Attic Condensation new extension

223vmax

I have recently built a larger extension (1200ft2). The plastering was completed 2 weeks ago and I've just been up in the attic and there is large amounts of condensation on the felt - its dripping in fact. The roof timbers are soaked. I called the roofer and he insists that its condensation from all the plaster work drying out in the house and condensing in the attic when the warm humid air meets the cold felt. It sounds like he is probably right but I'm seeking other opinions that may contradict his version. I've checked the soffits, and vents have been installed and clean and clear. I haven't installed any fibre insulation up there yet and the attic access hatch isn't very well sealed. The problem is much worse on the northern facing side of the roof.

Anyone any opinions please?

DOCARCH

I'd have to concur with your roofer.

I have seen this happen, especially in cold(er) weather (and seen clients panic!). The plaster can take many weeks to dry out properly.

Give it a couple of weeks and the moisture should disappear.

castleking1

I too would agree with your roofer. I had my house plastered in the summer. With the heating on for a good 3-4 months before i moved in, there was a serious amount of condensation on the inner side of the felt. Drips of water was all over the upper-side of the ceiling. I would encourage you not to put down the attic insulation until the summer. This will allow enough time for the plaster to dry out. If you put the insulation down now it will soak up the condensation like a sponge, leaving it inefficient. You may lose money on heating but save in the long run.

woodoo

I had this in my new build to. It was falling on the same areas of the plasterboard ceiling to the extent that i actually worried it would damage it. It went away though after a while.

Its just all the water vapour from plastering and floor screeds drying out. My roofer told me the same thing.

BryanF

what's the standard like of the vapour check / air-tightness membrane?