Cause of paint cracking and flaking off plaster walls?

[Michael Yadfar]

I bought an 1870 house a year and a half ago which was painted right before it sold. About half the walls are plaster and the other half have been redone with drywall. On the plaster walls, the paint is cracking and flaking off. There only appears only be one layer of paint with bare plaster behind so it was most likely wall papered before.


My question is what to do now? Obviously it’s probably going to have to be all scraped off, but what’s the cause and how can I prevent it from happening again?

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[Lee Schierer]

That is usually a sign of moisture and a dirty surface that was painted over. About all that can be done is to remove the flaking paint with a putty knife or scraper and then lightly sa and the area to feather the edges of the paint and clean the surface. The use some primer tinted to the finish color followed by a coat of the original paint if it is available. you may need to paint the entire surface if you can't match the original color.

[Edward Dyas]

The most common cause of the texture coming off sheetrock is person that did it didn't clean the rock off first. Often they sand the rock and then proceed with the texture and end up texturing over the dust which causes adhesion problems. I normally take a broom and sweep the walls and ceiling after the tape and bedding is done. Another cause is the texture might have been too dry. From what I can see in the picture that texture is done by thinning drywall mud and rolling it on with a paint roller.

[Tom M King]

1870 means it's probably lime plaster. They would have used a little Gypsum plaster as gauging, but still lime plaster. Lime plaster breathes, including moisture carried along. I do a lot of lime plaster, in old houses, but we don't paint it. It can be sanded, and scim coated, but requires putting a Lot of water on the wall, which has to go somewhere.

If there is a vapor barrier, and insulation behind the lath, it should hold paint. Sorry, but I have no experience painting lime plaster, even though I have a lot of experience making, applying, and repairing very old Lime Plaster.

[Jim Becker]

Moisture....is one major reason this happens. But wall paper paste that was not completely removed and then properly primed over can also cause the issue. I have both problems in this house in the 250 year old portion, as a matter of fact...

[Michael Yadfar]

What do you guys mean by moisture? Like humidity or moisture from the outside? The siding is in good shape but I’d be willing to bet there’s no vapor barrier. Considering the house was built this way, are the walls just made for wallpaper?

[Jim Becker]

What do you guys mean by moisture? Like humidity or moisture from the outside?

"Yes"...in my case, it's moisture penetrating the 18" thick limestone walls that's causing any moisture issues, but a frame wall could have similar issues, depending on its age and methods. Where I've had issue with flaking away from exterior walls, it's pretty much all been improper preparation for paint by the previous owner or their contractor after stripping wallpaper.

[Tom M King]

We don't paint lime plaster. Here is a webpage about one room we redid. Lime plaster is great stuff.

Gypsum plaster was no improvement in quality. It was just one of the many steps in building that gave way to faster, and cheaper. Some gypsum plaster had to be added, so it would set up in less than forever, but the more gypsum it has in it, the less durability it has against moisture. Moisture makes gypsum plaster (also called Plaster of Paris, because that's where it came from, for a Long time, because of a large Gypsum deposit there). This added ingredient, to make it set up faster, doesn't require but a few percent of the total ingredients. I have started using a few percent of White Portland Cement, and it makes it not only more durable, but waterproof.

Long story shortened some, but the chemistry is really simple, and the lime used in the mix is Hydrated Lime (long story about variables of that too), and over centuries, it gives up the Hydrogen atom when it's replaced with CO2, turning it back into Limestone.

Bacteria doesn't grow on Lime Plaster, and it breathes. The breathing works against getting paint to stick long term. It can be sanded, and that's how we remove centuries of dirt-with a power sheetrock sander. You can see the circles where we started on one wall.

People don't believe that Lime Plaster can be scim-coated. Experts will even tell you that it can't be. Plaster bonder is commonly used for recoating, which is really just a type of PVA glue that you apply, and it pulls water out of the top coat to make it bond. I have seen plenty of old recoated lime plaster walls, so figured out how to do it. I can't believe that the PVA will be as long term as some of the old plaster repairs I've seen. I may be the only person doing this now, but I'm not taking on any more work for the rest of my life.

http://historic-house-restoration.com/Plaster.html Please excuse formatting errors on my website. I haven't worked on the site in years, and it's accumulated a bunch of formatting errors, dropping parts of, and whole blocks of texts, so some of the reading may not make sense.