Plaster will not dry in timber build

5 Dec 2015
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United Kingdom
Hi - I wonder if someone can give me a steer as I'm not sure what to do.

I have a new build, in my garden, which is timber with a flat fibreglass roof. The floor was finished (ie the top level concrete) about 4 weeks ago and that is now virtually dry, and the plaster was finished about 3 weeks ago. The room has a ledge where the timber sits on cement blocks, so there is a fair bit going on behind the walls which may impact on drying - for instance, the metal brackets where the timber frame posts sits slightly stuck out so the plasterboard used had insulation attached and this was scraped away by the brackets to fit flush to the wood, if you see what I mean. Maybe this impacts on where moisture ends up, I don't know (eg does it tend o be worse by the metal posts?). I also note that the timber won't have been completely dry when installed, as it's been crappy weather!

Anyway, the plaster dried reasonably well but if anything it's got worse recently in certain areas (edges and around one light fitting) and certainly hasn't got better for the last 10 days or so. I wonder if this is coming from condensation on the outside of the plaster, as I'm sure that the roof etc is all sealed. If so, then I wonder how the plaster edges will ever dry in the winter?

Some pics are attached. I just don't know what I can do to speed this up, if anything.

I have a domestic dehumidifier running, but I'm not sure what to do about ventilation - perhaps I just keep everything closed as much as possible and try to retain a sensible temperature?


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Thanks for the reply. They didn't dry fully in these areas, but it seems like it may even have gotten slightly worse recently - but has certainly stopped getting better.

One thing I note is that some areas could be dried with a heat gun, if I'm careful, but not these spots on the edges - which makes me think it's pretty deep moisture on the inside. To be fair, the wood wasn't dry when the plasterboard went up given the weather and the roof and outside edges all look sealed, but it just seems like it's not getting better.

I also note that some moisture getting in by the door, but I'm got no idea where from. It's possible that it's condensation somehow I guess.
If the wood behind wasn't dry before over boarding then that could be the cause. The moisture has nowhere to go so the drying process, especially this time of year could take ages. I'd expect lots of plaster cracks too as the wood does dry out next year
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I hope it's that to be honest, as I didn't really end up on great terms with the builder so I don't want to call them back! Certainly, looking around the roof and windows etc I can't see anything that could lead to water getting in.

Thinking about it, as the plasterboard has the insulation layer on I wonder if it sort of channels moisture to the edges?

I think I've been a bit silly in that the heating has been off and on and I've blown air around with the window and door around when it seems dry outside. Should I just try to keep the room at 19 degrees or something and not open the window, with the dehumidifier on?

Edit - now I think about it more, the worst parts are around the door. Of course there are more ways for moisture to get in there but there were the 4x4 posts around the door and they were certainly nowhere near dry when set in place. For the windows, the frame was smaller but perhaps it makes sense for more moisture to be trapped in there.
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