What kind of wall is this and how can I repair it?

Question

UPDATE 04/08/2023 After spending a bit more time scraping away old paint/skim coat/wallpaper, I can confirm that the wall is plaster applied directly to brick. The plaster is in rough shape and large chunks are practically falling out of the wall. I was planning to patch and re-skim, but it's looking more and more each day like all of the plaster will need to be removed, and drywall put up in its place. Thanks for all of the answers.

In the master bedroom of my house, the front wall has some surface cracks that I'm trying to address before repainting. For some background info, this is an early 1900s rowhome. The interior of the house is drywall except for this particular wall in this room. There are no studs and knocking on the wall at various spots indicates to me that the wall is completely solid.

I stuck my finger under one of the cracks and a piece just flaked right off -- it's definitely not drywall, and I don't think it's plaster and lath, but I'm pretty unfamiliar with that kind of wall so I could be mistaken. There seems to be 3 layers -- the paint, a very thin layer of something that has a rust colored backing to it, and then what I thought was concrete until I started poking at it. As shown in the pictures, there was a hole that someone drilled into the wall, so I stuck a screwdriver in there and started scraping around -- it basically disintegrated into a powder. It looks to be about as thick as a piece of drywall, but it's made of something I'm not familiar with. Behind that, I'm not really sure.

Any ideas on the structure of this wall and what I can do to fix it? I've already done some drywall repairs with joint compound, but this is a bit out of my wheelhouse. I'm happy to take more pictures if they are needed.

EDIT -- After some more peeling and breaking apart of the top layer, I can now say with some certainty that the "middle" layer -- the one I identified as having a rust-like color -- is really old wallpaper. I exposed a section that is clearly a floral pattern:

On top of that is a paper-thin material -- the one with all the grey splotches -- I think this was some kind of adhesive at some point in the process.

^{Click to embiggen}

Answer 1

Based on the picture, plaster at the back, covered with hardboard (unless it's thinner than it looks and just wallpaper) with a printed surface, covered with some sort of skimcoat (plaster or drywall compound) (poorly adhered) and paint.

You could remove all the loose skimcoat, but that might turn out to be the whole wall; scuff the surface behind for better bonding and recoat. You could go ahead and remove the hardboard layer as well, and repair the plaster behind that. Somewhat a matter of how deep you want to dig into "bad things done to this wall" when trying to make them better.

Answer 2

Honestly, I’d get a real drywall guy in to do an old world finish. Paint matte or slightly more shiny and it’ll look awesome.

Alternatives include stripping everything (including ancient trim, which doesn’t like being stripped for re-use, plus budget for lead remediation) and applying new drywall. (If you strip the plaster/lath as well, you’ll probably find that your studs need a lot of massaging to be plumb, straight, and in plane with each other. (Hint: $$$)

Or spot patch regularly for the foreseeable future, because poorly bonded mud/ plaster/ whatever that is will keep cracking over time.

Answer 3

I didn't see where you discussed the makeup of your exterior wall, but I am assuming it is brick based on the ~1908 row house description. If so, one possible stackup (from exterior to interior) is:

• exterior brick
• air gap
• interior brick
• scratch coat of lime putty plaster (coarse sand or other reinforcement) directly on brick
• finish coat of lime putty plaster (fine sand or no sand)
• charming flower-print wallpaper
• somewhat less charming grey wallpaper
• plaster skim-coat with done with modern (post-WWII) setting plaster
• paint

Here is a photo from the butler's pantry in my house, showing plaster wall over wood lathe and two layers of wallpaper, the bottom of which is of similar-age to yours. (The blue paint is the result of a 1950s-era attack on all of the shellacked oak trim in the house, sigh.)

There are many variations in plaster wall construction; wooden lathe layer between the brick and the scratch coat, scratch coat reinforced with horsehair (1886 Boston brownstone), the finest Johns-Manville asbestos-reinforced plaster (my house, 1897), plasters that contain portland cement, plasters that contain plaster of paris (gypsum). I think you have lime plaster because of the age of the house and because its initially very high pH tends to weaken whatever wallpaper sizing is stuck to it. (One was suppose to let lime plaster walls cure for a year before painting/wallpapering, but then as now, time is money!)

The plaster skim coat looks to be of recent vintage and of high quality. In the days of yore, anyone who called themselves a plasterer could put up a flawless skim coat, but it is a lost art today. I am thinking that whoever did the skim-coat job would not have done it had there been an easier way to hide the various defects (water damage, etc) in the wall. You don't want to deal with whatever problems they decided to cover up, so I recommend you do the take the least invasive repair path you can get away with. This is where I respectfully disagree with "do it once, do it right" approach suggested by some my esteemed colleagues; unlike with a bad foundation, walls are mostly cosmetic. I think part of being happy in an old house is forgiving your old walls hairline cracks, bumps, and dips. Old walls are never going to look like drywall, and that's just part of old house charm :-). In my book, if an interior wall looks good, it is good! (The calculus changes if you also want to insulate, redo electrical etc; at some point, it's easier to just rip everything out and start over.)

The challenge is that while the skim-coat is attached to the wallpaper, the wallpaper appears to be rather tenuously attached to the wall. You are going to have to evaluate whether the skim coat is badly-adhered in only a few areas (which is fixable) or whether the entire skim-coat is ready fall off when you look at it. I think you will find this out pretty quickly when you go to remove the loose stuff.

Assuming it is only loose in some spots:

• remove the loose stuff with a spackling knife
• remove the wallpaper (i've had good results with "DIF")
• wash the plaster wall with clean water and let it dry out
• prime with a "plaster bonding adhesive" (Google this, there are a few brands, Plaster Magic, Plaster Weld etc). These help stick new plaster to old plaster. Don't skip this.
• Re-do the skim coat with a setting-type joint compound (e.g. USG "Easy Sand"). I like to fix big cracks with plaster of paris-soaked cotton balls, but plaster of paris is definely not "easy sand" so it should not be used as the top coat. If you are not a plaster pro, underfill everything with the setting-type plaster and let it set, then you can come back and touch it up with a thin second coat. I try hard to make the top layer smooth so that I can avoid sanding, which I hate.
• Let it sit for a few weeks before you paint.
• Paint.

A alternative to paint is paintable textured wallpaper. (Trademark names are "Lincrusta" and "Anaglypta"; there are cheaper brands.) These are expensive and take some real skill to install, but they can hide all kinds of problems in the underlying wall, and they look fantastic.

Good luck!

Answer 4

(I don't have enough reputation to comment, so will put my comment here as an answer)

If that is the common wall in your row house there is a possibility of that layer containing asbestos. It was used extensively as a fire-retardant material.

Have you tried the drywall compound? It should adhere to that surface. If not, some spackle might do it. I agree with the other comments; stripping that surface could lead to a ton of work. You would definitely want to get the material tested before you start creating dust with it. Very dangerous.