Installing interior or exterior doors requires proper balancing to achieve smooth motion. Level the frame and shims to achieve this aim so the door has an even reveal and fits flush against wall framing.
Begin by nailing shims onto the jambs, starting on the side that contains hinges. Shim evenly while regularly checking for squareness.
Measure the Door
Measure the door height with your tape measure by taking multiple measurements along its frame and noting which spot provided the largest measurement. Also, decide whether or not the new door will open inward or outward before ordering one.
Carefully unplug the casing around a door frame to reveal its rough opening or framing behind drywall, using a pry bar carefully remove any molding which covers this opening.
These measurements should provide an estimate of your rough opening’s width, height, and depth – essential information when purchasing prehung doors that fit properly.
Measure the Jambs
Check that the jamb header (top) is square with wall framing using a 6-foot level on the strike side of the door; if not, shimming header and king stud may be necessary.
Repete this process on both side jambs and studs, using less shim to support the head jamb since the door casing will provide support. When finished, double check all strike and latch sides with a level.
Cut the Jambs
Use a pry bar to carefully separate and dismantle both head and side jambs from their frames, then nail temporary cleats into the wall to serve as stops. Shim the hinge side of your frame to ensure it fits snugly within its rough opening.
Have a second person help hold the frame while you use shims to align it with the wall, using a carpenter’s level as needed to assess and adjust any necessary shims.
Cut the Door
Prehung door installation should only be undertaken with expert care; novice DIYers are best advised to hire an experienced carpenter. Prehung doors can be very heavy and difficult to navigate by themselves.
Shim the frame as necessary to bring it into alignment; typically shims should be nailed at 12-inch intervals to help avoid gaps later.
Install the Jambs
With help from your friend, carefully place the new frame into its rough opening. Nail temporary cleats to the wall opposite of the door opening as stops for your frame and use these to level off its head and side jambs until they are level. After leveling them off, use a 6-ft level to ensure its plumbness on either side of its hinge stud (known as “jack stud”).
The top door jamb may not require shims as its casing should keep it secure. Double-check that there is an even gap around the door slab to ensure its levelness and plumbness.
Install the Door
Use blocks to secure and align the hinge plates before installing the hinge pin and testing out how the door swings and closes correctly. After testing is complete, remove the blocks and test to make sure everything works smoothly.
Your door may require using shims in its bottom jamb to bring it up to an equal height with its top jamb, ensuring an even door hang. Once done, these shims should be hidden by door trim and doorknob plate.
Install the Hinges
Pre-hung doors can be weighty and difficult to get exactly right, which requires using a level or plumb bob to check wall surfaces and trimmer studs for plumb and squareness.
Shim underneath the head jamb until it is level with the studs, then do so on both latch sides of the frame. Once level, nail it to both studs and trimmer casing for additional support.
Chances are your existing trim will fit right in; otherwise, add it as an accent piece for added effect.
Install the Hardware
Prehung doors feature hinges attached directly to their frames, making installation much simpler but still requiring additional care in ensuring proper swing and close alignment.
To do this, you’ll require basic hand tools like a utility knife, hammer and tape measure; power tools such as a drill, circular saw, planer and finish nailer will speed up this process considerably.
Install the Trim
Professional installers can complete installation in approximately an hour; DIY tasks will likely take longer due to all the shims and adjustments necessary.
Shims are necessary because buildings settle, and even prehung doors must be level, plumb and square with both wall and frame. Once this step has been completed, drywall, trim work as well as painting or staining of the frame must be completed before final completion of this step can take place.