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Joist span tables - use these tables to determine lengths, sizes and spacing of ceiling joists.
Note: Ceiling joists of the first floor of a two-story structure often serve as floor joists for the second floor. If this is the case with your structure, use the Floor Joist Table to determine maximum joist length/load.
For example, the highlighted cell (below) shows that a 2" x 6" Southern Yellow Pine joist, with a grade of #2, and spaced 24" apart can have a maximum span of 10 feet - 0 inches (10-0), if you are designing your structure to support a plaster ceiling.
| Nominal Size | Spacing (o.c.) | Species and Grade of Lumber ( No Attic Storage - Drywall Ceiling) | |||
| Southern Yellow Pine | Southern Yellow Pine | Douglas Fir | Eastern Spruce | ||
| #1 grade (kiln dried) | #2 grade | #2 grade | Structural | ||
| 2" x 4" | 12 | 13-2 | 11-10 | 12-8 | 11-7 |
| 16 | 11-11 | 10-9 | 11-6 | 10-6 | |
| 24 | 10-5 | 9-5 | 9-11 | 9-2 | |
| 2" x 6" | 12 | 20-8 | 18-8 | 19-11 | 18-2 |
| 16 | 18-9 | 16-11 | 18-1 | 16-6 | |
| 24 | 16-4 | 14-2 | 15-7 | 14-5 | |
| 2" x 8" | 12 | 27-2 | 24-7 | 26-2 | 24-0 |
| 16 | 24-8 | 22-4 | 23-10 | 21-9 | |
| 24 | 21-7 | 18-8 | 20-6 | 19-0 | |
| 2" x 10" | 12 | 34-8 | 31-4 | 32-9 | 30-7 |
| 16 | 31-6 | 28-6 | 29-9 | 27-9 | |
| 24 | 27-6 | 23-1 | 26-0 | 24-3 | |
| Nominal Size | Spacing (o.c.) | Species and Grade of Lumber (Limited Attic Storage - Plaster Ceiling) | |||
| Southern Yellow Pine | Southern Yellow Pine | Douglas Fir | Eastern Spruce | ||
| #1 grade (kiln dried) | #2 grade | #2 grade | Structural | ||
| 2" x 4" | 12 | 9-1 | 8-3 | 8-9 | 8-0 |
| 16 | 8-3 | 7-6 | 8-0 | 7-3 | |
| 24 | 7-3 | 6-6 | 7-0 | 6-4 | |
| 2" x 6" | 12 | 14-4 | 12-11 | 13-9 | 12-7 |
| 16 | 13-0 | 11-9 | 12-6 | 11-5 | |
| 24 | 11-4 | 10-0 | 10-11 | 10-0 | |
| 2" x 8" | 12 | 18-10 | 17-0 | 18-2 | 16-7 |
| 16 | 17-2 | 15-6 | 16-6 | 15-1 | |
| 24 | 15-0 | 13-2 | 14-5 | 13-2 | |
| 2" x 10" | 12 | 24-1 | 21-9 | 23-2 | 21-2 |
| 16 | 21-10 | 19-9 | 21-1 | 19-3 | |
| 24 | 19-1 | 16-10 | 18-5 | 16-10 | |
The above spans are based on American Softwood Lumber standard sizes.
** Note: The data in the tables above were obtained from Architectural Drawing and Light Construction by Edward J. Muller.
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