Waste should come from a board layout and cut plan, not a single percentage copied across every deck.
Straight layouts establish the baseline
Calculate rows using actual board width plus required spacing. Then compare deck length with available stock lengths. A deck that matches stock length closely may produce little end waste; frequent butt joints can change that result.
Patterns consume material differently
Diagonal boards create angled offcuts at the perimeter. Picture frames and breaker boards need separate linear-foot calculations and supporting framing. Stairs, fascia, skirting, benches, and privacy screens are separate scopes.
Check product rules before optimizing cuts
Manufacturer requirements can control joist spacing, end gaps, fastener location, butt-joint treatment, and allowable overhang. A mathematically efficient layout is not useful if it violates the installation instructions or approved structure.
Sources & further reading
References behind this guide
These sources support safety, measurement, or industry context. Product instructions, approved plans, and local requirements control your project.