Installing a pre-hung door yourself can be an straightforward DIY project; but make sure that you take your time and have someone help with this endeavor.
Begin by unbolting and uninstalling the old door and casing from its frame. Pry open the door frame and slip a level underneath one hinge side jamb to ensure its bubble is in the center.
Preparing the Opening
Installing new interior doors is a fantastic way to refresh and make more functional your home, but installing prehung interior doors requires extra care to ensure they fit securely within their frames and flush against walls.
Start by dismantling the existing door by removing its hinge pins using a screwdriver and hammer. Next, pry out its head and side jambs using a flat pry bar without damaging framing or molding.
Check that the doorway opening is plumb and square by measuring from stud to stud on both sides of it. If it isn’t, use wood shims to raise jambs to the appropriate height before finishing off the job by selecting trim of your choice to fill the opening and caulking trim and joints afterward; this step is essential in keeping water out of your house and avoiding mold/mildew growth.
Hanging the Door
Prehung doors should always fit exactly level, plumb, and square in their opening. This is especially crucial when in an older home as buildings tend to settle over time while walls warp due to movement within.
Make sure the trimmer studs are plumb by checking them with a level or plumb bob. Use a framing square to ensure each trimmer stud is square with the wall; if necessary, shimming may help correct an out of square situation.
Once your trimmer studs are square, use a carpenter’s level to check that both walls and door jambs are even. Place it against the top of the door frame, note where its bubble centers itself and adjust shims until your frame reaches it’s correct height – or add them until its center!
Shimming the top and bottom of the door frame until it is flush with all four walls of drywall. If necessary, plane away any excess shims to reduce risk of splintering when hanging the new door.
Adjusting the Jambs
Once your door is installed and secured with shims, use a level to check its alignment with its frame. If necessary, add more shims until its bubble centers. In addition, ensure that both strike sides of jamb are plumb; and that there is an even gap around its perimeter.
If you’re working on an exterior door, apply a bead of z-flashing to avoid water damage from rain and wind. After caulking gaps between jambs and trim as well as sealing where the frame meets the floor.
Attach a couple of temporary cleats to either side of an opening to act as stops for door and frame assembly. Shim the head jamb and door trim until tight against these temporary cleats before nailing through these shims to the stud framing for attachment to latch side jamb and trim. Repeat these steps when installing door.
Installing doors that swing freely and close correctly requires precise measurements and adjustments, in addition to trimming to meet local codes or adjust for flooring height variations. As such, doors can often prove challenging.
Pre-hung doors are much simpler to hang than slab ones, yet still require basic carpentry skills for proper installation. They should not be tackled without professional assistance from experienced installers.
Have a helper hold the pre-hung unit while you remove its packing restraints. Referring to manufacturer’s guidelines for suggested shim placement along the sides and top of the door frame may also help if necessary, to make sure your new door is square with framing. Caulk all seams to create an even surface. By caulking all seams neatly you’ll save labor costs while covering up any outdated hinges or hardware which might date your room.