Span Calculator for Floor Joists - General Cases1,2
Spruce pine fir
Commercial Designation Grade
Maximum Span, ft.-in. (m)3
Joist Size, ft. (m) Joist Spacing, in. (mm) Restraining Method

Spruce pine fir (includes spruce [all species except coast sitka spruce], jack pine, lodgepole pine, balsam fir and alpine fir)

No. 1 and No. 2


Douglas fir larch | Hem fir | Spruce pine fir | Northern species


1. Spans apply only where the floors serve residential areas.

2. Subfloor must comply with minimum requirements from tables 17 and 18.

3. Buttons are in 6 in. (150mm) increments. For a more precise claculation refer to Table 15.