United States Department of Agriculture Forest Service Wood Handbook Forest Products Laboratory Wood as an Engineering Material General Technical Report FPL–GTR–190 Centennial Edition Centennial Edition Wood Handbook Wood as an Engineering Material Forest Products Laboratory • United States Department of Agriculture Forest Service • Madison, Wisconsin Abstract Summarizes information on wood as an engineering mate- rial. Presents properties of wood and wood-based products of particular concern to the architect and engineer. Includes discussion of designing with wood and wood-based prod- ucts along with some pertinent uses. Keywords: wood structure, physical properties (wood), mechanical properties (wood), lumber, wood-based com- posites, plywood, panel products, design, fastenings, wood moisture, drying, gluing, fire resistance, finishing, decay, preservation, wood-based products, heat sterilization, sus- tainable use April 2010 Forest Products Laboratory. 2010. Wood handbook—Wood as an engineer- ing material. General Technical Report FPL-GTR-190. Madison, WI: U.S. Department of Agriculture, Forest Service, Forest Products Laboratory. 508 p. A limited number of free copies of this publication are available to the public from the Forest Products Laboratory, One Gifford Pinchot Drive, Madison, WI 53726–2398. This publication is also available online at www.fpl.fs.fed.us. Laboratory publications are sent to hundreds of libraries Pesticide Precautionary Statement in the United States and elsewhere. This publication reports research involving pesticides. The Forest Products Laboratory is maintained in cooperation with the It does not contain recommendations for their use, nor University of Wisconsin. does it imply that the uses discussed here have been The use of trade or firm names in this publication is for reader information registered. All uses of pesticides must be registered by and does not imply endorsement by the United States Department of Agriculture (USDA) of any product or service. appropriate State and/or Federal agencies before they can be recommended. The USDA prohibits discrimination in all its programs and activities on the basis of race, color, national origin, age, disability, and where applicable, Caution: Pesticides can be injurious to humans, sex, marital status, familial status, parental status, religion, sexual orienta- tion, genetic information, political beliefs, reprisal, or because all or a part domestic animals, desirable plants, and fish or other of an individual’s income is derived from any public assistance program. wildlife, if they are not handled or applied properly. (Not all prohibited bases apply to all programs.) Persons with disabilities Use all pesticides selectively and carefully. Follow who require alternative means for communication of program informa- tion (Braille, large print, audiotape, etc.) should contact USDA’s TARGET recommended practices for the disposal of surplus Center at (202) 720–2600 (voice and TDD). To file a complaint of discrimi- pesticides and pesticide containers. nation, write to USDA, Director, Office of Civil Rights, 1400 Independence Avenue, S.W., Washington, D.C. 20250–9410, or call (800) 795–3272 (voice) or (202) 720–6382 (TDD). USDA is an equal opportunity provider and employer. CONTENTS Chapter 1 Wood as a Sustainable Chapter 6 Commercial Lumber, Building Material Round Timbers, and Ties Wood as a Green Building Material 1–1 Hardwood Lumber 6–2 Forest Certification Programs 1–3 Softwood Lumber 6–6 Literature Cited 1–5 Purchase of Lumber 6–12 Round Timbers and Ties 6–18 Chapter 2 Characteristics and Availability Commonly Used Lumber, Round Timber, and Tie of Commercially Important Woods Abbreviations 6–23 References 6–25 Timber Resources and Uses 2–2 Species Descriptions 2–3 Chapter 7 Stress Grades and Design Prop- Imported Woods 2–18 erties for Lumber, Round Timber, and Ties Scientific Name Index 2–41 Literature Cited 2–45 Lumber 7–1 Additional References 2–45 Round Timbers and Ties 7–13 Literature Cited 7–14 Chapter 3 Structure and Function of Wood Additional References 7–15 Biological Structure of Wood at Decreasing Scales 3–2 Chapter 8 Fastenings Microscopic Structure of Softwoods and Hardwoods 3–9 Wood Technology 3–12 Nails 8–1 Juvenile Wood and Reaction Wood 3–13 Spikes 8–9 Appearance of Wood as Sawn Lumber 3–13 Staples 8–9 Wood Identification 3–16 Drift Bolts 8–10 Literature Cited 3–16 Wood Screws 8–10 Lag Screws 8–12 Chapter 4 Moisture Relations and Bolts 8–14 Physical Properties of Wood Connector Joints 8–19 Metal Plate Connectors 8–25 Wood–Moisture Relationships 4–1 Joist Hangers 8–25 Thermal Properties 4–10 Fastener Head Embedment 8–26 Electrical Properties 4–15 Literature Cited 8–27 Friction Properties 4–17 Additional References 8–27 Nuclear Radiation Properties 4–17 Literature Cited 4–18 Chapter 9 Structural Analysis Equations Additional Reference 4–19 Deformation Equations 9–1 Chapter 5 Mechanical Properties of Wood Stress Equations 9–4 Stability Equations 9–7 Orthotropic Nature of Wood 5–1 Literature Cited 9–10 Elastic Properties 5–2 Additional References 9–10 Strength Properties 5–3 Vibration Properties 5–17 Chapter 10 Adhesives with Wood Materials Mechanical Properties of Clear Straight-Grained Bond Formation and Performance Wood 5–21 Natural Characteristics Affecting Mechanical Surface Properties of Wood for Bonding 10–2 Properties 5–26 Physical Properties of Wood for Bonding 10–5 Literature Cited 5–44 Adhesives 10–8 Additional References 5–44 Bonding Process 10–14 Bonded Joints 10–18 Testing and Performance 10–19 Standards 10–22 References 10–23 iii Chapter 11 Wood-Based Composite Ma- Chapter 16 Finishing of Wood terials Panel Products, Glued-Laminated Factors Affecting Finish Performance 16–2 Timber, Structural Composite Lumber, and Exterior Wood Finishes 16–16 Application of Finishes, Special Uses 16–24 Wood–Nonwood Composite Materials Finish Failure or Discoloration 16–25 Scope 11–2 Finishing Interior Wood 16–32 Conventional Wood-Based Composite Panels 11–2 Wood Cleaners and Brighteners 16–34 Glulam Timber 11–17 Paint Strippers 16–35 Structural Composite Lumber 11–20 Lead-Based Paint 16–36 Wood–Nonwood Composite Materials 11–22 Literature Cited 16–37 Literature Cited 11–26 Additional References 16–37 Chapter 12 Mechanical Properties of Chapter 17 Use of Wood in Buildings Wood-Based Composite Materials and Bridges Elastic Properties 12–2 Light-Frame Buildings 17–1 Strength Properties 12–3 Post-Frame and Pole Buildings 17–4 Panel Products 12–3 Log Buildings 17–6 Timber Elements/Structural Composite Lumber 12–5 Heavy Timber Buildings 17–6 Wood–Nonwood Composites 12–7 Considerations for Wood Buildings 17–9 Testing Standards 12–9 Literature Cited 17–12 Literature Cited 12–10 Chapter 18 Fire Safety of Wood Chapter 13 Drying and Control of Moisture Construction Content and Dimensional Changes Fire Safety Design and Evaluation 18–1 Determination of Moisture Content 13–1 Fire-Performance Characteristics of Wood 18–8 Recommended Moisture Content 13–3 Fire-Retardant-Treated Wood 18–15 Drying of Wood 13–5 Literature Cited 18–18 Moisture Control during Transit and Storage 13–13 Additional References 18–18 Dimensional Changes in Wood 13–15 Design Factors Affecting Dimensional Change 13–17 Chapter 19 Specialty Treatments Wood Care and Installation during Construction 13–18 Plasticizing Wood 19–1 Literature Cited 13–19 Modified Woods 19–4 Paper-Based Plastic Laminates 19–12 Chapter 14 Biodeterioration of Wood References 19–14 Fungus Damage and Control 14–1 Bacteria 14–9 Chapter 20 Heat Sterilization of Wood Insect Damage and Control 14–9 Heat Treatment Standards 20–1 Marine Borer Damage and Control 14–13 Factors Affecting Heating Times 20–2 References 14–15 Methods for Estimating Heating Times 20–5 American Lumber Standard Committee (ALSC) Chapter 15 Wood Preservation Enforcement Regulations 20–9 Wood Preservatives 15–1 Quality Mark 20–11 Selecting Preservatives 15–13 Other Considerations 20–11 Evaluating New Preservatives 15–13 Literature Cited 20–13 Preservative Effectiveness 15–13 Effect of Species on Penetration 15–15 Glossary Preparation of Wood for Treatment 15–15 Application of Preservatives 15–18 Index Quality Assurance for Treated Wood 15–25 Effects on the Environment 15–26 Recycling and Disposal of Treated Wood 15–26 References 15–27 iv FOREWORD We are proud to present this edition of the Wood The audience for the Wood Handbook is broad. Con- Handbook—Wood as an Engineering Material, pre- sequently, the coverage of each chapter is aimed at pared and updated to include fascinating new develop- providing a general discussion of the topic, with refer- ments in the field of wood utilization and released as ences included for additional information. Thousands part of the celebration of the Forest Products Labora- more publications are available on the FPL website tory’s first 100 years of service to the public. (www.fpl.fs.fed.us). Efficient use of our nation’s timber is of critical impor- Wood resources continue to play an important role tance. This handbook is intended to serve as a primary in the world, from packaging materials to buildings reference on the use of wood in a variety of applica- to transportation structures. Wood has been useful to tions—from general construction to use of wood for human societies for thousands of years; archeologi- decorative purposes. It provides engineers, architects, cal discoveries have shown wood was used by ancient and others who use wood with a source of information civilizations as a construction material, as a substrate on the various properties of wood, its relationship with for ornate decorative objects, and for providing the moisture, and characteristics of various wood-based final resting place for royalty. These discoveries materials. Continuing research holds promise for wider highlight the unique, long-lasting performance char- and more efficient utilization of wood in an increasing acteristics of wood, as many of these artifacts have number of applications. survived for thousands of years. FPL continues on its journey of discovery and public service; working with This handbook was prepared by the Forest Products cooperators from around the world, we are discovering Laboratory (FPL), a research unit within the USDA information that covers the entire spectrum of wood Forest Service. The FPL, first established in 1910 in science—from the use of wood in ancient societies to Madison, Wisconsin, was the first institution in the developing new theories that describe the fundamen- world to conduct general research on wood and its tal structure of wood based on the emerging field of utilization. The information that resulted from many nanoscience. If our forests are managed wisely, and if of its scientific investigations of wood and wood prod- we continue to build our intellectual capacity to meet ucts over the past century is the primary basis for this the challenges of evolving human needs and chang- handbook. ing wood characteristics, this amazing material that is The Wood Handbook was first issued in 1935, and wood will serve the public well for years to come. slightly revised in 1939, as an unnumbered publica- Christopher D. Risbrudt, Director tion. Further revisions in 1955, 1974, and 1987 were Michael A. Ritter, Assistant Director published by the U.S. Department of Agriculture as Theodore H. Wegner, Assistant Director Agriculture Handbook No. 72. The 1999 revision was published by the FPL as General Technical Report USDA Forest Service FPL–GTR–113 and reprinted for broader distribution Forest Products Laboratory by the Forest Products Society. v PREFACE This edition of the Wood Handbook—Wood as an to include the most current references, in addition to Engineering Material builds upon past editions, in many historic ones, to help guide the reader to appro- particular the 1999 version, with some important addi- priate sources of information. tions and modifications: This 2010 edition was reviewed by numerous individ- • A chapter has been added that highlights the im- uals from industry, academia, and government. Several portance of wood as an environmentally respon- dozen industry, university, and government colleagues sible, sustainable material (Chapter 1). reviewed various sections and chapters of this edition • Low-magnification micrographs of cross sections during various stages of revision. We gratefully ac- knowledge their contributions. of commercial wood species have been added (Chapter 2). The following individuals provided in-depth technical • An extensive discussion on the microscopic struc- reviews of this edition in its entirety: Donald Bender ture of wood and its foundational elements are (Washington State University), David Green (USDA presented (Chapter 3). Forest Products Laboratory, retired), John Erickson • Reference to the most recent research on proper- (USDA Forest Products Laboratory, retired), Howard Rosen (USDA Forest Service, retired), World Nieh ties of the wood cell wall, at the nanoscale, has (USDA Forest Service), Robert White (USDA Forest been included (Chapter 5). Products Laboratory), and staff of the American Wood • To address the need to find uses for wood obtained Council, American Forest & Paper Association. We from trees killed by invasive insect species as they gratefully acknowledge their contributions. propagate through various regions of the United States, a chapter has been added on heat-treating Although listing every technical author and contributor and sterilization procedures for wood products to the Wood Handbook would be nearly impossible— (Chapter 20). early editions did not even list individual contributors • Important updates are included on wood–mois- by name—we do acknowledge the authors of previous editions; they all made significant, noteworthy contri- ture interactions and wood preservation practices butions. (Chapters 4 and 15). Finally, we thank our many research cooperators from The Wood Handbook originally focused on construc- industry, academia, and other government agencies. tion practices that utilized solid-sawn wood. Since its By working with you we are able to continue develop- first printing, the state-of-the-art in wood construc- ing the technical base for using wood, wood-based tion practices and the range of wood-based products materials, and wood structural systems in a technically available to the consumer have changed considerably. sound manner. Excellent printed reference and websites have been developed by various trade associations and wood Robert J. Ross, Editor products manufacturers that document, in detail, cur- USDA Forest Service rent design information for the ever-changing range of Forest Products Laboratory products available. We have made a concerted effort vii CHAPTER 1 Wood as a Sustainable Building Material Robert H. Falk, Research General Engineer Few building materials possess the environmental benefits Contents of wood. It is not only our most widely used building mate- rial but also one with characteristics that make it suitable Wood as a Green Building Material 1–1 for a wide range of applications. As described in the many Embodied Energy 1–1 chapters of this handbook, efficient, durable, and useful wood products produced from trees can range from a mini- Carbon Impact 1–2 mally processed log at a log-home building site to a highly Sustainability 1–3 processed and highly engineered wood composite manufac- tured in a large production facility. Forest Certification Programs 1–3 As with any resource, we want to ensure that our raw ma- Forest Stewardship Council (FSC) 1–4 terials are produced and used in a sustainable fashion. One Sustainable Forestry Initiative (SFI) 1–4 of the greatest attributes of wood is that it is a renewable resource. If sustainable forest management and harvesting American Tree Farm System (ATFS) 1–4 practices are followed, our wood resource will be available Canadian Standards Association (CSA) 1–5 indefinitely. Programme for the Endorsement of Forest Wood as a Green Building Material Certification (PEFC) Schemes 1–5 Over the past decade, the concept of green building1 has Additional Information 1–5 become more mainstream and the public is becoming aware Literature Cited 1–5 of the potential environmental benefits of this alternative to conventional construction. Much of the focus of green building is on reducing a building’s energy consumption (such as better insulation, more efficient appliances and heating, ventilation, and air-conditioning (HVAC) systems) and reducing negative human health impacts (such as con- trolled ventilation and humidity to reduce mold growth). However, choosing building materials that exhibit positive environmental attributes is also a major area of focus. Wood has many positive characteristics, including low embodied energy, low carbon impact, and sustainability. These charac- teristics are important because in the United States, a little more than half the wood harvested in the forest ends up as building material used in construction. Embodied Energy Embodied energy refers to the quantity of energy required to harvest, mine, manufacture, and transport to the point of use a material or product. Wood, a material that requires a mini- mal amount of energy-based processing, has a low level 1Green building is defined as the practice of increasing the effi- ciency with which buildings use resources while reducing building impacts on human health and the environment—through better siting, design, material selection, construction, operation, mainte- nance, and removal—over the complete building life cycle. 1–1