HARDWOOD LUMBER CALCULATION
American Lumber is classified according to the standards set by the American Hardwood Association (NHLA). NHLA’s standards are set with the furniture trade trend, which conducts a standard measurement for hardwood lumber. It setting a certain percentage of clean, defect-free wood for each wood grade.
NHLA’s classification is based on the ratio of clean wood per piece of wood. This measure of proportions is called clean logs. With the exception of the FAS rating, the grade of a log is determined from the proportion of these clean logs and does not take into account defects outside the clean log zone.
WOOD MEASUREMENTThe NHLA grades are determined on an imperial measurement system using inches and feet. Additionally, the rules were developed with random width and length of lumber in mind. A board foot is the unit of measurement.
- Board Foot (B.F.):
- One board foot is one foot long, one foot wide, one inch thick (One foot = 0.3025 meters; one inch = 25.4 mm)
- To determine the board feet in a board:
- Multiply the width in inches by the length in feet and divide by 12. If the lumber is thicker than one inch, multiply by the thickness.
Surface measure (S.M): The surface measure is the square-foot surface area of the board. The percentage of clear woof needed for each grade is based on the surface measurement (S.M) and not the board feet, so all boards are rated the same regardless of thickness.
- To determine S.M.:
- Multiply the full width of the board by the standard length of the board and divide by 12, rounding to the nearest whole number.
- Examples of determining S.M.:
- 6 ½” x 8’ / 12 = 4 1 /³ = 4’ S.M.
- 8” x 12’ / 12 = 8’ S.M.
- 10” x 13’ / 12 = 10 10/12 = 11’ S.M.
- Once the grade is established, multiply S.M. x thickness to get board feet.
Example: 6 ½” W x 8’ L x 2” TH = 8 BF
- Note: The grade is based on S.M., not board feet.
- Board Foot (B.F.):
WOOD MESUREMENT | METRIC CONVERSION:
- 1” = 25.4mm
- 1m = 3.281 feet
- 1m3 = 424 board feet (B.F.)
- 1m3 = 35.315 cubic feet (Cu. Ft.)
- 1,000 B.F. (MBF) = 2.36 cubic meters (m3 )
STANDARD THICKNESS FOR ROUGHSAWN & SURFACED LUMBER MEASUREMENT
The thickness of rough sawn lumber is represented in quarters of an inch. Defects such as cracks, stains, and bends are not taken into consideration when grading rough sawn lumber if the surface is at standard surfaced thickness (S2S).
MEASUREMENT OF KILN DRIED LUMBER
- Net Tally: Actual board feet after kiln drying
- Green Tally: Actual board feet before kiln drying
- Widths can be ¼” below the minimum required.
- Thickness can be 1 /16” below the minimum required.