Wood Grades and Grading
The rules adopted by the National Hardwood Lumber Association are considered standard in grading hardwood lumber intended for cutting into smaller pieces to make furniture or other fabricated products. In these rules, the grade of a piece of hardwood lumber is determined by the proportion of a piece that can be cut into a certain number of smaller pieces of material, commonly called cuttings, which are generally clear on one side, have the reverse face sound, and are not smaller than a specified size.
The best grade in the Factory lumber category is termed FAS. The second grade is F1F. The third grade is Selects, which is followed by No. 1 Common, No. 2A Common, No. 2B Common, Sound Wormy, No. 3A Common, and No. 3B Common. Except for F1F and Selects, the poorer side of a piece is inspected for grade assignment. Standard hardwood lumber grades are described in Table 5–1. This table illustrates, for example, that FAS includes pieces that will allow at least 83-1/3% of their surface measure to be cut into clear face material. Except for Sound Wormy, the minimum acceptable length, width, surface measure, and percentage of piece that must work into a cutting decrease with decreasing grade. Figure 5–1 is an example of grading for cuttings.
This brief summary of grades for Factory lumber should not be regarded as a complete set of grading rules because many details, exceptions, and special rules for certain species are not included. The complete official rules of the National Hardwood Lumber Association (NHLA) should be followed as the only full description of existing grades.
Standard Hardwood Lumber Gradesa,b
| Grade and allowable lengths | Allow. width (in) | Allowable surface measure of pieces (ft2) | Minimum amount of piece in clearface cuttings (%) | Allowable cuttings | |
|---|---|---|---|---|---|
| Max. no. | Min. size | ||||
| FASc | 6+ | 4 to 9 10 to 14 15+ | 83-1/3 | 1 2 3 | 4 in. by 5 ft, or 3 in. by 7 ft |
| F1Fc | 6+ | 4 to 7 6 and 7 8 to 11 8 to 11 12 to 15 12 to 15 16+ | 83-1/3 91-2/3 83-1/3 91-2/3 83-1/2 91-2/3 83-1/3 | 1 2 2 3 3 4 4 | 4 in. by 5 ft, or 3 in. by 7 ft |
| Selects 6 to 16 ft (will admit 30% of 6 to 11 ft) | 4+ | 2 and 3 4+ | 91-2/3 —d | 1 | 4 in. by 5 ft, or 3 in. by 7 ft |
| No. 1 Common 4 to 16 ft (will admit 10% of 4 to 7 ft, 1/2 of which may be 4 and 5 ft) | 3+ | 1 2 3 and 4 3 and 4 5 to 7 5 to 7 8 to 10 11 to 13 14+ | 100 75 66-2/3 75 66-2/3 75 66-2/3 66-2/3 66-2/3 | 0 1 1 2 2 3 3 4 5 | 4 in. by 2 ft, or 3 in. by 3 ft |
| No. 2 Common 4 to 16 ft (will admit 30% of 4 to 7 ft, 1/3 of which may be 4 and 5 ft) | 3+ | 1 2 and 3 2 and 3 4 and 5 4 and 5 6 and 7 6 and 7 8 and 9 10 and 11 12 and 13 14+ | 66-2/3 50 66-2/3 50 66-2/3 50 66-2/3 50 50 50 50 | 1 1 2 2 3 3 4 4 5 6 7 | 3 in. by 2 ft |
| Sound Wormye No. 3A Common 4 to 16 ft (will admit 50% of 4 to 7 ft, 1/2 of which may be 4 and 5 ft) | 3+ | 1+ | 33-1/3f | —g | 3 in. by 2 ft |
| Sound Wormye No. 3B Common 4 to 16 ft (will admit 50% of 4 to 7 ft, 1/2 of which may be 4 and 5 ft) | 3+ | 1+ | 25h | —g | 1-1/2 in. by 2 ft |
| aCurrent grading rules are written only in the inch–pound system of measurement. bInspection made on poorer side of piece, except in Selects grade. cFAS is a grade that designates Firsts and Seconds. F1F is a grade that designates FAS one face. dSame as F1F, with reverse side of board not below No. 1 Common or reverse side of sound cuttings. eSame requirements as those for No. 1 Common and better except that wormholes and limited sound knots and other imperfections are allowed in cuttings. fAlso admits pieces that grade not below No. 2 Common on the good face and reverse side of sound cuttings. gUnlimited. hCuttings must be sound; clear face not required. |