Header (framing)

Every door and window interrupts the wall studs that would normally carry the roof and floor loads straight down, so framing needs a beam to pick up that load and reroute it. That beam is the header. It takes the load that would have passed through the missing studs and redirects it around the opening, down through the king and jack studs (also called trimmers) on each side, and into the foundation.

Headers are sized to the span and the load above them. A small interior door might need only a doubled 2x6. A wide great-room window or a multi-car garage door can require a deep engineered beam such as an LVL (laminated veneer lumber) or a steel section. The 2018 International Residential Code, Chapter 6 and Section R602.7, gives the prescriptive header sizes for common spans, and anything beyond those tables gets an engineer's design.

For example, a Scottsdale custom home with a 16-foot multi-slide patio door that opens the great room to the backyard needs a large engineered header above that opening. Skip it or undersize it and the roof load pushes down on an unsupported span, which leads to sagging, sticking doors, and cracked drywall above the opening.

Do not confuse a header with a truss or a beam in general. A truss spans the whole roof; a header spans a single opening in a wall. A header is one specific type of beam, the one that solves the problem of holding the structure up where you cut a hole in the wall for a door or window.