Ceiling rock lath repair


Old 11-28-17, 07:28 PM
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Location: Florida
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Ceiling rock lath repair

I have a ceiling that made of "rock lath", a gypsum base, then a brown coat, then a finished coat, then someone added the ugly texture, and paint.

I noticed a hair line crack in the ceiling, and when I pushed on it there is tiny bit of give. So I took out a sharp putty knife and started to remove whatever is loose. As I do it more and more came loose.

It seems the very thin finish coat has been delaminating from the brown coat. After I cleaned up everything that's (and removed the ceiling fan that's in the way) this is what I have.

Closer pictures:

What is also revealed is where the finished coat has delaminated, there is also a crack line on the brown coat.

I pushed on the brown coat around the crack, and there is no "give". It doesn't look like the brown coat is pulling away from the gypsum base or the roof framing. I am a bit puzzled as to the cause of these crack lines. There is no moisture, no leak. A complete new roof was put on two years ago.

Also, as my putty knife was cleaning off the delaminated finished coat, much of it was a narrow strip (about 3" wide) of nylon mesh tape. So this is not original, someone had previously attempted a repair and it is now beginning to fail.

I called the previous owner of property - I bought this place two years ago and put on a new roof soon after. He said he doesn't remember when they repaired the ceiling, may be 4, 5 years ago.

Any suggestion on a strategy to repair this that would last?

Should I do anything to the brown coat? Should I take a small wood bit and drill through the crack to see if there is lumber behind the crack? Should I secure some plaster washers through the crack if there is lumber behind it? It doesn't appear the ceiling is sagging but I do worry a bit about the fasteners, I know the gypsum base was secured to the joists with nails, then the brown coat was floated.
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Old 11-29-17, 03:10 AM
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Screws might help. The cracks came back because there was some movement. What is above the ceiling?
Old 11-29-17, 05:41 AM
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It's a flat roof, so above the ceiling is a series of 2X8 spaced 16" apart. Then tongue and groove roof deck over that, with a two ply hot mop asphalt roofing.
Old 11-29-17, 07:31 AM
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Unless there were water stains it's most likely a settlement crack. Double check for any movement, secure if needed and then make your repair.
Old 11-29-17, 07:45 AM
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Your plaster is not flexible. So if there is any deflection (bending) of the joists due to settling or weight (workers dropping rolls of roofing) the plaster will crack where there is bending.

Could be past water leaks... (causes framing to swell... same result.) Could be lathe nails getting loose.

I would prefill the cracks with Durabond setting compound, wiping tight. Followed by tape and lightweight setting compound. Finish with regular joint compound.
Old 11-30-17, 01:30 PM
Join Date: Jul 2003
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In the second picture you can tell there has been a repair because the texture is messed up.
You call the texture ugly. Do you want to cover it up while you are in the business and in the mess?
The repair procedures describe above are fine. Matching the texture is possible but matching along cracks is more difficult.
Now would be a good time to scrape more off if it will come then skim the whole top to get a smooth ceiling. Then you don't have to worry about matching the patch.
One other thing In what part of the country are you? Is or was there electric heat in the ceiling?

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