Wood Framing Products
To ensure construction of a safe and durable structure, wood products need to conform to appropriate product standards as specified in building codes. Traditional solid-sawn lumber became the first wood framing product to be governed by a set of industry standards in 1924. Since that time, industry standards have been established for many other engineered wood framing products. Today, the building consumer can choose from a wide range of excellent wood framing products of consistent quality and uniformity.
Lumber and Timbers
Dimension lumber, 2″ to 4″ in thickness, includes solid-sawn and end-jointed lumber. In a floor system, solid-sawn lumber is most commonly used for floor joists, sill beams, and girders. Timbers, 5×5 and larger, are frequently used for girders and sill beams in a floor system.
Lumber and timbers must be properly grademarked. Grade marks (Figure 2) identify the grade, species, moisture content, producing mill, and inspection service. The American Softwood Lumber Standard PS 20, of the U.S. Department of Commerce, establishes lumber sizes, methodology for assigning design values, nomenclature, inspection, and re-inspection procedures, the National Grading Rules, an accreditation program, and other functions.
Southern Pine Lumber
Due to its dependable strength and superior treatability, Southern Pine is a preferred lumber species for building a raised wood floor home. Southern Pine lumber is readily available in a wide range of grades and sizes.
Southern Pine lumber is graded according to the Standard Grading Rules for Southern Pine Lumber published by the Southern Pine Inspection Bureau (SPIB). Strength and stiffness values for Southern Pine products in current SPIB rules have been approved by the Board of Review of the American Lumber Standard Committee. These design values enable determination of allowable spans for lumber in specific end uses, including floor joists. Refer to the SFPA publication, Southern Pine Use Guide, for complete grade descriptions, design values and sample specifications.
Foundation piles are typically peeled, round, pressure-treated Southern Pine timber members, driven and embedded in the ground. Timber piles may be required as a deep foundation for a raised floor system in areas where soil conditions dictate. ASTM D25 Standard Specification for Round Timber Piles establishes physical properties and manufacturing requirements. Round timber piles in service for foundation, land and freshwater use should meet AWPA standards in Use Category 4C and/or Commodity Standard C-3, Piles — Preservative Treatment by Pressure Processes.
Glued Laminated Timber
Glued laminated timber, or glulam, is comprised of individual pieces of lumber end-jointed together to produce long lengths, and then bonded together with adhesives to create the required beam dimensions. Glulam is generally used as a girder or beam in a floor system. Glued laminated timber must meet the provisions of ANSI/AITC A190.1 American National Standard for Structural Glued-Laminated Timber, or the manufacturer’s proprietary code report.
Metal Plate Connected Wood Trusses
Wood trusses are assembled using dimension lumber and metal connector plates. Trusses used as joists in floor systems are usually the parallel-chord type. Assemblies using prefabricated wood trusses shall meet the provisions of the governing building code, and any additional requirements as set forth in ANSI/TPI 1 National Design Standard for Metal Plate Connected Wood Truss Construction and the truss design drawings.
Prefabricated Wood I-joists
Wood I-joists are manufactured using sawn or structural composite lumber flanges and structural panel webs, bonded together with exterior-type adhesives, forming an “I” cross-section. I-joists are commonly used for floor joists. Assemblies using wood I-joists shall meet the provisions of ASTM D5055 Standard Specification for Establishing and Monitoring Structural Capacities of Prefabricated Wood I-Joists, the governing building code, and any additional requirements as set forth in the manufacturer’s proprietary code report.
Structural Composite Lumber
Structural composite lumber (SCL) is manufactured with parallel-laminated veneers or a network of wood strands laminated together with a waterproof adhesive. Common forms of structural composite lumber include parallel strand lumber (PSL), laminated veneer lumber (LVL), and laminated strand lumber (LSL). Structural composite lumber is generally used as a girder, beam or band joist (rim board) in a floor system.
Structural composite lumber is required to meet the provisions of ASTM D5456 Standard Specification for Evaluation of Structural Composite Lumber Products, the building code, and any additional requirements as listed in the manufacturer’s proprietary code report.
Structural Wood Panels
Wood panels can be manufactured in a variety of ways — as plywood (cross-laminated wood veneer), as oriented strand board or OSB (wood strands arranged in cross-oriented layers), or composite panels (veneer faces bonded to wood strand cores). Structural wood panels are commonly used as floor sheathing in a raised floor system.
Plywood used in structural applications shall meet the provisions of U.S. Department of Commerce Voluntary Product Standard 1 (PS1) Construction and Industrial Plywood, or U.S. Department of Commerce Voluntary Product Standard 2 (PS2) Performance Standard for Wood-Based Structural-Use Panels, or the manufacturer’s proprietary code report. Oriented strand board (OSB) used in structural applications shall meet the provisions of Voluntary Product Standard 2 (PS2) Performance Standard for Wood-Based Structural-Use Panels or the manufacturer’s proprietary code report.
Rim board can be manufactured using plywood, OSB, glulam, or SCL. Rim board is designed to work in concert with a wood I-joist system, filling the space between the sill plate and the bottom wall plate, or between the top plate and bottom plate in multi-floor construction.
Wood structural panel rim board must meet the provisions of the Performance Standard for APA EWS Rim Boards or the manufacturer’s proprietary code report. Glulam rim boards are a resawn grade of glued-laminated timber manufactured in accordance with the Performance Standard for APA EWS Rim Boards and ANSI/AITC A190.1.
1 Additional product information (design values, span tables, etc.) about the materials described in this section can be obtained online from various wood industry organizations. See Links in this web site. ASTM = American Standards for Testing and Materials; AWPA = American Wood Protection Association; ANSI = American National Standards Institute; AITC = American Institute of Timber Construction; TPI = Truss Plate Institute; APA; APA EWS = APA Engineered Wood Systems.