When framing openings in floors with a header and trimmer joists, what maximum header joist span is allowed with a single member header?

When framing openings in floors with a header and trimmer joists, what maximum header joist span is allowed with a single member header?

• A. 4 feet
• B. 7 feet
• C. 6 feet
• D. 5 feet

Answer: (A)

When framing a floor opening, the header carries the load of the joists that span the opening. A single member header has limited bending strength, so its span must be kept short. The prescriptive allowance for a single-member header under floor loads is four feet. If the opening is larger, you’d need a built-up header (two or more members) or additional supports to safely transfer the load. That’s why longer spans like five, six, or seven feet aren’t permitted with a single header.

When framing a floor opening, the header carries the load of the joists that span the opening. A single member header has limited bending strength, so its span must be kept short. The prescriptive allowance for a single-member header under floor loads is four feet. If the opening is larger, you’d need a built-up header (two or more members) or additional supports to safely transfer the load. That’s why longer spans like five, six, or seven feet aren’t permitted with a single header.