Is this damp in my unfinished new build?

[Linguaphile]

Back a few months ago there was a flood and water got into the ground floor of our new build. The builders say that it’s just moisture that needs to evaporate, and they’ve got fans on it and windows open to dry it out, but I’m concerned. Is this something that will go with time or do I need to be worried??

I personally think it's damp and mould.

How do they correct that??

They need to find where it's coming from. Ceilings and low down indicates a big problem and more than one source.

I think initially the water came in from the ceiling and then sat on the floor...

Fans are going to do feck all.

They need industrial sized dehumidifiers running over the weekend with windows closed to help dry it out.

Well me and my partner have been looking at project houses to buy and do it up. I'm not an expert but we viewed a couple of houses where damp and mould was an issue and they looked like that(or worse!)

It doesn't look horrendously bad but I'd be concerned (sorry not trying to freak you out)

The mould on the ceiling: I'd try to wipe it off. Get a rag and some multi spray see if it comes off. The damp I'm not sure about 😳 You mentioned the flood but is there any windows, plumbing or roof issues that makes the house not 100% watertight? You need to investigate. Otherwise yeah it might just dry out. But I'd look into that! In the cases we seen when viewing old/project houses a damp proof course was always on the 'urgent to do list'

I am no expert, but i would be concerned that the damp from a flood hadn't already dried out with the 8 weeks of no rain/heatwave we've had.

Hmm, okay. The house was dry as a bone for months, but unfortunately they had to drill holes in some of the ceilings for the electrics which went up into the garage floor for an evening, and there was a flood that night that basically let in a ton of water through the floor. So we know where it came from and we know it hopefully isn’t happening again (garage floor is now a foot higher and there’s drainage, plus the water was only a problem when the temporary holes were drilled), but once it got in the wall stayed damp for weeks. They put the fans on it last week and the spot on the wall does look smaller, but these spots on the ceiling just appeared his week when they got in the big fans. 🤔

yes

fans will accelerate drying off the surface of the wall (yes they will) though it would dry quicker if they stripped the plaster off to expose the blockwork. A thoroughly wet wall takes months to dry. Opening an upstairs window or the loft hatch will enable the water vapour (which rises) to escape from the house.

If it was due to a leak that has now been fixed, there is no reason to suppose it will come back.

Oh Pigletjohn thanks for this, you have made me breathe a huge sigh of relief. It’s good to know that it takes months for a really wet wall to dry. Yes, there is no leak now. So the fans should do the job you think? I doubt they’ll replaster as that would be a cost they’d have to eat, and fans are free. 😕 It’s at least a month until they do the interior decorating. Will it be done by then do you think? And why have the ceiling spots suddenly appeared? Would that be because the fans have dried it out enough to show that the ceiling was also wet?

This is what the wall looked like 2 weeks ago.

the water vapour (being lighter than aijr) rose up to the ceiling and made it damp.

If the room door(s) had been open, and the loft hatch or a window upstairs, it would probably have escaped. The amount of water vapour will diminish as time goes by.

Some people think that heat dries out a wall, but it's not, it's ventilation.

Plastering a wall and a ceiling in a single room just costs a few £hundred. How much are they charging you for your house?

It’s not a cheap build... land plus house are around €950k, which believe it or not is a bargain for the area, and we’ve otherwise been very pleased with the build quality as we’ve watched it come together. I’ll ask and see if they plan to replaster!

I gather you are outside the UK. If the wall is plasterboard on insulation or airgap, or the wall is timber frame, them it really needs stripping off so it can dry before it rots.

Yes, we're in Luxembourg. It's cinderblock underneath, then a thick layer of plaster, so neither of the things you mention. Hopefully that's a good thing...? And it's actually an internal wall, not one against the earth or another house.

yes, that's not prone to rot. And I suppose the floor's concrete.

When decorating, avoid anything impermeable on the walls, such as wallpaper or murals, for the first year. We have a special non-vinyl emulsion paint which allows new plaster to dry through it, it's porous. I expect you have something similar.

Wooden flooring will tend to warp and later crack, but a flooring contractor should measure remaining dampness before agreeing to lay it.

Defo damp. We had this in our new build flat. It was very bad in both bedrooms and only got worse. Are you under warranty? I had a man round who told us to move out!