Patching and Plastering - Determining the extent of damage

Hi All, I'm new here and apologize in advance if my problem has been discussed elsewhere and I couldn't find it.

I own a four family flat. Ever since my father-in-law started teaching me things about home improvement I caught the bug and bought this thing as a diversion from constantly doing projects around the home. My wife got tired of always living in a partially finished house.

Anyway, it's a 1925 building and I've learned a few things about lathe and plaster since I bought it four or five years ago now, but I really need to 1) check my understanding for accuracy, and 2) fill in the holes of my knowledge to solve a problem I have.

To develop the problem, it has been my understanding that a gypsum base-coat goes on first for both strength, and because it can dry all the way through, even if it's put on thick, without being exposed to air. The truth in this statement could be at the heart of my problem

I noticed a crack when showing an apartment in this building that had previously been remodled. Upon further investigation, this crack was formed due to an expanding bulge in a plaster wall, right above the corner of where new thermal windows had been installed three years earlier. I investigated the matter by "chipping" away at the bulge. In doing so, I noticed that the plaster/gypsum underneath was powdery and fell away quite easily. In fact, it seemed as though it was only being held in place by the several layers of paint that had built up over the years. I began tapping with a wonderbar at the surrounding area and found that a huge section of this wall was mostly powder like that. Once I had destroyed a good 6-8 square feet of wall with this process, I pulled the unit off the market to give myself time to investigate how to fix such a problem.

Is this common? Could old gypsum or plaster fall apart like that do to the pressure of installing new windows? There was maybe a 3-5 square INCH section where the sturdier stuff under the decayed powder was darker than everywhere else. Could a leak have caused this? I'm on the verge of losing the whole building if I can't get this problem solved quick and the unit rented out. Any advise or instruction would be greatly appreciated!

Welcome to the forums!

Could you supply a pic or 2 using a free site like Image hosting, free photo sharing & video sharing at Photobucket (http://www.photobucket.com) ?

Our plaster expert will probably be along later :thumbup: I don't do plaster but I have repaired plaster using drywall products. If the lath is intact you can start with a setting compound like durabond [it won't crack if applied thickly] and finish with joint compound which is eaiser to sand. If the lath is missing, I'll insert drywall just shy of the plaster level and build it up with durabond.

I would scrape out the crumbly stuff and paint a concrete bonding agent on the hole's sides. At the very least a paint primer. Then the setting compound, as mentioned, then paper tape and box mud. FAQ About Old Plaster (http://www.plaster-wall-ceiling-solutions.com/old-plaster-questions.html)
Be safe, Gary

Yes, Post the pictures.
This sounds like water damage.

Gypsum plaster can take some getting wet but not multiple times and not if it stays wet.

Thing is it seems like you would have some other signs of water damage if this were the case. Maybe this has been repaired before with joint mud. That would explain the softness of the stuff you dug out. Is there a clear line of demarcation between what it soft and what is not?

Did you get into it deep enough to see if the lath (not lathe) are still intact?

Post some pictures ASAP. We can tell you how to fix this. It is simple to repair the plaster. We like to keep it mysterious. It will cost you your first born to learn the secrets.

No, there is nothing, well, I take that back, probably nothing about replacing the windows that would cause this. Is there a unit above? Is there a replacement window above?

Are there any other signs of water damage?

Is there sand in the stuff you describe as powdery?
How thick is each layer?

Hey Gang, I want you all to know that I'm still here. A coworker at the college where I teach went in the hospital, and I've been slammed trying to help out in his absence. I'm hoping to find some time to get out there and take some pictures soon, but in the meantime, I didn't want you guys to think that I hadn't come back to read your postings.

I may not have mentioned or made clear that this is an exterior wall that I'm dealing with. No lathe, just plaster over brick framework (...to my knowledge). I kind of suspect the tuck-pointing now that I've seen what you all have written. But dispite this being a "do it yourself" sight, I don't do second-story tuck-pointing myself. I gotta hire a guy to check that out (heights - AAACK).

I hope to get some answers and pictures posted in the next week or so, but thank you for your patience with me between now and then. Thank you again for the opinions and thoughts on this matter!

Scott

No problem Scott, somebody is usually around here most anytime.......... lurking :D:p:D

Give a shout when you're ready.