Deck Joist Span Calculator
Southern pine 2x8 joists at 16 inches on center span 11'-10" on DCA 6 Table 2. The table overhang on that row is 2'-0".
Joist cells read on from the DCA 6 deck-guide file. Opening choice is southern pine, 2x8, 16 in. The actual-span box starts empty.
A deck joist span calculator and deck joist span chart for the maximum clear span and the overhang column. Spacing is 12, 16, or 24 inches. The chart below is Table 2, cell for cell.
Board and fastener counts for a deck you already framed: deck calculator. The beam those joists land on: deck beam span calculator.
Deck joist span and overhang
DCA 6 Table 2 is a deck joist table. It is not an interior floor-joist table. The span is the clear distance between supports and does not include the overhang. The overhang you build is the shorter of the table overhang and one quarter of the span you actually build.
Results
Advertisement
Table 2, maximum joist spans and overhangs
Source: American Wood Council, Prescriptive Residential Wood Deck Construction Guide, DCA 6, based on the 2015 International Residential Code. Table 2 is on guide page 4. Footnote 1 pairs a live load of 40 psf with a dead load of 10 psf, at No. 2 grade, in wet service. Footnote 2 says the span uses L/360. Footnote 3 says the overhang cannot exceed L/4, or one quarter of the actual main span, and assumes cantilever length/180 with a 220 lb point load.
Each species block is one row group in the guide. One block is DF-Larch, and hem-fir plus spruce-pine-fir sit in that same block. Footnote 4 says incising is assumed there. The closing block is redwood alongside western cedars, with ponderosa pine and red pine included. Footnote 5 says that block uses northern species and skips incising. A 2x6 cell carries footnote 6. Both 18'-0" span cells at 12 inch spacing carry footnote 7, a footing-design cap.
Southern Pine
| Joist | Span 12" | Span 16" | Span 24" | Overhang 12" | Overhang 16" | Overhang 24" |
|---|---|---|---|---|---|---|
| 2x6 (note 6) | 9'-11" | 9'-0" | 7'-7" | 1'-0" | 1'-1" | 1'-3" |
| 2x8 | 13'-1" | 11'-10" | 9'-8" | 1'-10" | 2'-0" | 2'-4" |
| 2x10 | 16'-2" | 14'-0" | 11'-5" | 3'-1" | 3'-5" | 2'-10" |
| 2x12 | 18'-0" (note 7) | 16'-6" | 13'-6" | 4'-6" | 4'-2" | 3'-4" |
DF-Larch with hem-fir and spruce-pine-fir
| Joist | Span 12" | Span 16" | Span 24" | Overhang 12" | Overhang 16" | Overhang 24" |
|---|---|---|---|---|---|---|
| 2x6 (note 6) | 9'-6" | 8'-4" | 6'-10" | 0'-11" | 1'-0" | 1'-2" |
| 2x8 | 12'-6" | 11'-1" | 9'-1" | 1'-8" | 1'-10" | 2'-2" |
| 2x10 | 15'-8" | 13'-7" | 11'-1" | 2'-10" | 3'-2" | 2'-9" |
| 2x12 | 18'-0" (note 7) | 15'-9" | 12'-10" | 4'-4" | 3'-11" | 3'-3" |
Redwood with western cedars, ponderosa pine, red pine
| Joist | Span 12" | Span 16" | Span 24" | Overhang 12" | Overhang 16" | Overhang 24" |
|---|---|---|---|---|---|---|
| 2x6 (note 6) | 8'-10" | 8'-0" | 6'-10" | 0'-9" | 0'-10" | 0'-11" |
| 2x8 | 11'-8" | 10'-7" | 8'-8" | 1'-5" | 1'-7" | 1'-9" |
| 2x10 | 14'-11" | 13'-0" | 10'-7" | 2'-5" | 2'-7" | 2'-8" |
| 2x12 | 17'-5" | 15'-1" | 12'-4" | 3'-7" | 3'-9" | 3'-1" |
Commentary Table C2 reprints the same overhangs and says shading, which this page does not copy, marks the cells where deflection controls. The numbers themselves are the Table 2 overhangs. Some 24 inch overhangs are shorter than the 16 inch overhang on the same size. That is the printed cell, including southern pine 2x10: 3'-5" at 16 inches and 2'-10" at 24 inches.
Advertisement
Worked lookups
- Southern pine, 2x8, 16 in, no built span typed: span 11'-10", overhang 2'-0".
- DF-Larch group (hem-fir and spruce-pine-fir share it), 2x10, 16 in: span 13'-7", overhang 3'-2".
- Southern pine, 2x12, 12 in, with a 12 ft span typed: table overhang 4'-6", one quarter is 3'-0", so the shorter overhang is 3'-0". 12 × 12 = 144 inches, and 144 ÷ 4 = 36 inches, which is 3'-0". The table overhang is 54 inches, so 36 inches governs.
What this chart is not
The guide’s opening limits it to single-level residential wood decks. Where the guide and the IRC differ, the IRC applies, and the authority having jurisdiction approves the work. Do not read an interior floor span, a roof rafter span, or a manufactured I-joist span out of Table 2. Counting how many joists fit across a deck you have already sized is the deck board page.
Deck joist span questions
What span does southern pine 2x8 at 16 inches get?
Leave species on Southern Pine, size on 2x8, and spacing on 16 in. Leave the actual-span box empty. Allowable span reads 11'-10". Table overhang reads 2'-0". One quarter of your span reads Enter the span you will build. Shorter overhang reads Enter the span you will build.
What does the Douglas fir group list for a 2x10 at 16 inches?
Set the species group to DF-Larch with hem-fir and spruce-pine-fir, size to 2x10, and spacing to 16 in. Allowable span reads 13'-7". Table overhang reads 3'-2". The note mentions footnote 4, incising assumed for that group.
How does a 12 foot built span change the 2x12 overhang?
Set Southern Pine, 2x12, and 12 in spacing. Type 12 in the actual-span box and leave the unit on ft. Allowable span reads 18'-0". Table overhang reads 4'-6". One quarter of your span reads 3'-0". Shorter overhang reads 3'-0". The note includes footnote 7 because that cell is the 18 foot footing cap.
Why is a 2x6 called out separately?
Set Redwood with western cedars, ponderosa pine, red pine, size 2x6, spacing 24 in. Allowable span reads 6'-10". Table overhang reads 0'-11". The note adds footnote 6: the ledger is at least 2x8 nominal, and any joist or rim that carries a guard post is at least 2x8 nominal. Footnote 5 also applies: northern species values, no incising.
Can this table size a floor joist inside the house?
No. Table 2 is in the American Wood Council deck guide that is based on the 2015 IRC. The loads are 40 psf live and 10 psf dead, wet service, No. 2 grade. An interior floor uses a different span table. The adopted code and the local inspector govern the deck.
Where does the one-quarter limit come from?
The joist-size section says the overhang length is the lesser of the allowable overhang, LO, or one fourth of the joist span, L/4. The span itself is measured from support face to support face and does not include the overhang. Leave the optional box blank and the panel reports only the table overhang.