When many of us think of lumber, we think of uniform wooden planks, separated by wood type. However, the process of milling logs into the lumber we know today is more complicated than simply sorting logs by type. In fact, there is a process called Classification This helps to classify wood into more than just type or appearance.
In this guide, we’ll explain the basics of wood grading, helping you understand how the quality of the wood affects the quality of your solid wood furniture.
What is the classification of wood?
Lumber grading is the process of classifying wood based on its quality and strength. Lumber grading refers to its structural integrity and appearance, which are critical factors in determining its best future use. Grading is usually done by visual inspection, although more precise methods, such as machine stress grading, are used in certain applications.
Why is wood grading important?
Choosing the right grade of wood for your project ensures safety, durability and longevity over time. For example, high-grade wood is ideal for structural components, where strength is the most important quality, while lower-grade wood may be better for non-structural applications.
Wood Grading Basics
1. Softwood classification
Softwoods typically used in construction are graded by the American Lumber Standards Committee (ALSC) based on visual inspection. Here’s a quick summary of the major softwood grades:
Select Structural (SS): This is the highest grade, and provides the best combination of strength and appearance. It is often used in critical structural applications where both aesthetics and strength are important. No. 1 and No. 2: These two grades are slightly lower than Select Structural. No. 1 is still very strong and is often used in load-bearing structures, while No. 2 may have more knots or defects, making it suitable for something like framing. No. 3 (Utility): This grade has more defects and is usually used where strength is less important, such as temporary structures or non-load-bearing walls. Construction Grade: This is a broad category that includes No. 1 and No. 2 grades but is specifically designated for general construction purposes.
2. Classification of hardwoods
Hardwood lumber is commonly used for furniture, flooring, and cabinetry. The National Hardwood Lumber Association (NHLA) grades hardwood lumber, focusing on the yield of usable wood from a board.
FAS (First and Second): This is the highest grade of hardwood, and provides a high percentage of clear, flawless wood. It is ideal for fine furniture and cabinetry because it provides large, clean pieces of strong, aesthetically pleasing wood. Select: Slightly lower in quality than FAS, Select grade lumber may have more knots or defects, but still provides good yields and is suitable for most furniture projects. No. 1 Common and No. 2 Common: These grades allow for more defects, such as knots and cracks. They are often used in less visible parts of furniture or in applications where the appearance of the wood is not as important.
Factors affecting wood grades
There are many factors that affect the quality of wood, including:
Knots: Knots are natural defects in the wood where the branches were attached to the tree. The size, location, and frequency of knots affect the strength and grade of the wood. Veins: The straightness, intensity, and regularity of the grain affect both the strength and aesthetic appeal of the wood. Splits and cracks: These are cracks in the wood that occur during drying. Large or numerous splits can weaken the wood and lower its grade. Diminishing: The presence or absence of bark along the edge of a board. Diminishing reduces the usable portion of the wood and can lower its grade.
Understanding Wood Grade Stamps
When purchasing lumber, you will often find grade stamps on the wood. These stamps provide basic information about the wood, including:
Manufacturer Identification: The manufacturer that produced the lumber is often identified by a number or name. Grade: The lumber grade is clearly marked, such as No. 2 or Select Structural. Type: The type of lumber is often indicated by an abbreviation, such as DF for Douglas Fir or SPF for Spruce-Pine-Fir. Moisture Content: The stamp may also indicate whether the lumber was kiln-dried (KD) or air-dried (AD). Moisture content is important because it affects the stability, strength, and resistance to warping or shrinkage of the lumber after installation.
How Wood Grade Affects Solid Wood Furniture
So why is the quality of wood used in furniture making important?
In general, the grade of wood plays a role in the quality, appearance, and longevity of solid wood furniture. Higher grade lumber, such as FAS (Firsts and Seconds) or Select, yields a greater yield of clear, flawless wood—ideal for visible surfaces like table tops, chair legs, and cabinet fronts. These grades ensure that your furniture has a smooth, uniform appearance with minimal knots, warping, or imperfections.
On the other hand, using lower quality woods may introduce more variations and natural characteristics into the piece, such as knots and grain irregularities. While these imperfections add a sense of uniqueness or charm to the piece, they may also require more careful selection and cutting to ensure that the piece is visually pleasing.
At Vermont Woods Studios, the local artisans we work with are able to source the highest quality wood to create the artifacts you know and love. That’s because unlike larger manufacturers who can’t source the highest quality wood due to the large quantity required, the Vermont artisans we work with are able to carefully select smaller, higher quality batches of wood.
For solid wood furniture made from the finest wood, be sure to take a look at our collection of handcrafted wood furniture to the highest standards of quality, longevity and beauty.
