ᐅ What to use for filling ceiling joints?

Hello dear experts. In our new build, I need to conceal the joints in the concrete ceiling. I have attached a picture for you. Could you please give me advice on which material I should use to fill the joints so that it doesn’t crack? I would also appreciate some tips on the general procedure. Thank you very much! Best regards, Stephan!

Hello Tomtom,

Thank you for your reply.

The ceiling shown in the picture will eventually be our living room ceiling. We are not planning to use textured wallpaper since the walls are plastered. So, do you mean that we also need to plaster the ceiling?

Best regards, Stephan!

Wegga schrieb:
Hello Tomtom,

Thank you for your reply.

So the ceiling shown will eventually be our living room ceiling. We’re not planning to use textured wallpaper, since we have plastered the walls. So you mean we also have to plaster the ceiling?

Best regards, Stephan!

Good morning!

Don’t plaster (15 mm (0.6 inch) coat), apply a skim coat (1 mm (0.04 inch) layer)! We have gypsum plaster on the walls and precast ceilings like yours.

Just try a bit of white paint and see how the seemingly smooth wall and ceiling surfaces look.

For the walls, we decided on a paint with a mineral additive – it’s like paint mixed with sand, just more expensive and easier to apply.

After one coat, the ceiling looked like Swiss cheese with countless tiny holes, which really looked terrible. Trying to patch and sand those spots partially didn’t work. Our neighbor tried patching, sanding, and smooth fleece – but that only highlighted every tiny imperfection – so we ended up going with what we initially didn’t want: textured wallpaper! It’s nothing special, but my wife is happy.

Regards,
Tomtom.

Many thanks for your experience report. It helps me a lot! I will start with a joint in the basement and see how it goes or how I manage it. Thanks, regards Stephan!

First of all, it is important to determine whether you are dealing with hollow-core slabs or precast concrete slabs. Joints in precast concrete slabs can be easily filled without cracks after cleaning and pre-wetting, using a modified filler compound (always follow the manufacturer’s instructions precisely). The surface should be finished with a tapered finishing compound or a similar product. Hollow-core slabs, such as "Dennert slabs," have a very long shrinkage phase (volume reduction) and require reinforcement in the joint; otherwise, they should be treated as described above.

So, the joint was filled by me, or rather a friend of mine. The filler used 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 skim-coated the ceiling with Ardamur filler, applying just a few millimeters (about 0.1 inches). Then I painted over it with dispersion paint. I used Faust Mega-White from the Praktiker hardware store, slightly diluted with water (about 10%). In one room, the entire ceiling peeled off, and in two other rooms, there are a few spots showing the same problem as in the photo. Very frustrating, as I’m not sure exactly what I did wrong. What do you think? How should I proceed?