Species spread — the same #2 2×10 in Douglas fir-larch, SPF, Hem-fir, and Southern pine
The same #2 2×10 @ 16″ o.c. (40/10 psf, L/360): Douglas fir-larch 15′-7″, SPF 15′-5″, Hem-fir 15′-2″, Southern pine 14′-0″ — a spread of only ~1′-7″. SP’s post-June-2013 SPIB values ended its old lead: at #2 it now trails. Species moves spans by inches; depth and spacing move them by feet.
What this diagram shows
A bar chart comparing the maximum floor-joist span of the identical joist — number-2 grade 2-by-10 at 16 inches on center, 40 psf live and 10 psf dead load, deflection limit L/360, the IRC Table R502.3.1(2) case — across the four framing species sold in the US. Douglas fir-larch spans 15 feet 7 inches, spruce-pine-fir 15 feet 5 inches, hem-fir 15 feet 2 inches, and Southern pine 14 feet 0 inches. The full spread is only about 1 foot 7 inches. Southern pine carries a flag: its design values were re-established by SPIB effective June 2013 with size-specific bending values, so older tables that showed Southern pine leading the pack are out of date — at number-2 grade it now trails the other species. The takeaway: species shifts a span by inches, while joist depth and spacing shift it by feet.
Joist Span Calculator
Free joist span calculator: max spans for floor and deck joists by species, grade, size, and spacing per IRC R502.3.1 and R507.6. No signup.
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