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Delaminating Midcentury Drywall/Plaster Hybrid Surface

Delaminating Midcentury Drywall/Plaster Hybrid Surface

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  #1  
Old 11-26-19, 12:08 PM
C
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Delaminating Midcentury Drywall/Plaster Hybrid Surface

Hi All,

The ceiling of my midcentury ranch has two problems:

1. hairline cracks; and

2. what appears to be a delamination of the plaster/drywall hybrid material (my house dates to the early 50s when both plaster and drywall were layered together in wall and ceiling construction).

Since the ceiling has a sandy perlite texture, I'm wary of digging out the cracks to re-tape or re-mud since I will never be able to achieve the same texture. For the delamination, I'm wondering if installing plaster washers along the delaminated areas would pull the ceiling back flush to the surrounding plaster/drywall. Since the lath above the drywall/plaster could be steel mesh, I'm not sure if screws and plaster washers will ultimately attach to anything (or worse, go through a fragile part of the roof).

I'm also curious if anyone's had success with caulk for filling hairline cracks. The cracks seem quite old, so I'm not sure if there will be ongoing movement.

Any and all advice very welcome!

Thanks in advance...
 
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  #2  
Old 11-26-19, 06:21 PM
T
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If you are confident that you have a hybrid system what you have is gypsum lath, not drywall, though they do look somewhat similar. Maybe the finish coat is coming loose from the brown coat, or maybe the brown coat is coming loose from the lath. If you have gypsum lath this is very unlikely. Or maybe the lath has pulled loose from the joists.
The only hope of using plaster washers is if you can hit the joists. If it is loose brown coat or loose lath you can't rely on washers to pull it back but if you prop up whatever is loose the washers will probably hold it. Now maybe, just maybe the finish is coming loose. The pictures make me think that is not the case. But if the finish is coming loose then you can peel it off and figure out how to refinish. We can help you with that.
Use the smallest masonry drill bit you can find. Maybe you can find one less than 1/8" in diameter. Drill into the cracks and see if you hit a joist. You should be able to tell if you hit a joist. Then probe a little and try to figure how much gap there is between the surface and the joist.
Explore a little more and report back.

I am not a fan of caulk to fix cracks. Fixing cracks in a texture of any kind is very hard. It often looks worse than the crack. If you use washers have you figured out how you are going to hide or camouflage them?
 
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Old 11-27-19, 07:33 AM
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A little more info

Thanks so much for the thoughtful and detailed response. I've included some images that provide a closer look at the lath/plaster setup and the perlite texture. These cutouts are from can lights installed in the basement, so the lath setup could be a little different for the slanted ceiling of the top floor. Note that in the basement, this lath/plaster combo was installed over wire mesh.

Re some of your other questions/points.

óI think the problem is deeper than the finish. It looks like the plaster or lath is cracked and falling away.

óFor plaster washer coverup, I was thinking of using the can light leftovers to cut out one-inch wafers that would be installed, likely using compound or soft mud as glue, over the indents created by the plaster washers. Crazy, I know, but I canít think of anything else.

óFor the cracks, what else might you recommend? Iím happy with mitigation if thatís the best that can be hoped for.

To the extent that this area of ceiling is exposed to natural light in all seasons, Iím thinking that it will be almost impossible to render a cosmetically perfect outcome for this fix (and the great danger is making it far worse). That said, any painting fixes here? Super flat paint? Iím not really worried about ceiling failure and gut rehab is not an option.

Thanks againÖ
 
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Old 11-27-19, 04:26 PM
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You have gypsum plaster over gypsum lath. An early version of that was perforated about 5/8" every four inches to afford a mechanical bond. It was learned that was not necessary. Plaster crystals bond through the paper into the gypsum inside. As to wire reinforcement. This was not done everywhere. We did it on large ceilings. It helped reduce cracking. You have good construction. I am guessing ghe wire reinforcement is woven wire probably 20 ga but could be 17 ga. Not expanded metal lath.
Get something really solid to stand on and push up on either side of a crack. Does it push up a pretty large area? If so probably lath is loose. How heavy does it seem? if heavy then the lath is probably loose. If easy to move and seems light then either the brown (unlikely) or the finish is loose. I am betting on the lath. Now your texture could indeed have perlite aggregate. I am betting sand that would pass through a window screen and a lot of that has been smoothed over with paint and some of it looks larger than it really is because of paint buildup.
If you use washers they must hit joists. If the brown coat is separated from the lath which I doubt no screws will hold the two together. Get the ceiling aligned with jacks or props. don't expect the screws to pull it up. If you ue washers and get them to countersink I think your best bet to camouflage them is a swipe or two with joint mud then when that is dry a lick or two with some joint compound thinned down and with some perlite of the right grit size or sand with the right grit size and prime and paint.

Cracks, I guess try caulk or tape and mud them and be prepared to resurface the whole ceiling to get a match. If it comes to this check in here. I have a suggestion but I am tired typing.
 
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