Does Your Lumber Make the Grade?

By Paul Bianchina

During a trip to the lumber yard, have you ever wondered why some stacks of lumber look worse - and cost less - than other stacks? Or why the wood has a stamp with lots of strange abbreviations?

All types of lumber, both hardwood and softwood, are sorted by quality during the milling process. This sorting - called lumber grading - is done by certified, highly experienced graders in accordance with national grading standards. Lumber is graded according to both appearance and structural defects and affects how that lumber will ultimately be used.

Softwood Grades

"Hardwood" and "softwood" are common terms used to group wood into two broad categories. The categories are defined primarily by the tree's cell structure, but in general softwood refers to wood that comes from needle-bearing trees such as pine, fir, cedar and redwood, and hardwoods come from broadleaf, deciduous trees such oak, maple and walnut.

Softwoods are used primarily for construction and finish trim, as well as some cabinetry and other woodworking applications. There are several grade classifications for softwood lumber, but for construction purposes these are the most common ones found at your local lumber yard:

• Utility: A low grade intended for light framing and utility uses only, in sizes up to 2x4;
• Standard and construction: for light framing use in sizes up to 2x4;
• Stud: A specific designation for lumber ranging from 2x2 up through 4x4;
• Select Structural, #1, #2, #3 (in order from highest to lowest grade): These are the most common designations for framing lumber in sizes ranging from 2x2 up through 4x14.

Each piece of softwood lumber receives its designation through an evaluation of the entire piece and is based on the assumption that the piece will be used in its entirety. For example, a 16-foot long piece of 2x6 lumber may contain knots or other flaws in one part of the board and be completely free of defects in another part - taken as a whole, the grader may stamp this piece as a #1 or a #2 under the assumption that most of the entire 16 foot length will be used as one piece.

Grades are important in determining whether a particular piece of lumber is suitable for a particular task. A piece of lumber graded as #1, for example, will span a greater distance than one graded #2. All building codes utilize these grades in determining allowable span and spacing for rafters, floor joists, ceiling joists and other applications.

Grade Stamps

Once the grade has been determined, the piece of lumber is stamped with a marking called a Grade Stamp. This stamp, with all its abbreviations, contains five basic pieces of information that are very useful to the builder, and they are placed on the stamp in a consistent manner to make identification easy.

• Supervising body and mill: In the lower left corner of the stamp is the abbreviation of the supervising grading body, such as the Western Wood Products Association. In the upper left corner is a name or number identifying the mill where the wood was cut.
• Grade: In the upper right corner of the stamp you will find the grade - a number 1, 2 or 3 for those grades, or an abbreviation such as "STAND" (standard), "UTIL" (utility) or "STRUCT" (select structural). Other abbreviations may be used as well.
• Moisture content: Below the grade designation is an abbreviation showing the moisture content of the wood at the time it was graded (the moisture content may be higher or lower when you actually purchase it at the yard). There are three standard designations: "MC-15" (moisture content 15), which means that the wood has a maximum moisture content of 15 percent; "S-DRY" (surfaced dry), which has a moisture content between 15 percent and 19 percent; and "S-GRN" (surfaced green), which has more than 19 percent moisture.
• Species: In the lower right corner is an abbreviation for the species of wood. In some instances, it may indicate a group of wood species with strength characteristics that are similar enough that it's not economical to grade them separately. These designations include: "D FIR" (Douglas fir); "DOUG FIR - L (Douglas fir or larch); "HEM FIR" (hemlock or fir); S-P-F (spruce, pine, fir); "WEST CDR" (western cedar); and "WEST WOODS" (western woods, an all-inclusive term used by some western mills to include several common western softwoods).

When in doubt about the grade of wood or its suitability for a particular use, always check with your lumber yard or local building department.

Copyright 2002-2006 Inman News Features. Distributed by Inman New Features.