Repairing Cracks in Plaster

Cracks in plaster walls are fairly common and are normally caused by wall movement.  If the crack is abnormally wide or deep, you may have a larger problem than a simple crack.  This howto covers how-to fix a shallow crack with real plaster.  Drywall compound may be substituted but shouldn't be used to repair historic plaster. 

Items needed:

Plaster of paris (compound)
Mesh repair tape
6" tape knife
Bucket to mix plaster

Safety Suggestions and Tips
Wear safety glasses
Follow safety warnings on package.
Work quickly if using plaster
Level of difficulty

Time Required:
 2 hours


Cut out damaged plaster
Cut out damaged plaster

Step 1:

Cut the edges of the crack back to the extent of the damage.  If you are not using mesh fabric to help the repair, , under cut the edges of the crack to give the plaster something to hold onto.

Apply mesh
Apply mesh

Step 2:

Apply the mesh (if you are using it) over the crack.  Mesh is especially helpful on cracks that keep coming back.  The mesh should overlap the edges of the crack by at least an inch.  If you are not using mesh, dampen the area to be repaired.

Apply compound/plaster
Apply compound/plaster

Step 3:

If you are using plaster, mix it up now.  Follow the directions on the container.  It is normally 1 part cold water to 2 parts plaster.  Work quickly as plaster starts to harden rapidly.

Finished repair
Finished repair

Step 4:

Using a 6" (or so) tape knife, spread the plaster into and onto the mesh (if you are using it).  Work the plaster down so it just covers the mesh fabric.  Let it dry overnight, sand it to remove all ridges and apply one more coat.  Feather the edges into the existing wall to conceal the repair.