The schedule gives allowable clear spans for this loading of 5 feet 2 inches for a two-ply 2x10, 6 feet 5 inches for a three-ply 2x10 and 7 feet 4 inches for a four-ply 2x10. The clear opening between jack studs measures 6 feet 8 inches. Which header satisfies the schedule?
- AA two-ply 2x10 header
Two plies allow 5 feet 2 inches, a foot and a half less than the opening. This is the answer reached by comparing against the wrong row or by picking the smallest header in the schedule.
- BA three-ply 2x10 header
Three plies allow 6 feet 5 inches against a 6 feet 8 inch opening. It is short by 3 inches, which is the classic near-miss error from rounding the opening down to the nearest half foot.
- CTwo 2x10 plies with a plywood spacer between them
A plywood spacer makes the assembly the right thickness for the wall cavity, nothing more. Filler material is not a structural ply and does not change the allowable span in the schedule.
- A four-ply 2x10 header
Why D is correct
The opening measures 6 feet 8 inches, or 80 inches. The two-ply row allows 62 inches and the three-ply row 77 inches, both short of the opening. The four-ply row allows 88 inches, so it is the first header in the schedule with an allowable span greater than the clear opening.
What this question is testing
Whether the candidate can read a header schedule row by row, compares the measured clear span against the allowable span in consistent units, and knows that non-structural filler does not add capacity.
On the job
Header schedules get read dozens of times on a framing inspection, and errors cluster at openings that fall just past a row boundary. Framers order headers by opening size early in the job and then a window changes. Inspectors measure the clear distance between the jack studs, not the window unit size and not the rough opening callout on the plan, because the schedule is written in clear span.
Memory technique
Plywood spacers fill space, not spans.
Exam tip
Convert both numbers to inches before comparing, and measure between the jacks.
Where to look it up
IRC Chapter 6, wood wall framing, headers, together with the header schedule on the approved plans.