Plaster-and-lath walls are common in older homes. The plaster can deteriorate with old age, leaving unsightly cracks, chips and splits in the wall. This is not only ugly, but the flaking chips and dust can be inhalation and choking hazards for children. Fortunately, plaster walls can be repaired in the same manner as modern drywall -- with fiberglass mesh tape and some joint compound. In fact, you can even match the swirled or dimpled texture of the existing plaster wall -- as is common in many older homes -- with just a few tools.
Place plastic sheathing on the floor along the wall that needs repair. Tape it in place with masking tape to secure it so it doesn't constantly move around. If the wall needs multiple surfaces repaired, close the door and open a window to keep children out and provide fresh air circulation.
Put on a dust mask to prevent inhaling plaster dust and debris. Chip away flaking and peeling plaster from around the area to be repaired with a 6-inch drywall knife. If the area is small, use a smaller putty knife. Chip away only the flakes that are easily lifted. If you push too hard, you will keep raising a new edge.
Wipe dust and dirt away from the area to be repaired with a slightly damp sponge. Rinse the sponge out in a bucket of water as needed.
Peel off some fiberglass tape away from the roll and cut it with a utility knife. Apply the tape to the crack or seam. One side of the tape is sticky and will adhere to the wall. Cut away all obvious long strands of mesh. Left untrimmed, the strands just end up sticking out of the wall, making it harder to trim them after the joint compound has dried.
Apply drywall joint compound onto the tape with a 6-inch drywall knife. Drag the blade at approximately a 45-degree angle to force the compound into the tape's mesh. Smooth out the edges of the joint with the knife. Don't over-do this coat. This first coat is merely to cover the mesh tape with compound and solidify the repair.
Apply a second coat of joint compound with a 12-inch drywall knife after the first coat has dried. The larger knife allows you to cover a larger area with compound, making the repair less conspicuous. The goal is to put enough joint compound on the wall to cover the repair with a slight "bump" that bridges one side of the repair with the other. That bump won't be noticeable once the repair has dried and has been sanded or textured.
Sand the repair with a drywall sanding block after the joint compound has dried. Feather the edges of the compound so the repaired area transitions seamlessly into the surrounding wall. If the repair covers a large area, use a slightly damp sponge to smooth and sand the repair instead of a sanding block. This keeps dust down.
Apply a very thin coat of joint compound over the repair on a textured wall. Wait approximately 20 minutes, then dab or drag the surface very lightly with the bristles of a masonry texture brush for a dimpled or swirled effect -- the head of a clean kitchen broom also works well. For a more aggressive, raised texture, lightly place the flat bottom of a masonry trowel on the surface of the compound, then pull straight up. This raises lots of tiny little "peaks". The tops of the peaks can be sanded down after the compound has dried.
Sweep or vacuum all chips, flakes and dust after the repair has dried. If you are going to paint the wall, be sure to prime the repaired area first with a drywall primer prior to painting.