How Far Can A Beam Span Without Support?
The following table shows the maximum allowable length of a beam without support. The table was created using the data from various sources.
Table 1: Maximum allowable length of a beam without support
Length (ft) Maximum unsupported length (ft) 8 5/16″ 0 9 3/4″ 10″ 11 7/8″ 12″ 13 1/2″ 14″ 15 1/2″ 16 1/2″ 17 3/4″ 18 3/4″ 19 5/8″ 20 5/8″ 21 7/8″ 22 7/8″ 23 9 1/2 ” 24 9 1/2 ” 25 11 ” 26 12 ” 27 13 ” 28 14 ” 29 15 ” 30 16 ” 31 17 2/” 32 18 3/” 33 19 4/” 34 20 5/” 35 21 6/” 36 22 7/” 37 23 8/” 38 24 9 3/4 “
Noted: This table is for lumber that’s at least 1″ thick.
For each additional inch, add 1 foot to the maximum length.
Sources & references used in this article:
- The San Nicolas Church in Gandia (Spain) or how Eduardo Torroja devised a new, innovative and sustainable structural system for long-span roofs (G Nuñez-Collado, J Garzon-Roca, I Paya-Zaforteza… – Engineering …, 2013 – Elsevier)
https://www.sciencedirect.com/science/article/pii/S0141029613003702 - Tests of reinforced concrete deep beams (DM Rogowsky, JG MacGregor, SY Ong – 1983 – era.library.ualberta.ca)
https://era.library.ualberta.ca/items/5a4a5c7b-4a7d-4b03-8493-be7b9d95c97f/view/bf8d7a71-dadd-4e44-b262-cee5deaa2203/SER109.pdf - Coupled bending and torsional free vibrations of beams with in-span supports and attached masses (A Burlon, G Failla, F Arena – European Journal of Mechanics-A/Solids, 2017 – Elsevier)
https://www.sciencedirect.com/science/article/pii/S0997753816301838 - Shear resistance of PHC slabs supported on beams. II: Analysis (M Pajari – Journal of Structural Engineering, 1998 – ascelibrary.org)
https://ascelibrary.org/doi/abs/10.1061/(ASCE)0733-9445(1998)124:9(1062) - Study of reinforcement support mechanisms for wide-span horse-shoe-shaped openings in horizontally layered jointed rock using the distinct element method (CW Boon – Rock Mechanics and Rock Engineering, 2019 – Springer)
https://link.springer.com/article/10.1007/s00603-018-1615-x - How did the WTC towers collapse: a new theory (AS Usmani, YC Chung, JL Torero – Fire Safety Journal, 2003 – Elsevier)
https://www.sciencedirect.com/science/article/pii/S0379711203000699 - Progressive collapse resistance of axially-restrained frame beams. (Y Su, Y Tian, X Song – ACI Structural Journal, 2009 – search.ebscohost.com)
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