Sizing Joists and Rafters Using Span Tables Chapter 28 Sizing Joists and Rafters Using Span Tables

Links for Chapter 28 Wood Characteristics Lumber Size & Span Engineered Lumber

Wood Characteristics Each species is followed by a grade number which is either #1 or #2 for structural lumber Douglas fir-larch (DFL#2) Southern pine (SP#2) Spruce-pine-fir (SPF#2) Hemlock-fir (Hem-Fir#2)

Determining Size and Span Span table headings Title - Make sure correct one is being used Loads - Indicates LL and DL value Deflection - Describes the stiffness of the beam by its tendency to bend under a load Size and Spacing of Lumber - Gives the size and spacing allowed for framing lumber

Sizing Joists and Rafters Select proper table and follow these steps: Locate column that represents proper lumber species and grade Identify the lumber spacing Find column that corresponds to the appropriate load The number is the maximum allowable span 14-5 indicates maximum span of 14’-5”

Engineered Lumber Each manufactures’ tables may vary slightly Select proper table and follow these steps: Determine the deflection limit Identify the loading condition Select the on-center spacing Scan down the column until the distance that exceeds the span is located

Cantilevered Floor Joists Select proper table and follow these steps Use the first two columns to identify the joist Locate the roof truss that meets or exceeds the needed conditions Find the roof total load at the top of the table Select the spacing column

Cantilevered Floor Joists

Engineered Rafters Select proper table and follow these steps: Determine roof loading Determine appropriate slope column Move down column to find value that meets or exceeds required span