Span

The distance between supports, or the width crossed by a structure.

Longer spans demand deeper beams or greater force in trusses, cables, and arches. Column-free halls require compromise among span, material, and cost.

Asking what crosses a large room is a basic way to read structure. A cantilever is a projecting span supported at one end.

The Crystal Palace, station halls, arenas, and bridges are stages for long-span construction.