Patching and Plastering - Not sure what this wall is made of. Ideas?

I'm renovating the attic of my 1890s-era home. While removing some old ratty wallpaper in the stairway to the attic, I realized the wall beneath has a lot of issues. Multiple large cracks. A few sections are crumbling. At first, I thought it was a plaster wall, but now I'm guessing not.
While there is a very thin coating of plaster-type material, the inside is more like some sort of gray concrete that crumbles away if that thin protective layer is disturbed.

Anyone have any idea what this might be? I have no way of knowing when the wall was actually built. It could have been anytime during the past 100 years. Considering the fragility of the wall, I've considered pulling it down (it's only in the stairwell) and replacing it with drywall.
The big question I have - Is there any chance that interior gray material could have asbestos in it?

Here are couple photos. (The second one shows a section where the wall meets a wooden border)


http://farm3.static.flickr.com/2543/3851382930_d78e8660f4.jpg

http://farm3.static.flickr.com/2610/3850585897_be730b36ef.jpg

Preservation Brief 21: Repairing Historic Flat Plaster--Walls and Ceilings (http://www.nps.gov/history/hps/tps/briefs/brief21.htm)

FAQ About Old Plaster (http://www.plaster-wall-ceiling-solutions.com/old-plaster-questions.html)

Be safe, G

Thanks for the link.
I'm guessing that it must be a rock lath that I'm encountering. There definitely is no wood lath under the wall.
If that's the case, It seems like a repair will be a little trickier.


Rock Lath. A third lath system commonly used was rock lath (also called plaster board or gypsum-board lath). In use as early as 1900, rock lath was made up of compressed gypsum covered by a paper facing. Some rock lath was textured or perforated to provide a key for wet plaster. A special paper with gypsum crystals in it provides the key for rock lath used today; when wet plaster is applied to the surface, a crystalline bond is achieved.

What you might have is plaster over brick or some other type of masonary. The plaster used on these walls was very thick and hard as a rock. I doubt you have sheet 'rock' lath walls in a house that old. I'm not sure where you got that info but drywall was invented in the late 1930's for use in building housing for military during world war II.

The info came from the "Preservation Brief 21: Repairing Historic Flat Plaster--Walls and Ceilings."

The plaster coating on this particular wall is roughly 1/8 inch thick. The crumbling rock-type layer beneath it is 1/2-inch thick.

What troubles me is that some areas of the wall are quite firm. But other areas have a lot of give to them. This is particularly true around the cracks and the hole that I have shown in the first photos. It just doesn't feel all that stable.

I bet if you dig through the crumbling "concrete" you will find wood lath. What you have is gypsum plaster with a whitecoat (lime and gauging plaster) finish. I am a little surprised that the plaster is that thick. Usually the plasterers skimped a little on the walls in attics and made it thinner, therefore weaker and more prone to cracking. Now you can't really blame them for saving some material, after all, they had to get it up there the hard way and a few hods full of mud saved some hard work. Look up "hod". Read that preservation brief again and read what it says about plaster over wood lath. Dig out a little of the stuff you have and see if there is wood lath behind it. The age of the house would indicate wood lath and the plaster looks to be in too poor shape to be done over gypsum lath.

Plasterers were notorious for doctoring up their mix. Yes, there could be asbestos in it but not likely. If it's there it was added by the plasterers not the company that made the plaster. You are a lot more likely to find hair in the plaster than asbestos. People always say "horsehair" I suspect it's hog bristle or cow hair simply because more hogs and cattle are killed than horses in this country and their hair would be easier to get.

In fact, I'd like to see someone analyze the hair in plaster to see what species it is. But that is a topic for another time.


What you really want to know is can you take it down. Sure just get a flat shovel and scrape the plaster off the lath. Then pull the lath off. Save a few unbroken ones. You might need them for shims or something. They are most likely cedar though some were made of redwood or fir.

And be prepared for a bigger mess than you can possibly imagine there is 120 years worth of dust in that attic just waiting to get airborne and fill your whole house and your lungs.

Otherwise this is a piece of cake.