![]() ![]() ![]() ![]() You May Also Like David Adjaye-designed new lux tower tops out in Manhattan This is an excerpt of 2015 WFCM Table 3.25B2 which helps clarify live load deflection criteria for different ceiling finishes. 117 to 313 km/h (110 to 195 mph) 700-year return-period, three-second gust basic wind speeds and.0 to 3.35 kPa (0 to 70) psf ground snow loads.Tabulated engineered and prescriptive design provisions in WFCM chapters two and three, respectively, are based on the following loads from American Society of Civil Engineers (ASCE) 7-10, Minimum Design Loads for Buildings and Other Structures: revised header spans to reflect L/240 live load deflection limits for members supporting only a roof and ceiling as shown in 2015 IRC and IBC tables.new tables to provide prescriptive wood-frame solutions for rafters and ceiling joists in response to new live load deflection limits for ceilings using flexible finishes (including gypsum wallboard) or brittle finishes (including plaster and stucco) as adopted in the 2015 IRC and.updated design values for visual grades of Southern Pine reflected in tabulated spans for lumber framing members as referenced in the 2015 NDS Supplement: Design Values for Wood Construction.Primary changes reflected in the 2015 edition of the WFCM standard include: A range of structural elements are covered, including sawn lumber, structural glued-laminated (glulam) timber, wood structural panel sheathing, I-joists, and trusses. The WFCM includes design and construction provisions for high wind, seismic, and snow loads for connections, wall systems, floor systems, and roof systems. This month, the 2015 edition of the ANSI/AWC Wood Frame Construction Manual ( WFCM) for One- and Two-Family Dwellings will be explored to provide guidance for wood-frame construction in residential as well as commercial structures that fit within its scoping. The 2015 edition of the Wood Frame Construction Manual ( WFCM) for One- and Two-Family Dwellings provides guidance for wood-frame construction in residential as well as certain commercial structures. These standards primarily govern engineering design and construction of wood structures to resist all applicable loads including high wind and seismic forces. Over the last two months, this author has covered updates to the 2015 National Design Specification ( NDS) for Wood Construction and 2015 Special Design Provisions for Wind and Seismic ( SDPWS). To help translate what the latest changes to building codes mean for opportunities in wood construction, the American Wood Council (AWC) recently introduced four new standards that are adopted by reference in the 2015 International Building Code ( IBC) and the 2015 International Residential Code ( IRC). ![]() Collar ties, contrary to popular belief, do not prevent walls from spreading.By Buddy Showalter, PE Photo © BigStockPhoto/flippo.Where they are required, they should be installed on every other rafter where rafters are on 24-inch centers.Collar ties are probably not needed if approved metal connectors were used to fasten the rafters to the ridge.InterNACHI inspectors should not call out a lack of collar ties as a defect unless they know that collar ties were required in the jurisdiction where the home is located at the time the home was built. They may or may not be required, depending on the jurisdiction.In high-wind areas, uplift can tear a roof off of a house if it's not properly attached.Ĭollar ties and ridge straps should be installed on roof with a minimum slope of 3:12, a maximum wind speed of 100 miles per hour, and a maximum roof span of 36 feet. They must be spaced no more than 4 feet (1219 mm) apart. They must be at least 1 inch by 4 inches (25 mm by 102 mm). If collar ties or ridge straps are installed to connect opposing rafters, they must be located in the upper third of the attic space. Ridge straps are permitted to replace collar ties. A collar tie is a tension tie in the upper third of opposing gable rafters that is intended to resist rafter separation from the ridge beam during periods of unbalanced loads, such as that caused by wind uplift, or unbalanced roof loads from snow. ![]()
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