![]() So many lumber yards have LVLs with 2.0E, but how can you be sure what the Fb is? I got the feeling when I spec out a 2850 how do I know that's what the Fb really is? I know Fb can be 2850, 2900, or 3100 for 2.0E? If I specified Fb = 3100 the 2 ply beam would work for sure. When I asked bending strength they all said they don't know they just know the E. The last question is that I called around some lumber yards to just see if they have 2.0E LVLs and what the bending strength is. Because of this my thought is that the deflection in reality is not really 5wl/384EI, but could be 1wl/185EI because it more resembles a two span beam with one span loaded.I know it's a gray area and judgement, but I'm trying to get a 2 ply beam to work. Since the beam is not simply supported in 's a 115" span with the second span partially over a closet (bearing for 48") and partially spanning an opening (approximately 32"). The interaction ratio is 1.0 for bending. ![]() By increasing the E to 2.0 and Fb to 2850, I can get the beam to work. beam for the 115" span they show I need 3 plies of 7.25" LVL (they don't want to go taller than that with LVL since the joists will be 2x8s). I started a thread yesterday regarding sistering the joists. ![]() The opening is 115", then there is a closet which the beam will sit on, and then span the opening over the entrance which is 32 inches. the contractor wants to install one long LVL (18' long). There are several openings they want to make and have the ceiling open. With the purlin/bracing installed, the long rafter span would be broken into two shorter spans, thus allowing the rafter to carry additional load.īefore you decide on lumber sizing and span, consult your local building code officials to determine design loads for your area.I'm designing an LVL to support floor joists and remove a bearing wall. You can break up a long span of rafters by installing a purlin and bracing on the underside. When calculating the span of joists or rafters, use the horizontal distance between vertical supports. The number 1 grade material is more expensive than the #2 grade, but if you can use fewer or smaller number 1 grade joists or rafters in your design, you may actually save money.ĭepending on the availability and cost of various size framing materials, it may be more economical to use larger joists or rafters in your design because you can typically use fewer of them. For example, you can span a #1 grade (no knots) southern yellow pine joist a greater distance than a #2 grade of the same species (with knots). The lengths and sizes of joists vary depending on the species and quality of the lumber used. To calculate maximum spans of additional species of lumber, use the Span Calculator or the Span Tables for Joists and Rafters on the American Wood Council website.Ĭonsiderations when using the Rafter and Joist Span Tables Contact your local building code officials to determine the building code for your area. Weigh all of the elements when designing wood structures. Some areas have wind and seismic conditions. ![]() For example, some localities get large amounts of snow, whereas others get none. Before determining the maximum spans for joists and rafters, you must know the load requirements for your region. ![]()
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