![]() 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 Some information contained in it may be outdated. I use this chart: A 15' long 2x12 will span the two 7 1/2' spans and support a 362#/LF total load at a L/360 deflection limit, so this will do.Please note: This older article by our former faculty member remains available on our site for archival purposes. This cuts the span in half so you can use a smaller beam. I would lag it into every stud, but I also like to support it at both ends and in the middle, with a stud laid flat against the wall and lagged into a stud. The ledger along the wall needs design as well. Support with a 4x4 post or 3 2x4's as columns in the walls. Using a readily available 1.9E LVL, a double 11 1/4" deep LVL beam will support a LL of 284#/LF and a total load of 416#/LF, so this is more than adequate. The beam has a contributing area of 6SF x 50#/SF total load, for a total load of 300#/LF. The actual span is 9'-6", so this will work. Using that, and a 10#/SF dead load, Spruce-Pine-Fir for material and a deflection limit of L/360, 2圆's will span 9'-5". ![]() ![]() This should be adequate for what you describe. I use this calculator for sizing joists:Ī 40#/SF live load is typical for residential floors. Joists I like to space at a maximum of 16" on center, to support the floor sheathing properly. Run perpendicular to the joists and provide solid blocking under all seams. I like 3/4" T&G plywood, glued and screwed and staggered for the decking. ![]()
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