How to Replace an Exterior Door Jamb

If the jamb of your exterior door has become cracked, rotted, or damaged in any way, you may have to replace it. Luckily, the process of replacing an exterior door jamb is relatively manageable with a little patience and attention to detail. Below you will find a rundown of the steps needed to complete this project.

Mark Off Bad Sections

Before you install your new exterior door jamb, you will need to carefully remove all pieces of the previous jamb that were damaged by cracking, rotting, or warping. To do this, use a pencil to mark off spaces bracketing the damaged portion of the jamb starting from around 2 inches above the damaged portion of the jamb and ending around two inches below the damaged portion.

Remove the Bad Portions of Door Jamb

Using a saw, carefully cut along the marks you have already made to designate the area of the door jamb that is damaged. Cut into the door jamb until you have cut all the way through the wooden pieces. Once you have cut all the way through, you should be able to slide the damaged pieces of your jamb out easily.

If you are replacing the entire jamb, cut away a section of the jamb in this manner and then use your hands or a prybar to remove the remaining sections of your door jamb. Be sure to remove all traces of the previous door jamb, as you will need a fresh surface to work with to complete the project.

Measure Sections of Jamb that Need to Be Replaced

Once you have removed one or more pieces of the previous door jamb, you will need to measure the portions removed with a tape measure so that you will know how much of the new jamb you will need to cut. Be precise, as it will be important to have a snug fit in this space.

Cut New Jamb Pieces

Once you have taken your measurements, mark off the proper dimensions on the matching wooden frame boards that you have purchased. Then, with even, straight cuts, cut out the proper length of the wooden frame that you will need to fit in the space you have already created.

Prime Both Ends

In order to form a proper seal in your door jamb, apply wood primer to the ends of both the new section of the jamb that you will be installing and the sections of wood that are still in your door frame.

Install Jamb Pieces

First, apply wood glue to the back and ends of the piece of the wooden jamb that you will be installing. Then, insert the wooden jamb piece into the space that you have created in the jamb. If any wood glue seeps out of the joints, wipe this away.

Fill in Gaps

If any gaps exist in the wood after you have inserted the wooden jamb piece, fill these gaps with wood putty, wiping away any excess when you are finished.

Sand and Paint

Once the wood putty has dried, sand down the joints between the two pieces of the wooden jamb and paint the entire new jamb to make it appear flush with the other pieces of the jamb.