Drying out time after plastering

Lemlin

Getting different opinions from different people on this so wanted to see what people on here would say.

Basically, floors in my house were poured at the end of February. After three weeks, slabbing started. Slabbing was started last week and its hoped should be done next week for plastering to start on Monday week (the 4th of April). Plasterers say they will take two weeks so they should be done by the 15th of April.

My original plan was to leave the house to dry out until June (skimming would have been completed 6 weeks by then and the floors would be in 3 months) but we are in a rush to get into the house and a few people have mentioned that I'm going over the top leaving it that long to dry, particularly in this weather.

For example, plasterer has stated walls should be dry enough within two weeks to start working away, while someone else mentioned that I could start tiling after two weeks and then start second fix carpentry after tiling is done (roughly 4 weeks after plasterers finish because tiling might take about two weeks) because 2 weeks might be too early for wood to be put into the house.

Bear in mind, I don't know when we'll have the heating system up and running.

What do people think?

Lemlin

Nobody?

d o'c

I wouldn't try and force the moisture out with duhumidifiers or heat.
Let it dry out naturally, I don't think your timeframe is OTT...
too much heat too soon, and lots of shrinkage cracks in walls etc..
but
I wouldn't do any 2nd fix carpentry until the heating is on, and any items for fixing... doors,timber floors,skirtings etc I'd have them in the house, packaging opened for some time before fitting,

hard to put an exact time on all this, there could be some humidity check system these days if you wanted to get teccy

Don't know if you've timber joists or conc slabs,
I would never complete ceilings slabs too soon in a house with precast hollowcore at FFL

Lemlin

d o'c wrote: »

I wouldn't try and force the moisture out with duhumidifiers or heat.
Let it dry out naturally, I don't think your timeframe is OTT...
too much heat too soon, and lots of shrinkage cracks in walls etc..
but
I wouldn't do any 2nd fix carpentry until the heating is on, and any items for fixing... doors,timber floors,skirtings etc I'd have them in the house, packaging opened for some time before fitting,

hard to put an exact time on all this, there could be some humidity check system these days if you wanted to get teccy

Don't know if you've timber joists or conc slabs,
I would never complete ceilings slabs too soon in a house with precast hollowcore at FFL

Well my plan would be to let it dry naturally for two weeks and then perhaps put on the heating.

Can tiling be done even while the areas for wood are drying out further? I've about 100 square yards of tiling and 250 square yards of flooring to be done so it'd be a start if I could start the tiling after two weeks and then start the wodd areas after that.

I've concrete slabs. What do you mean by completing ceiling slabs too soon in a house with precast hollowcore? Do you mean plaster them or what?

sydthebeat

the rule of thumb is 1 mm per day.

peterc14

d o'c wrote: »

Don't know if you've timber joists or conc slabs,
I would never complete ceilings slabs too soon in a house with precast hollowcore at FFL

Sorry to but in... I have conc slab and at similar stage as OP... what you mean by this?

d o'c

I mean I wouldn't fit plasterboard to ceiling metal grid/battons too soon.

The cores in precast hollowcore can hold water. From above and below the slabs seem bone dry,you won't see any damp on the slab itself, they are too dense, a bit like glass. The vital grout seems to let water in, then it can't get out.
If you've had a fair bit of rain after prescast slabs have been laid until felting, beware.
If prestressed chances are they'll have an upward camber, the water will tend to each end, less so in the middle.

Signs are a damp patch at the ends of the slab seen on the blockwork,mainly internal walls.
In my case some damp patches were there before, during,\ and after roofing. Others didn't appear until the roof was on for a few months!!.

My house had a fair bit of exposure to rain, but it was mainly dry for 3-4 weeks while the roof went on.
I had some cores, in some slabs, with water, randomly around the house.

Intially I was waiting and waiting for the patches to dry up naturally, it was summer. I drilled 1 small drain hole in each core near the damp patch, if I drilled through 1 and it was dry, i redrill left or right until the flood came.
On average I got 2 gallons of water from EACH core.(4-6,metre length slabs)

What i found strange was how it took a few months for some of the wet cores to show up on the walls after roofing

I don't know why they don't have weep holes at the ends of these slabs

peterc14

DOC..Thanks for reply. I have prestressed slabs and for months after roof went on one room in particular was drenched with water. After scratch coat went on outside, the room eventually seems to have dried (not sure if there is a link). Also a lot of beneath the slab had loads of droplets of water though this may have been condensation?

I had thought that it was water trapped in the cores but the shear amount of it made me think it was something else, however as you experienced similar maybe this is it.

For the last 3 weeks the slabs and walls seem to be dry as a bone...does the water in the cores eventually dry without drilling holes... I have not drilled holes but the metal ceiling is up 2 weeks now and all seems dry... do you think I still would need to drill drain holes?

Lemlin

sydthebeat wrote: »

the rule of thumb is 1 mm per day.

Do you mean one metre squared because it couldn't possible be one milimetre per day?

House has already had a good chance to dry out as slabs were placed in August, roof went on in September, windows in at start of October and there's been a scratchcoat on it since January.

Roof was also foamed with insulation in February and cavity beading has been in since October.

Insulated slabs are being done now and plastering is starting next Tuesday.

sydthebeat

no, i mean 1 mm per day

ie a 20mm internal skim and plaster, expect 20 day drying time
150 concrete floor expect 150 day drying time.

http://www.cement.org/tech/cct_drying.asp

An industry rule of thumb for estimating the drying time necessary for concrete floors to reach acceptable moisture content is 1 month of drying for each inch of concrete thickness (1 mm per day).

peterc14

Agree with Syd... 1mm per day... same for floors.

d o'c

Peter,
I wouldn't go drilling unless there is a damp patch on the wall, mositure on the soffet of the slab wouldn't worry me, as you say just moist air condensing while house is drying out.
I used an 8mm bit, try hit the centre of the core (approx 30mm drill depth)and avoid the rebar
there are paralell shadows on the slab when you get the knack, you'll know where the hollow sections are.don't drill too often or too close together while trying to find the hollows. If you get through and find water, don't drill any more, drain, and see if patch drys out ..

Grouted slabs along their length don't seem to be a problem, it's when the open ends are grouted the water seems to get in from above and gets trapped inside.

I don't know how long it would take to eventually dry out, but i can tell you the last core i drained 8 months after roof was on...
only I work on the house, so no wet trades spilled water upstairs or anything like that.
just under 2 gallons came out,only 1 core in that particular slab had water( 1200mm wide slab) within 1 week wall was bone dry,dry since.

Lemlin

peterc14 wrote: »

Agree with Syd... 1mm per day... same for floors.

That's grand so, floor went in at end of February and is 80mm of screed on top of 160mm insulation so already half way there. By the end of April, the 80 days will be up.

sydthebeat

Lemlin wrote: »

That's grand so, floor went in at end of February and is 80mm of screed on top of 160mm insulation so already half way there. By the end of April, the 80 days will be up.

remember that this is just the time period where the concrete will stop exhausting water vapour in order to match the relative humidity of the dwelling... it doesnt mean you cant do things like laying floors etc.. it just means you need to be concious of properly venting the dwelling during this period and not allowing this vapour to condense on internal wood fittings, which would be bad, m'kay....

Lemlin

sydthebeat wrote: »

remember that this is just the time period where the concrete will stop exhausting water vapour in order to match the relative humidity of the dwelling... it doesnt mean you cant do things like laying floors etc.. it just means you need to be concious of properly venting the dwelling during this period and not allowing this vapour to condense on internal wood fittings, which would be bad, m'kay....

So when can I start laying floors in people's opinion is the question?