Info on Stucco and Plastering-January, 2023-sixty-seventh issue
Lath on lath
An inspector here in southern California suggested I get my workers to put a second layer of wire lath high on the walls to be stuccoed to help prevent cracking. I'm not sure if he means another whole layer of paper-backed wire or just wire. I haven't found this suggestion in any guides or manuals to stucco, and it's not code requirement, just his suggestion.
Any thoughts on this?
He means without the tar paper backing. Maybe the reason for the suggestion is the lath put on wasn't overlapped well, or nailed to tight to the wall. You probably are alright the way it is. If more lath is put over the lath that there is now, care must be used not to
nail the lath way too tight.
This gives me a reason to bring up something I have wanted to say for a long time.
Years ago, a trend was to put a small piece of lath over the corner of windows or doors. Cracks frequently appear
from the corners of windows or doors, because the opening is a weak spot in the plaster membrane.
I tried doing this because it sounds like a good idea, but it doesn't work.
.The reason this doesn't work is that there isn't room behind the lath. If two pieces of lath overlap at the corner of the window, then
the lath is now a half inch out past the surface. A third piece of lath with be out 3/4" past the wall surface, or out to the finished thickness.
If this small piece is nailed down to tight, no there isn't room for mortar to key behind the lath, creating a weak area. Even though this seems like a good idea, putting an extra piece of lath over the corner of the window does more harm than good.