Design Tools

Building Calculators

Find span, joist, connections, height, and area calculators here.

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 are span tables for various species and projects. When using these span tables, be sure to check plans to determine design conditions, as well as codes for allowable loads. There are specific span tables available for joists and rafters or headers and beams.

 

Adding wood posts into bracket

American Wood Council

Northeastern Lumber Manufacturers Association

Southern Forest Products Association

WoodWorks

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