Header

The header is the horizontal member that spans the top of a garage door opening, connecting the two side jambs at the top of the framed opening. It bears the weight of the structure above - wall framing, roofline, or masonry - and transfers that load down the jambs to the foundation. The header defines the top of the usable opening dimension and sets the reference point for all vertical measurements in a garage door installation.

In wood-frame construction, a garage door header is typically built from doubled 2x10 or 2x12 lumber, or engineered lumber (LVL), sized for the span. A 16-foot two-car opening often needs a header 14 inches deep or more to carry the load without sagging. In masonry or concrete construction, the beam above the opening is called a lintel rather than a header, though both terms appear in field use.

What attaches to the header:

• The torsion spring center bracket mounts to the header face, centered above the door.
• The opener rail's header bracket bolts to the header to anchor the far end of the rail.
• The stop molding along the top of the opening nails to the header face.
• The top weatherstrip or header seal compresses against the top section when the door is closed.

Headroom - the vertical distance from the top of the door opening to the nearest ceiling obstruction - is measured from the header upward. A standard-lift installation requires a minimum of 10 to 12 inches of headroom above the header. Low-headroom track configurations reduce that requirement but alter the spring and bracket geometry.

An undersized header that deflects under load can cause problems. The spring assembly shifts, the center bracket loosens, and the door binds at the top. A sagging header shows up as the gap between the spring shaft and the door top being unequal on the two sides.