Joist Spans Species Size Beam 12′ Southern Pine 2-2×6 4′-7″ 2-2×8 5′-11″ 2-2×10 7′-1″ Click to see full answer. Thereof, how far can a wooden I beam span?Spans are clear distances between supports, and are based on composite action with glued-nailed APA Rated® sheathing or Sturd-I-Floor® panels of minimum thickness 19⁄32 (40/20 or 20 o.c.) for joist spacing of 19.2 or less, or 23⁄32 (48/24 or 24 o.c.) for a joist spacing of 24.One may also ask, how far can a steel beam span without support? 25 feet Herein, what size lumber can span 20 feet? Re: 20 foot clearspan beam size In that case, you need something like a 12-16″ GLULAM or LVL to span the 20′ and can use simple 2×8-10 dimensional lumber 16″OC as floor joists.What is the maximum span of an I joist?Our joists are available in depths from 9 ½ to 16 inches and lengths up to 52 feet for Residential consideration and depths from 18 to 24 inches for Commercial. IB MAX-CORE I-Joists are recognized as an innovative solution to the building industry’s floor and roof framing needs.