How to Repair a Skim Coat on Brick

Prep the area. Plaster is incredibly dusty, both when mixing and when smoothing out the skim coat. Lay drop cloths underneath the area where you will be working. Put on gloves, a long sleeved shirt, a mask and safety glasses to protect your skin, eyes and lungs.

Clean away any loose plaster. Use a chisel and your hand and scrape away any plaster bits and pieces that may be around the holes. You do not want any plaster pieces getting into your skim coat.

Mix together your plaster. Plaster of Paris and other commercial plaster mixes typically just need water. Put a small amount of plaster in a bucket and mix it according to the manufacturer's instructions. Do not make too much plaster. It is easier to make a few small batches since this medium sets very quickly.

Skim over the holes. Apply a small amount of plaster to a flat trowel. Sweep it up over the hole. Feather out your edges to blend them in. Work from the bottom up. Do not overcoat the area. Use very thin coats and build them up if necessary. Let the plaster set for 45 minutes.

Sand down the patched area. It is difficult to achieve a perfect skim coat. Use a hand block sander with a fine grit and go over the patched area to smooth it out and blend it with the rest of the old skim coat.