Feature
A Southern Pine 2x8 deck joist spans 13 ft 1 in at 12 inches on center, dropping to 9 ft 8 in at 24 inches.
The maximum span for a deck joist by lumber size, species group and on-center spacing, transcribed from the AWC DCA6 and IRC R507.6 deck-load span tables.
By Errol Nakamura · filed · revised — · 1 min
Codes are local and manufacturers publish their own limits. Confirm any figure here against your local authority and the printed instructions on the bag, box or panel before you buy or build.
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.