I cannot tell from the picture, but plaster walls have up to three layers. Base or 'scratch' coat (often with fiber), a float coat (some sand to level out the surface) and a then a finish coat (often with lime putty added)

If it is on brick it could have only two layers, a float coat to levels the surface, and a finish coat.

The finish coat is around 1/8 inch thick.

A chimney may have water intrusion problems from the flue if there is no rain cap (chimney 'cover') present.

Water could also be leaking into brick exposed above a roof line and running down.

This post was edited by brickeyee on Sun, Dec 2, 12 at 11:23

Thanks brickeyee. I believe the part that is coming off so readily is probably about 1/8 thick, so I imagine that is the finish coat. I'm leaning towards figuring out how to fix it myself, mainly because it doesn't have to be perfect and could be a learning experience.

It's strange we have water damage there, since when we moved into the house 5 years ago, the previous owners had to put a rain cap on. The damage happened after that. Could is also be coming in where the chimney meets the roof? I'm a little discouraged, because our neighbors supposedly had to have professionals come out to work on their chimney multiple times before they stopped the problem.

I'd have someone check the flashing for the chimney--that was the cause of my chimney's similar problem.

And this is a prime candidate for diy plastering, since it isn't visible. One other thing: why in god's name are you being so squeamish about fixing a simple crack in the other rooms? It's dead simple: make the crack a bit wider at the bottom and fill with compound...then use tape and another skim coat to bring it even with the rest of the wall. It's an old house, I guarantee you don't have a perfectly flat even wall anywhere in the house. :)

Thanks, Columbus. I believe it is probably the flashing.

I probably didn't clarify the other plaster problem too well. It's way more than a crack, at least I think it is. I've attached a picture. I imagine once I remove the part that is warped, it will be outside my expertise. Plus the walls are textured and I would prefer it to be the same. I'm not at all anal about these things normally, but this is right in the dining room and highly visible.

Of course, if I can't avoid paying a professional, I'm all for it. We just dropped a ton of cash on an addition and don't have tons to spend.

One area on my stairs about 2'x1' had that problem, turns out it was only the top layer--the rough coat underneath was fine. I cut away the loose bit, and filled it with compound, and sanded it even with the rest of the wall--can't even tell it was damaged.

If you can push the plaster back in place, you can use plaster washers to secure it, then cover with compound. Since you are working with textured walls, that would make it easier. Experiment on a spare piece of board or drywall to imitate the texture, and that would be what you do for the top coat.

If you have to remove the plaster in a small area, patch with a bit of drywall and tape and coat the seams and then do the texture.

This post was edited by columbusguy1 on Sat, Dec 1, 12 at 16:59

Janieful - That bulging crack is where an older, badly done patch has given up. You can see the different wall texture. Remove the loose material and dig back to solid plaster, then make a proper repair with real plaster in several layers.

If you can frost a cupcake or make a PBJ sandwich, you can patch plaster.

ADDING:
That closet problem is the more serious, because it indicates a leak that's been there for a while. Get a roofer in to fix the flashing and look for damaged shingles up hill from the chimney.

This post was edited by lazygardens on Sat, Dec 1, 12 at 22:01