Repairing finish on basement block foundation wall

Question

I have a room in a partially finished basement which was done by the previous homeowner which is needing repair to the walls. The house is old (1925), and the foundation is concrete block. The room in question is mostly below grade, and they have finished over the concrete block with some type of plaster, and painted it. I am now running into issues with the material falling off, and paint bubbling, so there is some obvious moisture coming through the wall. My issue is that I am not sure what material was used to finish the wall, it looks almost like drywall compound, but that seems insane to use on an exterior block wall. Here are some pictures of the issue:

More: https://imgur.com/a/rRV5aK9

Any advice on what the material I'm working with here would likely be, and my best approach to fixing the issues I'm having would be greatly appreciated. I'm assuming patching with joint compound isn't the correct solution here.

Answer 1

I think you answered your question when you stated "some type of plaster". That's exactly what it looks like to me. Plaster is usually applied over lath strips but can be applied straight to concrete but it doesn't last as long and is prone to crack, chip and damage to moisture. It is relatively easy to patch by just mixing more plaster, according to manufacture guidelines, and applying it to the damaged area after thoroughly removing the crumbly old plaster. Check the area for cracks before applying any plaster and repair any seams. There doesn't appear to be a lot of damage so this might be all that's needed.