Plaster ceiling - general terminology 3

[PSUengineer1]

I am looking for general terminology to describe the plaster ceiling in the attached pics. I would call pic #1: plaster on wood lath with a finish coat. I am not sure what the green board is behind the skim coat of plaster in photo 2. House built in 1930s. original ceiling. thanks.

 

[jayrod12]

My house (1950s construction) has gypsum board lath. so it was 1" of plaster on 1/2"x16" wide horizontal sheets of drywall. Ceiling was the same.

 

[dik]

Wood lath and they applied a 'scratch' coat approx 3/8-1/2 thick and then they applied a top or finish coat of plaster. A caution... most scratch coats had a binder in them. On early houses it was horsehair, on later houses asbestos and on other later houses no binder...

Dik

 

[OldBldgGuy]

1930s is at the end of the wood lath era, but it's a bit early for gypsum board lath. There would be 3 coats of plaster on the wood lath: scratch, brown, and finish. Scratch & brown may not be distinguishable in a section through the plaster without magnification, but the finish coat (typically lime at this age but possibly gypsum) has no sand or other binder in it and is easily distinguishable. Your pictures seem to show a textured finish over the original smooth finished plaster which probably had a green paint on it. I really doubt that the textured finish was original, and the green colour is definitely nothing that would be found within the original system. Even if you encountered sections of gypsum board lath, the paper covering was grey, not green, and it would be clearly paper which your green surface does not appear to be. The textured coating seems to be failing, as evidenced by the cracking and delaminating, and even based only on your 2 photos I'd be prepared to stick my neck out & say you have a "modernizing" texture job over an original ceiling and it's falling off.

 

[racookpe1978]

OldBldgGuy

I'm agreeing with you: Picture 1 shows a "repairable" section of lathe (which I thought was any kind of heavy plaster coated directly over strips of wood lathe ?) which could be salvaged if you want to keep the contemporary structure.


picture 2 shows terrible conditions. I'd start over with very thin sheetrock (3/8 of 1/2 thick) over the whole thing, then a new layer of a modern coating over that. Removing the old paint (with all of the garbage likely inside it and the old contaminates) is going to be too difficult. Entrap it, leave it if you legally can.

 

[dik]

Thanks OBG... forgot about the brown coat... in these environs, the scratch and brown coat were often the same material, and applied at the same/similar time. Forgot about lead paints... common at that time...

Dik

 

[Ron]

OBG and dik have nailed it. The second photo is likely a repaired area, since green board did not come out until much later. The second photo also appears to have a parge coat instead of a full thickness of plaster.