At the heart of every good door installation is a sturdy and accurately built door frame. If the door frame is flimsy or if it is not true, everything built on top of it will not work properly. The door may scrape or not fit 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, not does it use special, expensive materials. A door frame is composed only of two materials: two-by-fours and nails. So, creating a well-built door frame is less about materials and more about technique. As long as you measure precisely, cut the two-by-fours correctly, and nail them well, the door casing and trim will follow perfectly. Besides those few materials, your only tools are a hammer, saw, level, and measuring tape.

Main Elements of a Door Frame

A door frame is internal; you never see a door frame except when building it. All of the visible components are the door casing, trim, and the door itself: built upon the door frame but not the door frame itself. Think of a door frame like a four-sided picture frame: top, bottom, and two sides.

Top of the Door

• Header: The header is a horizontal two-by-four that runs the width of the door frame. It is the topmost part of the door frame. The top of the door’s exposed casing will attach to the header.
• Short Support Studs: Short vertical studs just a few inches long run between the header and the top plate.

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.

Sides of the Door

• King Stud: The king stud is a vertical two-by-four that runs from the top of 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.

Bottom of the Door

A horizontal two-by-four bottom (or sole) plate rests on top of 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.

Tip

If a door frame is supposed to be four-sided, why isn’t there a bottom side? Is it flush or do you walk over this bottom side? The door’s bottom or sole plate is initially built as a continuation of the wall system’s bottom plate. After the jack stud is nailed into place, the section of the plate between the two jack studs is cut out and discarded.