Repairing Ice Dam Damage
Cutting wallboard:
If you have to cut out a large section of plaster, and no wood strapping [backing] is present, then you will have to add some in. [Strapping refers to the strips of wood that are installed along the length of the interior of a ceiling.]
Use 1 x 3 “strapping” boards or rip strips of 2.5 to 3” wide plywood strips on a table saw and screw them in place for the new drywall patch to attach to. You want center this strapping half under the existing plaster and the other half exposed, to accept the new plaster board.
You will be installing the strapping perpendicular to the ceiling rafters and 16″ on center, installing two screws into each ceiling joist where the strapping crosses.
Fastening drywall or blue board:
Use 1-1/4” drywall screws to install and fasten your patch, keep your seams to ¼” or less.
Install one screw every four inches, approximately 3/8” to 1” in from the edge. Do not over drive your fasteners; your goal is to install them slightly under the wallboards paper surface. Later your address the seam and screws with mesh tape and drywall mud.
Note on Wood Lathe:
If the plaster is over wood lath, then removal will expose the lath and give you a backing to attach your drywall patch material and attach it with drywall screws.
Most “old plaster,” over wood lath is about a quarter to three-eighths inch thick. So you will need some thin drywall to patch in.
