The Right Header for Every Wall
Several code-approved options beyond the standard double 2x12 save material and energy.
Synopsis: Double 2×12 headers are still the standard for window and door openings, even though the IRC lists other options for headers that save lumber, minimize thermal bridging, and save space for insulation. Builder Mike Guertin provides a comprehensive look at header design and discusses how to figure out the right-size header for a given span. He also discusses several alternative designs to the double 2×12 and when they are appropriate: rim-board header, box header, and using a flat 2x instead of a header.
When I started framing houses in the late 1970s, the standard header for almost any size window and door opening was a double 2×12 with a 1⁄2-in. plywood spacer to bring the header flush with the stud edges in a 2×4 wall. When the header is pushed hard to the double top plate of an 8-ft.-high wall, its bottom sets up window and door head jambs 6 ft. 10 in. off the floor, perfect for standard 6-ft. 8-in. doors.
When high-performance homes gained market share in the late 1980s, the building industry looked for options to reduce the amount of lumber used to build headers — or to eliminate conventional headers altogether — in order to save resources, minimize thermal bridging, and provide more space for insulation. Double 2×12 headers are often oversize for the load, but they’re still the standard. In most cases, there is no structural advantage to installing headers that are larger than required, and there are downsides. Not only do they cost more than right-size headers, but the deeper a lumber header is, the more likely it is to lead to drywall cracks as green lumber dries or dried lumber expands during seasonal humidity changes.
When I look at the prescriptive options available in the IRC, I’m surprised by how many builders still frame the way I did nearly 40 years ago. I guess bigger and beefier looks stronger and impresses clients, and I admit that it’s easier to use the same-size headers throughout a house whether for a large patio door or a narrow window. Thoughtful header design takes planning and organization, but it’s a better way to build. Shallower headers, single-ply headers, engineered lumber, innovative use of rim joists, and even no headers at all save material, money, and energy.
Do you even need a header?
The 2015 IRC says, “Load-bearing headers are not required in interior or exterior nonbearing walls. A single flat 2-inch by 4-inch member may be used … for openings up to 8 feet in width” (R602.7.4).
In essence, the code doesn’t require a header unless the end of a floor joist, roof rafter, or truss lands on that wall or there’s a concentrated load bearing over the opening. You don’t even need to install structural jack studs, since there is no load for them to bear.
A header also isn’t required when a window or door is narrow enough to fit between studs on layout. This is more typical with framing on 24-in. centers. Then, when a window is less than 22 in. wide, you don’t need a header; you just install 2x head and sill boards to box out the rough opening.
From Fine Homebuilding #264
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