At the heart of every good door installation is a sturdy and accurately built door frame. If the door frame below the door jambs is flimsy or if it is not true, everything built on top of it will not work properly. On the other hand, if you do frame the door well, the door jambs and trim will look professional and the door itself will swing free and close tightly.
The good thing is a door frame isn't expensive or difficult to build. A door frame is composed only of two-by-fours and nails. Creating a well-built door frame is mostly about cutting the two-by-fours correctly and nailing them in the right places. No other materials are needed and your only tools are a hammer, saw, level, and measuring tape.
How a Good Door Frame Is Built
Top of the Door
- Header: The header is a horizontal two-by-four that runs the width of the door frame. It is the top-most part of the door frame. The top of the door's exposed casing will attach to the header.
- Short Support Studs: Short vertical studs run between the header and the top plate.
The top plate is a doubled-up series of two-by-fours that run continuously around the perimeter of a room or the home. The top plate is already part of the house and is not part of the door frame construction.
Bottom of the Door
A horizontal two-by-four bottom (or sole) plate rests on the home's subfloor. The building elements that form the sides of the door—the king stud and the jack stud—rest on the bottom plate. The sole/bottom plate might already be in place or you may need to add it.
Sides of the Door
- King Stud: The king stud is a vertical two-by-four that runs from the sole plate to the top plate. The top of the king stud touches the bottom of the top plate.
- Jack Stud: The jack stud is a vertical two-by-four that runs from the sole plate to the header. The top of the jack stud touches the bottom of the header and supports the header.
Equipment / Tools
- Electric miter saw
- Framing hammer
- Tape measure
- Bubble level or laser level
- 6 two-by-fours
- Box of 12d nails
Add the Bottom or Sole Plate
If you are cutting a door into an existing wall, there will already be a bottom plate. Otherwise, nail a continuous two-by-four across the width of the doorway. The two-by-four will extend across the doorway for now but later will be cut away. For a doorway with a rough opening of 34 inches, cut the bottom plate to 40 inches.
Add the King Studs
Cut the king studs so that they extend from the top of the sole/bottom plate to the underside of the top plate. This measurement will vary by ceiling height.
Tape the bubble level to each of the king studs as you place them. Or shoot a plumb line from the laser level.
Nail the king studs so that they are 38-1/2 inches apart, on-center. Toenail the king studs into place.
Add the Jack Studs
Cut two of the two-by-fours each to 80-1/2 inches. Nail the jack studs to the insides of the king studs. You can drive the nails into the king studs rather than toenailing the jack studs.
Cut and Add the Header
Cut the header to 37 inches long. Standing on a ladder, place the header on top of the jack studs. Nail the header into place by driving nails through the header and into the ends of the jack studs.
Add Support Studs Over the Header
Measure the distance between the top of the header and the underside of the top place. Cut off two pieces of two-by-four to that length. Toenail these support boards into the top place. The bottom sections of the support boards can be secured by driving nails upward through the header.
Cut the Sole Plate
Use the hand saw to cut away the section of sole/bottom plate that extends across the doorway. If the flooring is subfloor, you can cut directly down to the subfloor since minor cosmetic damage is not a concern. If the flooring is a decorative floor covering, place tape on the cutting area to avoid damage. Slow down your cutting toward the end to avoid biting into the flooring.
Another way to avoid damage to decorative flooring is to cut the sole/bottom plates to size ahead of installation.
Finishing the Door Frame
Check the door frame to make sure that no nails are protruding and that the studs are smooth. Pound down any protruding nails. The door frame is now ready for either a prehung door or for the construction of a door casing from scratch.