A Guide to Repairing Damaged Plaster With Plaster Washers

The obvious question is why isn’t it used as it once was. The answer is simple — money. Interior lath and plaster are expensive. Drywall is cheaper to produce and install.

Like anything else, plaster has its drawbacks, price aside. Anyone with plaster can tell you how it cracks, and just try hanging a picture in plaster. A plaster finish is infinitely more difficult to patch than drywall.

Common Plaster Ceiling Problems

One of the most common problems with plaster is sagging ceilings. This occurs when the key breaks and the connection to the lath is lost. However, a broken key isn’t always the cause of a sagging ceiling. Often, it happens when someone missteps in the attic — setting foot on the lath rather than on the ceiling joists. Such was the case in the classic holiday movie “National Lampoon’s Christmas Vacation” when a bumbling and unsuspecting Chevy Chase crashed through the ceiling onto a bunk bed below.

Risks of Stepping on Lathing

The effects of stepping on unstable lathing when in the attic space above a plaster ceiling can be sudden and destructive. The average load-bearing capacity of wood lath plaster ceilings is around 50 pounds per square foot. An adult’s body weight alone can exceed that. Always step only on ceiling joists and structural framing members when navigating attic spaces to avoid falling through the ceiling.

DIY Plaster Repair Solutions

Many years ago, we learned of a little-known plaster repair device called a plaster washer — a round metal disc about an inch in diameter used to hold up a sagging ceiling. The disc has a countersunk hole in the center through which you insert a drywall screw. The disc also has many smaller holes scattered throughout into which spackle or drywall joint compound attaches itself to conceal the repair.

Here’s how to take the sag out of your plaster ceiling using these nifty little gadgets. First, using a chisel or putty knife, remove any loose or crumbling plaster in the area that you need to repair. Slightly undercut the edges of the existing plaster to create a solid bond with the new plaster. Use a vacuum with an upholstery attachment along with an old paintbrush to remove dust and surface debris.

Installing Plaster Washers

Next, insert a galvanized drywall screw (1 5/8 to 2 inches) through the center hole of the plaster washer and place the screw head into a #2 bit on a screw gun. Drive the screw through the plaster and into the wood lath a couple of inches back from the edge of the hole or crack to be repaired. 

Tighten down the drywall screw just enough to pull the sagging plaster up against the lath and flatten out the convex washer. If the plaster doesn’t pull up and/or the screw doesn’t tighten up, you have likely missed the lath and should back out the screw and move it slightly. 

Keep in mind that there’s a narrow space between each strip of lath. Install several plaster washers around the area to be repaired. If there’s evidence that the lath isn’t securely fastened to the framing, use longer drywall screws in combination with the plaster washer and drive the screws through the plaster and lath and into the framing.

Plaster washers provide both a solid anchor point and positive lifting force to restore a sagging plaster ceiling. When installed properly with the correctly sized fasteners, they securely grab onto both the keys of plaster behind the lath and the wood lath strips themselves. This creates a bridging effect that pulls the sagging ceiling plaster back up flush against the lathing. Plaster washers offer a simple and economical DIY solution.

Patching Holes and Cracks

Once the plaster has been re-secured to the lath, use a six-inch taping knife to apply a plaster patching compound to fill in holes or cracks. Prior to applying the patch material, spray the lath and existing plaster with water. This will prevent moisture from being sucked out of the new patch material, which could result in cracking and a poor bond. You can fill small cracks with a paintable caulk. Allow the patch to dry overnight, and then sand it to level using 100-grit sandpaper and a sanding block.

Filling plaster cracks and holes with patching compounds specially formulated for plaster provides superior results compared to conventional drywall joint compound in terms of bond strength, workability, and crack resistance during curing. Look for plaster patching products labeled for repairs on historic plaster walls and ceilings. Gypsum- or lime-based compounds are preferable. Apply according to manufacturer instructions.

Applying Joint Tape and Compound

Conceal the plaster patch and plaster washers by covering them with self-adhesive fiberglass mesh joint tape. Use the taping knife to apply a thin coat of drywall joint compound over the patch area. Feather the joint compound at the edges of the patch. 

Allow the joint compound to dry overnight and apply a second coat, overlapping the first coat by a couple of inches in all directions. Allow the material to dry overnight and lightly sand using 100 grit sandpaper or sanding mesh along with a sanding pad or block. You may need to apply additional coats of joint compound and do more sanding to achieve the desired finish. Applying self-adhesive fiberglass drywall tape over repaired plaster areas before applying finish joint compound layers produces superior crack resistance during drying and down the road.

The high tensile strength mesh bridges any existing hairline cracks while reinforcing to control expansion, and contraction stresses in the compound as it cures. Feathering edges and multiple thin finish coats create a smooth, continuous surface ready for priming and painting.

Prepping and Painting Repairs

After the final sanding, use a damp rag and/or tack cloth to clean the patch area and prepare it for painting. Prime the patch with a high-quality interior acrylic latex primer and, when dry, apply one to two coats of paint to match the existing finish.

Be sure to use high adhesion primers specifically designed for new drywall and patched plaster areas when preparing repairs for finish painting. Quality acrylic latex-based wall primers promote maximum paint adhesion across different underlying surfaces while blocking stains and creating uniform textures and porosities for a consistent topcoat appearance. Apply finish paint per manufacturer specifications.

Working Safely on Plaster Repair

Plaster repair work of any type, but especially overhead ceiling work, creates large amounts of fine particulate dust and debris. Wearing proper protective equipment like safety goggles, N95 respirator masks, and hats is crucial for your health and also helps contain the mess.

So, Is Fixing Sagging Plaster Ceilings Doable for Homeowners?

For homeowners discovering sagging or failing plaster ceilings for the first time, the prospect of restoring them can seem far outside the realm of DIY abilities. However, while plaster repair takes specialized skills and materials as compared to drywall repair, fixing common ceiling issues like cracks and bulges proves quite doable as a DIY project. 

The secret to success is using the right tools for the job. Specialized plaster repair solutions such as metal plaster washers and fiberglass mesh tape take a lot of difficulty and guesswork out of the process for amateurs. With proper surface prep and high-quality plaster patching compounds, primers, and paints, you can refresh sagging ceilings and restore them to their original historic glory without the need for complete replastering or drywall installation. If you use patience and care, this is one DIY plaster upgrade well within reach.