Dimensional Lumber vs. Glulam Timber Beams
Comparing 2 standards across 16 specifications. 16 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 Glued Laminated Timber (Glulam) under ANSI A190.1 is an engineered heavy timber beam manufactured by face-bonding individual 2x softwood dimensional lumber laminations with structural adhesives. Featuring standardized widths of 3-1/8", 5-1/8", and 6-3/4" and depths in 1.5-inch increments, Glulam beams support spans exceeding 100 feet.
Specification Comparison Table
16 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
|
— | ANSI A190.1 / ASTM D3737 / APA EWS S475 |
|
Western Species Net Widths
|
— | 3-1/8" (79 mm) | 5-1/8" (130 mm) | 6-3/4" (171 mm) | 8-3/4" (222 mm) |
|
Southern Pine Net Widths
|
— | 3-1/2" (89 mm) | 5-1/2" (140 mm) | 7-1/4" (184 mm) | 9-1/4" (235 mm) |
|
Standard Lamination Thickness
|
— | 1.50 inches (38 mm) per lamination |
|
Standard Depths
|
— | Multiples of 1.5" (e.g., 6", 7.5", 9", 10.5", 12", 13.5", 15", 16.5", 18", up to 30+") |
|
Standard Stress Class
|
— | 24F-V4 (2,400 PSI bending stress / 1.8 × 10⁶ PSI MOE) |
|
Appearance Classifications
|
— | Framing (hidden), Industrial, Architectural, Premium (exposed) |