ᐅ Interior plaster on exterior wall → unusual odor

Hello everyone,

My name is Chris, I’m 26 years old and an electrical engineer. I’ve been living in my own house (single-family home) for a year now, and I’m currently renovating my entrance hallway. I’m trying to explain everything as clearly and detailed as I can, considering I’m not an expert^^

My front door leads into a small entrance area (hallway) of about 2 x 1.4 meters (6.5 x 4.5 feet). From the front door’s perspective, the left wall is an exterior wall. Straight ahead is a partition wall made of OSB boards, behind which is the kitchen. To the right, there is an interior door leading to the dining room.

The whole hallway used to have wood paneling without insulation, which I removed about a year ago. Behind that paneling, on the mentioned exterior wall, there was some mold. For the past year, the wall has been without any covering or similar.

Now I wanted to make the room look nice again and planned to cover everything with drywall. Since I read a lot that drywall on interior side of an exterior wall can lead to mold if it’s not completely airtight, I decided against this to avoid making a mistake^^

So I removed the old plaster and wallpaper, knocked off loose parts, and treated everything with a primer. I let it dry for about 6 hours, then re-plastered the wall. It turned out quite nice for a first attempt and it’s holding well.
I plastered using Knauf MP75 and Rotband, roughly in a 2:1 ratio, because I heard it helps the plaster dry better. For now, I only plastered the interior exterior wall. Nothing else was done yet.

That was about 2 days ago, and there is an increasingly strong odor coming from the area. It smells very damp, slightly moldy. This is definitely because I barely (almost never) ventilated the room. The reason is that I can’t leave the front door open, and the interior door to the dining room also can’t be left open because I have a large dog who would certainly take any chance to get out^^ I have now considered getting a dehumidifier so the wall can start drying.
By the way, the room is unheated!
A few hours ago, I placed a small electric heater in front of the wall and left the front door open. Not exactly energy efficient, but the plaster near the heater is already surface dry, which wasn’t the case before.

Basically, my questions are:
1. Is the smell understandable/normal in this situation?
2. If so, is it something serious, or better put, will it come back once the plaster is fully dry?
3. Will a dehumidifier actually help?
4. Did I do the right thing at all? :/ Besides possible missing insulation. The room is not supposed to be heated or warm. It should simply stay dry^^

Maybe a bit more info for the last question: the house was built in 1932. The mentioned wall is made of clinker brick (about 38 cm (15 inches)) and I believe there are Ytong (aerated concrete) blocks on the interior side (about 12 cm (5 inches)). I could make this out beneath the old plaster but I’m not entirely sure. So the wall construction from outside to inside would be: clinker brick – (air gap?) – Ytong – old plaster – new plaster.

I hope I explained myself clearly enough. Thanks in advance!

I would say, ventilate as much as possible—you have applied a lot of water to the wall. When I had rough plaster in my apartment, I believe the windows were wet on the inside every day for at least one week.

The wall is dry. The smell is gone. Everything looks good^^

cruunnerr schrieb:
The wall is dry. The smell is gone. Everything looks good^^

Just because the wall is dry on the surface doesn’t mean it is fully dried through.
If I were you, I would continue ventilating regularly over the next few days.