Hardwood lumber grades refer to the size and number of clear pieces that can be cut from a board and used to make a product. The National Hardwood Lumber Association (NHLA) maintains the rules for the complex grading system.
The standard hardwood lumber grades include:
The highest, most expensive grade. Minimum size board is 6” x 8’. Yields 83-1/3 percent of clear face cuttings. Minimum size of clear cuttings is 4" x 5' or 3" x 7'. Graded from the poorer face. Use for furniture, cabinetry and when clear, wide boards are needed for a specified project.
• FAS One Face (F1F) and Selects (SEL)
The two grades combine the standard grades of FAS (on the better face) and No. 1 Com (on the poorer face). Minimum size board for F1F is 6” x 8’ and for Sel is 4” x 6’. When only one good face is required or only smaller cuttings are needed, this is a cost-effective substitute for FAS.
• No. 1 Common (No. 1 Com)
Shop grade board. Both faces must meet the same requirement. Minimum size board is 3” x 4’. Yields 66-2/3 percent clear face cuttings. Minimum size of cuttings are 3" x 3' and 4" x 2'. A good value option if small cuttings are needed.
• No. 2A Common (No. 2A Com)
Minimum size board is 3” x 4’. Yields 50 percent clear face cuttings. Minimum size of cuttings is 3” x 2’. Use for paneling and flooring.
• No. 3A Common (No. 3A Com)
Minimum size board is 3” x 4’. Yields 33-1/3 percent clear face cuttings. Minimum cuttings are 3” x 2’. Use for rough applications like fencing, crates and palettes at an economical cost.
Softwood lumber grades are divided into two categories: Dimension, or construction, where structural integrity and durability are paramount, and Appearance, where aesthetics are the focus for grading. The American Softwood Lumber Standard PS 20 specifies guidelines for grading and helps to enforce them through third-party agencies across the U.S. and Canada.
Dimension lumber is used for framing and sizes and grades are as followed:
• Structural Light Framing
For applications where high strength is needed: Select Structural No.1, No.2 or No.3 grades (No.1 and No.2 grades include Dense and Non-Dense options). 2" to 4" thick, 2" to 4" wide.
• Light Framing:
Light-frame construction—wall framing, sills and blocking—use Construction, Standard, Utility grades. 2" to 4" thick, 2" to 4" wide.
• No. 1 Common (No. 1 Com)
Shop grade board. Both faces must meet the same requirement. Minimum size board is 3" x 4'. Yields 66-2/3 percent clear face cuttings. Minimum size of cuttings are 3" x 3' and 4" x 2'. A good value option if small cuttings are needed.
For vertical applications in load-bearing walls use Stud grade. 2" to 4" thick, 2" and wider.
• Structural Joists & Planks:
For use as joist, rafters and beams 5 inches and wider: Select Structural, No.1, No.2 or No.3 (No.1 and No.2 grades also include Dense and Non-Dense options). 2" to 4" thick, 5" and wider.
Plywood refers to a variety of products including medium density fiber board (MDF), chipboard, particle core board (PBC), hardboard and other wood veneers bonded with adhesive. Plywood is graded by the quality of the veneers.
The grading system utilizes the alphabet, where A has the best aesthetic (few blemishes and well sanded). Plywood grades typically come in pairs, with a letter referencing the quality of each side of the product.
General grading as follows:
• A Face and back veneers practically blemish-free.
Face practically blemish-free. Back minor knots and discolorations.
Face is blemish-free. Back may have large knots, plugs and jointed veneers.
Face and back have minor knots or discolorations.
Face has minor knots or discolorations. Back may have large knots, plugs and jointed veneers.
Face and back may have large knots, plugs and jointed veneers.
Face has knots and defects plugged. Back may have some that are not plugged. “Structural plywood” used for sheathing building surfaces before its covered with concrete, siding, flooring or roofing.
Well-glued. All broken knots plugged.
All defects permitted.
“Marine Plywood” that’s weather and boil proof.