![]() ![]() Live loads for sleeping areas are commonly 30 psf and 40 psf for living areas that experience more occupants and movement. Live load refers to people, furnishings, appliances, and other ‘movable’ non-structural elements. A 10-foot span would be 120”/360”, so a 1/3” deflection under maximum loads, which isn’t enough to damage plaster or drywall on the underside of floors.ĭead load refers to the weight of structural components and may be 5, 10, 15, or 20 psf (pounds per square foot) depending on location. Maximum load deflection is typically L/360 (length in inches over 360) for living and sleeping area floors and L/240 for attics with zero to limited storage area. There are other loads like wind loads, but those are the main ones. Residential loads are identified as dead load, live load, snow load, and combined or total load. The stronger the wood species, the greater its load-to-span ability. The stress on wood fibers due to compression on the surface closest to the load and the tension on the side furthest from the load help determine the span potential. Most residential construction loads are limited to the bending structural members can endure based on species and span distance. There are four main softwood species used in building construction across North America.īased on their density and test results, Douglas Fir-Larch (DF-L) will span the furthest, followed by Southern Pine (SP or SYP), Hemlock-Fir (Hem-Fir), and Spruce-Pine-Fir (SPF) under similar conditions. So, different wood species are identified as stronger and capable of spanning further distances based on their flexure strength.ĭimensional softwood lumber is commonly used in the construction industry for beams, joists, studs, and rafters in residential and other structures. Those, in turn, affect tension and compression flexure when applied parallel to the grain, which establishes bending in relationship to wood grain properties. Wood Speciesĭifferent species of wood have different strengths due to environmental issues that affect growth, wood density, and grain properties. So, it’s important to understand how different factors affect span. The spacing between joists or rafters also affects the span too as it disperses the weight across more or less supporting members.ĭepending on all factors, a structural 2×12 can span between 13’-7” and 25’-7” according to the 2021 International Residential Building Code (IRC). ![]() The main factors that affect the distance a 2×12 can span are wood species, grade, and load. What Factors Impact How Far a 2×12 Can Span?
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