How to Repair Cracks in Old Plaster and Lath Walls & Ceilings - Spencer Colgan

[Applause] [Music] okay here's what we're looking at for those of you who don't know what plaster and lath is this is what was used on ceilings and walls in construction prior to about 65 years ago so if you have walls and ceilings that's made of plaster and lath you'll find that you might have hairline cracks developing in corners or from a window down to the floor or whatever but I'm going to show you how to fix those cracks because plaster and laughs although it's an old system is extremely good material let's show you how to fix plaster and lath by first showing you a picture of what's behind this surface that I'm working on right now okay folks you see the horizontal pieces within like furring strips now do you see the vertical pieces behind those horizontal pieces well those are the vertical studs that hold up the wall and if you're dealing with a ceiling those are the joists overhead but nonetheless these horizontal members they're called keys and the idea is that the folks who did plaster from way back when would push the plaster through those spaces between those pieces of wood and that was called the keys like a piano keyboard and then the plaster the first coat would stick because it was pressed into those faces and would go behind those keys and grip well that's what we have going on behind this red wall we're going to clean out the loose plaster dig out the crack and then we're going to put a bonding agent that's going to seep into this horizontal framing the lath and then we're going to make it one with the wall when we put our mud in between those keys let's see how we do it when you press on this this moves if you plaster over this it may look perfect for about a week again and then after about 90 days this Ridge will develop because this is moving these are two separate pieces in order to make them one again we need to do a little digging [Music] [Applause] you [Music] [Applause] [Music] after you've gotten a channel cut out and you've exposed the laughs and you've determined that both sides of the wall are stable you can now clean out the dust and you want to start thinking about a bonding agent in this case I've used Larsen's bonding agent which is for interior plaster repair you dust it off you might want to vacuum it out and you simply apply the bonding agent gluing the laughs to the repair itself now here's an image of the Larsen's bonding agent I use as you can see if you look close we have exposed the key or the space in the horizontally placed wooden lath skeleton of this old plaster wall and so here you can see a vertical stud as well as here and across these studs are spaced out wooden lath members in order to get your plaster to stick to the skeleton of the structure we need the plaster to not only stick to the length but we needed to go beyond the spaces and then form a lock around these laughs members and so in order to make the plaster on this surface one with the lath we need to number one cut down our crack to the length number two we need to clean the surface as best we can getting off all of the loose particles especially the dust you can imagine what it would be like trying to stick plaster onto a dusty surface you and I both know it wouldn't really do a great job now would it once you're satisfied that you have cleaned the lab sufficiently and have gotten rid of the dust in and around the repair area well now you're ready for step number three step number three involves applying the bonding agent and here we're going to use a liquid bonding agent from Larsen's and what it does is simply make the length and all of the areas to which you are going to attach your new plaster stick and you don't want to apply this sparingly you want to apply this generously all this is going to do is dry and seep into the surface particularly the lab if you're not familiar with a plaster and lath wall I would like you to google it so that you can understand the t's here that's what they're called in a tree the wooden keys and you can imagine that the plaster when these engineers designed this system that these keys were simply a means by which the plaster would lose in between these keys and attach themselves by running over those keys and going behind them forming a lot faster service we're going to wait for this to dry and then we're going to apply five minute mud and we're going to press it into those keys and we're going to do it in a couple of steps taking five minute mud you want to pour the mixture into water and you want to follow the mixture ratio on the bag for those of you who don't use this material 5-minute mud is simply a mixture that dries up sets up I should say within five minutes so this is one that gives you a really good repair but not a lot of time into the repair if you can't because of lack of experience with the material well because you don't have an extra pair of helping hands please go with the 20-minute mud just as effective show you how to apply it into the repair area what I first want to do is press my five minute mud into the repair trying to get it just into the key that is the space between the two pieces of length and as you can see I'm pushing my material into that opening while it's still soft I'm pushing it so that it attaches itself not only to the cage but into the space of the tape so that it becomes one I'm digging myself a channel because I want to have a space I want to have his face into which I can place the next layer and so that's why I'm doing the application the way I'm doing it I'm pushing it into C I'm giving you the name you see it wouldn't be enough if I just did this what's this no that's just sitting in the opening you want to make it touch the left and wrap itself around the key of that laughs pushing that material into that space digging myself a channel and now now that my plaster has filled the key of spaces look at the little valley I have that will allow me to attach the next layer right haven't I built myself another key so to speak do you see what I mean see the channel I dug for myself of course I didn't want to knock it down before it hardens I don't want my channel exceeding every pair surface so now I have it flush and I'm ready to push continue to punch as I put the next layer on filling this up making it flush with the red painted wall now that I've given myself the requisite time let's put our last layer over this and make the surface flush remember we don't have a lot to work with this I'm pushing it in there with a lot of force I'm over filling the craft [Applause] now you can see that the white centre is now one with the lath that is the skeleton or the bone of this wall and it has become one with the bone and the skin of the red paint just like a human body that's connected completely from the bone the tendons the ligaments to the flesh that's the same idea here this is now one will make this nice and smooth with one final coat of topping compound and then we'll sand it and paint it okay we've given this about 20 minutes to set up and now we're going to put a topping compound over it to make the surface flush now take note we didn't use any mesh tape why didn't we use mesh tape on this think about it what does mesh tape do doesn't mesh tape provide a crisscross surface into which and through which plaster bonds itself and kind of locks itself against the surface you're repairing doesn't it so you may say why didn't you use mesh I did use mesh I used 100 year old mesh remember the keys through which we installed this plaster did you google what wooden lath looks like don't you realize that's the original mesh that's where fiberglass mesh ideas came from you see the lab provides the surface that you fiberglass mesh provides only the lab surface is a lot stronger it's attached to the frame of the house and we inserted this in between the keys of the lath very much like the same idea where you would insert this into the keys so to speak of fiberglass mesh the idea is the same you're locking mud in-between a checkered surface with fiberglass mesh but with laughs you're locking mud the room wouldn't live that's attached to the frame of the house with a bonding agent it's better than mesh you don't have to put mesh on this now let's make this look pretty shall we right out of the bucket install now we're talking compound you see the difference of the 5-minute mud you see how dark it is in there there's a chemical process going in there it's heating up it's a firming up it's hot so it's dark the drying process the curing process it's all accelerated while this remains white oh and it's gonna be white for a few hours but that's okay this is just so that we can make a look pretty calm really has nothing to do with structure everything to do with looks okay and we're gonna call that being done for the day now if I come back tomorrow and it needs a little coat on top of this I'm going to do it but I've brought the level of the surface all flush so my repair is now flush with the rest of the wall and there you have it folks that's how you repair a crack in a traditional plaster and lath wall break it down to the left sweep out or vacuum out your dust apply a bonding agent I use Larson's to make the lath one with the filler apply a 5-minute mud remember to tunnel out the surface so that your filler your 5-minute mud fits into a tunnel like crevice that's designed to hold it in if they're giving it 24 hours I came back and I put a coat of topping camp compound after giving it 24 hours I now came back and gave it a thin layer of Ready Mix topping compound you know the joint compound that you get at the big-box store in the green littered bucket or blue and you can use lightweight or regular because all you're doing is putting it on thinly and it dries within a half an hour or less and so that's it that is perfectly smooth along the line we'll give this a quick sand with a sponge and that crack is now gone the repair is now one with the skeleton of the framing you see the difference between putting mesh over a crack and filling it in and going down to the bone and putting the the plaster in between the framing members the laughs do you see how this is far more different than a simple topical repair I hope you do thanks for watching my video thanks for subscribing to my channel and join us back hit subscribe and hit the old button for all future videos thank you [Music] [Applause] [Music]

Channel: Spencer Colgan Wallpaper & Painting

Views: 15,233

Keywords: plaster, wall repair, plaster and lath, fix a crack

Id: jrcis4TDCHs

Length: 24min 35sec (1475 seconds)

Published: Fri Jun 05 2020