![]() The WSDD tables only list values for solid wood beams at deflection limits of L/360. The WSDD is an extremely useful book (WSDD costs $20. American Forest & Paper Association’s Wood Structural Design Data, provides span recommendations for solid-sawn wood beams up to 32 feet, but the table runs a hefty 140 pages. And even though span tables provide limited data, they are very long. Most beam tables only list values for whole-foot spans like 11’0″, 12’0″, etc. ![]() You merely look for the distance you need to span match the load per foot of beam to the appropriate Fb(strength) and E(stiffness) values listed and bang: you have a winner! Span tables are easy to use, but they have limitations. Sawn-Lumber span tables are convenient tools. Technical experts have computed many combinations of these variables and present a variety of solutions in the form of span tables. You can do these calculations yourself or you can use span tables. ![]() Formulas that determine the allowable span and size of a beam rely on a host of variables like species, grade, size, deflection limit and type of load. Structural ability of sawn- and engineered-wood beams are predicted through mathematical calculation. No matter what material we specify, beams must provide adequate strength, stiffness, and shear resistance. We will compare the performance and cost of sawn-lumber, LVL, Timberstrand, Parallam and Anthony Power Beam in several different applications. We know how to measure the forces acting on a beam, now we’ll use this information to choose the appropriate structural material to resist the loads. In Part 1, “ Calculating Loads On Headers and Beams“, we learned how to trace load paths and translate roof, wall and floor loads into pounds per lineal foot of supporting beam. Once the loads acting on structural beams are calculated, the next step is to size and select the appropriate beam. ![]() Some information contained in it may be outdated. MAXIMUM CANTILEVER SPAN (uplift force at backspan support in lbs.Please note: This older article by our former faculty member remains available on our site for archival purposes. TABLE R502.3.3(1) CANTILEVER SPANS FOR FLOOR JOISTS SUPPORTING LIGHT-FRAME EXTERIOR BEARING WALL AND ROOF ONLY a, b, c, f, g, h (Floor Live Load ≤ 40 psf, Roof Live Load ≤ 20 psf) MEMBER & SPACING Floor cantilevers supporting an exterior balcony are permitted to be constructed in accordance with Table R502.3.3(2). Floor cantilevers constructed in accordance with Table R502.3.3(1) shall be permitted where supporting a light-frame bearing wall and roof only. Dead load limits for townhouses in Seismic Design Category C and all structures in Seismic Design Categories D 0, D 1 and D 2 shall be determined in accordance with Section R301.2.2.2.1.įLOOR JOIST SPANS FOR COMMON LUMBER SPECIES (Residential living areas, live load = 40 psf, L/Δ = 360) b JOIST SPACING (inches)įloor cantilever spans shall not exceed the nominal depth of the wood floor joist.Note: Check sources for availability of lumber in lengths greater than 20 feet. TABLE R502.3.1(1) FLOOR JOIST SPANS FOR COMMON LUMBER SPECIES (Residential sleeping areas, live load = 30 psf, L/Δ = 360) a JOIST SPACING (inches)įor SI: 1 inch = 25.4 mm, 1 foot = 304.8 mm, 1 pound per square foot = 0.0479 kPa. The allowable span of ceiling joists that support attics used for limited storage or no storage shall be determined in accordance with Section R802.4. Table R502.3.1(1) shall be used to determine the maximum allowable span of floor joists that support sleeping areas and attics that are accessed by means of a fixed stairway in accordance with Section R311.7 provided that the design live load does not exceed 30 pounds per square foot (1.44 kPa) and the design dead load does not exceed 20 pounds per square foot (0.96 kPa).
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