Select Southern Pine No. 2 and the actual depth for 2x8, 2x10 or 2x12, then select spacing. This is a deck-table lookup, not a species or grade adjustment formula.
The table assumes 40 psf live load, 10 psf dead load, wet service and L/360 deflection. It does not establish floor, roof or other-species spans. Local adoption and the full guide govern connections and overhangs.
Table allowable clear span (feet) from actual joist depth (inches)
| Actual joist depth (inches) | 2x10 |
|---|---|
| Joist spacing (inches) | 16 inches on-center |
| Table allowable clear span (feet) | 14 |
| Table span at 24-inch spacing (feet) | 11.4 |
Common error: Using a rule of thumb for a real structure. A joist that looks strong enough can still bounce or sag, and a failed floor is dangerous.
Joist Span Reference: formula
American Wood Council: Span Options Calculator · AWC DCA 6-2015
Joist Span Reference: changing Actual joist depth (inches)
| Actual joist depth (inches) | Table allowable clear span (feet) | Table span at 24-inch spacing (feet) |
|---|---|---|
| 7.3 | 11.8 | 9.7 |
| 9.3 (example) | 14 | 11.4 |
| 11.3 | 16.5 | 13.5 |
Joist Span Reference: compare input ranges
| Input | Tested from | To | Table allowable clear span (feet): low input | Table allowable clear span (feet): high input | Swing |
|---|---|---|---|---|---|
| Joist spacing (inches) | 12 inches on-center | 24 inches on-center | 16.2 | 11.4 | 4.8 (34%) |
| Actual joist depth (inches) | 2x8 | 2x12 | 11.8 | 16.5 | 4.7 (33%) |
Joist Span Reference: individual input comparisons
| Input | Value | Table allowable clear span (feet) | Table span at 24-inch spacing (feet) |
|---|---|---|---|
| Actual joist depth (inches) | 2x8 | 11.8 | 9.7 |
| 2x10 | 14 | 11.4 | |
| 2x12 | 16.5 | 13.5 | |
| Joist spacing (inches) | 12 inches on-center | 16.2 | 11.4 |
| 16 inches on-center | 14 | 11.4 | |
| 24 inches on-center | 11.4 | 11.4 |
Joist Span Reference: values and definitions
| Quantity and definition | Value used |
|---|---|
| Actual joist depth (inches) — Southern Pine No. 2 only; 2x8, 2x10 or 2x12. | 2x10 |
| Joist spacing (inches) — Select 12, 16 or 24 inches on center. | 16 inches on-center |
| Table allowable clear span (feet) | 14 |
| Table span at 24-inch spacing (feet) | 11.4 |
Read the selected table row before measuring the clear span
The current tool uses DCA 6-2015 Table 2 for Southern Pine No. 2 deck joists, rather than the former depth-times-spacing rule of thumb. A nominal 2x10 has actual depth 9.25 inches.
At 16 inches on center, the selected table gives 14 feet allowable clear span; at 24 inches on center it gives 11 feet 5 inches. Clear span is measured between support faces. The table’s scope includes 40 psf live load, 10 psf dead load, wet service and L/360 deflection.
Those assumptions must match the design being checked. A nominal lumber name alone does not supply species, grade or design load. Use the lumber stamp and the applicable published row; an arbitrary grade multiplier cannot turn this lookup into a table for another species.
A floor, roof or a different deck loading needs the appropriate reference rather than this row. The span result does not settle beam sizing, joist bearing, connections, ledgers, footings or allowed overhangs. Those parts are addressed elsewhere in the guide and applicable code.
Compare the actual support layout with all relevant requirements, including local adoption, before treating a passing clear span as a complete structural design.
This is a lookup for the stated Southern Pine No. 2 deck-joist table. Its 2x10 row allows 14 feet at 16-inch spacing and 11 feet 5 inches at 24-inch spacing under the table’s assumptions.
A depth multiplier is not used to select another species or load.
Look up the span in the code's table for your species, grade and load, and let an engineer or the building department confirm it for anything that bears weight.
Calculate lumber on the board feet calculator, deck parts on the deck material page and framing geometry on the rafter length and stair stringer calculators. The footing size and rebar pages cover foundations, and the rectangle area page gives floor areas.
Can I apply a grade multiplier to this span?
No. Select the applicable published table for the actual lumber and load.
How far can a 2 by 10 joist span?
The permitted span depends on species, grade, spacing, loads, deflection limits and other conditions. Select the exact row in an applicable published span table. A nominal joist size alone is insufficient, and this reference does not approve a structural design.
Should I use span tables or a rule of thumb?
Use the published span tables from the American Wood Council or the building code, since rules of thumb can be off and unsafe.
What does closer joist spacing do?
It increases the span capacity and reduces floor bounce, because each joist carries less of the load.