Repairing Plaster: A Hybrid Approach

In 2014, when we moved into the house, the walls in the boys’ rooms were a mess, and fixing plaster cracks was pretty much our very first DIY job here. Then, we did have a wee cave-in of the ceiling in the living room in 2015, but overall, we hit the old house lottery in this department. Of all the problems we have in BHH, happily damaged plaster has not been one of the major ones. Since that is the case, I’ve been using a hybrid approach to repair plaster.

Last month, I started painting the living room bookshelves, and I found a few damaged plaster sections. I mentioned it on Instagram, and there were several requests to share the plaster repair process. This how-to post should get you started off on the right foot, whether you want to use my hybrid approach or stick to only traditional materials.

Edited 6/24/20 – I had a great conversation with Phoenix Restoration. When I wrote this post, I didn’t really pay attention to the fact that Plaster of Paris is a gypsum plaster vs. lime plaster. Gypsum plaster does not function the same way as old-fashioned lime plaster. It will simply wash away if water becomes an issue, whereas lime plaster holds up. Because I now know better, I wouldn’t recommend Plaster of Paris for any sort of large job–maybe a nail hole or two. To be honest, I mostly use joint compound for small repairs. However, I will be adding some lime plaster from Limeworks.us to my basement supply shelves. My apologies for not providing the very best information, and thank you to John from Phoenix Restoration for helping me learn.

How to Repair Plaster

This post contains affiliate links.

Supplies:

• 4″ putty knife, or your preference of tools for spreading wall patch
• Drill and 3/16″ masonry drill bit
• Plaster washers and screws
• PVA glue – I use plain old Elmer’s school glue
• Plastic syringes or a spray bottle – Syringes work best.
• Construction adhesive – My favorite brand is Loctite Power Grab. The formula works for many applications, including plaster.
• UGL Plaster patch
• Joint Compound (linking my favorite brand) or Plaster of Paris

Step 1:

Remove all of the loose plaster. I often use a shop vac and a scraper for this task.

Step 2:

Using a 3/16″ masonry bit, drill holes, every 2-3 inches, approximately 1″ away from the crack on both sides and all the way around any missing chunks of plaster. You may lose more plaster during this process, but that is normal. Simply incorporate the new sections into the repair.

The masonry bit will go through the plaster and bump up against the lath. If your drill bit goes between the lath, use a pencil to mark that hole with an X.

Step 3:

Mix a 50/50 ratio of PVA glue and water in a small container. Fill a syringe or spray bottle with the glue mixture, and squeeze or spray it into the holes. If the plaster cracks are very minor, I often skip this step.

The idea behind using the PVA water and glue mixture is that it will make the dust and debris behind the plaster congeal so that the adhesive will adhere with the most durable bond.

This step can be messy, especially if you are working on a ceiling. The glue mixture may pour out of the holes, so keep damp rags handy.

Let the glue mixture dry for a couple of hours.

Step 4:

Squeeze a generous portion of construction adhesive into every hole that is not marked with an X.

Apply adhesive liberally all the way around the edges of any missing plaster chunks.

After you apply the adhesive, fasten screws and plaster caps through the crack and into the lath, tightening gently.

Add screws and caps around the edges of the large, missing sections to draw the edges and adhesive firmly to the lath.

As the caps tighten against the plaster and pull it back to the lath, some adhesive may ooze out. Wipe it off the wall with a rag before it dries.

When the adhesive is dry, remove the screws and caps. You can reuse them many times.

Step 5:

Mix up some powdered plaster patch with water according to the package directions. I use UGL (shown below), which is a glue-based product that does not shrink.

I cannot believe I did not take photos to demonstrate the next part of this project. I am so sorry. Some day I will get the hang of this blogging thing. Hopefully, my directions will suffice.

For smooth walls, apply the plaster patch to the missing sections only, pressing it through the lath just like an old-fashioned scratch coat. You may score it if you like. For textured walls, you may press plaster patch into the holes you drilled too.

When the “scratch coat” is dry, apply a second coat almost even with the wall. This coat functions as your brown coat.

If your plaster walls are textured, you might use the UGL plaster patch as your finish coat too. It has a sandy feel to it. If you have smooth walls like I do, the finish coat will be joint compound, which is definitely not a plaster restoration product, OR Plaster of Paris, which can be.

For the finish coat, fill all the holes and cracks to bring the entire repaired section level with the smooth walls. Use long, confident strokes, and smooth out your putty knife marks as you go. Imperfections can be sanded, but the less sanding you have to do, the better.

Tip: Plaster of Paris dries lightning fast. Mix up a small batch at first until you get used to the mixing, application, and drying process.

Once the finish coat dries, apply more as necessary or hand sand the entire area to a smooth finish.

When the repair is complete, continue with your plans to paint or wallpaper. For these bookshelves, I painted a faux bois effect.

Final Thoughts

Some people like using a finishing trowel and a hawk as tools to apply the final coat. I find both to be too large and heavy for my dainty lady hands and T-rex arms. Instead, I use a 4″ putty knife. For a full wall or large section, it would probably be time to toughen up buttercup, because using a 4″ putty knife would be a ridiculous waste of time.

For a much larger plaster repair, including walls and ceilings, there are some excellent restoration systems available, such as Big Wally’s and Plaster Magic. These branded products are quite expensive. That’s why for small jobs like the back of my bookshelves, I use this lower-cost, hybrid approach.

If you have any questions, let me know if the comments.

Pin it for later!