Design a code-compliant staircase from total rise.
The International Residential Code (IRC) requires: max 7-3/4" riser height, min 4" riser height, min 10" tread depth, and 36" minimum stair width. All risers in a staircase must be within 3/8" of each other — inconsistent risers are a trip hazard and a code violation.
The Pythagorean theorem gives stringer length: √(rise² + run²). For 2×12 stringers, ensure at least 3.5" of solid wood remains in the stringer after cutting the step notches.