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I have no idea what kind of wall this is. Both my walls that are near radiators have this bubbling plaster look. I have read that painting with temperature differences may cause the bubbling (such as painting in the winter and then the heater is turned on). It was recommended to paint in the summer when the windows can be left open to equilibrate the temperature as the paint dries.

Not sure what to do about the bottom. How do I repair this wall? It seems to be paint --> very thin layer of plaster --> concrete. Does the whole wall need to be taken down? Should I just scrape off the plaster and respackle? I was thinking of sanding down the bubbles, respackle, and repainting. Does the whole wall need to come off?

Bottom of wall enter image description here

Top of wall enter image description here

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up vote 7 down vote accepted

I suspect that it is caused by moisture migration through the plaster. I would definitely scrape off the damaged paint and sub material first. Check for moisture, better to use a moisture meter if possible. Look for other areas below the floor for any evidence of water infiltration. May have been a one time thing, but I would be looking for the root cause, which I think may be water. Once you are satisfied the area is dry, remove all loose or crumbly plaster down to a solid base. If the voids are deep, I would use a thinset, setting type filler first, then a Spackle or drywall compound to get a smooth finish.

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I should have mentioned, this is a common problem in areas around a chimney where water has leaked around the sides of the chimney or migrated through bad mortar joints. Thus the importance of finding the source of water. – shirlock homes Mar 25 '11 at 10:54

I'd second Shirlock...that appears to be a moisture problem. Is the plaster bubbling, or just the paint?

Are those solid concrete walls? If not, I don't think that's concrete you're looking at, but traditional old-school plaster. Plaster was put on in two layers...scratch coat and finish coat.

If it's just the paint, and ALL layers of paint are pealing off as a whole, I'd say the issue is moisture. That can be a much different beast to remedy.

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The plaster bubbled too... I'm not sure if it's solid concrete. I live in a co-op building which was built in the 1960's (if that helps?). – Rhea Mar 22 '11 at 23:08
DAO1 is right, the finish plaster coat is comprised also. That is why you should use a thin set product to repair the damage, unless you want to try to mix some plaster. Thinset and a smooth top coat will be easier and cheaper. – shirlock homes Mar 23 '11 at 10:50

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