Terminology

• Ply: a veneer layer
• Face / back veneer: outer plies graded A, B, BB, C/D, WG, X, WBP (Western grades)
• Interior / exterior glue: urea-formaldehyde / phenol-formaldehyde or resorcinol-formaldehyde
• E0: low-emission product with effectively zero formaldehyde emissions
• Marine plywood: graded under BS 1088 or IS:710
• 4 × 8 ft sheet: standard 1,220 × 2,440 mm panel

History and demand

Invention

• About 2600 BC: rudimentary plywood in ancient Egypt
• 1850s: industrial use began; 1858 John Henry Belter patented a chair-back technique; 1880s larger-scale use

First uses in construction

• 1905: the 4 × 8 ft sheet size first used by the Portland Manufacturing Company for the Portland World Fair

Sourcing

• China made 73.1 percent of world plywood in 2017 (FAO data via IndexBox); China's capacity was about 205 million m3 in 2023
• 2023 exports by value: China 34 percent, Indonesia about 12.3 percent, Brazil about 5 percent

Composition and production

Raw materials

• Thin wood veneer and adhesive; interior panels typically use urea-formaldehyde, outdoor and marine panels use water-resistant resorcinol- or phenol-formaldehyde

Manufacturing process

• Logs peeled into veneer, dried, glued, and pressed at 140°C (284°F) or higher and up to about 1.9 MPa

Product forms

• Panels 1/8 to 3 in. thick (3.2 to 76.2 mm); aircraft plies as thin as 0.40 mm total

Properties

Physical

• Density (European): birch about 680 kg/m³ (42 lb/ft³), mixed 620 kg/m³ (39 lb/ft³), conifer 460 to 520 kg/m³ (29 to 32 lb/ft³)

Mechanical

• Core layers increase separation between the outer layers, raising bending resistance

Standards

Material specifications

• DOC PS 1, DOC PS 2, and ANSI/APA PRP 210: wood structural panel standards named in the building code

Uses in buildings

Building elements

• Wood-Framed Walls, Wood-Framed Floors, Shear Walls: wall, roof, and floor sheathing and structural panel diaphragms
• Wood I-Joists: web material
• Cast-in-Place Concrete Walls: form facing for concrete placement
• Cabinetry and Casework: casework panels

Pros and cons

Pros

• Cross-graining reduces splitting when nailed and limits swelling and shrinkage
• Strength is more uniform in all directions
• Large panels in thicknesses up to 3 in.

Cons

• Interior-glue panels have limited water resistance
• Formaldehyde glues (low-emission E0 products exist)

Manufacturing and cost

Main manufacturers and suppliers

• Weyerhaeuser
• Roseburg
• Georgia-Pacific

Trade association: APA – The Engineered Wood Association.

Sources

• Wikipedia: Plywood, https://en.wikipedia.org/wiki/Plywood
• UpCodes: 2024 IBC Chapter 23 wood, https://up.codes/viewer/department-of-defense/ibc-2024/chapter/23/wood
• Wikimedia Commons: Plywood.jpg, photo by Rotor DB (CC BY-SA 3.0), https://commons.wikimedia.org/wiki/File:Plywood.jpg
• Timber Industry News: China plywood production companies fell in 2023, https://timberindustrynews.com/?p=13359
• IndexBox: world plywood market, https://indexbox.co.uk/store/world-plywood-market-report-analysis-and-forecast-to-2020/