2×4

2×4, or two-by-four, is a widely used size of dimension lumber in North American construction. The name reflects the rough, nominal cross-section before finishing. In actual terms, a standard 2×4 measures roughly 1.5 inches by 3.5 inches (about 38 mm by 89 mm) after milling and drying. Lumber is sold in various lengths, with common stock lengths including 8, 10, 12, 14, and 16 feet.

Most 2×4s are softwood, sourced from species such as pine, spruce, or fir, and are typically kiln-dried to reduce moisture content. For exterior or moisture-prone applications, they may be pressure-treated to resist decay and insect damage. The term “nominal” is used because the finished product is smaller than the rough-cut size.

Uses and standard practice: The 2×4 is primarily used for wall framing, where it serves as vertical studs and as blocking or bracing within stud walls. Spacing and load considerations are governed by building codes and depend on factors such as local climate, load paths, and lumber grade. In addition to framing, 2×4s are employed for non-structural purposes such as shelves, furring, and temporary supports.

Variants and comparisons: While the standard 2×4 remains common, engineered wood products and larger or smaller dimension lumber are used for additional strength or specific design needs. In metric markets, the closest equivalents are often referred to as about 38×89 mm, with some catalogs rounding to 40×90 mm.