This project explains how to fix a sagging exterior door by adjusting the door hinge setback in the door jamb.
How to Fix a Sagging Door
The front door was sagging, making it hard to close the door because it would contact the jamb and threshold. The gap is clearly visible in the following photo.
Required Tools
The following tools are required for this project:
- Carpenter’s square
- Carpenter’s level
- Pencil
- Wood chisel – 1 inch wide
- Cordless drill
- Hammer
- Philip’s screw driver
- A helper – preferred for the awkward part of removing the door
Why is the Door Sagging?
To determine why the door was sagging, I checked the following with a carpenter’s square and bubble level:
- The door was level
- The hinges were securely fastened and not bent
- The door frame was out of square (i.e. slightly slanted)
Out of Square Door Frame
The door was sagging because the door frame was out of square, caused by minor setting of the house foundation over the past 8 years. To fix the problem, I could either tear out the entire door frame and install a new door with two side lights (small windows on each side of the door) which would be expensive, or I could reset the middle and top door hinge mortises to compensate for the out-of-square frame and be done in 30 minutes.
Other Causes for a Sagging Door
Exterior doors are often heavy and can sag because the door hinges are pulling loose from the door jamb and/or the 2×4 framing. Door hinges often have short screws that do not reach far enough into the door frame to support the weight and regular use of the door. Shims behind the door jamb can create a significant gap between the finished door jamb and the 2×4 framing, which require long hinge screws to sink into the wood framing for structural support.
If your door is level and the door frame is square, weak hinges and/or hinge fastenings may well be the problem. If you believe the hinges are weak or loose, see this project for installing heavy duty hinges and long hinge screws.
Sagging Door Repair
To fix the door, it needs to be leveled by cutting the middle- and top mortises about 1/8 inch deeper. This will pull the door to the left and upward so the door bottom clear the threshold.
Begin by removing the hinge pins by driving them out with a hammer and Philips screw driver. A helper is needed to support the door and avoid bending the other hinges.
The door hinge leaf and mortise are shown after the door is removed. A mortise is the recessed pocket cut into the door jamb such that the hinge leaf is flush with the wood surface.
Remove the four screws in the hinge leaf with the cordless drill/driver.
Wood Chisel
A wood chisel should be razor sharp to make easy and precise cuts. A diamond sharpening stone with a coarse and fine side does a superb job of quickly putting an edge on tools and knives. Diamond stones are more expensive than natural stones, but well worth it.
Cut the Hinge Mortises
Cut the outline of the mortise to the a depth of 1/8 inch (use your judgement – but a little goes a long way!) as shown in the following photo. Make the perimeter cuts first for a clean “stop” when shaving out the interior. Notice the flat side of the chisel is held against the outside of the mortise.
Position the chisel 1/8 inch below the mortise surface and lightly tap the hammer to shave away the wood:
Continue shaving away the wood across the face of the mortise:
After removing the bulk of the material with the hammer, shave off any high spots by hand:
I cut the middle hinge mortise 1/8 inch deeper the same way. The bottom hinge is not modified.
Rehang the door as follows:
- Reinstall the hinge leafs with the four screws.
- Set the door on the hinges and reinstall the hinge pins.
- Check for proper operation.
The door opens and closes effortlessly now. I have to remind the kids it’s not necessary to slam the door.
The sag is fixed in the next photo. The door edge is now aligned with the jamb:
Door Bottom Weatherstrip
A sagging door can damage the weatherstrip (a.k.a. door sweep) on the door bottom. This project explains how to replace a door bottom weatherstrip.
Thanks for reading,
Bob Jackson
