How to Save Old Plaster | This Old House

[Music] so mike what do you have for challenges when saving this old blast tom uh the challenge with this particular house is that it's the original plaster and the reason why we think that it's the original plaster is because we can see the sand and the lime that actually makes up the original uh what we call a scratch coat and what i've discovered is that not only in addition to animal hairs that i believe this is made out of oyster shells oh really so it's not surprising being from charleston and you see a bunch of oysters in your plaster so some of that oyster shell that you can see is actually coming through here in these little inclusions that you see on the plaster oh yeah and so what we'll do is we'll just take a bunch of this really rotted out plaster yeah that's pretty put in the way it is so you'll cut that and drag that all out clean drag it all out and then we'll clean it up a little bit see how it just crumbles out yeah that's just gonna say that's pretty soft it just cuts right out there's nothing holding it yeah so now that i've removed all the loose material let me show you around the other side okay yeah so this is the hole that we were just looking at and you can tell that it's missing some of these keys yeah the keys are what hold the plaster onto the wall what you see is that this one is fairly loose that key is broken that key is broken so automatically that wall is going to fail in that certain area but it's nice and sturdy here in other areas you have it where the lath is so close that the plaster is not even coming through so that's not a very good connection right so that plaster on the other side by here can fail real easy exactly and so what we've done already is we've sprayed an emulsifying agent on there just to give it a little bit more tensile strength and then what we'll do is we'll take a pva which is a polyvinyl acetate basically a bonding agent yep and then we'll just take this and we're just going to lightly apply this to the lath and what that does is it serves as not only a bonding agent but it also delays or retards the absorption of the water from the plaster into the wood because that's what the wood wants to do it wants to take in all that moisture what we'll do next is we'll mix up a very similar mix to what we've what the original plaster was part sand part lime and a little bit of gauging plaster no oyster shells no extra shells this time a little harder to do this time around okay throw that all in there so you have a lot of time to work with this you do until you add the gauging plaster when you add the gauging plaster then it starts to set up pretty quick the great thing about this particular mix is that we're using hemp fiber instead of animal here it's a little bit easier to obtain it's kind of hard to find yeah animal fiber now and now you're going to throw it on your hock you'll throw it on the hook so you're laying that on pretty gently i am leaning on gently if i push it too hard then we're going to push the existing keys that are strong and damage those damage those and we don't want to do that and so what this is doing is this is going to bond all the broken keys back here that you can see oh so the face of the broken key is going to bond to the bond to the the new plaster yep smooth it out just a little bit no one's going to see this so it doesn't need to be pretty okay that burlap it is burlap you just push it in there push it gently push it against this serves as an additional reinforcement and kind of keeps it all together yeah so you're making a sandwich making a plaster burlap sandwich yep what's next next we will attack the front side so now you're going to build that up and and bring it right flush with the wall are you going to do it in layers because the original plaster is so thin i can actually do this all in one layer and it's such a small area and then it'll take probably a day to really set up before i can apply the finished coat all right well that's going to be great it's going to be lasting for a long time at least another 170 years oh great all right well i'm kind of hungry for oysters want to join me let's go let's go thanks for watching this whole house has got a video for just about every home improvement project so be sure to check out the others and if you like what you see click on the subscribe button to make sure that you get our newest videos right in your feed

Channel: This Old House

Views: 100,259

Keywords: This Old House, DIY, Construction, Home Improvement, Ask This Old House, Building, plaster, Tom Silva, Charleston, Season 39, 4-6 minutes

Id: 5zmoIyD6Wrg

Length: 4min 56sec (296 seconds)

Published: Wed Aug 05 2020