Lumber: Board Classification

S2S - Surfaced 2 Sides - These boards have been surface-planed on top and bottom.

S2S1E - Surfaced 2 Sides One Edge.<

S3S - Surfaced 3 Sides - These boards have been one-edge surface-planed on top/bottom and straight line ripped on one edge.

S4S - Smooth 4 Sides - These boards have been planed and sanded on all 4 sides to their finished dimensions and are usually sold by the linear foot.

FAS - Firsts and Seconds. Generally clear of large knots, FAS boards may be Rough cut, S2S, or S3S.

Rough - Not surfaced on any side.

Board Dimensioning
Boards are listed in most cases by their nominal dimensions. Actual sizes for S4S finished lumber should be as follows:

1 x 2
3/4" x 1-1/2"
2 x 2
1-1/2" x 1-1/2"
1 x 3
3/4" x 2-1/2"
2 x 3
1-1/2" x 2-1/2"
1 x 4
3/4" x 3-1/2"
2 x 4
1-1/2" x 3-1/2"
1 x 6
3/4" x 5-1/2"
2 x 6
1-1/2" x 5-1/2"
1 x 8
3/4" x 7-1/4"
2 x 8
1-1/2" x 7-1/4"
1 x 10
3/4" x 9-1/4"**
2 x 10
1-1/2" x 9-1/4"**
1 x 12
3/4" x 11-1/4"**
2 x 12
1-1/2" x 11-1/4"**
** Has been known to vary