Definition
A beam is a horizontal structural element that resists loads applied laterally to its axis. Beams transfer loads from floors, roofs, and walls to columns, walls, or foundations. Common beam types include wood joists, steel I-beams, glulam beams, and concrete beams. Beam size depends on span length, load weight, material strength, and deflection limits.
Formula
For wood beams: F is the fiber stress rating, b is beam width, d is beam depth, and L is span length. Always consult local building codes and a structural engineer for beam sizing, as improper sizing can lead to catastrophic failure.
Example
Floor Joist Example
For a 12-foot span supporting a bedroom floor (40 psf live load + 10 psf dead load), 2x10 southern pine joists spaced 16 inches on-center are typically sufficient. For longer spans or heavier loads, engineered I-joists, parallams, or steel beams may be required. Always verify with span tables and local codes.