Explaining Lumber Grading
“Wood is a natural material and by its very nature may contain different characteristics and defects that need to be understood and allowed for in any given application. The grading of sawn wood into categories as it is processed helps to determine to a large extent the value and potential use possible for each board of sawn lumber.”
– American Hardwood Lumber Council
From the moment green timber falls to the moment that lumber is shipped, industry deals with the distinctions of wood: species, sizes, defects and moisture content (MC). Worldwide, lumber producers “grade” softwoods, hardwoods and exotic woods in order to assure builders and consumers of their quality. That grading system influences a number of industries:
- Builders, inspectors and other professionals use these grades to ensure that quality lumber is used where it is needed.
- Structural engineers take these grades into structural design considerations.
- U.S. and Canadian building codes require graded, stamped lumber to be used in framing.
Put simply, lumber grading serves quality assurance needs. Building trades rely on those stickers at the end of every board for the structural performance of every structure that they will be used to build.
The Simplified Process of Determining Hardwood Lumber Grades
The grading rules are quite complex and require study. A very simplified, condensed overview on the steps for grading a piece of hardwood lumber is as follows:
- Determine the species. Some species must be processed according to special rules.
- Determine the surface measurement (SM). SM is the width, in inches and fractions, times the standard length in feet with no fractions or rounding, divided by 12 with the answer rounded to the closest whole number.
- Determine the poor face, which is the side with the lowest grade.
- Assume a trial grade for the piece of lumber and then see if all the conditions for that grade are met.
- Determine if lumber size requirements (length and width) are met for the chosen grade.
- Determine the number of clear cuttings that are permitted.
- Determine the cutting yield required by multiplying the surface measurement (SM) by the grade values respectively. The required yield is expressed in cutting units. A cutting unit is 1 inch wide by 1 foot long.
- Locate cuttings to obtain the maximum area; then calculate the cutting area. Make sure the cutting sizes are not below the minimum size for the trial grade.
- When the piece grade is No. 1 common, check the reverse side to see if the reverse is FAS grade. If so, and if a few other requirements are met, then the piece is Select or FAS 1-Face.
- Check to make sure that the piece qualifies for the anticipated grade in all other respects, which include the amount of wane, the amount of pitch outside the cuttings and so on.
The Common Element of Moisture
A wood’s MC content must be measured and managed in order for lumber to meet all grade-related strength and performance standards. Each wood species has indigenous MC characteristics, which is why lumber manufacturers deploy moisture meters for wood throughout their manufacturing operations. From in-line moisture measurement/management systems to the hand-held wood moisture meters, MC measurement and management applies to all graded lumber categories.
Hardwood Lumber Grading Categories
Several assessments lead inspectors to grade lumber according to certain categories. There are eight hardwood lumber grades in widespread use at this time. FAS is the highest and No 3B Common is the lowest grade. A brief description of the basic grades are as follows:
FAS: Shorthand for “First and Seconds”. FAS is the highest grade of hardwood lumber.
FAS 1-Face (abbreviation: F1F): A “Select” piece of lumber which is six inches and wider.
Select: A No. 1 Common piece of lumber (the poorer side of the wood piece is assigned as No. 1 Common grade) and the reverse side (the better side) grades FAS. The price of Selects and 1-Face is usually the same as FAS. Often, Select grade lumber is used in the Northern U.S., while 1-Face is used in the South.
No. 1 Common is the standard furniture grade lumber and provides a good selection of long, medium and short cuttings at a reasonable price.
No. 2A Common (also known as No. 2 Common) is the standard grade for cabinets, millwork, and other uses requiring medium to short cuttings.
No. 2B Common is the same as No. 2A Common, except that stain and other sound defects are admitted in the clear cuttings. It is an excellent grade for painting.
No. 3A Common is often combined with No. 3B Common, and the combination is sold as No. 3 Common, which is widely used for flooring and pallets.
No. 3B Common is graded on the basis of sound cuttings rather than clear cuttings. It is widely used for pallets and crates.
Understanding grading categories can help with both selecting the appropriate wood stock for your intended woodworking project and, with the help of an accurate wood moisture meter, for ensuring a successful and satisfying end product service life as well.
Knowing the importance of moisture measurement and management all through your woodworking or wood flooring projects is crucial to achieving the best in performance and durability. Wagner Meters offers accurate solutions for those moisture management priorities.
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