Hybrid Wood and Steel Details– Builder's Guide

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Hybrid Wood and Steel Details–Builder’s Guide3 MaterialsCold-Formed Steel Contact with WoodMetallic coated steel does not react with dry wood. Drypressure-treated lumber is also not corrosive to zinc, and nospecial requirements are needed to fasten steel to woodframing. Galvanized nails and screws have beensuccessfully used to join wood and steel for years.3.1.3 Web Holes, Cutting,Splicing, and PatchingWeb holes may also be referred to as “punchouts,” “utilityholes,” “perforations,” and “web penetrations.” In structuralframing members, web holes are typically 1.5 inches (38mm) wide x 4 inches (102 mm) long and are located on thecenterline of the web and are generally spaced at 24 inches(610 mm) on-center.Coping, cutting, or notching of flanges and edge stiffeners(lips) is not permitted for load-bearing members without anapproved design. Structural members may be spliced;however, splicing of studs and joists is not a commonpractice and is notrecommended. If astructural memberrequires splicing, thesplice connection mustbe installed inaccordance with anapproved design. Splicingof tracks is permitted.Nonconforming holes aretypically patched byapplying a steel plate,track, or stud section tothe patch and thenfastened with No. 8screws at 1 inch (25.4mm) on-center.Cutting or notchingof flanges and lips ofstructural steelmembers shall notbe permitted withoutan approved design.Splicing of structuralmembers shall notbe performed withoutan approveddesign.3.1.4 In-Line FramingIn-line framing is the preferred and most commonly usedframing method. The advantage of in-line framing is that itprovides a direct load path for transfer of loads from roofmembers all the way tothe foundations. If in-lineframing is not possible instructural walls, a loaddistribution member,such as a double woodtop plate or a structuralsteel track, may berequired for the loadtransfer.3.1.5 ResourcesLoad distributionmembers, such assteel headers ordouble wood topplates, shall be usedwhen in-line framingis not possible instructural walls.There are numerous resources available from various steelindustry, government, and user organizations. A fewselected organizations are listed below with their webaddresses:• Steel Framing Alliance(www.steelframingalliance.com)• Light-Gauge Steel Engineers Association(www.lgsea.com)• Steel Stud Manufacturer’s Association(www.ssma.com)• International Iron and Steel Institute(www.worldsteel.org)• American Iron and Steel Institute(www.steel.com)• Partnership for Advancing Technology in Housing(www.pathnet.org)• NAHB Research Center Toolbase Hotline(www.toolbase.org)8
Hybrid Wood and Steel Details–Builder’s Guide3 Materials3.2 Wood FramingWood has been used for centuries as a building material,especially for home construction. It is the most commonlyused material in the housing market in the United States.Framing members used in houses are harvested and milledfrom millions of available acres of forestland spread acrossNorth America. Wood is divided into two main categories—hardwood and softwood—and several subcategories andgrades depending on the wood species characteristics,intended use, and the method of processing the lumber.Hardwood comes from deciduous trees (e.g., oak, maple,hickory, and so forth) while softwood comes from conifers(e.g., pine, spruce, fir, and so forth).More than 90 percent of dimensional lumber used in NorthAmerica comes from four commercial softwood speciesgroups: Spruce-Pine-Fir, Douglas Fir-Larch, Hem-Fir, andSouthern Pine. Species groups or combinations are anassemblage of species of wood that have commoncharacteristics. Table 3.4 shows the abbreviations used forthese common species groups and the lumber gradestamps. This section focuses almost exclusively on thesesoftwood species groups because they account for a largeproportion of construction applications in the United States.It also focuses on newer engineered wood products becauseof the products’ growing importance and use as “valueadded”substitutes for traditional lumber (i.e., “solid sawn”lumber).Table 3.4–Major Wood Species CombinationsMajor Species Canadian U.S.CombinationsSpruce-Pine-Fir S-P-F S-P-F [S]Douglas Fir-Larch D.Fir-L [N] D.Fir-LHem-Fir Hem-Fir [N] Hem-FirSouthern Pine - SYPThis section provides an overview of the following topicsrelated to wood framing:• Basic Characteristics of Wood and Lumber (Section3.2.1)• Lumber Applications and Sizes (Section 3.2.2)• Grading of Lumber (Section 3.2.3)• Engineered Wood Products (Section 3.2.4)For an in-depth treatment of these and other topicsregarding lumber products and their use, the reader isreferred to the following limited selection of resources:• Wood Engineering Handbook [12](Download: http://www.fpl.fs.fed.us/documnts/FPLGTR/fplgtr113/fplgtr113.htm)• National Design Specification (NDS) for WoodConstruction [13](Download: http://www.awc.org/HelpOutreach/eCourses/STD103/NDS2001/)• Residential Structural Design Guide [14](Download: http://www.huduser.org/publications/destech/residential.html)• Metal Plate Connected Wood Truss Handbook [15](http://www.woodtruss.com/index1.html)In addition, numerous resources are available from variouswood industry, government, and user organizations. A fewselected organizations are listed below with their Webaddresses:• USDA Forest Products Laboratory(www.usda-fpl.gov)• American Wood Council(www.awc.org)• American Forest and Paper Association(www.afandpa.org)• APA—The Engineered Wood Association(www.apawood.org)• Wood Truss Council of America(www.wtca.org)9
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