Old House Plaster Repair Guide

Plaster repair - for those of you who don't live in an old house or don't watch HGTV, the concept of plaster repair is probably a foreign one. For me, it definitely was, as I only remember living previously in homes that were built with drywall. But prior to World War II, plaster walls were a staple to building any home. They are composed of wall studs (vertical posts), lath (horizontal wood slats, like spread apart beadboard), and three coats of plaster (usually composed of animal hair and gypsum or lime). Here in our house, that's basically all we have and although they are a cool historical aspect, they kind of are a pain in the butt. A lot of times in older homes that have these type of walls, as the homes settle as the ground shifts, cracks appear in the walls or ceilings. That's one of the bigger challenges we faced in updating our house - how to fix those cracks and even out our walls. 

notice the cracks above the window

As we are renovating we are running into two specific issues in terms of plaster repair: 1) cracks in the plaster and 2) fixing loose plaster that has broken away from the wall. At the Old Home Expo a couple months ago, Mikael attended a plaster repair workshop, which helped him immensely in our plaster repair process. After repairing plaster in our living room, dining room, and foyer, I consider Mikael our in-house expert on the process. Although he doesn't agree, I've convinced him to share a rudimentary guide on plaster repair with some tips he's come across in the process. But just a disclaimer, neither of us claim to be professionals and before you start working on this kind of stuff, you should consult a professional, which we aren't! We just hope you find our guide helpful!

To begin, let's look at cracks in the plaster, as that's the most common problem for many old home owners. 

First, check that the plaster around the crack is not loose around it - it shouldn't give to pressure around the area. If that's the case, use a 5-in-1 tool to scrape a V-shaped channel along the crack. Next, using a vacuum remove any debris or dust from the channel. With a damp sponge or rag, wipe the freshly uncovered plaster in the channel to slightly hydrate it. This will allow the patch to better bond with the old plaster, because if the old plaster is still dry it will remove the moisture too quickly from the patch, causing it to fail. With a pre-mixed tub of Dap patching plaster (found at Ace Hardware in the paint section), use a two-inch putty knife to apply the patching plaster to the channel. Use that same putty knife to wipe across the filled in channel to even out the surface and make it flush with the wall. Allow to dry. If it looks like the patching plaster has shrunk after drying, apply another thin coat. Once complete, use a fine grit sanding block to sand the patch and smooth the area.

Now for loose plaster patches, which sometimes happen as the plaster pulls away from the lath behind due to shifting or unfortunate nail holes, etc. 

To fix detached plaster, apply pressure to the area to determine where the plaster has broken away from the wall. With a 3/16 masonry bit, drill holes through the loose plaster and attempt to hit the lath with one hole every 3-4 inches or so. If you do not hit the lath, mark the hole with a pen (it will be obvious when you hit the lath). Using a 1.25 inch spade bit, drill out the top coat of the plaster in the holes that hit the lath (from this point on, ignore the ones that did not hit the lath). At this point, use a spray bottle filled with concrete fortifier (in the building materials section at Home Depot) and spray once or twice in each drill hole and wait 15 minutes. 

Using Loctite Power Grab All Purpose adhesive, inject one or two pumps into the holes. Next, screw plaster washers into each hole while the adhesive is wet using 1.5 inch drywall screws. Make sure that the plaster washer once screwed in is sunken beneath the surface of the surrounding plaster. 

Wait a couple of hours for everything to dry. Once dry, wet the area with a sponge or towel and use patching plaster to fill all of the holes then sand with a fine sanding block once that has dried.

We hope that helps any of you who are wondering how to DIY plaster repair in your home! If you have any questions or comments, feel free to share below!


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