Structural Lumber Overview

Many Western species share similar performance properties and are grown, harvested and manufactured together. These products are marked as a species combination to simplify marketing, design and engineering and allow design values to be assigned under a group rather than as individual species.

Western dimension lumber is manufactured in both single species and species combinations.  Douglas Fir, Ponderosa Pine, White Fir and Western Red Cedar are the most common single species sold as dimension lumber products.   

Structural lumber (including dimension lumber) is visually and/or mechanically (MSR) graded for its strength and physical working properties (appearance is secondary, unless specified). Basic end-use classifications are organized by size classifications and performance capabilities. 

Light Framing grades fall under the dimension lumber (2-4 inches thick and 2 inches and wider) classification and are intended for use where the highest strength values are not required, such as wall framing, plates, sills cripples and blocking.  Light Framing grades are available in sizes 2x2 up to 4x4.

Structural Light Framing grades also are classified as dimension lumber and were developed to fit engineering applications where the highest design values are needed. Structural Light Framing grades are available in sizes 2x2 up to 4x4.

Stud grade lumber is for vertical uses, such as load bearing walls.  It is often sold in specified lengths for typical construction uses.  Stud grade is the only grade in Stud category, in sizes 2x2 up to 4x18.

Structural Joists and Planks grades are products that are 5 inches or greater in width.  This lumber is for applications where high strength values are required, such as floor joists, rafters, headers, small beams, trusses and general framing.  Structural Joists and Planks grades are produced in sizes 2x5 up to 4x18.

MSR (Machined Stress-Rated) lumber is intended for broad range of engineered applications where low variability in strength and stiffness properties is primary product consideration, e.g. trusses, floor or ceiling joists or rafters. MSR lumber is distinguished from visually stress-graded lumber in that each piece is nondestructively tested and marked to indicate the modulus of elasticity (E).  Grades are designated by Fb and E.  MSR grades can be produced in sizes 2x2 up to 2x12.

Finger-Jointed lumber makes efficient use of available wood resources and can be manufactured in long lengths. Because it is typically fabricated from dry material, it is exceptionally dimensionally stable.  Structural-glued products are available in a variety of species, grades and sizes for both general and specifically-intended end uses. It is accepted for use under all model building codes and is interchangeable with solid-sawn dimension lumber of the same size, grade and species, and is grademarked accordingly. 

Timbers are designed for construction uses where material larger than Joists, Planks and Studs is required.  There are two timber use categories, Post and Timbers (5x5 and larger) and Beams and Stringers (5 inches and thicker, width more than 2 inches greater than thickness).  The various grades are used in all types of building – home, industrial, farm and in special engineered construction such as bridges, auditoriums, stadiums and the like.  Some grades are selected for appearance and strength.  Other grades are designed for serviceability with strength and appearance qualities to provide reliable and economical construction.  

Structural Decking is widely used for roofing and flooring and is valued for insulating and fire resistive qualities. Decking is often used in combination with heavy timber construction.  Decking grades are usually surfaced to a single Tongue and Groove (T&G) in 2 inch thickness and double T&G in 3 inch and 4 inch thicknesses and may be ordered with a V or rounded edges, striated, grooved or in other patterns.   Structural Decking is produced 2-4 inches thick and 4 inches and wider. 

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