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A deck joist carries a heavier design load than an interior floor joist — 40 psf live plus 10 psf dead, in wet outdoor service — so it spans shorter than the floor-joist tables for the same board. The chart below has the maximum joist span for every combination of nominal size, species group and spacing, read from AWC DCA6-2015 Table 2 and cross-checked against IRC 2021 Table R507.6. Each figure is the No. 2 grade value at an L/360 deflection limit, with a separate column for the maximum cantilever past the beam.
Filter by species, size or spacing, sort any column, and hover a chart point for its exact span.
Deck joists carry a heavier design load than an interior floor — 40 psf live plus 10 psf dead, in wet outdoor service — so their allowable spans are shorter than the floor-joist tables for the same lumber. Every span below is the No. 2 grade figure from the deck code, at an L/360 deflection limit.
| Species Group | Nominal Size | Spacing | Max Joist Span | Max Overhang | Load Basis |
|---|---|---|---|---|---|
| Southern Pine | 2x6 | 12″ | 9'-11" | 1'-0" | 40 + 10 psf |
| Southern Pine | 2x6 | 16″ | 9'-0" | 1'-1" | 40 + 10 psf |
| Southern Pine | 2x6 | 24″ | 7'-7" | 1'-3" | 40 + 10 psf |
| Southern Pine | 2x8 | 12″ | 13'-1" | 1'-10" | 40 + 10 psf |
| Southern Pine | 2x8 | 16″ | 11'-10" | 2'-0" | 40 + 10 psf |
| Southern Pine | 2x8 | 24″ | 9'-8" | 2'-4" | 40 + 10 psf |
| Southern Pine | 2x10 | 12″ | 16'-2" | 3'-1" | 40 + 10 psf |
| Southern Pine | 2x10 | 16″ | 14'-0" | 3'-5" | 40 + 10 psf |
| Southern Pine | 2x10 | 24″ | 11'-5" | 2'-10" | 40 + 10 psf |
| Southern Pine | 2x12 | 12″ | 18'-0" | 4'-6" | 40 + 10 psf |
| Southern Pine | 2x12 | 16″ | 16'-6" | 4'-2" | 40 + 10 psf |
| Southern Pine | 2x12 | 24″ | 13'-6" | 3'-4" | 40 + 10 psf |
| Douglas Fir-Larch / Hem-Fir / SPF | 2x6 | 12″ | 9'-6" | 0'-11" | 40 + 10 psf |
| Douglas Fir-Larch / Hem-Fir / SPF | 2x6 | 16″ | 8'-4" | 1'-0" | 40 + 10 psf |
| Douglas Fir-Larch / Hem-Fir / SPF | 2x6 | 24″ | 6'-10" | 1'-2" | 40 + 10 psf |
| Douglas Fir-Larch / Hem-Fir / SPF | 2x8 | 12″ | 12'-6" | 1'-8" | 40 + 10 psf |
| Douglas Fir-Larch / Hem-Fir / SPF | 2x8 | 16″ | 11'-1" | 1'-10" | 40 + 10 psf |
| Douglas Fir-Larch / Hem-Fir / SPF | 2x8 | 24″ | 9'-1" | 2'-2" | 40 + 10 psf |
| Douglas Fir-Larch / Hem-Fir / SPF | 2x10 | 12″ | 15'-8" | 2'-10" | 40 + 10 psf |
| Douglas Fir-Larch / Hem-Fir / SPF | 2x10 | 16″ | 13'-7" | 3'-2" | 40 + 10 psf |
| Douglas Fir-Larch / Hem-Fir / SPF | 2x10 | 24″ | 11'-1" | 2'-9" | 40 + 10 psf |
| Douglas Fir-Larch / Hem-Fir / SPF | 2x12 | 12″ | 18'-0" | 4'-4" | 40 + 10 psf |
| Douglas Fir-Larch / Hem-Fir / SPF | 2x12 | 16″ | 15'-9" | 3'-11" | 40 + 10 psf |
| Douglas Fir-Larch / Hem-Fir / SPF | 2x12 | 24″ | 12'-10" | 3'-3" | 40 + 10 psf |
| Redwood / Western Cedars | 2x6 | 12″ | 8'-10" | 0'-9" | 40 + 10 psf |
| Redwood / Western Cedars | 2x6 | 16″ | 8'-0" | 0'-10" | 40 + 10 psf |
| Redwood / Western Cedars | 2x6 | 24″ | 6'-10" | 0'-11" | 40 + 10 psf |
| Redwood / Western Cedars | 2x8 | 12″ | 11'-8" | 1'-5" | 40 + 10 psf |
| Redwood / Western Cedars | 2x8 | 16″ | 10'-7" | 1'-7" | 40 + 10 psf |
| Redwood / Western Cedars | 2x8 | 24″ | 8'-8" | 1'-9" | 40 + 10 psf |
| Redwood / Western Cedars | 2x10 | 12″ | 14'-11" | 2'-5" | 40 + 10 psf |
| Redwood / Western Cedars | 2x10 | 16″ | 13'-0" | 2'-7" | 40 + 10 psf |
| Redwood / Western Cedars | 2x10 | 24″ | 10'-7" | 2'-8" | 40 + 10 psf |
| Redwood / Western Cedars | 2x12 | 12″ | 17'-5" | 3'-7" | 40 + 10 psf |
| Redwood / Western Cedars | 2x12 | 16″ | 15'-1" | 3'-9" | 40 + 10 psf |
| Redwood / Western Cedars | 2x12 | 24″ | 12'-4" | 3'-1" | 40 + 10 psf |
Spans are the clear distance between supports for No. 2 grade lumber; a higher grade or a snow-load region changes the figure. The overhang column is the maximum cantilever past the outer beam, itself capped at one quarter of the backspan. Douglas Fir-Larch, Hem-Fir and Spruce-Pine-Fir are tabulated together with an incising factor assumed.
Every span assumes a 40 psf live plus 10 psf dead deck load, No. 2 grade sawn lumber, wet-service (outdoor) conditions and an L/360 deflection limit — the basis stated in AWC DCA6-2015 and adopted verbatim into IRC 2021 Table R507.6. Southern Pine spans longest; the low-density redwood and western-cedar group spans shortest. These are prescriptive maximums, not an engineered design.
- AWC DCA6-2015, Prescriptive Residential Wood Deck Construction Guide — Table 2, Maximum Joist Spans and OverhangsAmerican Wood CouncilPrimary source. Every span and overhang value above is transcribed from Table 2, including the footnotes: 40 psf live / 10 psf dead, No. 2 grade, wet service, L/360, and overhang capped at one quarter of the actual span.
- IRC 2021 Table R507.6, Deck Joist Spans for Common Lumber SpeciesInternational Code Council · via UpCodesThe code-adopted version of the DCA6 table; confirms the 40 + 10 psf load basis and L/360 deflection, and the Southern Pine and Douglas Fir-Larch spans checked cell-for-cell against DCA6.
- Deck Joist Sizing and SpacingDecks.comSecondary corroboration for the incised Douglas Fir-Larch / Hem-Fir / SPF 2x6 spans, which some non-incised transcriptions list slightly longer.
- How Far Can Deck Joists Cantilever?Fine HomebuildingContext for the overhang column: the 2021 IRC treats the cantilever as a separate backspan lookup rather than a reduced joist span.
Values were read directly from the AWC DCA6-2015 PDF (Table 2) and cross-checked cell-for-cell against IRC 2021 Table R507.6 on UpCodes. Feet-inches were converted to decimal feet only for sorting and for plotting the chart; the displayed values are the exact tabulated figures. No span was interpolated, averaged, or carried over from an interior floor-joist table.
Three 2x6 cells are disputed across transcriptions: the Douglas Fir-Larch group at 16″ (8 ft 4 in here) and 24″ (6 ft 10 in), and the redwood group at 24″ (6 ft 10 in). This page uses the incised DCA6-2015 values; non-incised transcriptions of R507.6 list these slightly longer (8 ft 8 in, 7 ft 2 in, 7 ft 0 in). Beam spans, ledger sizing, footing size and guard-post framing are separate DCA6 / R507 tables and are out of scope here. Spans assume No. 2 grade; Select Structural or No. 1 lumber, ground-snow-load regions, and engineered (non-prescriptive) designs will differ. Local code amendments always control over any national table.