This old house goddamit - how to remove weird skim plaster coat remnant
August 16, 2021 12:04 PM   Subscribe

I am scraping and painting a plaster wall. What I found under the wallpaper will surprise you!

Okay, so I have been peeling eighties wallpaper off an early 20th century plaster wall. What's weird is that different spots on the wall have different stuff under the wallpaper, some of which I am not sure how to remove.

Under some of the wallpaper is basically nothing - remove the top layer of wallpaper and the thin brown paper second layer and it's just paster. Under other parts of the wallpaper is a layer of paint over a thick brown paper. This is peeling away from the plaster and I am removing it. But under part of the wallpaper is paint with no brown paper, just a skim coat plaster layer. There is no skim coat on the rest of the wall. This skim coat is around the bottom of the wall mostly, but parts of it stretch up into the middle. See photos - where you can see a brown edge under the paint, that's the paper. Where you see a white edge, that's the skim coat.

I do not have the skills to apply a new skim coat of plaster on the wall, nor do I have the money to hire someone. My plan has been to repair the plaster, fill the holes, etc, prime and paint, which is what I have done in other rooms in the house. What do I do about the skim coat areas? I feel like I have to remove it at least partially, but how? Is there something else I should be doing?
posted by Frowner to Home & Garden (15 answers total) 4 users marked this as a favorite
I would assume that the skim coat is there to patch holes or something and removing it would be a bad plan. Why do you need to remove it? It should take primer + paint just fine.
posted by restless_nomad at 12:11 PM on August 16, 2021 [2 favorites]

Response by poster: I need to do something about the skim coat because the skim coat is only on part of the wall. It sticks up from the plaster. If I paint over it, there will be raised areas all over the wall. I do not have the skills to re-skim the wall myself.
posted by Frowner at 12:13 PM on August 16, 2021

Hm. Well, you can certainly take an omni sander and sand it level. I've done that with wall texture - it's tedious and messy, but works fine.
posted by restless_nomad at 12:14 PM on August 16, 2021 [4 favorites]

The professional way to do this is to just skim coat over the whole thing with joint compound. You use a very wide joint knife (like 24") so it smooths out the bumps. If the plaster is falling apart you add reinforcing mesh. You can sand down the surface in advance but I think a lot of contractors will just use more mud instead.

ETA: I see you said that you don't have the skills to plaster over -- you could just sand, but TBH the tools and supplies are pretty cheap and you'll get the hang of it fast. Drywall mud is much easier to use and much faster to dry than plaster.
posted by goingonit at 12:32 PM on August 16, 2021 [10 favorites]

I would also worry that taking off the skim coat bits would leave me with sections of wall I needed to repair from the lath up, and I know I’m not good enough to do that.

Maybe you can sand just the edge of the skim coat to feather it into the rest? Or a combination of beginner drywall-mud skimming and sanding until it’s as flat as it seems likely to get.

And maybe a lime wash paint that’s supposed to look irregular and old-plaster. In my experience these look really good sometimes, good in an 80s way mostly, and terrible in an 80s way sometimes.
posted by clew at 12:41 PM on August 16, 2021 [1 favorite]

It's a little bit unclear to me from the pictures whether you're simply dealing with the divergence between bare plaster and a layer of lead paint or whether there's actually a plaster skimcoat going on. But in any case, I'm seconding goingonit: we've been dealing with very similar issues and I can confirm that the best way to handle this is to skim coat with joint compound (drywall mud). It takes a little bit of practice (the temptation is to use too much mud at first), but you'll get there. Sanding risks getting lead paint dust everywhere (ask me how I know), and it's also easy to sand too much, and then you risk far worse problems. The skim-coat method yields glass-smooth walls when done right, and my husband got to the point where he could do a wall perfectly in under 10 minutes. I am slower and less good, but the results are still acceptable and I would strongly recommend over sanding. I believe my husband prefers for this purpose the lightweight (maybe "finish layer" or something?) pre-mixed mud from any home improvement store.

All this assumes that the plaster is (1) not falling apart, and (2) secured to the underlying lath. If you see big cracks, and/or if there is movement (if you can push on any part of the wall and it moves a little bit), you're going to need more intensive work involving a drill, construction glue, washers, and drywall mud (I can link to tutorials, just shout). We've done this too and it worked surprisingly well.
posted by ClaireBear at 12:56 PM on August 16, 2021 [3 favorites]

Yeah just sand the edges!
posted by showbiz_liz at 1:11 PM on August 16, 2021

Have you used a steamer? That should get all the brown paper off, and the brown paper really should come off before you paint. Where the brown paper has paint on top of it, score the paint, heavily, and the steamer should get the paper off. Where there is paint, but no paper underneath, you can leave the paint alone. Once you've got all the brown paper off, proceed to a skim coat as suggested above. You have scratches and dings that need to be fixed anyway so you might as well do the whole thing. (Don't try sanding the edges of the painted brown paper, you will never get a level surface that way.)
posted by beagle at 1:27 PM on August 16, 2021

It's hard to tell from pictures, but if it wasn't visible under the wallpaper could you re-paper the wall with a thick lining paper and paint over that?
posted by stillnocturnal at 3:04 PM on August 16, 2021 [1 favorite]

Thirding doing a skim coat with joint compound. You're going to have to sand everything smooth to some degree, might as well have it be fresh compound that you applied. Even if you're not super skilled enough sanding and time will get you to a better looking place.
posted by Ferreous at 3:22 PM on August 16, 2021 [1 favorite]

Since nobody else has suggested this take it with a BIG grain of salt. But I once spent a LOT of time on my dining room walls and when I told my brother-in-law what I did he said "You know, you could have popped the wood trim and just put 1/4" sheet rock over everything and then reinstalled the trim?" I know it's not fire rated, but I don't know if there are other downsides. I suppose it depends on how bad exactly the walls are.
posted by forthright at 3:51 PM on August 16, 2021 [3 favorites]

The big disadvantage of laminating with sheetrock is you have to redo the mouldings, light switches, windowsills, everything.
posted by goingonit at 3:59 PM on August 16, 2021 [3 favorites]

I should clarify that if you skim coat with drywall mud, you're still going to have to do a light sanding (of the new skim coat) to even things out: the better job you do, the less sanding you'll have to do after. A few tips:
- Make sure the mud is *completely* dry before you sand: you'll know because it changes in color from light beige to white.
- When you sand, probably start with 150 grit sandpaper (unless you've done a very uneven job, and then maybe 100 grit), and rub over it lightly in a circular motion. You can put it on a foam sander block to do this if you find it easier (I found a harder block, e.g. wood, created lines, so I wouldn't recommend that).
- Don't push too hard or the grains in the sandpaper will leave trails in the delicate mudded surface, and you also risk the circular pattern of your sanding becoming apparent.
- Follow the 150 grit sandpaper with progressively finer grits of sandpaper (200, 220).
- While sanding, position a painter's light at an oblique angle to make sure you've caught all the tiny dips and high points in your skim coat. You'll almost certainly have a few pock marks to deal with because the mud shrinks as it dries, and your tool will almost certainly also create edge lines (which is why the bigger the better, in terms of tool size, as long as you can wield it). You will probably find it easier to do a few light mud touch-ups after sanding rather than to try to get it perfect in one go.
- When you sand, the dust settles *everywhere* and is surprisingly messy, so try to get all carpet and soft furnishings covered or out of the room first, or resign yourself to some serious vacuuming and deep cleaning after (which is, ahem, what we've done).
- If you've done a good job mudding, the sanding should take 5 minutes a wall (on the other hand: if, like my first wall, you've done a far too heavy job mudding, it might take an hour of sanding and then several more rounds of mud and sanding to make aesthetically acceptable).
- When you're all done, paint the whole thing with a sealer/primer. For this, find a primer that says something like "for new drywall". This ensures that you don't get "flashing" from the mud. After this, you're ready to paint. I assume you've painted before, but in case not: for both the priming and painting, a roller yields far better results than a paintbrush (you'll need to use a paintbrush for the corners, of course). Also, don't skimp on quality paint. We used Sherwin Williams' Emerald line in almost the flattest sheen (I think we used their flattest wall sheen except for closets - maybe semi-matte or something?), and it turned out fabulously: you couldn't see roller marks or anything (and I'm not a great painter). It was a very lush and forgiving paint. We still needed two coats though. Conversely, we had first tried Sherwin Williams' contractor paint and it was thin and awful.
- All this might sound tricky, but you'll get the hang of it, and it's very satisfying to get right.

In response to someone above: we actually did do quarter-inch drywall over textured ceilings (we already had committed to replacing existing crown molding with larger, and so had torn it off, which counseled the 1/4" drywall option for the ceiling). But we didn't do the 1/4" drywalling option for the walls because of the molding and depth issues that forthright and goingonit mention. Quarter-inch drywalling still involves mudding over seams and screw-holes etc. and then sanding, and then also fiddling with molding and depth, so I really think you're going to be better off just skim-coating. What you have going on doesn't look too bad, and I really think you can even it out fairly quickly with a quick skim-coat and sand. I'm happy to give further advice here (or even FaceTime help) if you need it, so just let me know: I feel like I should do something good from the 2+ year renovation hell we've been through! :-)
posted by ClaireBear at 5:01 PM on August 16, 2021 [4 favorites]

Plaster -- I got nothin'.
Repairing drywall -- third house build/repair in a dozen years.
Husband likes the Plus 3 Sheetrock joint compound for quick strong repairs. It dries fast, so mix up small batches as needed. Once it begins to dry out, throw it out and start with a fresh batch.
I prefer the All Purpose Sheetrock joint compound for general mud work -- "taping, bedding, sanding, priming, painting" routine for new and existing drywall.

Repair any cracks, holes, gaps, and broken areas. Surface must be clean and dry, and loose materials removed. The husband likes paper joint tape that must be bedded into the mud, and I like self-adhesive joint tape. Larger taping materials are available for large repairs.

Mix joint compound and water in a mud tray to cake batter consistency. I've never used my drywall hawk. Trowel it on, smooth it over area like frosting a cake, feather out the edges to nothing (be careful, it drips off, particularly when working ceilings). I do one wall at a time, since working corners and keeping both surfaces smooth is a pain.

Feathering -- angle the trowel so one edge is on dry surface, the rest of trowel is gently touching most of the wet surface (this is why longer trowels exist). Skim along the edge, taking down excess mud along edge.
Wipe the trowel edge clean after each skim with a fresh paper towel, or dried compound will put streaks in the wet mud.

Thin coats are key. Otherwise, the outside surface dries and the interior stays moist.
I give the compound a day to dry, just in case. I do at least three very thin coats.
I have tried sanding between coats, and took off way too much mud. Now I use the trowel edge to -- gently -- scrape down the edges and bumps of dried mud before adding the next coat.
Use progressively longer trowels to work out from the wall corner/damaged area. This gives a smoother transition from drywall compound to uncoated areas.

Final coat is dry -- time to sand lightly. There are drywall sanding sponges for this, or use fine sanding paper wrapped on a block of wood or fastened on a sanding block. Pole sanders are excellent for large areas like ceilings.
Use safety goggles and a face mask when sanding. Compound powder gets everywhere, so keep the room closed off and vacuum when done.

Here is information on what a level 5 finish is. I prefer a lightly textured surface. I skim coat the whole wall or ceiling with a thick nap paint roller and drywall compound thinned to a pancake batter consistency. Be careful about overworking the skim coat, or it will pull off the existing drywall compound layers. You can sand the skim coat down and try again.
posted by TrishaU at 7:37 PM on August 16, 2021

I hired someone to skim coat one kitchen wall. Done in a day.
Don't waste your time and money trying to do it yourself.
posted by Enid Lareg at 8:38 AM on August 17, 2021 [2 favorites]

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