DIY: Repairing Damaged Plaster
Repairing the damaged plaster is no simple matter. It is an art and takes skill and patience. You also need to have a good working knowledge of the tools and materials that you will need for a project such as this. What you need: a hawk (typically a 12-inch-by12-inch sheet of metal with a detachable wooden handle centered and fixed to its underside), a rectangular trowel (for applying, spreading, shaping and smoothing mortar), a strip of aluminum called a slicker, a pointed trowel (a smaller, pointed version of a rectangular trowel, a metal angle float (flanged edges for corners), a scarifier (good for roughening the base coat in preparation for a finish coat), a pointing tool (made of stainless steel and is used for filling in cracks or chips) and finally, a stippling brush (to duplicate the surrounding textured surfaces). Phew! That was a long list and we haven’t even started yet.
The first thing you do when repairing damaged plaster is install a gypsum or metal lath. To repair large holes spanning studs or joists, first pry off any loose plaster with a putty knife and find the two stods or joists nearest the edge of the damaged plaster. Draw a rectangle around the area, then use a utility knife and chip away the plaster down to the lath with hammer and cold chisel. Cut gypsum lath (wire screen) to cover the open. Nail it in place with lath nails long enough to penetrate the wood support. Before applying an mortar, brush the edges of the old plaster and about 5 inches of surpace with a bonding agent. Wait an hour until the bonding agent becomes tacky before beginning to plaster.
Now you are ready to prepare the motor and apply the base coat. If it’s a big patching job, use a wheelbarrow. If it’s a smaller hole (like the size of a 10 year old’s foot), you can separate the water and the dry material in a plastic mortar box. Add a little water and stir until the mixture is the consistency of soft butter. Transfer the mixture to a mortarboard (a 4-foot-by-4-foot piece of plywood) for the final smoothing of the mixture with the toe of a trowel.
Use your rectangular trowel to transfer the mortar to the hawk. Separate a portion of the mortar from the larger pile on your board. Take the hawk and tip it toward you and cut a slice of mortar from the far edge of the smaller portion. Start at the bottom edge of the damaged section with your trowl, making an upward sweep in one smooth motion. Apply the mortar no more than half an inch thick. Let the first layer set for several minutes before applying any additional mortar.
Wet the slicker and hold it vertically against the wet mortar and drag it across the mortar you’ve just applied. Begin at a corner when you do this. Moving the slicker up and down as you slide it across keeps the mortar from building up upon the edge of your slicker. Repeat this crosswise.
Remove access mortar from inside corners with the toe of your trowel. Let the base coat set for a few minutes, then roughen up the surface with the scarifier. Now, you must wait 24 hours, allowing the base coat to set. To save yourself some time, instead of mixing your own final coat, buy finishing plaster, available at Home Depot or Lowe’s. It sets quickly, so be ready. Start at the top of the damaged plaster area, spreading a thin layer over the base coat in the same manner you used in troweling the base coat. Two 2-by-2 feet sections at a time and wait for the first layer of your finish to set before applying a second layer that brings the section up to the level of the surrounding surface. Wet and smooth the freshly plastered surface of the first section with a large wet brush. As each new section is added, use the wet brush to blend the sections together, creating a smooth, clean surface.
That’s all. You’re done.
