Joist Span Calculator

Find maximum allowable joist spans by size, spacing, species, and grade. Covers floor and ceiling joists.

πŸ“ Joist Span Calculator

Results

Joist Size2x10
Max Span (SPF #2)16.0 ft
Adjusted Span16.0 ft

πŸ’‘ How to Determine Joist Span

Maximum joist span depends on four factors: lumber size, spacing, species/grade, and the type of load (floor vs. ceiling). Floor joists carry heavier live loads (40 psf residential) than ceiling joists (20 psf, no attic storage). Larger joists at closer spacing span farther.

Standard SPF #2 at 16" OC: 2Γ—6 spans 9.5 ft (floor) or 12.5 ft (ceiling). 2Γ—8 spans 12.5 ft (floor). 2Γ—10 spans 16 ft (floor). 2Γ—12 spans 19 ft (floor). Higher grades (Select Structural, #1) allow 5–10% longer spans.

2Γ—10 SPF #2 at 16" OC: max floor span = 16 ft. At 12" OC, span increases to 17.5 ft. At 24" OC, span decreases to 13 ft. Always verify with your local building code.

Joist Span Calculator FAQ

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