Home Renovation DIY: Repairing cracked plaster

DCIM999GOPROOne of the major projects that we’ve undertaken in the house is to fix broken plaster where we can. The walls of our century-old home are made of lath and plaster. We knew that we wanted to keep as much of it as possible, which seems to be the atypical route.

Getting rid of lath and plaster means that you have an essentially blank slate to put any wiring, duct work and in insulation before dry-walling the walls. Especially when older plaster is in bad repair, it seems to make even more sense. Nevertheless: We decided that we wanted to try to fix it where we could, and resign ourselves to trashing it where we could not (we’ve actually saved the lathe for a future project).

Tearing down plaster is actually an awful process: It is very messy, extremely heavy, and altogether unpleasant. The worst part, though, is that I really like plaster. I read a lot about some of the benefits of plaster (it absorbs sound better than drywall, for example, and it’s a lot more resilient to damage, too), and moreover, the idea of tearing it down without trying just didn’t sit well with me.

So here is how we went about fixing damaged plaster!*

Materials

Stabilizing

  • Drill and 3/16″ masonry bit
  • Caulking gun and concrete adhesive of your choice (we used LePage® PL® Premium Construction Adhesive)
  • Drywall screws and “down cup” plaster washers
  • A Phillip’s head screwdriver
  • Shop-Vac

Surface Repair

Step 1: Stabilizing the plaster

Cracks in plaster occur when plaster falls away from the lath, and so the first step is to secure the plaster to the lath. A crowd favourite is an American product called Big Wally’s Plaster Magic, which came to fame largely through their appearance on This Old House. Popular opinion is that they are really and truly awesome. However, the fact that it wasn’t readily available to purchase in Canada as well as the shipping fees and wait time had us wondering: Is there an alternative to Big Wally’s Plaster Magic that we can find closer to home? After a lot of reading, we found out that a number of people had done experiments of their own using every kind of construction adhesive they could get their hands on to stand in for Big Wally’s. And this is an experiment that you can do for yourself! Get a few tubes of construction adhesive, some random chunks of discarded lath and plaster from your home, and see if you can find a winner.

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repairing cracked plaster using construction adhesiveDrill holes running about 2″ away from the crack on either side, and 2″ between the holes. For good measure, we drilled another set of holes 2″ away from those holes (i.e. 4″ from the crack) and 4 ” apart to help secure the plaster if it had fallen away from the wall further from the crack itself. If you miss the lath, simply mark that hole to avoid it later.

Remove debris by vacuuming each of the holes with a Shop-vac, or spraying the holes with compressed air.

Use your caulking gun to put construction adhesive into each hole. You’ll know you’ve put in enough when it starts to spill out of the hole. Use a putty knife to wipe up any extra glue.

Bring the plaster into mechanical contact with the lath by using your drywall screws, “down cup” plaster washers, and a drill. Start by stabilizing the wall further from the crack, and work your way in. We made additional holes instead of using the one with glue in them.

Wait at least 48 hours to ensure it is set and then remove the washers. When you remove the “down cup” plaster washers, you’ll know the plaster has re-attached because there will be no more bounce in the plaster when you apply light pressure.

Step 2: Repairing the surface cracks in the walls

DCIM999GOPROApply drywall tape on any surface cracks in the plaster; not only will it greatly help you achieve a smooth wall surface, but it will also help further reinforce the damaged wall.

Apply a messy layer of the joint compound. The first layer doesn’t have to be pretty, though you want to try to get it as smooth as possible.

Continue to apply and lightly sand when it is try until you achieve a smooth surface. It may be handy to have a damp sponge on hand; it can be a big help to smooth the joint compound.

*Disclaimer

I am not a professional, and so I’ll definitely update this post in a few months to let you know how this type of plaster repair has aged. Please do your own research before undertaking this project, and make sure to choose your products wisely! This project is not for the faint of heart: One room has taken as nearly a month of weekends to fix. Mind you, the plaster damage was relatively extensive. However, if I could do it over again I definitely would. I am so glad that my old plaster walls are getting a face lift.

3 thoughts on “Home Renovation DIY: Repairing cracked plaster

  1. Hello! Thanks for the info on what you used. Has it held up well for you? I am getting ready to start my own plaster repair and I’m cringing at the price of Big Wally’s.

    1. Hi Larissa! I should follow up on this post with some pictures. About 95% of the work that we’ve done has held up, but I’ve noticed a couple cracks — quite small in just a couple rooms — that have resurfaced as winter set in. Really it’s not that big of a problem, considering that some of the walls that we repaired were quite brittle in some spots. I think there’s some margin of error for how much you can make sure the glue, lath, and plaster all make contact. At any rate, if I were to do it over I would definitely use this technique instead of Big Wally’s.

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