Deck Joist Cantilever Rules and Limits
The distance your joists can safely cantilever or overhang a drop beam is determined by the size of the joists, the wood type and grade of the lumber and the spacing between joists. Many building departments limit joist cantilevers to 24" maximum. You must use at least five framing nails to attach the rim joist to the ends of your joists.
The American Wood Council states that cantilevers are limited to 1/4 the span of the joists.
| Joist Spacing (o.c.) | 12" | 16" | 24" | |
|---|---|---|---|---|
| Species | Size | Allowable Overhang | ||
| Southern Pine | 2x6 | 1'-0" | 1'-1" | 1'-4" |
| 2x8 | 1'-10" | 2'-0" | 2'-4" | |
| 2x10 | 3'-1" | 3'-5" | 2'-10" | |
| 2x12 | 4'-6" | 4'-2" | 3'-4" | |
|
Douglas Fir-Larch, Hem-Fir, Spruce-Pine-Fir |
2x6 | 11" | 1'-0" | 1'-2" |
| 2x8 | 1'-8" | 1'-10" | 2'-2" | |
| 2x10 | 2'-10" | 3'-2" | 2'-9" | |
| 2x12 | 4'-4" | 3'-11" | 3'-3" | |
|
Redwood, Western Cedars, Poderosa Pine, Red Pine |
2x6 | 9" | 10" | 11" |
| 2x8 | 1'-5" | 1'-7" | 1'-9" | |
| 2x10 | 2'-5" | 2'-7" | 2'-8" | |
| 2x12 | 3'-7" | 3'-9" | 3'-1" | |
Maximum allowable overhang cannot exceed 1/4 of the actual main span.
