How to Replace a Door Jamb

Door jambs should last for decades before needing to be replaced, but of course, accidents happen. You may be able to fix a broken door jamb using wood-filler and a bit of sanding paper, but in some cases you might have to install a new door jamb.

Read on and we’ll walk you through how to replace a door jamb – just bear in mind that if you’re going to attempt this, you’ll want the help of a volunteer (especially if you’re attempting it for the first time).

Removing a Door Jamb

Before you do anything else, you’re going to need to remove the existing jamb. 

There’s no point in measuring yet – it’s better to measure the opening rather than the old jamb, as the smallest discrepancy can lead to a door that catches on the floor, or the door lining.  

Before getting started, you’ll need to assemble a few materials. 

You’ll need:

  • A flathead screwdriver
  • A crowbar
  • Allen key
  • Hammer
  • A tape measure

Step 1: Remove the door

You can’t remove the jamb while the door’s still in the frame. 

To remove the door, pull out the hinge pins and lift the door out of its frame. You can do this by tapping them up from below using a thin Allen key and a hammer.

Make sure to leave the hinges attached to the jamb.

Step 2: Remove the trim

To access the frame, you’ll need to get rid of the trim. Work your way around the edges using your crowbar. Don’t use too much force or you risk splitting the trim in half.

Step 3: Remove the jamb

Here’s where you take out the jamb itself. It’ll be attached to the frame, either with nails or screws. If it’s the latter, use your screwdriver (or a drill with a screwdriver bit attached) to work the screws loose. If it’s nailed in place, pull out the entire jamb with your crowbar. 

Again, don’t use too much force.

How to Measure a Door Jamb

Now that you’ve removed the old jamb, you’ll need a tape measure. 

You’ll be measuring vertically, from the floor to the exposed header. Ideally, you want the two lengths to be within a few millimetres of one another. A small discrepancy might not be noticeable; a larger one will need correcting.

Next, measure the location of the hinges. You can do this using the length of jamb you’ve preserved, measuring from the end of the jamb to the centre of each hinge. Take several measurements to be sure.

Fitting a Door Jamb

To fit your door jamb, secure it into position on the hinge side first. Use screws rather than nails, as this will make it easier to adjust the jamb later on. 

You’re going to need a spirit level and a few carpenter’s shims to get the jamb totally vertical. 

You can use a set-square to ensure everything is properly aligned, before securing the jamb in place. You can then repeat the process on the other side.

Lastly, you need to attach the hinges. 

There’s quite a lot of potential for error here, so make sure your measurements are accurate, and that your hinges are going to align properly with those on the door. 

It might be that your hinge-pins don’t slide in easily at first. To compensate for this, just use your hammer (or better yet, a mallet) to force them into place (just a little bit of force is all that it takes). 

This is where your volunteer is going to come in especially handy – they can hold the door up, while you to slide it into position and drop it into the hinges. 

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