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Thread: Cracked plaster ceiling repair.

  1. #16
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    Small wonder the ceiling is cracking! It’s not the original ceiling that was plaster on wooden lath. This ceiling is 3 to 4 inches below the remaining wood lath. The plaster is attached to an expanded metal lath. I cut some holes to discover this. Thinking the 3 to 4 inch gap meant 2x4’s had been sistered to the original joist for support for the newer metal lath. NOT SO. I have probed many feet with a plumbers tape in all directions of several widely spaced holes. There appears to be no connection between the new ceiling and the framing. All I can find are places where strips of the original wood lath has been pulled down and nailed to the metal lath. See picture. The pulled down lath strips seem to have no connection to the original framing. First picture shows a wood lath atop the metal lath/new plaster taken from below, and the second the same wood lath with a long nail attaching the metal lath. You can see that wood lath strip missing from the joist above it. WT Heck? This makes no sense to me. Was expanded metal lath with plaster so rigid it needs virtually no support framing? Tom?
    Last picture shows the top of the newer plaster down through a crack where you can see bits of the metal lath
    Last edited by Michael Weber; 09-22-2021 at 2:30 PM.
    My three favorite things are the Oxford comma, irony and missed opportunities

    The problem with humanity is: we have paleolithic emotions; medieval institutions; and God-like technology. Edward O. Wilson

  2. #17
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    That was built to fail. Any plaster needs very stable support.

    The wooden lath probably had lime plaster on it. Still not a job for the inexperienced. That's really about the only type I do now. It's Very expensive though. Lime Plaster was carried over into the 20th Century, but I expect by old builders sticking to old ways, sort of like me.

    Changes from Lime Plaster, to Gypsum plaster, and then to Sheetrock, were each steps towards faster, and cheaper, with lessening quality along the way.

    Your least expensive way will probably be to get all the old stuff taken down, and get someone to install sheetrock. I hate sheetrock, but it is, by far, the least expensive route. Sounds like you will lose the crown, which I'm expecting was installed after the lowered ceiling was. Sheetrock can be done so you can't tell that it's wallboard, but has to be done by someone capable.

  3. #18
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    Thanks Tom, I was hoping you would answer with your extensive knowledge. I do not want to lose the crown. Could the ceiling be taken down to close to the crown without removing it? Then appropriate thickness supports be attached to the original joists that would cause the Sheetrock to be level with the old ceiling and the two blended together? Does that make sense? I know there are different finish levels for Sheetrock. Are you referring to what is called a level 5 finish to make it resemble plaster? Or is there something else?
    This is going to be such a mess. The joy of old houses
    My three favorite things are the Oxford comma, irony and missed opportunities

    The problem with humanity is: we have paleolithic emotions; medieval institutions; and God-like technology. Edward O. Wilson

  4. #19
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    That should work fine. Yes, called level 5, these days, but that's the way I always did it, when I was building new houses, before I ever heard of different "levels" of finishing.

    Best is sprayed on surfacer, but it takes someone with equipment (ceramic pump airless sprayer), and experince. https://www.usg.com/content/usgcom/e...-surfacer.html

    You'll be limited to what contractors you can find there, though. It's not a job you want to do yourself.
    Last edited by Tom M King; 09-22-2021 at 4:13 PM.

  5. #20
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    Thanks Tom. This has been interesting as heck. My imagination has been working overtime picturing options that would give a unique or special result. Something I usually do before starting a project before reality sets in and I just settle for adequate. Appreciate your help once again.
    My three favorite things are the Oxford comma, irony and missed opportunities

    The problem with humanity is: we have paleolithic emotions; medieval institutions; and God-like technology. Edward O. Wilson

  6. #21
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    Noooo not sheetrock!! It will never be near as nice as plaster. (obviously, do what you need to do)

    But ask around first. In our part of the country it's easier to find a real plasterer for residential work than a sheetrock guy and the cost tends to be higher for sheetrock because the guys both hate it and have to make multiple return trips to finish the job. It also makes a godawful mess with sanding dust that you don't have to deal with with plaster. Standard residential finish here (MA) is plaster on blueboard, a wall finish really superior to even the best drywall job. The walls are perfectly flat and have a much harder surface that withstands a lot more abuse. Perhaps you can find a transplanted New Englander yearning to get to do a real plaster job.

    As an aside, I asked my plasterer how long it took him to learn his craft and he told me about 2000 hours of work over a two year period as an apprentice in Ireland before he was allowed to work on the main floor of a house and another several thousand hours before he got fast enough at it to make a living. I love to watch him work, it's like magic, working with a trowel in each hand leaving behind a flawless surface.

  7. #22
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    Roger, you live in the "plaster geography" for sure. Not so, here...other than in historical buildings, etc., it's rock on the walls. Even a skim coat of compound over that is a rarity!
    --

    The most expensive tool is the one you buy "cheaply" and often...

  8. #23
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    It’s the same where I live in a middling city in a mundane state. I doubt very seriously there is much local demand for plaster work or skill to provide it.
    My three favorite things are the Oxford comma, irony and missed opportunities

    The problem with humanity is: we have paleolithic emotions; medieval institutions; and God-like technology. Edward O. Wilson

  9. #24
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    Our home is 120 years old, and had plaster over redwood lathe. Yes, one may widen the cracks with a chisel and try to re-attach the plaster to the lathe where the keys have broken or become separated with drywall screws. Then fill in the cracks with plaster repair slightly below the final level and then top off with a very thin layer of drywall compound. I have not had very good success with this method, but it is what one normally does.

    The better method is to forgo the patch and like Jim suggested, just a thin layer of 1/4" drywall, properly taped and mudded has lasted longer.
    Regards,

    Tom

  10. #25
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    Thomas, I would do exactly that except there is nothing to attach the Sheetrock to. Not even wood lath. It appears the entire ceiling of plaster on metal lath is magically floating 4 inches below the original wood lath. I’ve probed many feet in all directions with both an electricians tape and a cheap boroscope in an effort to find any structural support. The only support I’ve seen is random strips of the original wood lath removed from the joists 4 inches above, laid across and nailed to the top of the metal lath. It’s a strange thing and I’m looking forward to more complete findings. I’ve ordered a dust shroud with vacuum port for my variable speed grinder in an effort to reduce dust. I’ll open a more substantial area for a better look. As Tom King said, it looks like a ceiling designed to fail.
    My three favorite things are the Oxford comma, irony and missed opportunities

    The problem with humanity is: we have paleolithic emotions; medieval institutions; and God-like technology. Edward O. Wilson

  11. #26
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    As a owner of an old plaster over wood lathe house here are my thoughts & observations. Plaster cracks due to stress caused by movement that is usually expansion and contraction but can be from settling too. The important thing is that once you have a crack the two opposing edges will always be moving forever more. The best temporary repair is to remove lose material and then seal the area with whatever latex paint you need to get rid of. I have very sandy plaster and need this step to get a bond. Use mesh tape to cover the crack so that as movement continues it is spread over a wider area rather then the narrow edge of the paper tape. I have also had good luck filling deep voids with plaster of paris and the rapid set time is a bonus. Top coat with joint mud, paint and enjoy for one year. After a full year of temperature and humidity changes it will slowly start over and get worse every year. Ceilings have more stress and movement along with paint adhesion issues due to an old coating (calsimine?) that was used when originally finished. I recommend just going ahead and covering with sheetrock to be done with it.

  12. #27
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    Maybe you need to enlarge the hole so you can get your hear and a lamp in there..."something" has to be holding up that metal lath!!
    --

    The most expensive tool is the one you buy "cheaply" and often...

  13. #28
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    Repairing plaster with plaster (using plaster washers and fiberglass mesh tape to hold things up and in position) is much more successful than using drywall mud on it. I've repaired many cracks that didn't return, at least over the course of a decade.

    I've never done the 1/4" drywall thing, but I've pulled plenty of it down after it drooped and bubbled, repaired the plaster it was covering, and then been good for many years.

  14. #29
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    Quote Originally Posted by Jim Becker View Post
    Maybe you need to enlarge the hole so you can get your hear and a lamp in there..."something" has to be holding up that metal lath!!
    Yep. With luck tomorrow. Making the 3 holes i did made a huge mess and I’m working on a less messy approach to cutting out larger sections.
    My three favorite things are the Oxford comma, irony and missed opportunities

    The problem with humanity is: we have paleolithic emotions; medieval institutions; and God-like technology. Edward O. Wilson

  15. #30
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    When we do such work in a room, everything is taken out, the floor vacuumed, then we put down 4 Mil plastic sheeting, and 1/8" hardboard (Masonite) to cover the whole floor. When we finish, the Masonite is vacuumed, and mopped, taken up, and the plastic folded in. After the plastic is taken up, the floor is as clean as it was after we vacuumed it, to start with.

    You need a Shop Vac with the yellow HEPA bag in it for vacuuming the fine dust.

    Doors, and windows are masked off, and completely covered with plastic. You can't trust blue tape for the first line of defense, so clean release duct tape goes first, and the plastic is fastened to that with masking tape. You can see the woodwork masked off in the picture in the next post.

    Washers were mentioned. I never use washers, or anything, to hold up loose plaster. If a piece is loose, it comes down. Some will say they're "saving" the old plaster, but it's going to get covered up anyway, and the humps, bumps, and unevenness on the wall will not look like it did originally, anyway.

    I use plaster to repair plaster, but sometimes the quick setting "non-sandable" joint compound mix is best for a few things. It has Portland cement in it, and is very strong. Plaster will stick to it if saturated with all the misted water it will hold before the finish coat of plaster is applied. Misting has to be very fine, or if too much is sprayed on, the weight of the water on the surface will pull too much back out. You want the mist fine enough that you can see it get soaked up. A pump sprayer for fly spray on horses works perfectly.
    Last edited by Tom M King; 09-25-2021 at 9:04 AM.

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