Floor Joist Span Tables
Maximum allowable floor joist spans per IRC Table R502.3.1(1) for residential construction. 40 psf live load, 10 psf dead load, L/360 deflection limit. Select your species and grade to find the maximum span for your joist size and spacing.
2x6 Floor Joist Spans
2x6 floor joists handle the shortest spans — typically 9 to 11 feet at 16" o.c. depending on species. Common in additions, closets, walkways, and short bays. For primary living spaces, 2x8 or larger is generally preferred.
| Species & Grade | 12" o.c. | 16" o.c. | 19.2" o.c. | 24" o.c. |
|---|---|---|---|---|
| Douglas Fir-Larch — #1 | 12'-6" | 11'-4" | 10'-8" | 9'-10" |
| Douglas Fir-Larch — #2 | 12'-0" | 10'-11" | 10'-2" | 9'-2" |
| Southern Pine — #1 | 12'-6" | 11'-4" | 10'-8" | 9'-10" |
| Southern Pine — #2 | 11'-10" | 10'-9" | 10'-0" | 9'-0" |
| Hem-Fir — #1 | 11'-10" | 10'-9" | 10'-1" | 9'-4" |
| Hem-Fir — #2 | 11'-3" | 10'-3" | 9'-7" | 8'-8" |
| Spruce-Pine-Fir — #1/#2 | 11'-3" | 10'-3" | 9'-7" | 8'-8" |
2x8 Floor Joist Spans
2x8 floor joists span roughly 12 to 14 feet at 16" o.c. depending on species and grade. Common in additions, smaller rooms, second-story floor framing in tight layouts, and as ceiling joists where loads are lighter.
| Species & Grade | 12" o.c. | 16" o.c. | 19.2" o.c. | 24" o.c. |
|---|---|---|---|---|
| Douglas Fir-Larch — #1 | 16'-6" | 15'-0" | 14'-1" | 13'-0" |
| Douglas Fir-Larch — #2 | 15'-10" | 14'-5" | 13'-5" | 12'-1" |
| Southern Pine — #1 | 16'-6" | 15'-0" | 14'-1" | 13'-0" |
| Southern Pine — #2 | 15'-7" | 14'-2" | 13'-2" | 11'-10" |
| Hem-Fir — #1 | 15'-7" | 14'-2" | 13'-4" | 12'-3" |
| Hem-Fir — #2 | 14'-10" | 13'-6" | 12'-7" | 11'-4" |
| Spruce-Pine-Fir — #1/#2 | 14'-10" | 13'-6" | 12'-7" | 11'-4" |
2x10 Floor Joist Spans
2x10 floor joists at 16" o.c. are the most common residential floor framing configuration — typically spanning 16 to 19 feet depending on species. Sufficient for most rooms without intermediate support.
| Species & Grade | 12" o.c. | 16" o.c. | 19.2" o.c. | 24" o.c. |
|---|---|---|---|---|
| Douglas Fir-Larch — #1 | 21'-0" | 19'-1" | 17'-11" | 16'-6" |
| Douglas Fir-Larch — #2 | 20'-3" | 18'-4" | 17'-0" | 15'-5" |
| Southern Pine — #1 | 21'-0" | 19'-1" | 17'-11" | 16'-6" |
| Southern Pine — #2 | 19'-11" | 18'-0" | 16'-7" | 14'-11" |
| Hem-Fir — #1 | 19'-11" | 18'-1" | 17'-0" | 15'-8" |
| Hem-Fir — #2 | 18'-11" | 17'-2" | 15'-11" | 14'-5" |
| Spruce-Pine-Fir — #1/#2 | 18'-11" | 17'-2" | 15'-11" | 14'-5" |
2x12 Floor Joist Spans
2x12 floor joists handle the longest standard spans — up to about 23 feet at 16" o.c. with the strongest species and grade. Used for great rooms, open floor plans, and anywhere a center beam or post is impractical.
| Species & Grade | 12" o.c. | 16" o.c. | 19.2" o.c. | 24" o.c. |
|---|---|---|---|---|
| Douglas Fir-Larch — #1 | 25'-7" | 23'-3" | 21'-10" | 20'-1" |
| Douglas Fir-Larch — #2 | 24'-7" | 22'-0" | 20'-5" | 18'-9" |
| Southern Pine — #1 | 25'-7" | 23'-3" | 21'-10" | 20'-1" |
| Southern Pine — #2 | 24'-3" | 21'-7" | 19'-7" | 17'-7" |
| Hem-Fir — #1 | 24'-3" | 22'-0" | 20'-8" | 19'-0" |
| Hem-Fir — #2 | 23'-0" | 20'-7" | 19'-1" | 17'-6" |
| Spruce-Pine-Fir — #1/#2 | 23'-0" | 20'-7" | 19'-1" | 17'-6" |
Full Tables by Species & Grade
Douglas Fir-Larch — #1
| Joist Size | 12" o.c. | 16" o.c. | 19.2" o.c. | 24" o.c. |
|---|---|---|---|---|
| 2x6 | 12'-6" | 11'-4" | 10'-8" | 9'-10" |
| 2x8 | 16'-6" | 15'-0" | 14'-1" | 13'-0" |
| 2x10 | 21'-0" | 19'-1" | 17'-11" | 16'-6" |
| 2x12 | 25'-7" | 23'-3" | 21'-10" | 20'-1" |
Douglas Fir-Larch — #2
| Joist Size | 12" o.c. | 16" o.c. | 19.2" o.c. | 24" o.c. |
|---|---|---|---|---|
| 2x6 | 12'-0" | 10'-11" | 10'-2" | 9'-2" |
| 2x8 | 15'-10" | 14'-5" | 13'-5" | 12'-1" |
| 2x10 | 20'-3" | 18'-4" | 17'-0" | 15'-5" |
| 2x12 | 24'-7" | 22'-0" | 20'-5" | 18'-9" |
Southern Pine — #1
| Joist Size | 12" o.c. | 16" o.c. | 19.2" o.c. | 24" o.c. |
|---|---|---|---|---|
| 2x6 | 12'-6" | 11'-4" | 10'-8" | 9'-10" |
| 2x8 | 16'-6" | 15'-0" | 14'-1" | 13'-0" |
| 2x10 | 21'-0" | 19'-1" | 17'-11" | 16'-6" |
| 2x12 | 25'-7" | 23'-3" | 21'-10" | 20'-1" |
Southern Pine — #2
| Joist Size | 12" o.c. | 16" o.c. | 19.2" o.c. | 24" o.c. |
|---|---|---|---|---|
| 2x6 | 11'-10" | 10'-9" | 10'-0" | 9'-0" |
| 2x8 | 15'-7" | 14'-2" | 13'-2" | 11'-10" |
| 2x10 | 19'-11" | 18'-0" | 16'-7" | 14'-11" |
| 2x12 | 24'-3" | 21'-7" | 19'-7" | 17'-7" |
Hem-Fir — #1
| Joist Size | 12" o.c. | 16" o.c. | 19.2" o.c. | 24" o.c. |
|---|---|---|---|---|
| 2x6 | 11'-10" | 10'-9" | 10'-1" | 9'-4" |
| 2x8 | 15'-7" | 14'-2" | 13'-4" | 12'-3" |
| 2x10 | 19'-11" | 18'-1" | 17'-0" | 15'-8" |
| 2x12 | 24'-3" | 22'-0" | 20'-8" | 19'-0" |
Hem-Fir — #2
| Joist Size | 12" o.c. | 16" o.c. | 19.2" o.c. | 24" o.c. |
|---|---|---|---|---|
| 2x6 | 11'-3" | 10'-3" | 9'-7" | 8'-8" |
| 2x8 | 14'-10" | 13'-6" | 12'-7" | 11'-4" |
| 2x10 | 18'-11" | 17'-2" | 15'-11" | 14'-5" |
| 2x12 | 23'-0" | 20'-7" | 19'-1" | 17'-6" |
Spruce-Pine-Fir — #1/#2
| Joist Size | 12" o.c. | 16" o.c. | 19.2" o.c. | 24" o.c. |
|---|---|---|---|---|
| 2x6 | 11'-3" | 10'-3" | 9'-7" | 8'-8" |
| 2x8 | 14'-10" | 13'-6" | 12'-7" | 11'-4" |
| 2x10 | 18'-11" | 17'-2" | 15'-11" | 14'-5" |
| 2x12 | 23'-0" | 20'-7" | 19'-1" | 17'-6" |
How to Read a Joist Span Table
A joist span table tells you the maximum distance a floor joist can span between supports without exceeding code limits for deflection and strength. The span depends on four variables: wood species (determines strength and stiffness), lumber grade (#1 vs #2), joist size (2x8, 2x10, etc.), and spacing (how far apart the joists are).
What the Spans Mean
The span is measured as the clear distance between supports— from the inside face of one bearing wall or beam to the inside face of the next. It does not include the bearing length (typically 1.5" minimum on each end).
Spacing Considerations
- 12" o.c. — Maximum spans, uses more lumber. Good for tile floors or heavy loads.
- 16" o.c. — Standard residential spacing. Best balance of span and material use.
- 19.2" o.c. — Divides a 4x8 sheet into 5 equal bays. Gaining popularity.
- 24" o.c. — Shorter spans, less lumber. Common for roof rafters, not ideal for floors.
Related Resources
- Interactive Joist Span Calculator — select your configuration and check your span
- Tile Deflection Calculator — check if your joists meet L/360 or L/720 for tile
- Beam Calculator — size the beams that support your joists
- Rafter Span Tables — spans for roof rafters