Installing a pre-hung door in your house is a rewarding DIY project, but before beginning it is essential that the opening is suitable. Wood shims should be used to adjust to size and make sure everything is plumb.
Begin on the hinge side by adding shims above each hinge between stud and wall, using your level to ensure all shims are aligned straight.
Measure the Opening
To select the ideal door size, remove any trim around the existing opening. Next, take three measurements of rough opening height (distance between studs). Choose the smallest measurement.
Decide whether your door should swing inward or outward before ordering prehung door units; most exterior doors tend to open inward while interior outswing options can also be chosen for ease of opening and closing. Knowing exactly which option you prefer will prevent an awkward-fitting door that’s hard to open or close.
Measure the Door
Just like you measured the door opening, measure the distance from the sill to the underside of the frame lintel on both left and right sides, using the lower measurement as your door height.
Install a level on the floor inside of the doorway and use a level to check its plumb position. If the level’s bubble moves towards one hinge side of the jamb, insert shims beneath the level until its bubble returns to being central, and tack the shims into place afterwards.
Measure the Jambs
Uninstalled doors may bind or not latch properly, requiring them to bind or fail to latch at all. To avoid this problem, it is crucial that the door frame remains level and plumb.
Start by inspecting the rough opening to identify any areas which are out of level, using a level to check both sill areas and jamb sides for any inconsistencies.
If any of the sides are out of level, add shims at hinge locations to correct them by installing them into the casing at various shim locations in order to correct them.
Cut the Jambs
Once the door frame has been placed into its opening, temporarily attach cleats to the wall to act as stops for it. Shim below as needed until its bubble reads plumb before securely fastening it in place.
Utilizing a 4-foot level, double check that the head jamb stud is level. If it falls lower than expected on one hinge side, use shims at latch side location until casing edge rests against stop evenly.
Measure the Casing
Prior to ordering your new door, remove the casing that encloses your existing opening using a wide flat pry bar, taking care not to hit or damage the wall.
Once the casing has been removed, measure the width of the rough opening between studs three times and record the smallest measurement. Shim the header (top) of the frame if necessary so an even margin exists between it and its wall stud above it.
Measure the Hinges
Make sure to provide accurate frame dimensions when ordering your pre-hung door, rather than ordering by the slab size alone. While ordering by slab size may save casing costs and ensure proper operation of your new door swinging correctly.
Shim the hinge side of the frame using several shims so that the gap between jamb and framing is even. Repeat this step on both the hinge and latch sides of the frame.
Measure the Hardware
Installing doors correctly can be one of the most rewarding projects in home improvement, yet one of the hardest. Failing to set them properly could cause the door to jam shut or not latch properly.
When installing a prehung door, start with an accurate level. Place it near the hinge side of the jamb and slide shims under it until its bubble is centered. Tack these shims into place using finish nails – repeat this process for both jamb sides.
Measure the Frame
Remove any interior casing around the frame, and measure the width of the opening – also known as its rough opening – so that you can order a prehung door that fits precisely.
Measure the height between the header and floor on both sides and use the lowest measurement as your standard. In addition, take note of whether or not an outswing door swings toward you at this point by placing your nose close to its hinge pins and watching which side opens first.