concrete floor drying times

[calvert]

How long should I leave a concrete floor before laying oak flooring directly onto it? The floor is 100mm of concrete with 75mm of screed. The whole 175mm is laid on 100mm Jabfloor on Visqueen dpc. The screed was laid 6 weeks after the oversite. All the work was done in good dry weather

 

[WoodYouLike]

Rule of thumb: every inch of concrete/screed needs 30 days to dry out naturally (i.e. not forced dried) = almost three months in your case

 

[calvert]

Thanks. I've had a very nice 42m2 oak floor laid and two months later it's turned into set of rolling hills! The chap who laid it has been out today with a meter and pronounced the concrete still damp (testing under the kitchen units). Any ideas on the cause and cure please? I watched the dpc and everything being laid, I know it was all done properly.

 

[WoodYouLike]

DPC is laid underneath the screed (normally) to avoid 'rising damp. Screed has it's own moist that needs to evaporate.
Cure = time, I'm afraid

But.... didn't the fitter check the moist of the screed before the floor was installed the first time?

 

[Nige F]

That`s it ..blame the fitter

 

[calvert]

Ah, is Nigel F a floor fitter? If so would you check how long a floor has been down on a new build before laying a finish like this? No offence intended, I just want to get some opinions. I queried the oversite being laid on the dpm at the time and the so-called architect was insistant. the bc officer inspected it at that as well.

 

[WoodYouLike]

Ah, is Nigel F a floor fitter? If so would you check how long a floor has been down on a new build before laying a finish like this?

Yes, always! Wood (specially Solid wood) and moist (too much) is asking for trouble.
New builds, new conservatories, new extensions, new concrete/screed floor, new 'patched-up' floors: always ask how long it's down, how thick the layer is (and also check the moist when someone talks about latex self-leveling screed, it DOES contain water/moist and will take at least 48 hours to 'dry)

DPC in a new build has nothing to do with the moist in the concrete/screed layer installed on top of it.

 

[JohnD]

there is also (especially in a kitchen) a small risk of a leaking water, waste or central heating pipe making the floor damp.

Sometimes you can see a colour difference with the eye, sometimes you need a thermal imager, sometimes you don't know unless you tape a piece of polythene to the floor and watch for moisture on the underside.