Slide background


Join our mailing list and receive our FREE newsletter, “The Cutting Edge”

NHLA Grading Rules for North American Hardwoods


The NHLA grades are based on the percentage of clear-defect free wood on a board. The measurements of this percentage are referred to as clear-cuttings. Other than the FAS grades, the grade of the board is determined from the percentage of these clear cuttings and do not consider defects outside of the clear areas.


MEASUREMENT

The NHLA grades are determined on an imperial measurement system using inches and feet. Additionally, the rules were developed with random width and length lumber in mind. A board foot is the unit of measurement.


METRIC CONVERSIONS

STANDARD THICKNESS FOR ROUGHSAWN & SURFACED LUMBER

Thickness of rough sawn lumber is expressed in quarters of an inch. When grading rough sawn lumber, defects such as checks, stain, and warp are not considered if they will surface out at standard surfaced thickness (S2S). The standard thicknesses and surfaced thicknesses with their metric equivalent are shown below.

Rough S2S
3/4 19mm 14.2mm
4/4 25.4mm 20.6mm
5/4 31.8mm 27mm
6/4 38.1mm 33.3mm
8/4 50.8mm 44.4mm
10/4 63.5mm 57.2mm
12/4 76.2mm 69.8mm
16/4 101.6mm 95.2mm

MEASUREMENT OF KILN DRIED LUMBER
Net Tally: Actual board feet after kiln drying
Green Tally: Actual board feet before kiln drying
Shrinkages: Widths can be ¼” below minimum required.
Thickness can be 1 /16” below minimum required.

THE STANDARD GRADES

All boards are graded from the poor face. The clear face percentage for each grade is determined by measuring the width of the clear area in inches multiplied by the length of the clear area in feet. The total is referred to as cutting units.

FAS

Minimum percentage clear: S.M. x 10 or 83 1 /³% (10/12)
Minimum size board: 6” x 8’
Minimum size clear cuttings: 4”x 5’ or 3” x 7’

Example: Determine S.M.
Determine poor face
Measure clear cutting available
Compare with required clear percentage
12’
8 ¼” 8 ¼” x 10’
8 ¼” x 12’ / 12 = 8’ S.M.

Clear cutting: 8 ¼” x 10’ = 82 cutting units
Required cutting units = S.M. x 10 = 80 cutting units
Grade of the board is FAS


Note: Both faces must meet this Minimum Requirement.
FAS = FAS on two faces.

FAS ONE FACE (F1F) AND SELECTS
Minimum size board: F1F: 6” x 8’ Sel 4” x 6’
These two grades combine the standard grades of FAS (on the better face) and No. 1 Com (on the poor face).

NO. 1 COMMON

14’
6’ 6” x 4’ 6” x 7’
6” x 14’ / 12 = 7’ S.M.

2 clear cuttings = 6” x 4’ = 24 c.u.
6” x 7’ = 42 c.u.
66 cutting units total

Required cutting units = S.M. x 8 = 56 c.u.
Grade of board is No. 1 Common.
Note: Both faces must meet this Minimum Requirement. No. 1 Com. = No. 1 Com. on two faces.


NO. 2A COM
Minimum percentage clear: S.M. x 6 or 50% (6/12)
Minimum size board: 3” x 4’
Minimum size cuttings: 3” x 2’
Note: When No. 2A Com. on poor face, the better face does not matter.


NO. 3A COM
Minimum percentage clear: S.M. x 4 or 33 1 /³ % (4/12) Minimum size board: 3” x 4’
Minimum size cuttings: 3” x 2’

FAS F1F SEL 1Com 2ACom 3ACom
Minimum Board 6” x 8’ 6” x 8’ 4” x 6’ 3” x 4’ 3” x 4’ 3” x 4’
Minimum Size Cuttings 4” x 5’
3” x 7’
3” x 3’
4” x 2’
3” x 2’ 3” x 2’
% Clear SM x 10
(83 1/3%)
SM x 8
(66 2/3%)
SM x 6
(50%)
SM x 4
(33 1/3%)
# Clear Cuttings SM / 4 SM + 1/3 SM/2 Unlimited

When specified for export, a comparison can be made respectfully between export grade names of Prime and Comsel with the NHLA grades of FAS and No. 1 Com. It is necessary to consult with your supplier as to the exact specifications being applied to these export grade names.