Under 2 hours
Split-jamb prehung doors work well in situations where the rough frame is wider than a standard opening. They feature jambs that are split in half lengthwise and the trim casing is already attached to each edge of the jamb, so no mitering is necessary.
Split-jamb door installation is different than other interior doors, since each half of the jamb is installed separately, beginning with the side that holds the hinges. This guide explains how to install split-jamb doors in your home.
Choose a Door and Determine Door Swing
The first step is choosing the correct door to install. Like slab doors, split-jamb doors come in a variety of styles and sizes, so measure your opening and choose one that fits your space.
Next, determine the "handedness" of the door. In a doorway from a hall to a bedroom, the door should swing into the bedroom. Inside a room, the door should swing towards the part of the room that makes the best use of room space. The actual "handedness" of the user isn't important. The door should swing toward a wall or into the least used part of a room so that it doesn't block traffic.
Measure Rough Opening
Measure the door's rough opening width at the top and bottom of the frame. Also measure the height on the right and left sides. The smallest measurements should be 2 inches larger than the size of the door.
Next, check the rough opening for squareness by measuring across the diagonals of the door. Check to make sure the floor is level and that the walls are plumb. The squareness, level and plumb doesn't have to be perfect, but the more accurate they are, the easer installation will be. Also the height and width variances can be adjusted and covered by door trim when the door frame and door are cut to length.
The variances in the walls being plumb are the most difficult to adjust. If it is within 3/8 inches, the difference can be adjusted for when the door trim is installed. Just fill the gap with caulk. For greater variances, trim some of the drywall that is hidden by the door trim or case molding. A drywall or foam rasp is a good tool to use for this job.
Finally, extreme variances in the walls being plumb can be fixed by moving the bottom of the wall with a block of wood and sledge hammer, but this is only an option if floor coverings have not been installed. It is also a job that's best to tackle if you have experience hanging doors.
Place the Door into the Opening
Remove the staples, strapping, nails and plastic clips holding the door frame and door together. Separate the door frame carefully.
Working with a partner, have one person center the door into the opening. Insert the bottom first, then lift the top into place.
If you are staining or painting your door after installation, seal it with two coats of paint on all six sides including the edges. This prevents moisture from seeping into and buckling the wood.
Secure Shims into the Frame
Shims secure the door frame so that it doesn't move when the door opens and closes.
- Open the door and work from the inside.
- Support the door with an air wedge or a rolled up towel.
- Block and shim the jamb at the hinge locations.
- If your door is larger and has more hinges than a standard door, you will have to use additional shims above each hinge.
- Double-check to make sure that the door is still square and plumb. Adjust the shims as needed.
- Replace one screw per hinge with a 3-inch screw to make the door installation more secure and to reduce the number of nail holes.
- Secure the shims with 8d finishing nails.
- Follow these same steps to shim the jamb on the lock side of the door.
- Secure the remaining shims with finishing nails.
- Use tapered shims inserted opposite of each other so that the jamb doesn't twist.
- Score the shims with a utility knife and break off so that they are even with the face of the finished wall surface.
Nail into the Frame
Working from 6 inches below the top of the frame, drive 8d finishing nails into the hinge side of the frame. If using a power nailer, use 2 1/2-inch, 15 or 16 gauge nails.
- Penetrate through the jamb and shim, making sure the frame remains square and plumb.
- Drive another nail approximately 6 inches above the bottom of the frame, and the third nail into the middle.
- Follow these same steps to secure the lock side of the door.
- Use a shim behind each nail and trim them with a utility knife. Test opening and closing the door; adjust as needed.
Secure the Frame Center
Finally, slide the second part of the frame into place.
- Use a rubber mallet or a block of wood and hammer to tap in place.
- Nail through the jamb stop and secure together.
- Secure the trim to the wall with two side-by-side nails every 12 inches from top to bottom.
Make Finishing Touches
Install the door knob and lockset to finish. If needed, grease all hinges so that the door opens and closes smoothly.