A 1-3/4” 2.1E 2800 beam with 100% load duration that is 7-1/4” deep will span up to 16', an 9-1/2” deep will span to 20', and 11-7/8” deep to 26'. A 14”, 16”, and 18” deep will all span 30', but 16” and 18” are typically doubled or tripled for greater loads.
The rule of thumb is 4X the length plus one on the ground floor and plus two on higher floors. For example, a 6-wide window would require a 4 x 8 header on the ground floor and a 4 x 10 on upper floors. So a 20-foot span would require a 4 x 22, the nominal sizes of lumber may restrict you to a 4 X 24.
You can span 20' for a ceiling with 9½" engineered (TJI) joists on 16" or 19.2" centers.
A 4 ply 2x12 beam can span 20 feet, but it is important to consider the load that the beam will be supporting. If the load is too heavy, the beam may sag or even fail.
A 1-3/4” 2.1E 2800 beam with 100% load duration that is 7-1/4” deep will span up to 16', an 9-1/2” deep will span to 20', and 11-7/8” deep to 26'. A 14”, 16”, and 18” deep will all span 30', but 16” and 18” are typically doubled or tripled for greater loads.
The most common lumber sizes for floor joists are 2x6, 2x8, 2x10, and 2x12. Larger joists can span across wider areas. For example, a 2x6 joist would have a 12-foot, 6-inch maximum span, and a 2x10 joist would have a 21-foot maximum span.
As the table shows, no 2×8's meet the span and spacing requirements, but a 2×10 with an E of 1,300,000 psi and Fb of 1093 psi can span 15 feet 3 inches – more than enough. A 2×12 with an E of 800,000 psi and Fb of 790 psi also works, since it can span 15 feet and 10 inches.
In general, a 2″×6″ lumber may span from 10 to 15 feet, while a 2″×8″ lumber may span from 13 to 19 feet. Likewise, a 2″×10″ lumber may span from 16 to 23 feet, while a 2″×12″ lumber may span from 18 to 27 feet. In addition, the 2″×4″ lumber may span from 7 to 9 feet.
According to this joist span table the absolute maximum span you can get with a 2x12 is 13'10" assuming a 100PSF live load.
Yes, a triple 2x10 beam can span 18.5 feet for a patio roof. According to the International Residential Code (IRC), a triple 2x10 beam with southern pine posts and 2x6x10 joists can span up to 20 feet. The IRC also specifies that the maximum live load for a patio roof is 30 pounds per square foot.
The maximum span of a 2x8 floor joist depends on several factors, including the wood species, grade, spacing between joists, and the expected load. In general, for residential construction using standard framing lumber such as Douglas Fir-Larch, a joist can span approximately 10 to 13 feet when spaced 16 inches apart.
LVL beams:A 4-ply LVL beam with a depth of 7.25 in can span 22 ft with a live load of 100 psf and a deflection of 1/800 of the span.
For a 10 x 20 cathedral (single peak) roof a normal ridge beam would be a pair of 2 X 12s glued and nailed together with a strip of 1/2” of plywood between them, creating a site-built lam beam 3.5” thick by 20' long. To this you'd have 2x8 rafters every 12” on center.
A common rule of thumb used for estimating the depth needed for a wood beam is the planned span/15. The width of the beam is commonly 1/3 to 1/2 of the beam depth. Deflection under full load should never exceed 1/360 of the total beam's span.
A #1 grade of Southern yellow pine (SYP) 2×8 roof rafter can span a maximum of 16'- 6” far apart at 16” OC. For the same size rafter, grade and spacing, SPF can allow to maximum span of 15'-1".
Consider your budget, desired timeline, and design preferences. If you prioritize a one-of-a-kind look and have some flexibility in time and cost, rafters might be the way to go. However, if speed, budget, and a traditional design are your top concerns, trusses are a great option.
“A 2×6 spaced 16 inches apart can span a maximum distance of 13 feet 5 inches when used as a rafter, 10 feet 9 inches when used as a joist, and 6 feet 11 inches when used as a deck beam to support joists with a 6-foot span.”
For a 20 foot span, wood beam needs to be minimum 18 inches deep. If smaller, beam will sag ugly! Better design with truss 2 feet deep or more depending on snow load. Almost any wood will do the same - geometry of beam or truss is the important thing.
The 2x12 grade 300 LVL has a load rating of 375 pounds per lineal foot, so it is sufficient for your application.
A triple 2x12 beam can typically span 15 to 18 feet for floor applications with standard residential loads. For roof or ceiling applications, it may span 12 to 14 feet. The span depends on factors like wood type, load, and deflection limits. Always consult a structural engineer for precise calculations.
In general a double 2x beam can support a span in feet equal to its nominal width in inches. A double 2x10 can thus span 10 feet.
2x4 11'-6" 2x6 17'-0" 2x8 21'-8" 2x10 25'-7" 24" O.C.