Installing a pre-hung door yourself can be an incredibly satisfying project for the DIY enthusiast. When installed properly, the door should move freely open and closed and latch securely into place.
Shimming the frame to ensure all gaps are even is an essential step of the job, making setting casing miters much simpler.
Measure the Door
Before selecting a pre-hung door, the first step in measuring its rough opening must be completed. To do this, pry open interior casing using a painter’s pry bar before using a tape measure to assess gap width between studs; measure three times and take the smallest measurement as your door’s width measurement.
Measure the height of both gaps on either side and note the lowest measurement. Confirm that your floor covering won’t affect the door height as well.
Once the door has been installed, use a level to check its fit against its hinge side compared with its latch side and add any necessary shims under it until its bubble centers again – this will help ensure your new door fits seamlessly, known as true-to-width fitting.
Remove the Existing Door
Installing a pre-hung door can not only add curb appeal, but also increase energy efficiency in your home. But to ensure optimal functionality and support of the new door, jambs must also be properly supported and fitted correctly to ensure it fits correctly and remains supported over time.
Start by uninstalling the existing door with a hammer and screwdriver to remove its hinge pins (start at bottom) using a combination of force. When free, pull it off the hinge pins by pulling down from the top edge, pulling and setting aside.
Set up the new frame using a speed square and level, shimming each location before fastening it securely to studs with casing nails (or cement screws for brick/cement framing) using casing nails or cement screws (as appropriate). Finally, test-fit your lock set in any holes bored into the door for proper functionality.
Install the Jambs
Before installing the door frame, nail temporary cleats to the wall opposite of your rough opening to act as stops for jambs. Secure them to the wall using a nail gun, making sure that their positions are straight.
Shim the head jamb until it is flush with both framing on either hinge side and latch side, then use a 6-ft level to check that its jack stud on either hinge side is plumb.
Shim the side jambs as necessary until they are flush with both sides of the drywall, then repeat for latch side shiming: reduce when there is too much reveal or add when reveal is uniform along top of door for optimal operation when casing is installed. This process ensures smooth operations when casings are installed.
Install the Casing
Assuming your walls are straight and level, installing casing should be straightforward. For added safety, glue or nail the miters securely so they don’t come loose during installation.
Once your casing rests flush against the wall, drive 8d finish nails through its hinge locations to secure it. Shim behind each hinge location if necessary to create an even and plumb door frame.
Place a 6-foot level against the floor at the base of your doorway, and ensure that its hinge side jack stud is plumb. If it isn’t, add shims between casing and jack stud until your bubble shows plumb – then secure and tuck the shims back into trim as necessary.
Install the Hardware
Pre-hung doors make hanging easier for DIYers by already including hinges that attach them to a three-sided frame, but do require precise measurements and some carpentry experience for successful installation.
Find a level spot on the doorframe using a level to see if the door is plumb and use wood shims to raise side jambs to account for any additional height of flooring that might come with installation.
Rough openings should be one to two inches larger than the actual dimensions of your door to allow extra wiggle room for level and plumbness adjustment – to ensure optimal functioning.