How to Replace an Interior Door: Prehung Door Replacement

Follow these steps and get perfect results.

Next Project

A full day




Less than $20


Learn how to install a prehung door. We'll show you foolproof tips and techniques to help you do a great job even if you're a beginning carpenter.

Tools Required

  • Cordless drill
  • Jigsaw
  • Level
  • Miter saw
  • Scribing tool

Materials Required

  • 2x4
  • 4d finish nails
  • 6d finish nails
  • 8d finish nails
  • Interior door and trim
  • Shims

Video: How to Hang a Door

Travis Larson, an editor for The Family Handyman, shows you how to remove a door and hang a new one or rehang the old one.

Project step-by-step (17)

Step 1

How to Install a Prehung Door Overview

Check the floor

floorFamily Handyman

Check the floor for level and the jambs for plumb. Measure the exact amount the floor is off level. The opposite jamb must be cut by this much to level the door in the opening. Hanging a door correctly is one of the most satisfying jobs in the home improvement world, but it’s often the most challenging. Unless it’s installed correctly, your door can have uneven gaps along the jamb, or it can bind or not even latch.

In this article, we’ll show you foolproof tips and techniques that’ll give you great results every time you need to know how to install a prehung interior door. All you need are simple carpentry tools and some basic home improvement skills and tools to easily master the techniques. Allow about an hour and a half for your first door, and once you get the hang of it, your next door will go in twice as fast. When learning how to install a prehung door, follow these steps:

When you buy your door, pick up a package of wood shims and 4d, 6d and 8d finish nails. Also get a straight 7-ft. 2×4 and cut another 2×4 the width of your opening (Photo 1) that are both straight as you sight down the edge. Since installing trim is part of the door installation, purchase some matching door trim and be sure you’ve got a miter saw to cut it. You’ll also need to pick up a lockset for the door even though we won’t cover the installation in this article.

Pro Tips for How to Install a Prehung Door

  1. An accurate level is crucial for a good installation. Check it by laying it on a flat surface. Memorize the bubble’s position. Then flip the level end for end and check the bubble. If the bubble doesn’t settle in the exact spot, find an accurate level.
  2. Check the length of your prehung door jambs. They may be longer than you need. You may have to trim both sides to minimize the space under the door. In most cases, the door should clear the floor by 1/2 in.
  3. If you’re setting your door into adjoining rooms that’ll be carpeted later, you can hold both jamb sides 3/8 in. above the floor and avoid having to trim your doors.
  4. Use blocks to level jamb bottoms. If you’re installing a door on an unfinished floor and need space under the jambs for carpet, just rest the jambs on temporary blocks while you’re hanging the door. Adjust the size of the blocks so the bottoms of the jambs are on a level plane. Leaves a space of anywhere from 3/8 in. to 5/8 in. under the jambs, depending on the thickness of the carpet and pad.
  5. Check the plug. Make sure the plug that holds the door slab in place is the type that can be removed after the door is installed. If it’s not, sometimes you can cut off the plastic strap and insert the plug back in through the doorknob hole. It’s difficult to move the door when the slab is flopping all over the place, but it’s worse to install a door that won’t open.
  6. It’s not always necessary to use shims on the top doorjamb—the casing will hold it in place. And on new homes and additions, walls can compress as they settle and push down on the top shims, causing the jamb to bow down. Only shim the top jamb if you’re working with a 3-ft.-wide door, and the top jamb arrives bowed from the factory.

How to Stop a Door From Swinging Open

Step 2

Level the floor

LevelFamily Handyman

Use a level to check the floor. Rest a level across the opening and level it with one or more shims. Mark the shim at the thickest point, and measure the thickness of the shim at the mark. That’s exactly how much you’ll need to cut off the jamb at the opposite side of the opening.

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