Rough-sawn lumber is cut to thickness directly off the mill and left unsurfaced. The face texture and saw marks remain, and the board retains full dimension.
This matters because wood moves during drying and acclimation. Leaving boards rough-sawn preserves thickness so they can be trued after they stabilize in their intended environment.
Rough-sawn output is not “unfinished lumber.” It is lumber at the correct stage of processing for projects that care about performance and final fit.
For old timber, rough-sawn is a practical choice because density variation and internal stress can differ from board to board.
