Lumber & sheet goods
The size printed on lumber is usually its nominal size, not the finished measured size. That difference matters when laying out cuts and estimating quantities.
Quick reference
| Item | Planning data |
|---|---|
| Nominal 2 × 4 | Typically measures about 1½ × 3½ inches after surfacing. |
| Nominal 2 × 6 | Typically measures about 1½ × 5½ inches after surfacing. |
| Nominal 4 × 4 | Typically measures about 3½ × 3½ inches after surfacing. |
| Sheet goods | A common plywood/OSB panel is 4 × 8 ft, or 32 sq ft nominal area; thickness, grade, span rating, and edge details still matter. |
Values marked common or typical are starting points, not a specification. Confirm the actual product data sheet, label, and project documents.
Pressure-treated lumber
Treatment category matters. Above-ground and ground-contact ratings are not interchangeable. Use the treatment level specified for the exposure and application; use compatible fasteners and connectors.
Choosing boards
Sight down each piece and inspect for excessive bow, twist, cup, splits, damaged edges, and large knots in critical locations. Wet treated lumber can shrink and move as it dries.
Plywood vs. OSB
Choose by rated use, thickness, span, exposure classification, and the assembly design—not appearance alone. Roof, wall, and floor sheathing have different requirements.
Common mistakes
Using nominal dimensions in a tight cut list; assuming every treated board is rated for ground contact; ignoring fastener compatibility; and sizing structural members from a generic online chart rather than approved design/code.
Continue planning
Further reading: Manufacturer or industry reference ↗. External guidance may not replace local requirements or product-specific instructions.