I am looking at a house built in 1952 with what appears to be cement based plaster on the interior walls. From what I can see, the wall was covered in gypsum panels 3/8″ thick x 16″ x 48″, and then covered with about 5/8″ cement plaster.
I am not familiar with this and need help finding a possible mix to make repairs. HELP!?
Replies
The panels are "rock lath".
The panels are "rock lath".
No Special Mix Needed
Like Dan said, it's rock lath. Basically narrow sheets of drywall. But that's not important when making repairs in plaster unless for some "authenticity" reason you want to use the same process that was originally used.
Here's what I do. I use drywall to fill any voids while still staying below the finished surface. The drywall must be adhered securely with glue and/or screws. Durabond fills any remaining small voids. Wide fiberglass mesh tape is used whenever there is a chance of a crack traveling. The mesh tape is bedded with Durabond. Finally, topping compound smooths everything out.
It should be noted that the original rock lath was not taped and the seams were not separately mudded. Gaps as large as 1/2" between sheets (especially where cut with a hatchet) were common, and easily filled with the first coat of plaster.
A good two-man rock lath crew could rock a house in a day, though it would then take two days to clean up the detritus.
Thanks for all of the feedback. I neglected to say the finish is sanded. It looks like a topping mix to me and I didn't know if there was something "special" about it....
Basically, the plasterer achieved the sanded finish by skipping the final coat of smooth plaster, leaving the "sand coat" (I believe it's called by some) visible. It was also not unusual for the plasterer to intentionally leave trowel marks visible (for a "rustic" effect) when doing a sand finish.
Since I have no plaster skills, if I were trying to match a sanded finish, I would do it by adding a texturing additive (such as Roll-A-Tex) to the prime coat. It takes a bit of experimentation, but it's probably the easiest way to do it.
That's the info I was looking for, thanks!
David