How is Lumber Classified?
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.
Boards are listed in most cases by their nominal dimensions. Actual sizes for S4S finished lumber should be as follows: