DIY Door Frame
- Proper door installation depends on ensuring everything is square and level, which starts with the door frame. Carefully measure the width and height of your new door, and plan on a frame 2 inches wider and 1 to 2 inches taller than the door to allow room for the door jambs and the shims used during installation. Measure to the floor rather than the bottom plate, which will be removed before you install the door. Use a pencil to mark these dimensions on the top and bottom plates (2 by 4 boards in the wall frame), and if existing wall studs are set at the right width for your frame, mark your door and frame height on them as well. If not, you'll need to measure and mark two 1.5-inch spaces on each side of your door opening to allow you to install king (full-length) and jack (door height) studs to form the sides of your door frame. Note that you may need to remove existing wall studs to clear a space for your door frame.
- With your measurements and marks made, you can cut your king and jack studs and nail them into place. Use a long, strong framing nail such as a 3-inch 12d, and toenail (nail diagonally) the king studs into the top and bottom plates at your outside 1.5-inch marks. You can then nail your jack studs to the king studs. Double check that the opening between the jack studs is the width of your frame (door width plus 2 inches), and use a level to ensure that the studs are perfectly vertical.
- The header is a section of 2 by 4 that rests between the king studs and atop the jack studs to form the top of the doorframe. Measure and cut a 2 by 4 to create a header, nail through it into the jack studs and then nail through the king studs into it. Next, measure the distance between the header and top plate, cut a 2 by 4 to length and nail it into place halfway between the two king studs. This is called a "cripple," and it will help strengthen and support the wall frame around your door. For extra support, you can also place cripples at the edges of the header, next to the king studs. Note that in load-bearing walls, you will need a stronger header, often made of 2 by 6 boards with a plywood divider between them.
- Use a carpenter's square and a 2- or 4-foot level to confirm that your door frame is level at each side and on top, and that your corners are all 90 degrees. You can make minor adjustments to positioning by tapping boards with a hammer or placing wood shims. You can now saw through the bottom plate and remove the part within the doorway to make the door frame full-size and ready for installation.
