A span is the distance between two intermediate supports for a structure. Span tables are used to size joists and rafters. Proper use of a span table is an important step in quality construction.
Span varies by species, size, quality of material and application. When determining span, pay attention to these three elements: lumber grade, lumber size and species type.
Below, we list a selection of span tables for various species and projects. When using these span tables, be sure to always check plans to determine design conditions, as well as codes for allowable loads. There are specific span tables available for joists and rafters, and headers and beams.
American Wood Council:
Northeastern Lumber Manufacturers Association:
Southern Forest Products Association:
Western Red Cedar: Western Red Cedar Designer Handbook