Header (Framing)
CSI Division 06, Wood, Plastics, and Composites
A horizontal structural framing member sized, usually from an engineering span table, to carry the load above a wall opening, like a door or window, around that opening instead of down through it.
Why it matters
Cutting an opening into a load-bearing wall removes the studs that were carrying weight straight down at that spot, and a header is what replaces that lost load path, redirecting the weight from above around the opening and back down through the framing on either side.
On a real project
A framer installing a window opening in a load-bearing wall sizes the header using a span table matched to the opening's width and the load above it, rather than guessing at a lumber size, since an undersized header can sag or fail under load over time.
Who this matters most to
A Carpenter sizes and installs headers over every opening in a load-bearing wall, checking the span table rather than relying on habit from a different job with different loads.
Where this goes wrong
A framer installs a header sized by eye rather than checked against a span table, assuming a size that worked on a similar-looking opening elsewhere. The header turns out to be undersized for this specific span and load, and the wall above the opening sags slightly as the house settles.