How to Prehang a Salvaged Door
Ask This Old House general contractor Tom Silva shows a homeowner how to turn an old door into a prehung door for a new opening
- Use a four-foot level to check if the existing floor is level. Make the bubble level and then measure the distance from the floor to the underside of the level. This will determine the long side of the jamb.
- Measure the height to the jamb header of any existing doors to ensure the new door matches.
- Use a miter saw to cut the jambs to length.
- Use a countersinking drill bit to predrill holes in the jamb pieces. Connect the jamb using 3” screws.
- Mark a ¼” reveal for the casing on the jamb with a pencil.
- Set the side casing on the line on the jamb and then attach with 8-penny finish nails.
- Allow the head casing to overhang the side casing by ¼” on each side and attach.
- Attach a temporary filler strip across the bottom of the jamb to hold it square when moved.
- Test fit the jamb assembly in the opening.
- Add wood shims to the door framing to make one side of the jamb plumb.
- Clamp the jamb flush with the drywall or plaster, then screw the jamb through the shims into the framing.
- Add shims to the other side of the jamb and attach in the same manner.
- Bring the door in and test it.
- Add shims behind the lock set.
- Cut the shims flush with the jamb.
- Add the casing to the other side of the door jamb.
The Door used for the install was original to the house and provided by the homeowner.
All of the tools, nails, and shims used can be found at the home center.