Wood species and grade
Southern pine No. 2
Douglas fir-larch No. 2
Hem-fir No. 2
Spruce-pine-fir No. 2
Western cedars No. 2
Rafter size
2×4
2×6
2×8
2×10
2×12
Spacing
12 in on center
16 in on center
19.2 in on center
24 in on center
Roof load
20 psf roof live load (no snow)
30 psf ground snow
50 psf ground snow
70 psf ground snow
Dead load
10 psf (asphalt shingles)
15 psf (heavier roofing)
20 psf (tile or slate)
Ceiling
Ceiling attached (L/240)
No ceiling (L/180)
Your span to check (optional)
Rafter span calculator ·
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