How to Install a Prehung Exterior Door

Remove the doorbell. Doorbells are either hard-wired and low-voltage or battery-operated models, so you should be able to handle this task without an electrician.

Score along the exterior trim with a utility knife and pry it off. New exterior doors have the exterior trim already attached, so there’s no need to save the old trim.

Unscrew the strike plate from the frame.

Carefully push the top of the jamb out, and the door frame should come free. It might stick a little at the bottom from the old sealant.

Install a sill pan or flashing tape to the sill. This will prevent water damage to the opening.

Sill Pan: Some sill pans can be created from bending sheet metal, or they can be purchased as a kit. Some kits come in three pieces to better fit the opening. To install, set the corner pieces on the sill and then place the middle piece over top. If it’s too wide, cut the ends with a hack saw. When the fit looks right, apply PVC cement where the middle piece will overlap the corner pieces and press it into place. Hold the pieces together while the PVC cement forms a strong bond. Now pull out the sill pan and apply three beads of caulk to the opening. Set the pan in place and press down. To finish, seal along the back, the edges and the seams of the sill pan. For tips on applying caulk, take a look at our DIY Basics video How Do I Use Caulk?

Flashing Tape: To use flashing tape to protect the sill, install it in sections. Apply the first pieces of tape to the bottom sill. You might need to use two pieces. Always overlap flashing tape in a way that water will run from top to bottom and inside to outside. After covering the bottom of the frame opening, install a few pieces about 6 inches up the sides of the opening.

Remove the transport plug and drill a hole for the doorbell wires.

Apply a bead of caulk to the back for the brick mould on the door. It should be applied along the two sides and the top.

Set the bottom of the door in the opening and tilt the top into place. Remember to feed the doorbell wires through the hole.

The next few steps involve installing shims around the interior frame and securing the door in place with screws. The shims keep the frame straight and free from distortion when attaching to the framing with screws. The shims will be placed around the frame above the three hinges and on the latch side at the top, middle and bottom. There should also be shims behind the strike plate. Watch How Do I Use Shims? for installation tips.

From the inside, check that the frame is centered in the rough opening and still plumb. Drill pilot holes through the hinges and drive screws partway in. Place shims above each screw location on the hinge side. From the outside, finish driving in the screws. Now the hinge side is secure.

Stand outside. With the door closed, check where the weatherstripping on the frame contacts the door. It should be equal at the top, middle and bottom. If it’s not, adjust the latch side of the door — in or out — and drill pilot holes in the frame at the top and bottom on the latch side. Drive screws partway into the holes.

Shim above the screws on the latch side and check the frame for plumb. When it looks good, drive in the screws at the top and bottom. Don’t drive in the middle screw yet.

Close the door and shim above the middle screw. Also shim behind the strike plate. Now drive in the last screw and attach the strike plate.

The door should be snug against the adjustable sill cap. To test this out, place a piece of paper over the sill and close the door. The paper should pull out with a little resistance but shouldn’t tear.

Adjust the cap screws to raise or lower the cap.

Apply caulk to the corners along the edges of the cap and then install the self-stick corner pads that were included with the door. The door opening might be too tight for the pads. If so, just seal the corner of the cap and don’t install the pads.

Insulate around the frame with blanket insulation or spray foam. Don’t use too much spray foam as it can push against the frame.

Install the interior trim. Seal along the edges of the interior and exterior trim with caulk.

Now that you’re done with your prehung door installation, go ahead and paint the door and frame. Some doors already have a coat of primer on them so they’re ready to paint. You can paint the door while it’s on the hinges or take it off and paint it on saw horses.