Here are some helpful abbreviations and charts.
A board foot is 12" X 12" X 1".
Abbreviations
| BF | Board feet |
|---|---|
| Com | Common |
| CLR | Clear |
| E | Edge |
| KD | Kiln Dried |
| RGH | Rough |
| RL | Random Lengths |
| RW | Random Widths |
| RLW | Random lengths and widths |
| S1S | Surfaced one side |
| S2S | Surfaced two sides |
| S4S | Surfaced four sides |
Sizes
A "quarter" system is commonly used in the hardwood lumber industry when referring to thickness. 4/4 refers to 1 inch think board. 6/4 is 1-1/2 inch, 8/4 is 2 inches, and so on.
| Quarter Size | Rough Dimension | S1S | S2S |
|---|---|---|---|
| 4/4 | 1" | 15/16" | 7/8" |
| 6/4 | 1-1/2" | 1-7/16" | 1-3/8" |
| 8/4 | 2" | 1-15/16" | 1-13/16" |
| 12/4 | 3" | 2-13/16" | 2-3/4" |
Grading
Most of the hardwood lumber in the United States and Canada is graded according to the rules established by the National Hardwood Lumber Association (NHLA). In fact, the NHLA grading rules form the basis for much of the international hardwood lumber trade. The standard grades of hardwood lumber as defined by the NHLA (in descending order of quality) are FAS, FAS 1-Face (F1F), Selects, No. 1 Common, No. 2A Common, No. 2B Common, Sound Wormy, No. 3A Common, and No. 3B Common. In practice, some of the above grades are rarely used in the commercial trade and others are typically combined. For example, FAS and FAS 1-Face are usually combined and sold as "Face And Better", FAS and Selects as "Sel and Better", No. 1 Common and Selects as "No. 1 Common and Better", and No. 2A Common and 2B Common as "No. 2 Common". The grade of Sound Wormy is rarely used commercially.
Grading is based on the size and number of clear cuttings that can be obtained from a board when it is cut up and used for furniture or other products. The higher grades require wider and longer cuttings of clear wood than the lower grades. The specified clear face yield is also realized in a smaller number of cuttings with the higher grades. In the lower grades, the larger number of cuttings permitted provide more leeway in cutting between defects to realize the yield. With a few exceptions, grade is determined from the worst side of a board.
The surface measure of a board is used to determine the number of cuttings permitted for a given grade. For example, the FAS grade specifies a minimum size of 4" x 5' or 3" x 7' for cuttings taken from a board that is at least 6" wide and 8' long. The maximum number of cuttings is nominally four to produce a clear-face yield of 83 1/3 percent. If the surface area of the board is greater than 6 square feet, an additional cutting is allowed if the yield can be raised to 91 2/3 percent.
In selecting wood for a woodworking project, consider the size of the boards required. In many situations, lower grades are a more economical choice than the higher grades; in particular, consider using Select or No 1. Common grade boards rather than FAS if a relatively larger number of small, clear pieces are required.
Note that unlike softwood grades, hardwood grades do not indicate the strength of the board. Another difference is hardwood grading does not require a certified or licensed grader. Purchasing lumber from well-established reputable sources increases your chances of consistently obtaining accurately graded lumber.
The standard hardwood lumber grades are summarized below:
| Grade | Minimum board length | Minimum board width | Minimum cutting size | Min. area of clear cuttings required |
|---|---|---|---|---|
| FAS | 8' | 6" | 4" x 5' 3" x 7' | 83-1/3% |
| F1F | 8' | 6" | 4" x 5' 3" x 7' | 83-1/3% |
| 4" x 2' 3" x 3' | 66-2/3% | |||
| Selects | 6' | 4" | 4" x 5' 3" x 7 | 83-1/3%, 66-2/3% |
| No. 1C | 4' | 3" | 4" x 2' 3" x 3' | 66-2/3% |
| No. 2AC | 4' | 3" | 3" x 2' | 50% |
| No. 2BC | 4' | 3" | 3" x 2' | 50% |
| No. 3AC | 4' | 3" | 3" x 2' | 33-1/3% |
| No. 3BC | 4' | 3" | 1-1/2" x 2' | 25% |
FAS
FAS derives from an earlier grade known as "First and Seconds". It is the best and most expensive grade. Boards 6" and wider, 8' and longer. Yields 83-1/3 percent of clear face cuttings with minimum sizes of 4" x 5', or 3" x 7'. Suitable for fine furniture, interior joinery, solid wood moldings, and other applications where clear, wide boards are needed.
FAS 1-Face (F1F)
One face meets FAS requirements and the poorer face meets Number 1 Common grade requirements. Usually combined with FAS lumber, thereby providing at least one FAS face.
Selects
Face side is FAS, back side is No. 1 Common. Boards are 4" and wider, 6' and longer. Yields 83-1/3 percent clear face cuttings with minimum sizes of 4" x 5', or 3" x 7'. A cost effective substitute for FAS when only one good face is required.
No. 1 Common
Often referred to as "Cabinet" grade in the USA due to its extensive use for kitchen cabinets. Boards are 3" and wider, 4' and longer. Yields 66-2/3 percent clear face cuttings with minimum sizes of 4" x 2', or 3" x 3'. Provides good value, especially if relatively small pieces can be used.
No. 2A Common
Also known as "Economy" grade. Boards are 3" and wider, 4' and longer. Yields 50 percent clear face cuttings 3" and wider by 2' and longer. Grade of choice for US hardwood flooring industry.
No. 2B Common
Same as No. 2A Common, except that stain and other sound defects are admitted in the clear cuttings. An excellent paint grade.
Sound Wormy
Same requirements as #1 Common and better but wormholes, limited sound knots and other imperfections allowed. Not commonly available.
No. 3A Common
Boards are 3" and wider, 4' and longer. Yields 33-1/3 percent clear face cuttings 3" and wider by 2' and longer. Economical choice for rough utility applications: crates, palettes, fencing, etc.
No. 3B Common
Boards are 3" and wider, 4' and longer. Yields 25 percent clear face cuttings 1-1/2" and wider by 2' and longer. Applications same as No. 3A Common.
Choosing the right wood for the job
With a few exceptions, exotic species are typically denser growers than domestic woods. Wood hardness is measured on the Janka Hardness Scale. Most US domestic woods range from 540-1820 pounds-force (lbf) on the scale and 1150-3600 lbf for exotics. Of course there will be outliers, but this is the trend.
Exotic woods are great for cutting surfaces because of this denser construction, however some exotics will affect skin and breathing so be careful and use safety precautions. Domestic woods are plenty hard for most applications and are available cheaper per board foot than most exotics, which often makes them better suited for larger furniture and big projects.
Milling vs Flattening
The term milling is often used for jointing, planing, and ripping materials into a specific size for a project. Also abbreviated by surfaced sides, an example is S3S or S4S which are surfaced 3 sides or surfaced 4 sides respectively.
Flattening is a term we use in the case of a wide glue-up or a large slab. It involves using a carbide cutter to take parallel layers off of each side, both leveling and reducing thickness.
Storage and maintenance tips
All solid wood, whether it is a board or a slab, will change and move with temperature and moisture in the air.
Storing
All wood regardless of species should be kept off of solid flat surfaces and from being stacked face to face for long periods of time. Never store lumber or slabs on the floor or concrete. The best action is to sticker between each piece to allow acclimation to your environment and to ensure that air and moisture exposure is the same on all sides of the wood. Both faces need the same amount of air flow.
Seasonal movement for solid wood and live edge slabs
When attaching wood tops and/or live edge slabs to legs or bases, room for movement is necessary. Climate bars for larger tops and slabs are a great idea. These are C-shaped pieces of steel which are usually routed into the bottom side of the top and have slotted screw holes to attach, which will allow this movement to occur naturally without putting tension on the wood. For smaller or thinner tops, Z Clips are perfect for attachment points. These clips can be purchased online and screw to the underside of the top, where they rest in a biscuit groove on the base to allow for subtle seasonal movement.