Understanding lumberyard terminology and processing is valuable knowledge for DIYers and homeowners. Even if your only experience comes from buying hardwood floors, it can help to have some basic knowledge of what goes into timber preparation. This can help you better understand why some products may be better for the job at hand.
Let’s review how lumber is processed, graded, and labeled before it is ultimately used in the real world (on something like your new hardwood floors).
From the Forest to the Lumberyard: Wood’s Journey
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Lumber starts to take form in the sawmill, where logs are cut into usable boards.
Softwood lumber comes from coniferous trees like pine, Douglas fir, and cedar. Softwood is typically cut at 2-inch intervals (e.g., 4, 6, 8, 10, and 12 inches wide) and standard lengths (e.g., 8, 10, and 12 feet).
Hardwood lumber comes from deciduous trees like oak, maple, cherry, walnut, and mahogany. Hardwood is cut to widths and lengths based on the log, which provides greater variety but less uniformity.
Regardless of the type, lumber thickness is often described in quarter-inch increments: a 1-inch board is referred to as 4/4 (four quarters), while a 2-inch board is 8/4 (eight quarters).
Drying Lumber
After sawing, lumber can be dried in a couple different ways.
- Air Drying: Boards are stacked with spacers to allow airflow, drying naturally over weeks or months.
- Kiln Drying: Heated chambers are used to speed up the process. Kiln drying also helps kill any insects.
Drying causes the wood to shrink in width and thickness, but even after drying, wood will expand and contract with changes in humidity. Experts know to account for this when they order materials.
Decoding Lumber
You may have noticed that lumber is stamped with a combination of letters and numbers. This helps buyers understand details about the timber preparation.
For example, every piece of lumber is stamped to indicate its moisture content.
- S-GRN (Surfaced Green): Moisture content over 19%.
- S-DRY (Surfaced Dry): Air-dried to less than 19% moisture.
- KD (Kiln Dry): Kiln-dried to less than 19% moisture.
- MC 15 (Moisture Content 15%): Dried to 15% or less.
- HT (Heat Treated): Heated to at least 133°F to eliminate insects.
Lumber dried to 19% provides a good balance of strength and stability with limited splitting or warping. It is typically used for building structures. MC15 lumber is used for most other purposes.
Air dried boards just one-inch thick can take anywhere from 30-300 days to dry to levels that make it useable.
Also, since boards dry faster from the ends, you will often see them coated. This helps prevent defects at the ends of the boards like splitting, that can be caused by drying.
The Planing Process
Once dried, most softwood lumber is planed to create smoothness and uniformity.
Planed lumber will be stamped either:
- S4S (Surfaced on Four Sides): Smooth on all sides.
- S2S (Surfaced on Two Sides): Smooth only on the faces, leaving the edges rough.
Now here’s an interesting tidbit. Did you know that a 2×4 isn’t actually 2 inches by 4 inches? That’s because it’s been planed, reducing the surface by approximately 1/8” on all sides. That means what we call a 2×4, in reality, measures 1½ inches by 3½ inches.
Rough lumber, sometimes called “rough sawn” lumber is not planed. It retains its full dimensions but lacks uniformity, making it less suitable for precision projects. Hardwood lumber is often sold rough, giving woodworkers more control over the final dimensions for things like cabinets and flooring.
Lumber Grading: Quality and Characteristics
Grading systems help buyers assess wood quality. Grading takes into consideration knots, splits, and other defects that affect the strength and appearance of the wood.
Softwood Grades
Softwood, from coniferous trees like pine and spruce, is graded for structural integrity and appearance.
Structural integrity is graded as follows:
- Select Structural: Minimal knots, excellent for high-stress applications.
- No. 1: High-quality with small knots, ideal for visible, structurally sound projects.
- No. 2: Standard framing lumber with more knots, suitable for most construction.
- No. 3: Lower quality with acceptable imperfections for less visible uses.
For appearance-grade softwood:
- A Select: Clear, knot-free.
- B Select: Minor defects.
- C Select: Nearly clear, suitable for single-visible-side applications.
- D Select: Small knots or defects throughout.
Hardwood Grades
Hardwoods, from deciduous trees like oak and cherry, are graded primarily for appearance:
- FAS (First and Seconds): The highest grade, mostly defect-free, used in fine furniture and cabinetry. Boards must be at least 6 inches wide and 8 feet long with 83% clear of defects.
- Select: Like FAS, but smaller boards are allowed, which provides some cost savings.
- No. 1 Common: More knots and defects, often used for cabinets and furniture with “character.”
- No. 2 Common: Even more defects, suitable for flooring or pallets where imperfections can add rustic charm.
Decoding Other Lumberyard Terms
When buying lumber, you may hear these terms:
- B&BTR (B and Better): Indicates high-quality lumber meeting B-grade or higher standards. Used for projects that require the best materials.
- VG (Vertical Grain): Boards with the growth rings vertical to the face of the board. This leaves a finer pattern to the wood.
- PT (Pressure Treated): Lumber treated to resist decay and insects, ideal for outdoor use.
- MDF (Medium Density Fiberboard): Engineered wood with consistent density and stability. An alternative to solid wood.
Choosing the Right Lumber for Your Project
Selecting lumber involves considering its intended use, the strength needed, and optimal moisture content.
Outdoor projects should be made with pressure-treated wood or naturally durable options like cedar. They can withstand the elements over time.
Structural projects, where strength and safety are the priority, must use lumber with appropriate grading.
Decorative pieces like furniture are almost always made of appearance-grade lumber.