Dimensional Lumber vs. Plywood & OSB Panels
Comparing 2 standards across 17 specifications. 17 key differences identified.
Dimensional lumber sizes under the American Softwood Lumber Standard (DOC PS 20) define the difference between rough-sawn 'nominal' green lumber designations and finished 'actual' Surfaced 4-Sides (S4S) dry dimensions. A standard 2×4 measures exactly 1.5 × 3.5 inches (38 × 89 mm) following planing and kiln drying.
Structural wood panels including softwood plywood and Oriented Strand Board (OSB) are standardized under Voluntary Product Standards DOC PS 1 and PS 2. Sized in standard 4×8 ft (1219×2438 mm) sheets, panels are classified by 'Performance Category' thickness with a -1/32" decimal reduction, where a nominal 1/2" panel measures 15/32" (0.469" / 11.9 mm).
Specification Comparison Table
17 Parameters| Parameter / Spec | ||
|---|---|---|
|
Governing Standard
|
DOC PS 20-20 / NIST / American Lumber Standard Committee (ALSC) | — |
|
Surfacing Condition
|
S4S (Surfaced 4 Sides) Kiln-Dried (KD19, moisture content ≤19%) | — |
|
2×4 Actual Dimensions
|
1.5 × 3.5 inches (38 × 89 mm) | — |
|
2×6 Actual Dimensions
|
1.5 × 5.5 inches (38 × 140 mm) | — |
|
2×8 Actual Dimensions
|
1.5 × 7.25 inches (38 × 184 mm) | — |
|
2×10 Actual Dimensions
|
1.5 × 9.25 inches (38 × 235 mm) | — |
|
2×12 Actual Dimensions
|
1.5 × 11.25 inches (38 × 286 mm) | — |
|
4×4 Actual Dimensions
|
3.5 × 3.5 inches (89 × 89 mm) | — |
|
6×6 Actual Dimensions
|
5.5 × 5.5 inches (140 × 140 mm) | — |
|
Governing Standards
|
— | DOC PS 1 (Plywood) / DOC PS 2 (OSB) / APA PR-N108 |
|
Standard Sheet Dimensions
|
— | 4 × 8 feet (48.0 × 96.0 inches / 1219 × 2438 mm) |
|
Metric Sheet Dimensions
|
— | 1220 × 2440 mm (European & Asian standard) |
|
1/4" Category Thickness
|
— | 15/64 inch (0.234" / 5.95 mm) | Underlayment |
|
3/8" Category Thickness
|
— | 11/32 inch (0.344" / 8.73 mm) | Wall sheathing |
|
1/2" Category Thickness
|
— | 15/32 inch (0.469" / 11.91 mm) | Standard roof sheathing |
|
5/8" Category Thickness
|
— | 19/32 inch (0.594" / 15.08 mm) | Heavy-duty roof / subfloor |
|
3/4" Category Thickness
|
— | 23/32 inch (0.719" / 18.26 mm) | Standard subfloor (T&G) |