How to Hang a Door With an Unlevel Floor

Measure the width of the door opening with the tape measure and then measure the same distance on a 2-inch by 4-inch board. Draw a pencil line at the cut location and cut the board off using a hand saw.

Insert the board into the bottom of the door so it spans the width. Place a level on top of the board and locate the air bubble. Insert wooden shims under one end of the board until the air bubble is in the exact center of the level.

Locate the end of the board that is elevated with shims and measure the height from the floor to the base of the board. This is the amount that the floor is uneven by.

Lay the prehung door on a work table or saw horses and move to the side that corresponds to the side of the door without the shims, meaning it was higher. Measure up from the bottom the amount the floor is uneven and mark it with a pencil. Cut the door jamb using a jig saw.

Insert the door frame into the opening, asking another person to hold it in place on the opposite side. Open the door and insert shims under it.

Look at the sides of the door frame where a small gap exists between it and the drywall. Insert two to three wooden shims on each side of the door frame so the door is even. Nail the door in place using finishing nails and a hammer, inserting each nail over the location of shims.

Cut the shims off flush with the wall surface using a utility knife.

Cut two strips of molding to the height of the door plus 1/2 inch and cut one strip to the width of the door plus 1/2 inch. Miter cut the upper corners of the long strips and both ends of the shorter strips to 45 degree angles. Install the trim around the door frame using finishing nails