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A Brief Guide to Lumber and Plywood Grading

(Also See - A Brief Guide to American Hardwoods.)


Most hardwood lumber is sold under the "quarter" (1/4) system: Four - 1/4" to an inch.
In other words "4/4 rough" equals 1" thick, 5/4 equals 1-1/4" thick, 8/4 equals 2" thick, etc.


Most hardwood is sold by the board foot (1bf. = 144 cubic inches).
To calculate board feet, multiply length in inches by width in inches by thickness and divide by 144" (i.e. 96"L x 6"W x I "T = 576" divided by 144" = 4 bf.).
Board footage is calculated on lumber prior to surfacing, and often prior to drying. Material less than one inch is tallied by the square foot.


FAS ( First and Seconds)
Provides long, wide, clear cuttings. Best suited for high quality work. Must yield 83 1/3% to 100% clear wood in cuttings at least 3" x 7' or 4" to 5'.
Select & Better
Both faces of the board are used in determining the grade. Best face must meet FAS, reverse must essentially grade No. 1 Common.
No. 1 Common
Provides clear cuttings of medium length and width. Includes a range of boards which will yield from 66 2/3% to 83 1/3% clear wood in minimum sized cuttings at least 3" x 3' or 4" x 2'.

ANSI Plywood Grading Standards for Hardwood Plywood

Plywood is graded with a two-character stamp, such as A-1, B2, etc.
The grades reflect the quality of the face veneer and back veneer respectively.
Here are the descriptions of the ANSI grading standards.

 Face Grade
Back Grade
Where excellent appearance is very important as in cabinets and furniture.
1 - 2
Provide sound surfaces with all openings in the veneer repaired except for vertical worm holes not larger than 1/16".
Where the natural characteristics and appearance of the species are desirable.
Some open defects. Repaired splits, joints, bark pockets, laps and knotholes can achieve a sound surface if specified by the buyer.
C - D
Provide sound surfaces but allow unlimited color variation. Repairs in increasing size ranges allowed respectively from C to D. Applications - where surface will be hidden or a more natural appearance is desired.
Some open defects. Knotholes up to 4" in diameter are permitted. open splits, and joints limited by width and length.

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