How to finish and insulate the attic?

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My wife and I bought a house with a new but unfinished dormer.

Normally, I know that dormers are closed with OSB boards, or lie flat on rafters. But in the case of our dormer, the external cladding consists only of plastic facade profiles. Then follows a foil and rolled lead. Between the rafters of the dormer is about 6 cm insulation wool provisionally squeezed.

However, what surprises me greatly is that the dormer is completely open at the bottom. When I remove the insulation wool, I look at the roof tiles with poor insulation from the 60s. I can even look outside under the rolled lead. (The roof stays as is for now, though).

If the dormer were covered with OSB boards and "sealed" flat with the rafter, I would know what to do. Short and sweet:

New insulation wool, then vapor retarder, for example Isover Klimamembran and then Fermacell, since it is a bathroom.

But what needs to be done here now? The previous owner or the carpenter had only provisionally put insulation wool between the rafters here and then the project was abandoned.

Should I close the spaces between the rafters with cut OSB boards, fill the crack with construction foam and then continue with the insulation, vapor barrier and Fermacell?




I've never seen anything like this done by a carpenter. Only from pictures it is not possible to judge what can be done or saved. But as it looks, it must be done again properly. Lateral the bricks away and the lead custody also and then down to pull a proper sheet metal custody attach and then the bricks clean up to the dormer. If the dormer is covered laterally with sheet metal, you can only clamp felt behind it, but since you have to do it right again anyway.

What makes me a little worried (not to see properly in the pictures) is the whole statics of the dormer and the damaged statics of the old roof. So you don't build in a change and the load transfer from the rafter to the change takes place how? Here I would call in a specialist that looks really dangerous to me (also because of snow load)

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