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Thread: Cracked plaster ceiling repair.

  1. #1
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    Cracked plaster ceiling repair.

    This is a downstairs ceiling of a 1925 house with obvious previous repairs. While cracked the plaster appears to be still attached to itís lath. Short of a tear down or just more spot repairs, whatís a reasonable long lasting (if not necessarily permanent) solution for the pictured problem?
    You can see previous repaired area using paper tape and mud. I pulled the tape down to get a better idea of what was underneath. Itís been cracking slowly in that area for several years. A recent leak has suddenly worsened that crack as well as causing new cracking over a wider area. You can see rows of tape in the other picture which made me think wall board had been screwed to the ceiling but not so.
    E3001EB4-5B87-4196-9086-963C546BCA58.jpg0B4DDAF6-9BAD-43B0-B03C-BF307BB9104F.jpg
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  2. #2
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    What type of lath? This is one of the things I do in 200 year old houses, but they don't have Gypsum lath in them.

    It definately looks like sheetrock mud has been put over the plaster. I've fixed a lot worse looking plaster than what I'm seeing under that sheetrock mud, but I would get the mud off first, and only leave the plaster.

    The spacing of the separating drywall tape looks like it may be over Gypsum lath joints, judging by the spacing.

    Plaster repair, and especially ceiling plaster repair, is not for the faint of heart, but it can be done.

    I recently put this ceiling over a stained drywall ceiling in a lake rental house we own-pictures attached. Much less work than repairing a plaster ceiling. I just put that right over the ugly sheetrock.

    You can see my plaster repair on the Plaster page on my website. The software my website was built with is no longer supported, and the website has accumulated a lot of formatting errors, but I can't edit anything on it.
    Attached Images Attached Images

  3. #3
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    Run drywall screws into the lath at every rafter to prevent movement. I would say back when that was made a top quality job would have embedded burlap into the scratch coat on the entire surface not just corners. Any repair is going to show unless you remove plaster below flush. You could cover entire ceiling with drywall and leave plaster in place. Good time to cove ceiling to wall to hide transition.
    Maybe cut out bad area and build it up with drywall. Use wood shims to get thickness needed. That plaster is probably about one inch thick. so 3/8 shim under 5/8 drywall.
    Would spray foam help or hurt?
    Bill D.
    Some folks would install a suspended ceiling or a tin ceiling panel set up.
    Last edited by Bill Dufour; 09-17-2021 at 8:30 PM.

  4. #4
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    Do a This Old House search. They've tackled this very issue a number of times.

  5. #5
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    It might be worth a little time to see if there is a reason for the cracking like foundation shifting.

    jtk
    "A pessimist sees the difficulty in every opportunity; an optimist sees the opportunity in every difficulty."
    - Sir Winston Churchill (1874-1965)

  6. #6
    Quote Originally Posted by Jim Koepke View Post
    It might be worth a little time to see if there is a reason for the cracking like foundation shifting.

    jtk
    I had a similar thought. A repair would just be temporary if there is an underlying problem.
    "All that is necessary for the triumph of evil is that good men do nothing."
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  7. #7
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    Quote Originally Posted by Jim Koepke View Post
    It might be worth a little time to see if there is a reason for the cracking like foundation shifting.

    jtk
    Thanks for that happy thought. Lol. Crawl space for me tomorrow.
    Covering with a layer of Sheetrock was my first thought but there is large and elaborate crown I have no desire to mess with.
    Those strips of drywall tape under mud are on 20 inch centers which I find strange. All the framing I’ve dealt with over the last 10 years has generally been the standard 16 inches. The tape does run in the joist direction.
    I think maybe tomorrow I’ll do a little de-construction for a better idea of what’s up there.
    I did run across this product that might be useful if the ceiling is stable. https://www.erfurtmav.com/erfurt-mav...liner-plus-180 A heavy fiber enforced paper supposedly made for this application.
    Thanks for all the suggestions.
    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

  8. #8
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    The framing has done some moving since 1925, and plaster is unforgiving to that movement. The good news is that it's probably more stable than it ever has been, so plaster repairs can last.

    I'm one who has actually done these repairs, sometimes whole, large old houses, have come up with some of my own methods, and my advice will not be merely speculation, or guess work. We do need to know what kind of lath is under it though, as I asked earlier. Methods vary depending on what is under the surface.

    To save the original look, and not vary the look of the crown, a thin skimcoat, once it's been leveled down, will give the original, smooth look, and can be done, in spite of what "experts" will tell you. You can put a lasting skim coat on, without the use of things like "Plaster Bonder".

    That one 20x20 foot 1828 room on my Plaster page, was done with a skim coat of finish plaster, after we had repaired the mile of cracks. That was done in 2012, and is still crack free. The surface thickness was not changed to amount to anything-maybe 1/16" at the most.

    I have found that mesh put under sheetrock mud does not permanently fix cracks. They will telegraph through later.

    edited to add: I found this page that covers the different types of "rock lath", or the same thing as "gypsum lath". https://inspectapedia.com/interiors/...gs.php#GypLath
    Last edited by Tom M King; 09-18-2021 at 9:25 AM.

  9. #9
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    Thanks Tom. Your website is pretty awesome. Lots of useful info. Always interested in reading about rebuilding windows in particular. Weíre gone from home this weekend and it will be late Monday before I know for sure about the type of lath in the ceiling.
    Last edited by Michael Weber; 09-19-2021 at 2:56 AM.
    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

  10. #10
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    I'll check back on this thread. Do you have any helpers?

  11. #11
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    Tom, what about doing a solid, but rough repair of the plaster and then capping the whole ceiling with 1/4" sheetrock? 'Just curious if this is a valid method of repair, especially when there's an area that is persistent in breaking down over time? (I had to do a wall that way at our previous home in the 250 year old portion of the home)
    --

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

  12. #12
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    Quote Originally Posted by Tom M King View Post
    I'll check back on this thread. Do you have any helpers?
    I don’t, and my wife is pretty adamant about just hiring someone to do it. We will see.
    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

  13. #13
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    I'll skip to the end of my method, which would be to put a skim coat over the whole ceiling, after all the cracks have been addressed. My reasoning for this is to explain why help will be needed.

    Once you start the skim coat, assuming we are going to use a modern, bagged plaster, like US Gypsum Diamond. It's wonderful stuff to work with, but once you start putting it on a section, you can't stop. On the ceiling, you will need to be at the proper working height. Pros would probably use stilts, but I make portable stages that take about 1/3 of the rooms area, that can easily be jumped along.

    You have about ten minutes to put up what you have mixed up. You're not going to get the whole ceiling covered in ten minutes, most likely. That means it has to be mixed in batches as you go. The working edge has to be kept wet, so a person would work themselves to death trying to do it all.

    I had two helpers. One to mix. The other put plaster on my hawk, and jumped the stages along. Once you start, you can't stop until it's all done, and you have to Go, to keep the edge wet.

    It's fairly hard work. You have to push on the trowel, and it has to be done correctly. With no experience, it's going to require more physical fitness, and aerobic fitness, because you're going to be working harder than one would who has a fair amount of experience doing it.

    A ceiling is several factors more physical work, even for someone who has developed a feel for the trowel on walls first.

    This skips over all the steps of getting it ready for the finish coat. If you still want to tackle it yourself, I'll go over the way I would do it. If you hire someone, they will have their own methods anyway.

    After I did that 20x20 foot ceiling, on the webpage, I had a hard time opening my mouth wide enough to eat lunch, from looking up the whole time. I'm very used to physical work.

  14. #14
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    Tom, one of the things I admire and love to watch on shows like This Old House is guys applying plaster. They make it look so effortless and easy. It know it take years of experience and possibly an apprenticeship. It’s awesome to watch. Not something I’m going to attempt. At 75 and with enough time I could handle taping/mudding the cracks but suspect strongly I’m going to have to hire someone this time.
    Speaking of plaster skills. I’m always amazed watching plaster molding being manually made. Building them up by hand and forming with repeated passes of a pattern. On a bench or on a wall. Unbelievable.
    BTW I got a couple of great ideas from your website on window glazing. Thanks
    I sure do appreciate the time you’ve taken to help.
    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. #15
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    No problem. I need to put all my methods on my website, but it's so old that the software that it was made with is no longer supported. I have a lot of information on making Lime Plaster, and Mortar. When ever I slow down, I'll change the website to some modern software, but I don't know when that will be.

    Good luck with your house.

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