What is the maximum span for a single-member header used with floor openings?

What is the maximum span for a single-member header used with floor openings?

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

Answer: (A)

The limit comes from how far a single piece of lumber can span while carrying the loads from the floor above. A single-member header over a floor opening acts like a beam, and bending stress and deflection grow as the span increases. For typical residential floor loads, that safe limit is four feet. If the opening is wider, you’d use a built-up header (two or more members) or add posts to reduce the span so the load can be carried safely to the sides.

The limit comes from how far a single piece of lumber can span while carrying the loads from the floor above. A single-member header over a floor opening acts like a beam, and bending stress and deflection grow as the span increases. For typical residential floor loads, that safe limit is four feet. If the opening is wider, you’d use a built-up header (two or more members) or add posts to reduce the span so the load can be carried safely to the sides.