How to Repair Drywall With Plaster of Paris

Plaster of Paris is purchased in powder form and mixed with water. Prepare plaster of Paris according to the package instructions. Mix it in a disposable plastic or paper bucket by adding a few spoons of water at a time until you achieve a toothpaste consistency. Because plaster of Paris dries very quickly, the secret to working with it for drywall repairs is to mix only enough to work with over a few minutes. Mix additional small batches of plaster as needed.

To repair a hole larger than 6 inches in diameter, first fill the hole with backing material like newspaper to hold the first coat of plaster. Mix a small amount of plaster and trowel it into the hole, over the newspaper, using a drywall knife. Fill the hole in 1/2-inch layers. After you pack in the first layer of plaster, let it dry for 10 minutes. Apply another coat, let it dry, and then apply another, repeating until the patch is flush with the wall surface. For the final coat, mix the plaster of Paris a bit looser. Trowel it as smooth as you can with your taping tool. When it is dry, lightly sand it with fine sandpaper. You can then prime it and paint it.

To repair a crack in drywall, score the crack using a large screwdriver. Cut the crack deep into the drywall so that it forms a groove about 1/4-inch wide; this creates a bonding surface for the plaster of Paris. Apply mixed plaster of Paris to the crack as smoothly as possible with a drywall taping knife. Work from top to bottom, in small sections, mixing and filling as needed. Sand and paint.