I am currently re-GIBing (plasterboarding) the Master Bedroom. The old GIB was installed in the 90s with nails and was done rather poorly (10-20mm gaps between sheets, odd/off-cut sheets, sheets not joined on the Stud etc.) - we initially stripped the Wallpaper and painted the sheets, but after a particular Earthquake jolt (I'm in NZ), a load of cracks appeared in the GIB.

After pulling the old GIB off the wall, I noticed in a couple of spots some black mold in the inside of the sheet and some dampness behind the walls. I pulled the insulation out and inspected the exterior of the house and found a couple of hairline cracks in the plaster cladding very close to where the dampness was.

I'm currently letting the walls air out and dry off, I've given them a spray down with some mold-killer.

Given that it's summer here and it's now reasonably hot, I'm thinking that I leave everything off for the next 48 hours to let it really dry out, then I'll add some Silicone based seal to the hairline crack on the exterior wall, then replace the Insulation and then GIB up the walls.

Question: Should I seal the exterior wall immediately (Condensation ingress?) or will this slow the drying process and best to give it the 48 hours?

As a second question: I noticed that some of the Eaves aren't fully sealed on the underside of the roof, meaning from the wall, I can see sunlight through, I'm not sure if this is a design feature to allow for ventilation or just small gaps that have worked open with time - so should I seal them up?

For reference, the base of my house has vents for air circulation, so I'm thinking that the eaves should be sealed.

  • Eaves(under the roof over hang) usually provide attic ventilation.
    – crip659
    Commented Dec 27, 2022 at 22:19
  • If fans are handy they help speed up the drying time.
    – crip659
    Commented Dec 27, 2022 at 22:26
  • @crip659 We don't have an Attic, we have a Cathedral style roof, probably should have mentioned. Commented Dec 28, 2022 at 21:09
  • Depending on the build type, they still might be providing some roof deck ventilation.
    – crip659
    Commented Dec 28, 2022 at 21:21

1 Answer 1


The hairline crack isn't going to ventilate enough moisture to benefit the drying process. Seal it up when convenient to keep out further moisture from rain.

Be wary of using silicone, though. It's not paintable and can collect dirt.

  • Thanks for that, will jump up the ladder tomorrow, the stuff I'm gonna be using isn't a pure Silicone seal, it's called MS - Modified Silicone, it's paintable and for exterior applications. Commented Dec 28, 2022 at 1:38

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