Pre-hung doors can make your house more energy-efficient, increase safety and security and add curb appeal. Installing one should be straightforward when the existing jambs and frames are in good condition.
Use a level to ensure the wall surface and trimmer studs are level; if they’re not, adjust with wood shims placed beneath both hinge side of frame hinge and latch side frames.
Measure the Rough Opening
As part of installing a pre-hung door, the first step should be measuring its rough opening. A rough opening is defined as the space into which a door will fit when pre-hung; to take an accurate reading you must remove existing casing from both sides and top of single or double door units before taking measurements.
Once the casing has been removed, you will be able to see the door studs which encase the rough opening. With a tape measure, take measurements from one door stud to the next and write down their sizes.
Be sure to take multiple measurements, using the largest figure as your final size when pre-hanging doors. Avoid having an improperly sized jamb; otherwise it can lead to uneven door-hanging or even unhinging.
Remove the Existing Door
Step one in installing a pre-hung door is removing the existing one carefully from its frame, taking care not to damage any trim or drywall in the process.
If you don’t own door tools, a pair of vise grips may do the trick. If stubborn pins remain, use a long nail tapped with a hammer to start moving them along.
Do not attempt this alone as the door can be heavy. Once off, remove all hinge pins and set aside on a flat surface before checking to ensure an even reveal gap on both the strike and latch side – if this isn’t achieved with additional shims as necessary, your reveal gap won’t match up properly.
Shim the Jamb
If the floor slopes under your doorway, adjusting its jamb may be necessary to accommodate it. Use a level to check that its head jamb is plumb and slip in shims until its surface meets with that of the wall.
Shim the latch side of the frame in a similar manner. Once completed, close and test the door to make sure it swings open and closed without striking its frame.
Once hung and shimmed properly, doors should close smoothly without gaps, shut snugly when knocking on their sides, and latch when knocked on from either side. If this doesn’t happen when knocking, add more shims to the frame and try again; if that still doesn’t do it for you, adjust its swing direction by shifting hinges accordingly.
Hang the Door
Although installing a prehung door may seem simpler than building it from scratch, the process still requires careful consideration to ensure it closes flush and swings freely. Do the job right the first time around to save yourself time in later repairs!
Before removing an existing door, take note of its swing direction and handle placement (whether left- or right-handed), in order to order a properly fitting replacement. Also ensure the frame is level and plumb – if it isn’t, slip some shims under the level on hinge side and adjust until bubble centered; secure with tape. Repeat on latch side jamb for optimal results preventing your door from sagging over time.
Finish the Job
Prehung doors can be easier to install than slab ones (which don’t come equipped with hinges and frames), though this DIY project shouldn’t be attempted by novices; particularly since you will be dealing with studs and trim.
Once the new frame is in place, use a level to ensure it is square and plumb. Shim under side jambs and between trimmer stud and wall surface as necessary, and also elevate or lower latch side of frame depending on needs.
Once your frame is in place, use finish nails to secure the shims to the frame using finish nails through each of them. Trim excess shims so they won’t interfere with your trim and now your door swings freely and closes perfectly aligned – enjoy your new room!