Cracked plaster ceiling repair.

[Michael Weber]

This is a downstairs ceiling of a 1925 house with obvious previous repairs. While cracked the plaster appears to be still attached to it’s lath. Short of a tear down or just more spot repairs, what’s 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. It’s 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.
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[Tom M King]

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.

[Bill Dufour]

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.

[Frank Pratt]

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

[Jim Koepke]

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

jtk

[Frederick Skelly]

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.

[Michael Weber]

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-wallpaper-products/wallrock/wallrock-fibreliner-plus-180 A heavy fiber enforced paper supposedly made for this application.
Thanks for all the suggestions.

[Tom M King]

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/Plaster_Systems_in_Buildings.php#GypLath

[Michael Weber]

Thanks Tom. Your website is pretty awesome. Lots of useful info. Always interested in reading about rebuilding windows in particular. We’re gone from home this weekend and it will be late Monday before I know for sure about the type of lath in the ceiling.

[Tom M King]

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

[Jim Becker]

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)

[Michael Weber]

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.

[Tom M King]

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.

[Michael Weber]

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.

[Tom M King]

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.

[Michael Weber]

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

[Tom M King]

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.

[Michael Weber]

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:mad:

[Tom M King]

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/en/products/walls/drywall/primers/sheetrock-tuff-hide-primer-surfacer.html

You'll be limited to what contractors you can find there, though. It's not a job you want to do yourself.

[Michael Weber]

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.

[roger wiegand]

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.

[Jim Becker]

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!

[Michael Weber]

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.

[Thomas McCurnin]

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.

[Michael Weber]

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.

[Scott Clausen]

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.

[Jim Becker]

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!!

[roger wiegand]

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.

[Michael Weber]

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.

[Tom M King]

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.

[Tom M King]

This is the only picture I have in the gallery here, with the stages I build for this work. These are in a hallway that was about 7 feet wide, with 11 foot ceilings. The height puts my head 1" below the ceiling, when I'm standing. They're just built with 2x4's, and plywood, or OSB deck. For that job, we built three, and jumped them down the 40' long hallway.

I use supplied air for doing any such dusty work.

In this picture, the original plaster wall was proud of the picture rails in some places, so we spaced them out to work better.

edited to add: You have not seen my methods on TV. Almost anything you've seen on TV is completely different than what I do.