Choose board direction first
The dimension perpendicular to the boards controls the number of courses, while the parallel dimension controls board length demand.
Changing direction can change both seams and waste even when deck area stays constant.
Use actual face width and gap
Course spacing is the installed board width plus the intended gap.
Nominal lumber names should not replace measured or manufacturer-published dimensions.
Match courses to stocked lengths
Convert total run into available stock lengths only after the course count is known.
Breaker boards, picture frames, and required butt-joint patterns need separate layout treatment.
Use waste for real cuts
End trimming, defects, selective placement, pattern borders, and unavoidable offcuts can increase purchase quantity.
A simple rectangle using full-length boards may need a different allowance from a complex deck.
Verify the complete deck system
Surface-board quantity does not size joists, beams, footings, ledgers, guards, or connections.
Use product installation instructions and code-compliant structural design for the supporting system.