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How to Install a Pre-hung Exterior Door

Install an Exterior Door

A new steel, wood or fiberglass entry door adds safety and security to your home, as well as enhancing its curb appeal. Installing a pre-hung front door makes a positive first impression on your guests and makes a great do-it-yourself project for you.

Getting Ready for a New Exterior Door

A pre-hung door comes already mounted to a new doorframe. The hinges are installed and the lockset and deadbolt holes are pre-bored for standard installations.

Before removing the old door, it is a good idea to have the new one on hand. Check it for damage and make sure it will fit. Here’s what you’ll need to do before you purchase a new door.

  1. Remove the interior trim around the existing door.
  2. Measure the height, width, and depth of the door opening. he new door should be ½” less than the height of the rough opening and ¾” less in width. 
  3. Determine which way the door opens. Stand with your back to the hinges and note whether you would open the door with your right or left hand.
  4. Select the type of door you will install: wood, fiberglass or steel. Fiberglass and steel doors are more weather-resistant than wood doors.
  5. Give this information to a Lowe's associate, who can help you select the appropriate door for your home.
  6. When you get the new door home, read the manufacturer’s instructions. They should provide you with information regarding the removal of the factory-installed shipping braces or clips.Some braces and clips keep the doorframe square during installation.They will also help to clarify terms and identify parts.

Removing the Existing Door and Frame

  1. Carefully remove the existing door's exterior trim for re-installation on the new doorframe. Some doorframes come with the exterior trim pre-attached so you can discard the old trim. Also remove insulation surrounding the doorframe.
  2. Use a hammer and nail set, or screwdriver, to remove the hinge pins and detach the existing door from the hinges. For most hinges, insert the nail set in the hole at the bottom of the hinge pin and strike it upward with the hammer. Keep driving the pin upward until it comes out.
  3. Once the door is off the frame, remove the hinges from the doorframe.
  4. Remove the screws, or nails, that attach the sill and jamb to the house frame. If necessary, cut the nails off between the jamb or sill and the house frame with a reciprocating saw. Wear safety glasses and be careful not to damage the house frame studs.
  5. If possible, remove the small pieces of wood, called shims, from between the door jamb and house frame.
  6. Remove the old doorframe from the house frame.You may need to use a pry bar under the sill.
If possible, get help from a friend to remove the old door and lift the new door in place.

Installing the New Pre-hung Door

Inserting shims in door frame
  1. Dry-fit the new door in position to make sure it fits.
  2. Inspect the subsill (where the door will sit) to verify that it is square and level. Adjust the subsill as needed with shims following the door manufacturer's instructions. Also, check that the rough opening is square and plumb. If you’re not sure if your rough opening is square and plumb, call a professional for assistance. Thoroughly inspect the house frame for dry rot and pest damage and make needed repairs before proceeding.
  3. Make sure the new door will clear the finished floor. Measure the new door from the bottom of its sill to the bottom of the door. Then measure the height of the existing interior flooring to ensure that the opening door will not hit the flooring. If the new door won't clear, raise entire the doorframe with a piece of treated wood secured to the subfloor with caulk and screws.
  4. Weatherproof the subsill by applying a bead of caulk about 1" from the front and 1" from the rear of the rough opening, with a wave, or zig-zag, pattern in between. Apply caulk to the underside of the doorsill, too.
  5. Working from outside the house, set the bottom of the door against the opening, then raise the frame into place.
  6. Temporarily insert new shims near the top of the frame to hold the door.
  7. With shims, adjust the doorframe so that it is plumb and square in the opening. Insert shims between the doorframe and studs at the hinge locations. Shims keep the door level, plumb and square in the rough opening. Be sure to have at least 1/8” of clearance between the jamb and rough frame.
  8. Drive screws through the hinges and shims. Some manufacturers recommend inserting the screws below the shims. Check your
    manufacturer’s instructions.
  9. On the lock side of the door, place shims near the top and bottom of the jamb.
  10. Drive screws through the jamb and shims.
  11. Check that there is even spacing around the doorjamb. From inside, make sure there is even spacing at the door reveal. From outside, check that there is a 3/8" to 1/2" space between the door and the jamb stop at the top, middle, and bottom. Make any necessary adjustments to the doorframe.
  12. Insert additional shims around the frame following the door manufacturer's instructions. For added strength, place shims at the lockset and deadbolt positions.
  13. Remove any remaining shipping braces.
  14. Open and close the door, checking that it swings smoothly. Make any necessary adjustments. Some pre-hung doors have an adjustable sill. Check your manufacturer’s instructions for more information.
  15. Drive screws through any additional shims to secure the doorframe.
  16. Score the shims with a utility knife, then snap off the excess.
  17. Secure the sill following the manufacturer’s instructions.
  18. Apply minimal expanding spray foam insulation in the gaps around the frame
    and allow to dry.
  19. After the foam has dried, trim any excess with a putty knife.
  20. Reattach the door trim.
  21. If the door is not pre-finished, apply a coat of paint or stain as recommended by the door manufacturer. Remove the door from the hinges and work on sawhorses. Check the manufacturer’s instructions for painting or staining the bottom of the door. Don’t forget to paint or stain the trim, if needed.
Be careful not to get the foam insulation on your skin. Use rubber gloves for this step.