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Lath and Plaster ceiling cracks and sagging spots

Lath and Plaster ceiling cracks and sagging spots

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  #1  
Old 06-14-20, 11:36 AM
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Lath and Plaster ceiling cracks and sagging spots

My girlfriend's mom's house is an old craftsman bungalow kit home built in 1918 (we're in the SF bay area).

I'm going to fix up the place and one of the issues is the cracks in the coved ceilings. Some cracks just need to be opened up - I like to put fixall in there - and then taped/mudded but some of the sagging spots, looks like I might need to scrape out what is loose and then patch that up.

In the areas where it's falling, Does that look like the ceiling was re-floated and what us coming down is that newer pass of mud?

There are only a few spots like that. The rest of the ceiling is just cracks with no separation.

The sagging portions are maybe 1/16th thick.




 
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Old 06-14-20, 01:21 PM
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It looks like what you typically see when the finish coat has come loose from the base coat, such as due to a water leak or condensation coming thru a crack in the base coat.
 
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Old 06-14-20, 07:20 PM
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Thanks, XSleeper.

I'm not aware of any leaks. The pitch of the roof/attic space is a little narrow and is uninsulated. Other areas in the house have some cracking but these rooms are the worst.

The large portion in the last two pictures is from a Sunroom that is connected to the bedroom - which is in the first two pictures.
 
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Old 09-24-20, 10:11 AM
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The attic isn't insulated. Would this be an issue contributing to the finish coat coming loose, as XSleeper was saying?
 
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Old 09-24-20, 10:14 AM
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Possibly. A cold ceiling would cause condensation, and thousands of warm/cold/sweat cycles could easily cause the finish coat of plaster to separate from the base coat.
 
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Old 09-24-20, 01:07 PM
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Yes, it looks like the finish coat has separated from the brown coat. Scrape off all that is loose. The fix after that is simple as long as the brown coat is hard and still keyed to the lath. In a house this old in the Bay area it could be loose (earthquakes you know).
So here is how I would fix it with amateur friendly materials.
Scrape off what is loose. Clean the base coat with a coarse brush. Get all the dust off. If the base coat is sound then mix up some DuraBond 90 or some other setting type joint compound in a ninety minute set. Dry mix some of that with about 25% by volume of fine sand. Spread on a coat pressing it into the brown coat tightly then double back and fill it out to flush with the surrounding. Then float it with a wet green or red sponge float. You might have to rinse the float from time to time and wet the surface of the patch a little. Timing is uncertain. You will know when it's right. The float will bring the sand to the surface and approximate what you have. When it's right don't try to make it better. Now the sand will reduce the setting time. I don't know how much but it will be lwss than 90 minutes. If this does not work you can scrape it off if it hasn't set and come back here for another option. Or if it's pretty good but doesn't suit you you can mix some regular joint mud and paint and sand and try again. This formula will not build out the thickness you need so you will still need to flatten it out with some setting mud.
Probably TMI but you can experiment and have a little fun with this.
As for myself I don't do it for fun anymore.
 
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