How Lumber Grading Works
As you’ve probably noticed, lumber is designated with “grades.” After the lumber is cut at a sawmill, lumber grading helps determine how a cut of wood should best be used. Higher grade lumber has fewer knots and other defects when compared to lower grades. Softwood and hardwood are graded using separate systems, but both grading systems help woodworkers establish the quality of the wood. Softwood grading focuses more on strength than on appearance, while hardwoods are graded based on the amount of clear material available on a board.
Softwood lumber comes from coniferous trees like pine and fir. While knots and other defects can result in a lower grade, strength takes precedence over appearance.
The common grades used are:
- #1: (Construction grade)
- #2: (Standard grade)
- #3: (Utility grade)
- #4: (Economy grade)
These designations refer to the strength of the wood. There are also categories that classify softwood by its appearance:
- A: Clear, with no knots.
- B: A few minor defects are present.
- C: A few small, tight knots are visible.
- D: Knots and defects are present.
Some specialty softwoods, like redwood and cedar, have their own additional grading factors.
Hardwood is wood that comes from deciduous trees like oak, maple, and walnut. The rules for hardwood grading were established in the early 20th century by the American Hardwood Lumber Association (AHLA), and the guidelines serve to provide buyers and sellers with a consistent language with which to describe the quality of wood.
Upper grades of hardwood lumber are suitable for moldings, door frames, interior architectural elements, and furniture. Common grades are widely used in kitchen cabinetry, furniture, and hardwood flooring. Common grades can differ from upper grades only in the smaller and narrower size of the cuttings.
Not every abnormality in lumber is considered a defect. The natural patterns and variations in real wood are part of its appeal, and so not everything is considered a negative feature.
Some of the things that are not classified as defects by the AHLA guidelines include:
- Heartwood and sapwood
- Gum streaks
- Mineral streaks
- Sticker marks
Defects in hardwood include:
- Bark pockets
- Bird pecks
- Unsound (decayed) and sound knots
- Sticker stains
- Worm holes
- Grub holes
FAS and FAS One Face are considered the upper grades of wood, providing the most clear wood. FAS (“first and seconds”) boards are a minimum of 6” wide and 8’ long. The boards range from 83% to 100% clear, and clear cuttings must be at least 3” by 7’ or 4” by 5’. Both faces must meet the minimum requirements. FAS Once Face (F1F) boards have a good face, which meets FAS requirements, and a poor face, which is inferior in quality.
Common hardwood grades that are commonly used are Number 1 Common (No. 1C) and Number 2A Common (No. 2AC). Number 1 Common is often referred to as “cabinet grade,” as it’s widely used in the cabinetry industry. It’s also used for other furniture parts. Both faces must meet the right requirements.
Number 2A Common is often referred to as “economy grade.” It’s used in furniture and in hardwood flooring. It must be 50% clear of knots.
Which Grade Should I Choose?
For both hardwood and softwood lumber, grades reflect the ideal use of a cut of wood. For example, #1 grade southern pine is suitable for structural framing due to its strength. No. 1C hardwood is ideal for cabinetry and furniture. The right grade of lumber really depends on what you plan on doing with it.