How to Install a Prehung Replacement Door in an Older Home With Plaster Walls

Older homes often have cracks and gaps in plaster walls, especially around doorways where the plaster comes up against the wood frame of the doorway opening. While you are installing a replacement door is a good time to patch up any of the plaster, since you will be putting trim around the doorway. Use joint compound, a form of plaster that is easy to work with and dries quickly.

Prehung door with pre-mitered trim border
Level
Wood shims
Screwgun
Long wood screws (2 to 2 1/2 inches)
Razor knife
Joint compound
Drywall knife
Drywall sander
Trim nailer

Instructions

- 1
  Position the prehung door unit in the opening, with the door itself latched closed. Line up the edge of the casing with the surrounding frame in the wall.
- 2
  Set your level along one edge of the casing. Insert shims around the sides of the door unit, casing and wall frame until it is plumb.
- 3
  Open the door so you can get to the interior surface of the casing. Drive screws out through the casing into the frame. Set them every 10 to 12 inches along each vertical side.
- 4
  Cut off the overhanging shims with a razor knife.
- 5
  Spread patching plaster into any holes, cracks or gaps on the plaster wall immediately around the doorway, using a drywall knife. Let it dry for 12 hours. Sand it smooth.
- 6
  Install the premitered trim around the new door, using a trim nailer. The trim should span the casing of the new door, cover the shimmed space between the casing and the frame and land on the surrounding wall. Touch up the paint around the wall if necessary.

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