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Title: Chapter 4:Grading and properties of hardwood structural lumber

Author: Green, David W.;

Date: 2005

Source: Undervalued hardwood for engineered materials and components. Madison, WI : Forest Products Society ; Marquette, MI : Northern Initiative, [c2005]: Pages 31-50

Publication Series: Book Chapter

Description: Structural lumber markets have traditionally been dominated by softwood species. Historically, however, hardwood species have been extensively used for certain structural products such as timbers for railway and highway bridges, railway ties, mine timbers, and for pallets and containers. In the 1920s, when uniform procedures were first developed for structural grading, allowable properties were assigned to both hardwood and softwood species (Appendix D of Green and Evans 2001). In 1922, the National Lumber Manufacturers' Association (currently the American Forest & Paper Association) produced span tables for joists and rafters for both hardwood and softwood species. Allowable properties for hardwoods were included in the first edition of the National Design Specification in 1944, but did not appear in the 1960 edition. In the 1970s and 1980s, studies were published on the technical and economic feasibility of producing 2-inch-thick dimension lumber from several hardwood species including aspen, paper birch, basswood, and yellow-poplar (e.g., Maeglin and Boone 1983,1985; Gerhards 1983; Erickson et al. 1986). In 1988, a number of hardwood species were once again included in the 1988 revision of the 1986 National Design Specification (DeBonis and Bendtsen 1988). Despite this interest, the only hardwood species occasionally available on a commercial basis was yellow-poplar which was available in dimension lumber and manufactured into trusses. The historic lack of interest in 2-inch-thick structural dimension lumber from hardwood species can largely be attributed to low market acceptance and low profit margins for commodity lumber. In the early 1990s, the National Timber Bridge Initiative and decreased availability of western softwoods resulted in renewed interest in using hardwoods for structural applications. Recently, there has been some interest in producing 2-inch-thick commercial lumber for hardwoods for use in trusses and I-joists. This chapter will summarize the information on the properties and grading of 2-inch-thick dimension lumber resulting from research studies conducted since about 1990.

Keywords: Merchantable volume, lumber grading, grading, valuation, elasticity, lumber, mechanical properties, modulus of elasticity, yield, structural timbers, grading, hardwoods

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Green, David W. 2005. Chapter 4:Grading and properties of hardwood structural lumber. Undervalued hardwood for engineered materials and components. Madison, WI : Forest Products Society ; Marquette, MI : Northern Initiative, [c2005]: Pages 31-50


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