Hello
My first post here on the forum and I hope someone can help me.
I have a basement built with concrete block and then plastered. Inside the basement, I have sanded off a plastic paint from the wall, and now the wall is uneven and you can see the sanding marks. The plaster is, according to the guy at the building supply store, probably a self-mixed cement-based plaster (it's the original plaster, and the house is from the 60s).
Now I need to even out the wall before painting with a silicate paint. As far as I can see today, there are no moisture problems in the basement, but I still want to use something to even out the wall that allows moisture to pass through. It also needs to adhere well to the existing plaster. Mostly, it's about applying a layer of 2-3 mm, but in several places, the sanding has created indentations up to 1 cm deep, and they must be filled in.
It seems difficult to know what material to use for the wall. I've been to three different hardware stores and asked for advice. The advice I received from the different places varies, and I'm not getting any clearer when I try to read here on the forum.
From one hardware store, I was advised to use either:
Weber plaster mortar C Base 135
or
Weber wall repair 0-100
From another hardware store, I was advised to use Finja repair mortar 0-0.5 mm and that I need to prime the wall first. (The advice about primer was only given here, not from the other two places.)
And from the last hardware store, I was advised to use Beckers medium filler
It would be nice to avoid plastering the wall, and regardless, it is such a thin layer I want to apply that I don't want to mess with wooden battens and so on the wall to make it straight. I don't think it will be good if I only apply a 2-3 mm thick layer, and I don't want to have to plaster the wall by applying a thicker plaster layer. Then again, it's also an advantage if I can sand the wall afterward and make it completely even and nice with as fine a texture as possible (preferably completely smooth).
Has anyone experienced anything similar, and what are the pros and cons of the different suggestions I received above? The filler sounds very easy, if it works.
My first post here on the forum and I hope someone can help me.
I have a basement built with concrete block and then plastered. Inside the basement, I have sanded off a plastic paint from the wall, and now the wall is uneven and you can see the sanding marks. The plaster is, according to the guy at the building supply store, probably a self-mixed cement-based plaster (it's the original plaster, and the house is from the 60s).
Now I need to even out the wall before painting with a silicate paint. As far as I can see today, there are no moisture problems in the basement, but I still want to use something to even out the wall that allows moisture to pass through. It also needs to adhere well to the existing plaster. Mostly, it's about applying a layer of 2-3 mm, but in several places, the sanding has created indentations up to 1 cm deep, and they must be filled in.
It seems difficult to know what material to use for the wall. I've been to three different hardware stores and asked for advice. The advice I received from the different places varies, and I'm not getting any clearer when I try to read here on the forum.
From one hardware store, I was advised to use either:
Weber plaster mortar C Base 135
or
Weber wall repair 0-100
From another hardware store, I was advised to use Finja repair mortar 0-0.5 mm and that I need to prime the wall first. (The advice about primer was only given here, not from the other two places.)
And from the last hardware store, I was advised to use Beckers medium filler
It would be nice to avoid plastering the wall, and regardless, it is such a thin layer I want to apply that I don't want to mess with wooden battens and so on the wall to make it straight. I don't think it will be good if I only apply a 2-3 mm thick layer, and I don't want to have to plaster the wall by applying a thicker plaster layer. Then again, it's also an advantage if I can sand the wall afterward and make it completely even and nice with as fine a texture as possible (preferably completely smooth).
Has anyone experienced anything similar, and what are the pros and cons of the different suggestions I received above? The filler sounds very easy, if it works.
I'm in a similar situation. However, my walls are plastered with both cement-based and pure lime mortar (1974 and around 1940). I have been advised (by malarkalk.se) to first prime with hydraulic lime mortar on the cement-plastered areas and then use air lime mortar on all surfaces (weber 148 and 142 respectively). I then plan to only paint with lime paint (I want ground moisture to easily be able to migrate out of the walls at the bottom).
However, I will not strive for completely smooth and flat walls. I will settle for them looking reasonably flat.
/Johan
However, I will not strive for completely smooth and flat walls. I will settle for them looking reasonably flat.
/Johan
In my house from -43, there's plastered concrete hollow block in the basement walls. There was quite a bit of plaster detachment in the bottom 20-30 cm, partly due to ground moisture (capillary breaking layer was not something they built with at that time), and partly because later owners had painted the walls with some too dense paint that couldn't let the moisture out.
I milled away the paint (it was infernally dusty despite renting an industrial vacuum connected to the concrete grinder) and knocked off loose plaster. Then I replastered first with Weber's red base and then their plaster mortar C. I watered the wall first (and sprayed it for a few days after plastering) so that it wouldn't suck out all the moisture during curing.
On a wall where it was deepest (about 10 mm), I set battens, but I found it at least as difficult to get invisible joints and an even wall when removing the battens and adding new mortar in those grooves, as it was to just plaster freehand with a wide steel trowel and float.
When all the plaster had dried and cured, I painted with white silicate paint.
Now this has been in place for 4 years and still looks very fresh and nice, no signs of new plaster detachment. It's not a completely smooth surface, but perfectly sufficient for my needs.
I milled away the paint (it was infernally dusty despite renting an industrial vacuum connected to the concrete grinder) and knocked off loose plaster. Then I replastered first with Weber's red base and then their plaster mortar C. I watered the wall first (and sprayed it for a few days after plastering) so that it wouldn't suck out all the moisture during curing.
On a wall where it was deepest (about 10 mm), I set battens, but I found it at least as difficult to get invisible joints and an even wall when removing the battens and adding new mortar in those grooves, as it was to just plaster freehand with a wide steel trowel and float.
When all the plaster had dried and cured, I painted with white silicate paint.
Now this has been in place for 4 years and still looks very fresh and nice, no signs of new plaster detachment. It's not a completely smooth surface, but perfectly sufficient for my needs.
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