Plywood & OSB Panel Thicknesses (DOC PS 1 / PS 2)
Direct Answer
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).
Source: DOC PS 1-19 / DOC PS 2-18 (APA The Engineered Wood Association)
Specs
| 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) |
Performance Category Decimal Thicknesses
Under modern building codes, structural panels are labeled with a Performance Category (PERF CAT) rather than a fractional thickness. Sanding and compression during hot-press veneer bonding reduce panel thickness by approximately $1/32\text{ inch}$ ($0.031\text{ in}$) below historical fractions:
- $1/2\text{ Performance Category}$ $\rightarrow$ $15/32\text{ inch}$ ($0.469\text{ in}$)
- $5/8\text{ Performance Category}$ $\rightarrow$ $19/32\text{ inch}$ ($0.594\text{ in}$)
- $3/4\text{ Performance Category}$ $\rightarrow$ $23/32\text{ inch}$ ($0.719\text{ in}$)
APA Span Ratings and Tongue & Groove (T&G) Subflooring
APA stamps feature a two-number Span Rating (e.g., 32/16 or 48/24):
- The first number indicates the maximum allowable roof rafter/truss spacing in inches ($32\text{ in}$).
- The second number indicates the maximum floor joist spacing in inches ($16\text{ in}$).
For subflooring, $23/32\text{-inch}$ Tongue & Groove (T&G) panels feature profiled interlocking edge joints along the $8\text{-foot}$ sides that transfer wheel and foot loads between joists without edge deflection or squeaking.