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:

Span Calculator for Joists & Rafters

Span Tables for Joists & Rafters

Northeastern Lumber Manufacturers Association:

Design Values and Span Tables

Spruce-Pine-Fir Strength Values and Span Tables

Southern Forest Products Association:

Southern Pine Span Tables

Southern Pine Maximum Spans for Joists and Rafters

Southern Pine Headers and Beams

Western Red Cedar:  Western Red Cedar Designer Handbook