With some carpentry experience and some patience, a pre-hung door can be installed quickly in any house in just an hour or so. The key is making sure both jambs are level with one another as well as flush with studs to achieve proper installation.
Starting on the hinge side of the jamb, use a level to place shims until your bubble is centered, adding more as necessary until your desired bubble position has been attained. Next, hammer finish nails into both shims and jamb to complete this step.
Measure the Rough Opening
Measure the Rough Opening before Measuring Doors or Frames Carefully remove door casing (also known as trim) from around the frame before taking measurements at top, middle, and bottom using your tape measure – these should ideally be at least an inch larger than jamb width to allow for shimming to get it plumb and square.
Before measuring the height of your floor and determining if you want to shorten side jambs, take measurements for swing direction – commonly referred to as handedness or inswing/outswing – which includes whether they should swing inswing/outswing.
Remove the Old Door
Dependent upon your carpentry skills, this project may prove either straightforward or challenging. Should it prove complex, having someone around to assist lifting heavy pieces may prove invaluable.
Assume the hinge side of the door and use a screwdriver and hammer to gradually loosen and remove each pin, starting from the bottom one and working your way upwards. Work slowly so as not to cause injury by overstretching yourself or dropping the door onto you.
Take measurements of the height of your existing door and write them down, so that when ordering a replacement one it fits exactly as per its measurements. Remember to trim any new doors a bit to fit within their frame if necessary.
Remove the Jambs
Jambs are the sides of a doorframe that house casing and stud. For optimal results, they should sit 3/8 inch above the floor – use a level to ensure they remain straight and plumb.
First, align the hinge side jamb to be level with wall framing by adding shims until it’s plumb, followed by shimming every hinge location for optimal results. Finally, shim the latch side jamb.
Repeat on both sides until your frame is level and centered within its opening. Secure any loose shims with finish nails to the frame.
Install the Jambs
Once the door is level and plumb, it’s time to install its completed jambs. Start on one hinge side, adding shims as necessary until it meets up with its respective stud.
Assure that the shims are evenly spaced and nail them into position on both sides of the door (latch side and key side).
Once the side stops are secured, measure and cut a head stop to length before nailing it into place. With this part nearing completion, have a friend help out as needed for best results.
Install the Door Frame
Prehung doors combine both door and frame components into one package. They’re an ideal option if your existing door has become damaged, or if you want to repurpose it.
Shim the door frame from its hinge side to ensure it is level and plumb, using a tape measure and level to check both diagonals.
Nail the casing to the studs and shims, spacing nails 16 inches apart. You can easily hide nail heads with putty; once complete, paint or finish as desired.
Install the Casing
If you are installing a prehung door, take time to double-check all measurements and ensure everything is level. Also consider checking swing direction and handle placement as buildings settle over time, as this could cause small discrepancies in their measurements and placement.
Shim the casing at hinge locations to ensure it rests flush against the wall, then nail through shims into trimmer studs for secure mounting. Finally, complete installation by adding casing trim and door hardware as per usual.
Install the Hardware
Installing a pre-hung door may seem daunting at first, but any homeowner with basic carpentry skills should find it simple and achievable. To ensure success, work slowly and carefully until everything is level, plumb, and flush with the wall studs before adding trim or hardware.
Install the hinges on the latch side first. Next, place a level near the jambs of both hinges and adjust so that its bubble is centered. If your level indicates that either side is lower, use shims above them for adjustment.
If your carpentry skills are up to par, this project should go smoothly. But if you find yourself overwhelmed or run into issues early on, seek professional assistance immediately.
Checking wall and trimmer studs for plumb using a level or plumb bob is key in making sure everything is aligned, then make adjustments as necessary until the bubble of your level is centered. When finished, use finish nails to secure casing to shims and frame, followed by 8d nails through them into trimmer studs to keep everything secure.