the sub-floor concrete and the screed.

Robg , is there any code or standard for that mix ? (I guess probably this is the standard mix which is sold publicly in UK)
Title: Re: I'm laying a concrete floor.....
Post by: RobG on 04 September 2012, 14:53:14
Screed mix is generally 3 parts sharp sand to 1 part cement but you can go to 4:1 or at a push 5:1
Title: Re: I'm laying a concrete floor.....
Post by: cem_devecioglu on 04 September 2012, 14:56:54
Screed mix is generally 3 parts sharp sand to 1 part cement but you can go to 4:1 or at a push 5:1

in oil wells there were some special mixtures that dry quickly but very expensive.. nowadays there are also some "quick" mixes around but I cant  trust them :-\
Title: Re: I'm laying a concrete floor.....
Post by: cem_devecioglu on 04 September 2012, 14:58:48
here are some types
http://iti.northwestern.edu/cement/monograph/Monograph3_8.html (http://iti.northwestern.edu/cement/monograph/Monograph3_8.html)
Title: Re: I'm laying a concrete floor.....
Post by: markrnorton on 04 September 2012, 14:59:27
You should allow one week per cm thickness of concrete, up to 4 cm. Allow twice as much time for the remaining thickness more than 4 cm. In other words, for a thickness of 6 cm, you must allow minimum (4 x 1) + (2 x 2) = 8 weeks drying time. For concrete thicker than 6 cm, allow 4 weeks drying time per additional cm.
Don`t forget a membrane must be laid between the sub-floor concrete and the screed.

Is this drying time or time to reach full structural integrity ?
Title: Re: I'm laying a concrete floor.....
Post by: paul.lovejoy on 04 September 2012, 16:25:40
membrane DPM is normally under concrete slab but if i am say converting a gargage on an existing slab i do put one between the new screed as well as insullation  :y

whats the concrete floor for Tigger not that i will tell you when to lay the screed i am just nosey ;D ;D

we normally wait at least 4 weeks but then there are always other things to do RobG calcs probably spot on

plus coat the slab in unibon/pva the white gooey sticky stuff :o :o :o before you lay the screed

screed mix is a bit of an open bag  normally i use 4 : 1 although others say 3 or 5 :1

we are just laying a screed now and got a ready mix company in only a cubic metre @ £175 but time you pay for materials and labour to knock it up etc bloody good price me thinks plus they can put a retarder in it to delay it going hard if you want ::) :o
Title: Re: I'm laying a concrete floor.....
Post by: paul.lovejoy on 04 September 2012, 16:33:09
oh yes and if it is a big area dont get the ready mix with the drum get the big lorry that mixes on site you only pay for what you use :y
Title: Re: I'm laying a concrete floor.....
Post by: ozzycat on 04 September 2012, 16:39:13
oh yes and if it is a big area dont get the ready mix with the drum get the big lorry that mixes on site you only pay for what you use :y
:y :y :y :y + 1
Title: Re: I'm laying a concrete floor.....
Post by: Gaffers on 04 September 2012, 16:40:44
If I have learnt anything out here it is that if you are intending on putting anything heavy on the concrete wait at least 28 days.  You may have problems otherwise ::)
Title: Re: I'm laying a concrete floor.....
Post by: paul.lovejoy on 04 September 2012, 16:44:02
If I have learnt anything out here it is that if you are intending on putting anything heavy on the concrete wait at least 28 days.  You may have problems otherwise ::)

did not think you were that fat heavy well built ;D ;D mind you you l;ook good in shorts you beast :-*
Title: Re: I'm laying a concrete floor.....
Post by: Gaffers on 04 September 2012, 16:47:24
If I have learnt anything out here it is that if you are intending on putting anything heavy on the concrete wait at least 28 days.  You may have problems otherwise ::)

did not think you were that fat heavy well built ;D ;D mind you you l;ook good in shorts you beast :-*

I'm 3 stone lighter than you last saw me, tubs  :-*

It was an MRI scanner built in to a truck trailer.  Awesome bit of kit  :P
Title: Re: I'm laying a concrete floor.....
Post by: Sir Tigger KC on 04 September 2012, 20:34:03
Thanks for all the replies!!  :y

It's a lounge floor, so nothing too heavy will go on it....  ::)  Well...  ;D

I've got the DPM underneath the concrete slab.  Why do you coat the slab with PVA Paul? does it provide another layer of damp proofing?  :-\

I'm going to put laminate on it when it's done, so I guess another few weeks drying before I do that?  ::)

Thanks again!!  :y :y :y
Title: Re: I'm laying a concrete floor.....
Post by: paul.lovejoy on 04 September 2012, 21:20:34
Pva just really gives it a bit of a key and ensures its not dusty....a sealer if you will :y

but yes definatley give a bit of drying time before you lay laminate on it or you may have a few high points in the floor.

did a pub floor in solid oak stuck to screed etc no one said the screed was laid the previous week :o :o rush job anyway laid the floor a week later the pool table was nearly 300mm of the floor ;D ;D fortunatley in quote i did state minimum 28 day drying period plus i week for floor to aclimatise :y when i first got there took one look and it and decided beer time oh and a bag of bovril crisps the floor started to look better but the pool table was a bit pissed :y