What to fill the ceiling joint with?

Hello dear experts. In our new building, I should make the joints in the concrete ceiling disappear. Attached I am sending you a picture. Can you give me tips on which material I should use to fill the joints so that it does not crack? I could also use some tips on the approximate procedure. Many thanks! Regards, Stephan!

Hello Tomtom,

Thank you for your answer.

So the ceiling shown will become our living room. A textured wallpaper is not planned, since we have also plastered the walls. So you mean that we also have to plaster the ceiling?

Best regards Stephan!

Hello Tomtom,

Thank you very much for your response.

So the depicted ceiling will become our living room. A textured wallpaper is not planned, as we also plastered the walls. So you mean that we also have to plaster the ceiling?

Best regards, Stephan!

Good morning!

Do not plaster (15 mm layer), fill (1 mm layer)! We have gypsum plaster on the walls and fine ceilings like you.

Just take some white paint and see what happens to the wall and ceiling surfaces that look so even.

We then decided on a paint with a mineral additive for the walls – it’s like paint plus sand, just more expensive and easier to work with.

After one coat, the ceiling looked like Swiss cheese with countless tiny holes that really looked awful. The attempt to fill and sand partially failed. The neighbor tried filling, sanding, and smooth fleece – which then emphasizes every tiny unevenness – so we took what we actually didn’t want anymore: textured wallpaper! It’s nothing special, but the wife is happy.

Regards,
Tomtom.

Thank you very much for your experience report. That helps me a lot! I'll start with a joint in the basement and see how it goes or how I manage it. Thanks, regards Stephan!

First and foremost, it must be noted whether they are hollow core slabs or precast slabs. Precast slab joints can be easily filled after cleaning and pre-wetting with modified filler putty (always pay close attention to the manufacturer's specifications) without cracks, the surface with tapered finishing putty or similar. Hollow core slabs, e.g. "Dennert slabs," have a very long shrinkage phase (volume reduction) and the joint must be reinforced; otherwise, treat as before.

So, I or rather an acquaintance of mine filled the joint. The filler was "Ardex Ardamur". The material was very easy to work with. You can see the result in the photo. However, now I have a different problem with the ceiling. The paint is peeling off. I lightly scraped the ceiling with the filler Ardamur (a few millimeters). Then I painted over it with dispersion paint. Here I am using Faust Mega-Weiss from the Praktiker hardware store. Slightly diluted with water (about 10%). In one room, the entire ceiling peeled off, and in two other rooms I have a few spots showing a result like in the photo. Very annoying, because unfortunately I don’t know exactly what I did wrong. What do you think? How should I proceed?