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December 2021 #13269 Page #49
Can I Substitute Lumber of Another Grade or Species? By Glenn Traylor
an you make substitutions of different lumber grades and species? The short answer is: yes. Even so, you have to take several factors into consideration when making a substitution.
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To narrow the discussion, let’s focus on southern pine. The substitution must have design values equal to or greater than those of the specified lumber for each of the seven components that make up a species’ design values. These seven components are: • Extreme Fiber in Bending Fb • Tension Parallel to Grain Ft • Horizontal Shear Fv • Compression Perpendicular to Grain FcꞱ • Compression Parallel to Grain Fc|| • Modulus of Elasticity E and Emin • Specific Gravity G The Southern Forest Products Association (SFPA) publishes the southern pine design values in the Southern Pine User Guide available in PDF on its website as a free download (see excerpt below).
What about using Stud Grade? Stud grade is a composite of No.3 strength and No.1 edge characteristics for a better nailing surface. Note the highlighted item in the excerpt from the SFPA design values table. Because No.3 and Stud grade have the same design values in southern pine, they can be substituted as long as the gradestamp does not indicate “Stud Use Only” or “Vertical Use Only.” (This is permissible per ANSI/TPI 1–2014 Section 3.4.6.)
Excerpt from SFPA Southern Pine reference design values. Continued next page
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