Forgot insulation on the dormer wall - mold on wood - what to do?

Hello everyone,

We are building our house with a developer. Currently, we are in the process of drying the screed and the heating program is running.

During the roof insulation (beginning of October), the responsible company forgot to insulate the dormer wall and install a vapor barrier. Now, mold has developed on the exposed wooden wall of the dormer. Presumably, this happened because this wall, facing outside, consists only of wood and then metal - so cold + moisture = mold.

This wood is still somewhat damp (like the whole house, as we are in the drying phase) and repeatedly shows fuzzy mold spores. At first, the developer wanted to hold us responsible, since we are in charge of ventilation and heating. But because he did not fulfill his site manager duties, the insulation was simply forgotten. Therefore, we see him as responsible. As far as I understood him, he agrees with this.

He called the interior construction company to the site yesterday so they could install the missing insulation and vapor barrier. I sent these craftsmen away again because I believe that the wood must first be made mold-free. Additionally, I did not know whether they were just informed that the insulation was missing or were directly commissioned to install it.
I have already treated the wood with mold cleaner, but unfortunately, a few fuzzy spots have appeared again. The developer believes that this wood can also dry under the insulation and that this would not be a problem. Would this approach by the developer be correct?

I fear that this might lead to the mold spreading into the insulation and it slowly rotting. The wood might become dry, but the mold infestation is still there. I would be grateful for some experienced opinions, thank you!

So first of all: You are probably building with a general contractor (GU), not a property developer, read up on the difference.

Do you have it in writing that the insulation was forgotten? If not, get it in writing and preferably communicate everything in writing from now on. Inform the GU that mold has developed there and demand that they carry out remedial work, including a prior explanation of what they intend to do. Don’t do anything yourself, not even remove the mold on your own. That is the GU’s responsibility.

Content-wise: Remove mold with alcohol or other substances, check the wood, if undamaged, install the insulation properly and be happy.

How it’s possible to forget insulation on one side is beyond my understanding...

Thanks already for the quick response!

You are of course right, it is a GC and not a property developer. Unfortunately, I cannot edit the original post.

So far, I do not have this in writing, but I will demand it immediately.

My opinion as a layman would be to have the wood treated by the GC and wait with the insulation until it is dry. Due to the currently ongoing heating program, the moisture in the air is naturally extremely high.

I won't even try to understand it :D

Addendum: Did your expertise, which monitors the construction progress, not notice this either? Or are you so deeply involved in the house-building matter that you skimped on construction supervision?

Addendum: Your expertise, which accompanies the construction progress, didn’t notice this either?
Or are you so deep into the house-building matter that you cut back on construction supervision?

Our general contractor (GU) takes over the construction management according to the contract. The contract states that the construction manager must check the work of every trade and ensure that everything is in order. We strongly doubt that he has seriously performed this task. As mentioned, the roof insulation was installed at the beginning of October; he should have noticed it at the latest after that. Although we could have noticed it too, the responsibility clearly lies with the GU.

There is no independent construction supervision.

There is no independent construction supervision.

Too bad, because the construction manager has no contract with you, he doesn't care whether the house is free of defects. It just has to be acceptable and the damages should only become visible after the warranty period expires. It was a bad decision, but now it cannot be changed.