How to Install a Door Jamb Extension

A man installing a door jamb.
  • 3-4 hours
  • Beginner
  • $30-80
What You'll Need
Measuring tape
Extended door jamb

The door jamb is the doorframe of a door. Most door jambs are made of wood, and they are located both on the sides and directly above the door. The jamb on top is called the head jamb, while the jambs on the sides are called the side jambs.

Door casings are nailed together with the jambs. Most of the time, contractors will construct door jambs that match the thickness of the wall. However, slipshod works can sometimes occur, and what is left is a little hollow space before the door. Another reason is that the wall sometimes does not have a uniform thickness and sometimes has cladding layers. This makes the door look untidy and unsightly. The purpose of the extended door jamb is to match the thickness of the wall.

Step 1 - Determine the Length of the Door Jamb

The first thing you need to do is to determine how long the door jamb extension needs to be. Use a measuring tape to record the distance from the drywall to the door edge to determine the length. Determine the length of the side jambs and the horizontal jambs. Mark the outline of the door jamb using a pencil.

Step 2 - Create the Extended Door Jamb

There are a few ways to get an extended door jamb. You can either ask the help of a carpenter on the matter, or you can ask a home improvement store for some recommendations on the subject. Another option would be to take wood pieces from old wooden planks. When creating the door jambs, three will be needed to create the two side jambs and the horizontal jamb. The jambs should be ¾ inch to 1 inch thick. Try to match the shape of the outline as much as possible. Don’t make it too thick that it ends up blocking the entrance and don’t make it as thin as a sheet of paper. The job should be done on the floor.

Step 3 - Install the Door Jambs

Apply glue on the door jambs, paste the door jambs in place, and let it dry. Sometimes, the hinges of the door will get in the way. Use a measuring tape to measure the length of the hinges and cut out the appropriate shape from the door jambs. Ensure the jambs are a good fit. After that, nail the extended door jamb to the frame. It is advisable to use as few nails as possible so the door won’t look like it’s riddled with nails. When hammering in the nails, make sure that they are at least 1 inch in.

Additional Tips

If intending to use power-driven equipment like a drill, wear protective equipment like gloves and eye goggles.

Another solution to solve the hinge blocking problem would be to move the extended hinge by ¼ inches. Don’t worry if the shape doesn’t fit. Getting the correct shape does require some practice.