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A Brief Guide to Lumber and Plywood Grading

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



LUMBER DIMENSIONS

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.



BOARD FOOT CALCULATION

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.



LUMBER GRADES

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
A
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".
B
Where the natural characteristics and appearance of the species are desirable.
3
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.
4
Some open defects. Knotholes up to 4" in diameter are permitted. open splits, and joints limited by width and length.

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