Hi, I recently bought a house from '74 where in some areas the plaster is starting to crumble and come off, mostly at the bottom near the floor and where downpipes are close to spaces. I have now removed plaster and paint in one spot in the basement, it looks like the previous owner did some type of repair and painted with what seems to be some kind of plastic paint. Where I started to remove the plaster, parts of light concrete or older repair mortar also come off. Does anyone have a good recommendation for repair mortar/plaster for my basement walls? I am also aware that I should repaint these surfaces with silicate paint. Attaching a picture of the wall.
Water or moisture wrap, start by ensuring that all stormwater drains away from the house, especially the downspouts; there are many cubic meters that come from there and make their way to the foundation. Wait, the wall must dry up before taking any action.
It is dry now, I have removed the water on the outside and fixed it last summer. I may have been unclear, but the plaster damage has probably been there for quite some time, just relatively hidden behind the plastic paint.
In my basement, it was the same, perhaps mostly due to the use of dense wall paint. The plaster on the cast basement walls was coming off. I chipped away the loose plaster and replastered with Weber Base 135. This material becomes smooth, almost like filler, so it's easy to apply. I then painted with non-diffusion-tight paint after a couple of months, and it still looks good, 3 years later and without redraining 
If you have sorted out the stormwater and it is dry, you can tap down any loose parts and touch up with lime mortar (it breathes), which will certainly create a different texture on the wall where you've repaired it. When painting, it will be noticeable, so a full spackling might be necessary for a good surface over the entire wall, and paint with silicate paint that breathes, as they say, a link where they discuss it:
www.byggahus.se/forum/threads/mala-silikatfaerg-eller-vanlig-vaeggfaerg-pa-innervaeggarna-i-hela-huset.295475/
www.byggahus.se/forum/threads/mala-silikatfaerg-eller-vanlig-vaeggfaerg-pa-innervaeggarna-i-hela-huset.295475/
I used Finja's fine plaster c. Smooth and good. I don't like Byggmax's slightly cheaper plaster. A rule is not to use plaster that is harder than the one the wall is currently plastered with.
I think it's silly (color difference price-wise) to paint with a breathable paint when the rest of the wall has plastic paint. It can be hard to sand off the current paint, it's easier to chisel it off, and then you can repaint the entire wall with a suitable paint. If the wall is essentially dry and you've solved the problem, I would at least try that to begin with.
I think it's silly (color difference price-wise) to paint with a breathable paint when the rest of the wall has plastic paint. It can be hard to sand off the current paint, it's easier to chisel it off, and then you can repaint the entire wall with a suitable paint. If the wall is essentially dry and you've solved the problem, I would at least try that to begin with.
I don't think it's obvious to knock everything down, it depends on how it's attached. We also received that advice, and we also had moisture that had been absorbed up to about 30 cm, and it went well there, but on the rest of the wall it was solid as a rock. Additionally, it's a huge job to plaster everything again. We chose to sand off the paint, rent a flex-sander (not a giraffe) with an adapted vacuum cleaner and it goes pretty quickly, we did our basement, about 40 square meters, in a weekend. Then we repaired and did a thin skim coat with Finja's repair compound (Laga vägg?) and applied silicate paint on it. I think it turned out great.
It needs to be filled with a lot of mortar in some places where I have torn away, so you want something that really adheres and is durable. But as you said, not harder than the lättbetong.