How to Square an Uneven Door Frame

A white interior door sits ajar at the end of a hall.
  • 1-3 hours
  • Intermediate
  • $30-250
What You'll Need
Rubber mallet
Flat bar
Carpenter's square
Pre-hung door
Wooden shims
Another set of hands

When installing a door assembly, it is important to know that the door frame is level and square. Cutting corners will only cause problems with your ability to open and close the door easily. So, if you're having issues with a door sticking in your home, and all other problems have been checked, it might be time to fix the frame. If you follow the rules supplied in this article, you can readjust a previous installation error or decrease the amount of error possible on a new door install.

Step 1 - Remove Door and Trim

If you're adjusting an existing door frame in your house, first, you will have to remove the door itself and all of the trim surrounding the frame. The door is simple enough; just pull the hinge pins out of place, tapping them from beneath with a screwdriver and mallet if necessary.

For the trim, wedge a flat pry bar underneath the edge on one end of a section, and gently pull the casing away from the wall. Do the same thing for all of the pieces around the door frame and carefully set them aside to reuse later.

Step 2 - Square the Opening Off

hand turning the knob on a door

It is difficult to ensure that a door will be level and square if the rough opening is not (the rough opening is the bare bones structure before any work is done to begin a door install). So, before you begin, use a carpenter’s square to check the upper corners. This will save you time and effort later on. Remember, the more accurate your measurements, the more level your door will be.

Step 3 - Level Working Surface

Working with an uneven surface will also negatively affect the rest of the project, so check to see if the floor is level. If it isn't, make a mental note of the difference for future use. Writing it down is also a great idea.

Step 4 - Shim Door Frame

Placing a pre-hung door in the rough opening will give you an idea of how it will ultimately fit. This type comes complete with a pre-made frame surrounding it, so all you need to do is carefully slide it into place and shim wherever you need around the frame to level it in the opening. Remember that wooden shims can simply be made of wedges or blocks of wood.

Place a level against the door frame in your existing installation to see where you need adjustments. Then, like before, place wooden shims until it sits as it's supposed to. To keep the shims in place, nail them to the hinge. Make sure you trim any excess pieces with a saw so they sit flush with the wall.

Step 5 - Get a Level Sill

pile of wood shims

Next, adjust the door sill with a flat bar or wedge until it too is level. Place the wedge or bar under the latching side of the door frame and have a helper hold your door so you can check to make sure whether the top of the frame, or lintel, will need more adjustment.

Step 6 - Double Check

It is important in every project to double check your work. Take the time to measure the gap between the door frame and the original rough opening. Use and nail in more wedges where necessary. If you have the extra set of hands to spare, have someone re-measure if you feel it could be adjusted differently.

Step 7 - Secure Door Frame in Opening

Place your blocks of wood and/or shims into the open space over the lintel, and begin attaching the door frame to the original rough opening. Again, double check each corner to be square, before completely securing it into place.

Extra Tips

Do not worry about the finishing touches just yet. You can add framing to the door after applying the paneling or drywall. Also, head and side casings will finish off a new installation nicely, covering all your small shim adjustments.