Can I use spackling paste to fill in plaster top coat?
January 30, 2019 8:28 PM Subscribe
I'm preparing to paint a room with plaster walls. In several hand-sized spots around the room, the paint is coming away from the wall and exposing what I think is the brown coat of plaster. Can I get away with skimming the peeled-away areas with spackling paste (what I have is the light-bodied kind) or do I need to go get some joint compound (setting-type?) or patching plaster? Something else? Prime before spackling?
The underlying plaster isn't crumbling or significantly cracking. There's no need for this patching to be cosmetically perfect, I just don't want to apply something that isn't going to stick.
The underlying plaster isn't crumbling or significantly cracking. There's no need for this patching to be cosmetically perfect, I just don't want to apply something that isn't going to stick.
Yes, joint compound is easier to work with. Don't put it on too thick or it will take forever to dry. It will shrink as it dries, so you'll need to add another layer.
Sand (using a sanding block), fill imperfections, repeat.
A drywall knife that's larger than the hole will really help.
posted by H21 at 9:01 PM on January 30, 2019 [1 favorite]
Sand (using a sanding block), fill imperfections, repeat.
A drywall knife that's larger than the hole will really help.
posted by H21 at 9:01 PM on January 30, 2019 [1 favorite]
If it is just the paint peeling away from the plaster, and the plaster is smooth then you just need to scrape the peeling paint away with a putty knife (carefully to not gouge the underlying plaster) and repaint. It will take a few coats, but you will be all set. You will need a primer or a mist coat to "reseal" the plaster before you can put on a topcoat. To mist coat simply dilute simple flat white paint about 50% with water. It will be runny and drippy and a pain to use, but it will take longer to dry and will "stick" better to the plaster.
When we had our itchen redone there was a bad patch job in the ceiling that we had reskimmed to fix. In the remodeling I also made a hold in the wall that I also patched badly so the plasterers also reskimmed that section as well. When we painted I used the mist coat method and so far about 1.5 years later there is no peeling of the paint from the fresh plaster areas. You only need joint compound or spackling if you are dealing with holes or cracking at the joins of the plasterboard. All you want to do is paint.
posted by koolkat at 2:00 AM on January 31, 2019 [1 favorite]
When we had our itchen redone there was a bad patch job in the ceiling that we had reskimmed to fix. In the remodeling I also made a hold in the wall that I also patched badly so the plasterers also reskimmed that section as well. When we painted I used the mist coat method and so far about 1.5 years later there is no peeling of the paint from the fresh plaster areas. You only need joint compound or spackling if you are dealing with holes or cracking at the joins of the plasterboard. All you want to do is paint.
posted by koolkat at 2:00 AM on January 31, 2019 [1 favorite]
You will do best to prime any plaster/joint compound/mud before painting it. I like to use "drywall primer" specifically, but I'm not sure they sell it in small amounts. I've only ever bought it by the pail.
posted by some loser at 4:20 AM on January 31, 2019
posted by some loser at 4:20 AM on January 31, 2019
I agree, joint compound will work better, although as koolkat says you can just prime and paint over the plaster if there’s no noticeable difference in height.
I’ve done a bunch of this as a non-expert with a goal of “let’s make this look better than it did immediately after we removed the wallpaper from the never-primed, often-patched 100-year-old plaster” and I found a tool called a Magic Trowel very useful. It’s a variation on something called a knockdown knife but it’s really easy to blend in the edges.
posted by mskyle at 4:21 AM on January 31, 2019
I’ve done a bunch of this as a non-expert with a goal of “let’s make this look better than it did immediately after we removed the wallpaper from the never-primed, often-patched 100-year-old plaster” and I found a tool called a Magic Trowel very useful. It’s a variation on something called a knockdown knife but it’s really easy to blend in the edges.
posted by mskyle at 4:21 AM on January 31, 2019
It seems to me the ‘right’ answer is to scrape paint that is cracking off, not fill.
The former removes the underlying problem, the latter just punts it down the road, perhaps not nearly as long as you’d think.
That said, I think it will be less work to do the patchwork, so I can see the appeal— that’s why owners of old houses find all kinds of fun surprises.
posted by SaltySalticid at 4:58 AM on January 31, 2019
The former removes the underlying problem, the latter just punts it down the road, perhaps not nearly as long as you’d think.
That said, I think it will be less work to do the patchwork, so I can see the appeal— that’s why owners of old houses find all kinds of fun surprises.
posted by SaltySalticid at 4:58 AM on January 31, 2019
Response by poster: Thanks for replies so far. I am less interested in ease of use than in verifying which treatments will definitely adhere well to the brown coat of the plaster in the spots where I’ve had to scrape away the loosened paint.
By “brown coat” I’m not talking about plaster that happens to be painted brown but rather the mid-layer between the scratch coat and the finish coat. I believe this is what I’m looking at because it’s rough, not smooth like finish plaster.
posted by lakeroon at 5:38 AM on January 31, 2019
By “brown coat” I’m not talking about plaster that happens to be painted brown but rather the mid-layer between the scratch coat and the finish coat. I believe this is what I’m looking at because it’s rough, not smooth like finish plaster.
posted by lakeroon at 5:38 AM on January 31, 2019
If you are curious about adhesion do a test. Apply a tablespoon or so of the product in one of these damaged places, let it dry and then tug or pry at it and see if it adheres.
posted by bdc34 at 7:43 AM on January 31, 2019
posted by bdc34 at 7:43 AM on January 31, 2019
I think there's some regional vocabulary difference to be aware of - there's (a) old-fashioned 3-coat lime plaster, which is what you have I think (if you have a brown coat and this is an old house)..... and there's (b) what the UK and Australia call "plasterboard," which is called drywall/sheetrock in the US, and the "plastering" compounds that go with that for seam sealing between boards. It sounds like some of the advice above is maybe for (b), but it's not going to apply to (a).
We have 3-coat plaster and had a bunch of holes re-plastered last year. These were complete holes, cut all the way thru the plaster for electrical work; they were mostly about 2"x4" or maybe a bit bigger -- not huge holes. I asked the plasterer about whether it was okay to use spackling or similar things to fill, and he said no, because it - especially the lightweight stuff - will shrink a lot as it dries and eventually can just fall out. (It's fine for small holes like nail holes or little chinks that fall out. But not for bigger ones.) So - he did the full plastering job, and said, the best thing is to let this dry and cure, unpainted, for a month or more. There's drying and also a chemical change -- as the plaster cures it becomes more neutral in pH, and also becomes stronger from the chemical change. So you don't want to paint too early. But if you need to paint early, use a "masonry primer" which is made to work with the extreme pH of uncured plaster or concrete.
Your situation is different, since it's just the skim coat that's missing, so I don't know how much of the above applies.
Also if the skim coat is coming off in several largeish places, I would be suspicious of the rest of it. Was there some obvious source of damage? If you go around and tap on the wall in other places does it seem like it's loosening anywhere else? It would be annoying to paint and then have a bunch of other spots come loose.
posted by LobsterMitten at 9:44 AM on January 31, 2019 [1 favorite]
We have 3-coat plaster and had a bunch of holes re-plastered last year. These were complete holes, cut all the way thru the plaster for electrical work; they were mostly about 2"x4" or maybe a bit bigger -- not huge holes. I asked the plasterer about whether it was okay to use spackling or similar things to fill, and he said no, because it - especially the lightweight stuff - will shrink a lot as it dries and eventually can just fall out. (It's fine for small holes like nail holes or little chinks that fall out. But not for bigger ones.) So - he did the full plastering job, and said, the best thing is to let this dry and cure, unpainted, for a month or more. There's drying and also a chemical change -- as the plaster cures it becomes more neutral in pH, and also becomes stronger from the chemical change. So you don't want to paint too early. But if you need to paint early, use a "masonry primer" which is made to work with the extreme pH of uncured plaster or concrete.
Your situation is different, since it's just the skim coat that's missing, so I don't know how much of the above applies.
Also if the skim coat is coming off in several largeish places, I would be suspicious of the rest of it. Was there some obvious source of damage? If you go around and tap on the wall in other places does it seem like it's loosening anywhere else? It would be annoying to paint and then have a bunch of other spots come loose.
posted by LobsterMitten at 9:44 AM on January 31, 2019 [1 favorite]
A few pictures would be a great help to give better advice, or at least what I would do.
posted by koolkat at 11:52 AM on February 1, 2019
posted by koolkat at 11:52 AM on February 1, 2019
Response by poster: I had my spouse ask the workers who are redoing the ceiling in that same room and they thought regular joint compound would be fine, so that’s what I used. Applied last night, sanded this morning, will prime and paint tonight or tomorrow morning. It is adhering fine so far, but probably the original treatment looked good the first few days too!
posted by lakeroon at 12:43 PM on February 1, 2019
posted by lakeroon at 12:43 PM on February 1, 2019
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posted by mr_roboto at 8:50 PM on January 30, 2019 [2 favorites]