Header Span Chart — IRC R602.7(1) Built-Up Header Spans & Jack Studs
Exterior bearing-wall header spans from 2021 IRC Table R602.7(1): 2- and 3-ply 2x6–2x12 built-up headers with jack stud counts at 12/24/36 ft building widths.
Updated August 20, 2026
Built-up dimension-lumber headers over doors and windows in exterior bearing walls are sized from 2021 IRC Table R602.7(1), and the block tabulated below is its most-used slice: a header supporting a roof and ceiling only, at 30 psf ground snow load (the same column also covers lower snow loads where the roof live load is 20 psf or less). Spans are based on the minimum design properties of No. 2 grade Douglas fir-larch, hem-fir, southern pine, and spruce-pine-fir, so the table is species-independent. Building width is measured perpendicular to the ridge — a wider building sends more roof load to the wall, so the same header spans less — and widths between the 12, 24, and 36 ft columns may be interpolated per the table footnote.
NJ is the number of jack (trimmer) studs required under each end of the header; where the table prints NJ = 1, an approved framing anchor attached to the full-height stud may substitute for the jack. The published table has no 3-ply 2×6 row — step to a 2-ply 2×6 or a 3-ply 2×8 instead. Two caveats ride every row: the spans assume the top of the header is laterally braced by perpendicular framing (unbraced 2×8–2×12 headers must be multiplied by 0.70 or engineered), and headers carrying a floor above or heavier snow belong to other blocks of the full code table. Both tables below are generated from the same encoded Table R602.7(1) the header span calculator reads, so chart and tool can never drift apart.
2-ply (double) Built-Up Headers — Roof & Ceiling, 30 psf Ground Snow
| Header | Span @ 12 ft width | NJ @ 12 ft | Span @ 24 ft width | NJ @ 24 ft | Span @ 36 ft width | NJ @ 36 ft |
|---|---|---|---|---|---|---|
| 2-2x6 | 6 ft 0 in | 1 | 4 ft 7 in | 1 | 3 ft 10 in | 1 |
| 2-2x8 | 7 ft 7 in | 1 | 5 ft 9 in | 1 | 4 ft 10 in | 2 |
| 2-2x10 | 9 ft 0 in | 1 | 6 ft 10 in | 2 | 5 ft 9 in | 2 |
| 2-2x12 | 10 ft 7 in | 2 | 8 ft 1 in | 2 | 6 ft 10 in | 2 |
Spans per 2021 IRC Table R602.7(1), roof-and-ceiling loading, 30 psf ground snow, No. 2 grade lumber. NJ = jack studs required at each end; where NJ = 1 an approved framing anchor may substitute. Building width is measured perpendicular to the ridge.
3-ply (triple) Built-Up Headers — Roof & Ceiling, 30 psf Ground Snow
| Header | Span @ 12 ft width | NJ @ 12 ft | Span @ 24 ft width | NJ @ 24 ft | Span @ 36 ft width | NJ @ 36 ft |
|---|---|---|---|---|---|---|
| 3-2x8 | 9 ft 5 in | 1 | 7 ft 3 in | 1 | 6 ft 1 in | 1 |
| 3-2x10 | 11 ft 3 in | 1 | 8 ft 7 in | 1 | 7 ft 3 in | 2 |
| 3-2x12 | 13 ft 2 in | 1 | 10 ft 1 in | 2 | 8 ft 6 in | 2 |
Spans per 2021 IRC Table R602.7(1), roof-and-ceiling loading, 30 psf ground snow, No. 2 grade lumber. NJ = jack studs required at each end; where NJ = 1 an approved framing anchor may substitute. Building width is measured perpendicular to the ridge.
Sources & Further Reading
- 2021 International Residential Code, Table R602.7(1) — Girder and Header Spans for Exterior Bearing Walls (roof-and-ceiling block, 30 psf ground snow), as encoded and verified in the header span calculator
- UpCodes reproduction of 2021 IRC Table R602.7(1) (Connecticut State Building Code viewer) and the City of Waterloo, IA "Residential Headers — Section R602.7, 2021 IRC" handout — two independent reproductions, every span and jack-stud cell re-verified against both
Frequently Asked Questions
What size header do I need for a 6-foot window opening?
In a 24 ft wide building with the header carrying roof and ceiling at 30 psf ground snow, Table R602.7(1) allows a 2-ply 2×10 to span 6 ft 10 in (NJ = 2) — the smallest 2-ply header that clears 6 ft. A 3-ply 2×8 also works at 7 ft 3 in and needs only one jack stud per end.
What does NJ mean in the header table?
NJ is the number of jack studs — the trimmers under each end of the header that carry its reaction down to the plate. Where the table prints NJ = 1, the code lets an approved framing anchor attached to the full-height wall stud substitute for the jack stud.
Why does building width change the allowable header span?
Building width is measured perpendicular to the ridge and sets the roof tributary load on the wall: a 36 ft deep house delivers three times the tributary width of a 12 ft one, so the same 2-2×12 header drops from 10 ft 7 in of span at 12 ft width to 6 ft 10 in at 36 ft. Widths between columns may be interpolated per the table footnote.
Does this table cover headers under a second floor?
No. The block tabulated here is the roof-and-ceiling loading condition at 30 psf ground snow only. Headers supporting a floor above, a center-bearing girder, or heavier snow loads use other blocks of the full Table R602.7(1) rosters — and spans there are substantially shorter. Unbraced 2×8–2×12 headers must also be reduced by the 0.70 factor or engineered.
Try the Calculators
Header Span Chart — IRC R602.7(1) Built-Up Header Spans & Jack Studs — reuven.tools/reference/header-spans — verified against: 2021 International Residential Code, Table R602.7(1) — Girder and Header Spans for Exterior Bearing Walls (roof-and-ceiling block, 30 psf ground snow), as encoded and verified in the header span calculator; UpCodes reproduction of 2021 IRC Table R602.7(1) (Connecticut State Building Code viewer) and the City of Waterloo, IA "Residential Headers — Section R602.7, 2021 IRC" handout — two independent reproductions, every span and jack-stud cell re-verified against both