Jack Stud

A jack stud is a vertical structural element that sits below and supports a header to transfer its loads downward to the bottom plate and ultimately to the structure’s foundation. Its length determines the header height and is critical for rough openings of windows and doors. Typically, a king stud is placed adjacent to a jack stud and the two are nailed together to ensure both stay in place. Additionally, the jack stud is typically nailed from below, through the bottom plate, and will be toe-nailed into the header above.

Occasionally in window framing the jack stud will be cut into two pieces to allow the window sill plate to run through the jack stud and terminate on each side at the king studs. It is thought that this adds stability to the window frame while minimizing the need for additional support for the ends of the window sill plate. The width of the jack stud will match the size of the adjacent studs used for that particular wall and will normally be a stress-rated dimensional lumber. Jack studs, like many framing members, are known by a variety of names on a regional basis including “shoulder studs” or “trimmers.”