Drywall or mud didn’t adhere?
Just bought a house, wife asked to fill a crack under the window, thought no big deal, widen the crack and then fill with some spackle. Well not exactly what I was expecting, but this drywall-like material was only about an 1/8” thick and came off like crazy. I got all this off with my hand but I took a scrapper and got all the lose pieces off. Can I just get some joint compound and smooth this area over? I’m not sure what this is and would love some guidance, I’m not the handiest, maybe a 4/10, but I’ll try to fix it
Posted Sep 6, 2021, 12:42 AM UTC
610
that's a real three coat plaster wall. The first two coats are the base, they're made of plaster and sand. The top coat (called the finish coat and the white coat, depending on who's doing the talking) is a lime plaster, usually without sand. Unsanded, lime finishes can be made glass smooth, and as flat as you want to pay for.
What looks like what has happened is the white coat is delaminating, which is usually caused by water damage. First, make sure the window isn't still leaking; fix it if it is. Then you need to remove any unsound plaster. Then you refinish. There are two reasonable routes. One is to use a setting drywall compound like easysand or durabond (not a pre mixed "all purpose" mud). The other is to use lime putty and gauging (probably not worth the effort unless there is historical value to the wall, or you're weird) and match what's there.
Either way, use a bonding agent (larsen's plaster weld or equivalent) first, because the existing plaster will suck the water out of your new stuff, and you'll have a hell of time getting it stick properly without one.
Thank you for such a thorough reply! I’ll be following your advice on the repair tomorrow
You probably won't be able to get plasterweld tomorrow (it's not sold in box stores, only real paint and plaster places). You can use something like quikrete's bonding adhesive (home depot normally have it), which works fine. The two big advantages of plsater weld is that it's bubble gum pink, so you can see where it's been put (their concrete bonding agent is blue, same reason), and it's got a longer (days) working interval between application and coating with plaster.