ENGINEERED WOOD PRODUCTS PRIMER AWARENESS GUIDE American Wood Council American Wood American Wood Council ENGINEERED WOOD PRODUCTS PRIMER AWARENESS GUIDE The American Wood Council (AWC) is the voice of North American traditional and engineered wood products, representing over 75% of the industry. From a renewable resource that absorbs and sequesters carbon, the wood products industry makes products that are essential to everyday life and employs over one-third of a million men and women in well-paying jobs. AWC's engineers, technologists, scientists, and building code experts develop state-of-the- art engineering data, technology, and standards on structural wood products for use by design professionals, building officials, and wood products manufacturers to assure the safe and efficient design and use of wood structural components. For more wood awareness information, see www.woodaware.info. While every effort has been made to insure the accuracy of the infor- mation presented, and special effort has been made to assure that the information reflects the state-of-the-art, neither the American Wood Council nor its members assume any responsibility for any particular design prepared from this publication. Those using this document assume all liability from its use. Copyright © American Wood Council 222 Catoctin Circle SE, Suite 201 Leesburg, VA 20175 202-463-2766 [email protected] www.woodaware.info AMERICAN WOOD COUNCIL FIREFIGHTER AWARENESS GUIDES 1 This guide reviews the history and development of engineered wood products (EWP) in the marketplace and provides definitions that enable a fire service instructor to identify these lightweight products as they are used in building construction. This publication is one in a series of eight Awareness Guides developed under a cooperative agreement between the Department of Homeland Security’s United States Fire Administration, and the American Wood Council. Engineered Wood Products Primer MEETING THE NEEDS OF THE FIRE SERVICE come common for floors, roofs, and walls, and the use of The level of training and technical support available trusses in roofs had replaced rafters throughout the from the building industry has increased dramatically in homebuilding industry. Additionally, carpeting had be- the past twenty years. Engineered wood product special- come the preferred flooring choice. ists are now common in the construction industry and software has helped to communicate the intricacies of the Transition to Engineered Lightweight Construction many new products. Until now, however, the available In the 1980s, both environmental limitations and con- information has not been uniformly provided to the fire sumer demand spurred the transition to engineered light- service. This series of Awareness Guides has therefore weight wood construction. Environmental constraints re- been prepared to “train the trainer” and begin to inform duced the size of trees delivered to saw mills. With the fire service in a uniform manner about new wood larger-diameter logs unavailable, the wood industry de- product construction materials and methods being used in veloped technology to “disassemble” smaller logs and the marketplace. glue them back together lighter and stronger. It had be- The wood products industry is committed to deliver- come impossible to make a 20-foot long 2x12 floor joist ing educational material to the fire service with the goal out of a 9-inch diameter tree, or plywood out of 6-inch of reducing risk of injury from structural collapse in fires. tree tops that were full of knots. The choice was clear to These Awareness Guides will address questions raised by the wood industry—either use smaller diameter trees or the fire service during a series of industry visits to a num- witness a significant decline in the use of dimensional ber of state fire academies. lumber and panels in residential construction. At the same time, coupled with environmental con- PURPOSE OF THIS GUIDE straints, consumers expected the forest products industry This guide reviews the history and development of to use fewer trees with greater efficiency and less waste. engineered wood products in the marketplace and pro- Meanwhile, the square footage of residential homes was vides definitions that enable a fire service instructor to increasing, along with demand for deep, long, and identify these lightweight products as they are used in straight building materials. building construction. New Design Standards BACKGROUND Design and material standards for new structural As noted above, the past fifty years have seen unprec- products also began to change. Previous standards had edented changes in building construction. The changes in been prescriptive. For example, by this cookbook ap- wood frame construction during this period have also proach, plywood or another panel product would have to been significant, paralleling the numerous changes within be manufactured according to a strict recipe designating the fire service. The wood industry has adapted to a num- adhesives to be used and type and dimension of materials. ber of opportunities and constraints. As a result, there are The newer standards developed were instead based many lightweight structural products and construction techniques for building residential wood frame houses. After World War II, the explosive growth of Ameri- Photos and graphics courtesy of can suburbs was unlike any other time in history. In the Weyerhaeuser Company and 1950s, most homes were constructed with solid sawn APA – The Engineered Wood Association. lumber framing, with diagonal board sheathing placed on For more information, visit www.apawood.org floors, walls, and roof. Hardwood plank flooring was commonplace. In the 1960s, plywood sheathing had be- 2 EWP PRIMER AWARENESS GUIDE simply on performance. A product could be manufac- smaller components into a structural member and de- tured with any adhesive, as well as type or dimension of signed using engineering methodologies should be con- material, as long as it performed in accordance with the sidered engineered. Engineered products are developed requirements of manufacturing standards and the build- to use materials efficiently. Therefore, many engineered ing code. wood products are lighter in weight than the conventional The evolution of performance-based standards cre- product they are designed to replace. ated the ideal opportunity for product innovation in the For the sake of definition here, engineered wood marketplace. Building code organizations, in turn, devel- products are structural components or assemblies that oped evaluation services to manage approval of the in- are offered as alternatives to solid sawn lumber. Struc- flux of newer products offered as alternatives to those al- tural composite lumber, I-joists, and wood trusses are ready listed in the building code. examples. (See www.woodaware.info for a link to the Interna- Most of these products are proprietary (uniquely de- tional Code Council’s Evaluation Services.) signed from a specific manufacturer) and are marketed under different trade names. Each of these products, how- DEFINING ENGINEERED WOOD PRODUCTS ever, has to comply with building code requirements be- In response to consumer demands, the wood industry fore its use in structural applications. developed technologies to use smaller trees more effi- ciently. These technologies moved homebuilding to HOW ENGINEERED WOOD PRODUCTS a new era of more fiber-efficient and lightweight ARE MANUFACTURED engineered materials—thus the term “engineered wood There are three primary manufacturing methods to products.” dismantle a log and reassemble it into an engineered There are different opinions as to what is an engi- wood product—stranding, peeling, and sawing—as neered wood product (EWP). From the fire service per- shown in Figure 1. spective, any product consisting of a combination of Figure 1 EWP Manufacturing Methods Log ▼ There are ▼ ▼ ▼ three primary Strand Rotary Peel Saw manufacturing ▼ ▼ ▼ methods to Oriented Strand Board (OSB) Plywood Lumber dismantle a log (Alternating) (Alternating) (Parallel) and reassemble Laminated Strand Lumber (LSL) Laminated Veneer Lumber (LVL) it into an (Parallel) (Parallel) engineered wood Oriented Strand Lumber (OSL) Parallel Strand Lumber (PSL) product— (Parallel) (Parallel) stranding, peeling, and ▼ ▼ ▼ sawing. Together with Adhesives or Other Types of Reinforcement ▼ I-Joist, Glued-Laminated Beam, Structural Insulated Panel, etc. AMERICAN WOOD COUNCIL FIREFIGHTER AWARENESS GUIDES 3 Stranding Conversion Efficiency of Stranding involves slicing a log into 1-inch to 12-inch Figure 2 strands, similar to a cheese grater. The strands are dried in Engineered Wood Products a large rotary drum, where resin is applied. The strands are then dropped into a forming bin and pressed together to form the product. These products can be thin and flat, Conversion Efficiency like plywood, or long and wide, like lumber. Stranding is the most efficient method to convert a log into an engineered wood product, because it uses the Laminated Veneer Lumber smallest pieces (Figure 2). Smaller strands pack more ef- ficiently into rectangular sections. The net result is in- creased utilization of a tree and less waste delivered to the Parallel Strand Lumber landfill. For example, a 100 cubic foot log produces only 40 cubic feet of solid lumber, but 76 cubic feet of engi- neered wood products. More efficient conversion of the Laminated Strand Lumber natural resource results in benefits to the industry, con-