Nominal vs Actual Lumber Dimensions
| Nominal Size | Actual (Dry) | Common Uses | BF per 8' piece |
|---|---|---|---|
| 1ร2 | 3/4" ร 1-1/2" | Furring, nailers, trim | 1.33 |
| 1ร4 | 3/4" ร 3-1/2" | Trim, shelving, casework | 2.67 |
| 1ร6 | 3/4" ร 5-1/2" | Sheathing, shelving, siding | 4.00 |
| 1ร8 | 3/4" ร 7-1/4" | Fascia, shelving, paneling | 5.33 |
| 1ร10 | 3/4" ร 9-1/4" | Shelving, stair risers | 6.67 |
| 1ร12 | 3/4" ร 11-1/4" | Shelving, stair treads | 8.00 |
| 2ร4 | 1-1/2" ร 3-1/2" | Wall studs, blocking, nailers | 5.33 |
| 2ร6 | 1-1/2" ร 5-1/2" | Exterior walls, floor joists, rafters | 8.00 |
| 2ร8 | 1-1/2" ร 7-1/4" | Floor joists, rafters, headers | 10.67 |
| 2ร10 | 1-1/2" ร 9-1/4" | Floor joists, stair stringers | 13.33 |
| 2ร12 | 1-1/2" ร 11-1/4" | Stair stringers, beams | 16.00 |
| 4ร4 | 3-1/2" ร 3-1/2" | Deck posts, fence posts | 10.67 |
| 4ร6 | 3-1/2" ร 5-1/2" | Beams, headers, posts | 16.00 |
| 6ร6 | 5-1/2" ร 5-1/2" | Structural posts, heavy timber | 24.00 |
Floor Joist Span Table โ Douglas Fir-Larch #2 @ 16" O.C.
โ Values below are reference spans for Douglas Fir-Larch #2 at 16" OC with L/360 deflection limit (live load) and 40 psf live + 10 psf dead. Always verify with the current IRC span tables or a structural engineer for your specific species, grade, and loading.
| Joist Size | Spacing 12" OC | Spacing 16" OC | Spacing 19.2" OC | Spacing 24" OC |
|---|---|---|---|---|
| 2ร6 | 10'-9" | 9'-9" | 9'-3" | 8'-6" |
| 2ร8 | 14'-2" | 12'-10" | 12'-3" | 11'-3" |
| 2ร10 | 18'-0" | 16'-5" | 15'-7" | 14'-4" |
| 2ร12 | 21'-9" | 19'-10" | 18'-10" | 17'-4" |
Rafter Span Table โ Douglas Fir-Larch #2 @ 16" O.C. (20 psf snow)
| Rafter Size | Spacing 12" OC | Spacing 16" OC | Spacing 24" OC |
|---|---|---|---|
| 2ร6 | 14'-5" | 13'-1" | 11'-5" |
| 2ร8 | 19'-0" | 17'-3" | 15'-1" |
| 2ร10 | 24'-4" | 22'-1" | 19'-3" |
| 2ร12 | 29'-5" | 26'-9" | 23'-4" |
Stud Spacing & Wall Height Guide
| Stud Size | Typical Spacing | Max Wall Height | Notes |
|---|---|---|---|
| 2ร4 | 16" OC | 10'-0" | Standard interior, non-bearing exterior in mild climate |
| 2ร4 | 24" OC | 8'-0" | Non-bearing partition walls only |
| 2ร6 | 16" OC | 14'-0" | Exterior walls (energy code), tall walls |
| 2ร6 | 24" OC | 10'-0" | Advanced framing / OVE (Optimum Value Engineering) |
Stud Count Formula: (Wall Length รท Stud Spacing) + 1, then add 3 for each corner, 2 for each T-intersection, and 2 for each window or door rough opening. Add 10โ15% waste.