Old Wall Material


Old 08-03-16, 10:51 AM
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Question Old Wall Material

House was built circa 1955. Walls appear to be made of two layers of sheet rock on top of each other finished wit a skim coat of plaster. Exterior walls have lathe on the joints, then the sheet rock? attached to them. Material is of a coarser, sand mix than current sheet rock.

Any idea what it is. It is dense as hell, trying to find joists behind this stuff. Stud finders failing and hard to hear difference by tapping. Any ideas on what it is and how to find joists?

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Old 08-03-16, 11:07 AM
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Usually if the drywall is double laminated it isn't plaster. It could be drywall lath and then plaster.

pics could be helpful
Old 08-03-16, 06:18 PM
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Probably gypsum lath, similar to but different from conventional drywall, then gypsum plaster then whitecoat finish.
Is the layer closest to the studs 3/8" thick? Then the next layer, th sandy one 3/8 -1/2" then the last layer behind the paint about 1/16"

What do you want to do?

Can you describe the lath that is over the joints?
Old 08-03-16, 07:04 PM
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Probably gypsum lath as said. I haven't had luck with any electronic stud finder.

After getting an idea of where you think the joists are, check for nails with a magnet.
I use the 'stud 4 sure' pictured below. The magnets inside are very strong and finding a nail or nailing pattern is easy, just use a sweeping motion along the ceiling.

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Old 08-03-16, 08:09 PM
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I have an older electronic stud finder with an extra deep stud sense setting. I've been somewhat successful with that.

Keep in mind.... most electrical boxes are mounted to the sides of studs. Once you locate which side of the box it's on you can measure the other studs off of that one.

Even when I'm sure I've located a stud I'll use a sharp ice pick to confirm the stud is there. It's much easier to fix a tiny hole.
Old 08-04-16, 05:16 AM
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While I've never used an ice pick to check for a stud I have used my cordless drill with a small bit - does the same thing and might be easier if the walls are plaster.
Old 08-04-16, 11:36 AM
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I see you are Looking for joists. This is a little harder than studs. Light fixture boxes are not always on the side of a stud. There are some other tricks. Maybe just maybe there is a heat or A C vent in the lid. They are usually built so they screw onto the joists at 16" OC. If I am right about the construction of your lid you might be able to find the joists at night. Over the years the lath and plaster sometimes sag slightly between the joists. This is worse if they are spaced 24" OC. Get a light shining sideways by close to the ceiling and look for signs of a shadow where the joist is. This will get you in the neighborhood. Use the smallest masonry bit you can find in a drill and stay out about a foot from the wall and hunt for the joist. The first one is always hardest to find. Or you can go into the attic and drill a tiny hole beside the joist and see where the bit comes through. This might leave a crater on the finished ceiling. Drilling from the bottom up will make a smaller hole you can fill with spackel. The ceiling you have is superior construction. I hope you can preserve it.
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