![]() ![]() Strength-reducing characteristics like knots, grade and slope of grain are controlled during manufacturing process so that the end product represents a more efficient use of the wood fiber. The claims are basically true, but you do pay for the improved performance. Fv does not change when you double the thickness.Įngineered Wood manufacturers are quick to point out that their products provide superior strength and stiffness. Make sure the shear value (Fv) for the species and grade you use exceeds the Fv listed in the span table. If you size a roof beam like a structural ridge that has a L/240 limitation, you would multiply the minimum E-value by 0.666 (785,000 x 0.666 = 522,810 in this case). The table lists spans with a deflection limit of L/360, normal for floor loads. The required E-value does not change when you double the 2×6 because as you double the allowable load, you are doubling the thickness of the beam. Therefore, a double 2×6 carries 2 x 347 = 694 pounds per lineal foot. Note: a single 2×6 will support 347 pounds per lineal foot of beam. (in AF&PA Design Values for Joists and Rafters #2 hem-fir = Fb psi & E psi- so use span table column Fb 1100)Ĭhoose the row for the size of lumber used in the double header: use 2×6 in this example. Select the Fb column of the lumber you intend to use Pick the span you want (pick 4’0″ for example) Just do the following:ĭetermine the total load per foot of beam But you can trick WSDD tables into giving you values for double or triple 2-by beams with other deflection limits. 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. LVL is available through our network of UK distributors, for contact details of your nearest distributor visit our Distributor Map.Īlternatively, contact our Timber Systems Division team directly, individual contact details can be found in our Contacts section.Please note: This older article by our former faculty member remains available on our site for archival purposes. LVL has excellent construction properties and is: For further details see the LVL technical manual below. Our close relationship with Stora Enso provides James Jones & Sons Ltd with the confidence to offer a full range of LVL grades and billet sizes. JJLVL-Beam is a natural choice for highly loaded beams, whereas JJSLVL-Rim is the most cost-effective solution for rim material in timber frame structures. The LVL that James Jones supplies to the market is available in two grades, JJLVL-Beam and JJLVL-Rim, and three standard thicknesses - 30, 45 and 75mm, with depths to match the full JJI-Joist range. As a material, LVL is exceptionally strong with excellent load bearing capacity, homogeneous quality and good workability. LVL is an advanced wood product suitable for a wide range of structural applications, available in beam depths which complement our JJI-Joist range.
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