Secure Old Plaster in a Pinch

Don Mathis writes:

Often sagging plaster needs to be secured and stabilized. One common method is to add a mechanical support with a dimple washer, a concave washer that literally holds the plaster in place. However, if you're on the job and don’t have a washer specially designed to secure plaster, you don’t have to stop work for an extra trip to the supply store. You can make your own washers.

I make my own plaster washers using a section of plumber strapping (metal strapping perforated with holes for fasteners). First I shape the strapping into a dimple shape around a hole using a ball peen hammer against a gouged piece of wood. Then I trim the strapping into a small disk that is now concave.

I use a Dremel tool with a diamond disk to make the the recess in the plaster to receive the washer. Be sure to use some sort of dust mitigation as this part can get messy. Secure the washers in the recesses with drywall screws.

After installing the mechanical supports, I cover the secured portion of the ceiling with adhesive-backed fiberglass on a 36-inch roll then start the skim coat.