Wire Lath and Plaster Ceiling Repair
I need help repairing a ceiling in the basement of an old church. Construction is plaster over wire lath. in some areas, there are long cracks (3-4 feet) that go all way to the wire lath. In these areas the plaster has separated from the lath and I can see movement when I push up. I’m familiar with using plaster washers when the lath is wood, but what’s the method when the lath is wire? I really don’t want to take down the entire ceiling, so I’m looking for a way to re-attach loose plaster to the wire underneath where possible. Some of the plaster is in pretty bad shape (likely water damage) and will have to be removed. I plan on using setting compound for the base coat. Any suggestions on bonding agents to tie the new stuff to the old? Thanks in advance.
Stan
PS. This was originally posted in General Discussions.
Replies
Setting compound?
Setting compound won't key into the wire lath and stay there very long.
Remove the bad plaster down to the lath and you will likely find that the wire lath was stapled up and has come loose in those areas. Reattach the lath (stables aren't bad, but water loads on the back can pull them out), After getting a firm foundation lay in a good scratch coat and brown coat of plaster. Leave it shy of the finish (white) coat or at that point you can use setting compoud.
If you don't get the wire lath fixed first, you are just asking for future failure and call backs.
Lath Seemed ok
I don't think the lath itself detached. It looks more like some water damage and age caused the plaster to detach from the lath. In similar cases with wood lath, I was able to reattach the plaster using plaster washers spaced along both sides of the crack. (Of course, big chunks that were loose had to come down). This reduced the amount of demo (and plastering skill) needed to do the repair. Is there anything similar for wire lath?
stan
You can still use the plaster washers through the metal lath if you hit the joist. I've not had much luck with them holdin or pulling up very well in just the metal lath. That means if the ceiling joist are on 16" centers, that is as close to the crack as you ar going to get.
Maybe lay a long straight edge acroos the ceiling in several directions and see if it has any sagging areas around the crack. Don't count the normal small highs and lows some plaster finishes have.
My experience with plaster that has water damage from above is that the scratch coat and brown coat are ussually shot. It gets so weak and crumbly that repair finishes over it fail sooner than later. My first test when looking at a repair job like that is to scrape any exposed brown coat that is showing. If it is hard and tight the repair is pretty straight forward. If it is soft and easily crunbles to a sandy type texture, it means taking it back to the mesh and starting over.