How to Install a Pre-Hung Door in 11 Steps

If you haven’t already removed your door, you’ll want to follow this step first before installing your pre-hung door. If you’ve already removed your door, door trim, and jamb, skip ahead to measuring the rough opening. Start by making a rough sketch of your door. On it, you’ll jot down if you have an inswing or outswing door, a right-hand or left-hand door, as well as the placement of your door handle. You’ll need this information to order a pre-hung door. 

To determine the handedness and swing of your door, stand outside the room. Then, place your back on the hinged side of the door and note which hand is closest to the doorknob. If your right hand is closer, it's a right-handed door, and vice versa. Now, open your door. If it swings toward you while standing outside the room, it’s an outswing door. If it swings away from you, inside the room, it’s an inswing door.

To remove the door, take off the hinge pins with a screwdriver and hammer. Have a friend on hand to steady the door and work upward, starting with the bottom hinge. Don’t be afraid to use a bit of force to remove the pins if they’re stuck.

To remove the door trim, cut around the edges using a utility knife—this will separate and loosen the trim. Remove the door header and side trim using the back of your hammer as leverage. Put the trim you removed to the side. Once all the trim is removed, focus on the door jamb.

First, remove any screws (including the hinge screw and plate) and loosen the nails that hold the door jamb in place. Use your hammer as leverage to pull the jamb away from the wall and completely remove the door jamb. In some cases, with older or thicker door jambs, it may be necessary to use a reciprocating saw to remove the jamb. If needed, carefully make a cut halfway up the door jamb on each side. This will make it easier, so you can remove the door jamb in pieces. Make sure a friend supports the upper pieces of the door jamb so they don’t fall.

Once you’ve successfully removed the door jamb and trim, carefully remove any remaining nails or screws from the wall and clean away debris from the rough opening. If you plan to smooth, paint, or make any alterations to the surrounding wall, now’s the time. You can always make touch-ups later if necessary.

Accurate measurements are key to learning how to hang a pre-hung door. Double-check your measurements before purchasing your door, and when in doubt, ask a pro. To measure the width of the rough opening, measure the two-by-four present at the door header or the distance between the two existing door studs. The pre-hung door needs enough clearance so you can square it. The rough opening should be 1 ½ to 2 1/2 inches larger than the pre-hung door, including the jamb. 

Then, you’ll want to measure from the floor to the top of the rough opening to get its height. Pre-hung doors will have extra space at the bottom of the side jambs for minor adjustments. Keep in mind that there will be a difference in the measurements if you’re also installing new flooring versus working with existing flooring. The door must clear the floor by about 1/8 to 1/2 of an inch (check your local building codes). Leave approximately 2 inches if you’re installing a new floor.

Then, measure the wall depth so you can match the door size and avoid the door or jamb protruding from the wall. Compare your measurements to the previous door and allow for adjustments.

Take the time to double-check your measurements and measure at different points on your door. Buildings can settle over time, resulting in some inconsistencies in level and plumb. Knowing about these factors beforehand can help you troubleshoot any issues with your pre-hung door.

If you purchased an unpainted door, you’ll need to learn how to paint your door first. But if you’ve prepped and measured your door and it’s already painted, it’s time to install it. You’ll want a friend on hand to help with the heavy lifting. 

Before you begin, ensure the door you ordered meets your desired specifications. Assuming all is well, remove any packaging or cardboard that could interfere with installation. When in doubt, refer to the manufacturer’s instructions. Then, with a friend, position the pre-hung door in the rough opening. Check to make sure the door can open and close freely and that the door jamb is the correct height.

Next, adjust the door jamb as needed. If it’s too tall and won’t fit in the rough opening, measure the height difference and use your circular saw to remove extra wood from the end of your door jambs. If the side jambs seem too short—or you need to leave room for flooring—use wood shims underneath the side jambs to raise the height for the pre-hung door.

Now comes the tricky part: installing your pre-hung interior door. Don’t worry, we’ve got the details ready for you. First, you’ll level it using your carpenter’s level and measure the door to see if it’s level and plumb. You’ll need to do some adjusting so your door is square and the jambs are flush with the wall. If the top of the door is not level, add shims at the bottom jamb to raise the uneven side until the door is level.

Then, you’ll need to ensure it's plumb. Start at the top of the hinge side jamb and add shims above each hinge between the jamb and the wall. Use your level to check that it’s plumb and adjust as necessary. Use a finish nail to secure the shims. You may want to avoid driving the nail completely into the wall so you have some room to make adjustments after you shim the other side. 

Next, add shims on the latch side of the door directly across from the hinge side shims. Measure with your carpenter's level and add extra shims to plumb the door where necessary. Secure this side with finish nails, just as you did on the hinge side. 

Check the manufacturer’s guidelines for other suggested shim locations for your pre-hung door. There may be locations along the top or bottom of the door. You’ll want to have shims in place anywhere you’ll use a finish nail—which can vary—but it’s usually at intervals between 12 and 16 inches.

Once you think your door is adjusted and in place, use your carpenter’s level to double-check the adjustments you made. Use a carpenter’s square to check that your doorframe is 90 degrees in each corner, AKA square. Now is also a good time to check that your reveal—the gaps between the door and the doorframe—is even all the way around the door.

Then, open and close the door, confirming that everything aligns and the lock side of the door is making aligned contact with the jamb stop. Adjust the shims as needed. This will help ensure that your door hardware lines up once the door is in place. This is also a great time to double-check the swing and floor clearance of your door. If you make any adjustments to the shims, you should re-check that the door is level, plumb, and square.

Once you’re sure, nail your wood shims to the wall with finish nails. You or a friend may want to hold the shims to prevent them from spinning. Then, carefully trim the edges of the shims using whatever method you are comfortable with. Make sure to cut your shims so they don’t reach beyond the drywall and won’t interfere with installing your door trim. We recommend carefully scoring the shims with a utility knife so they can be easily snapped off. For safety, close your utility knife before snapping off the shims.

Now that your door is installed, it’s time to add the finishing touches, trim, and door hardware. First, have your helper steady the door and replace the hinge screws, starting with the bottom screw plate. Unscrew the center screw and remove it. Drill a pilot hole, then replace the center screw with a 3-inch head screw for extra stability. Repeat this process on all of the door hinges.

Next, you’ll want to install your door hardware. Often, you’ll need to buy these finishing touches separately. You’ll want to attach the doorknob, lockset, and strike plate. This step should be a cinch if you’ve done a good job keeping your door level, plumb, and square. Finally, as a finishing touch, add trim. If you saved your original trim, you can reattach it. Some pre-hung doors come with pre-installed trim, in which case you might be set—or the trim might simply snap into place.