Framing & StructuralQuestion 375 of 700
A spiral stairway is permitted in a dwelling under special rules. Which requirement is characteristic of a code-compliant spiral stair?
a.Treads must be at least 11 inches deep at every point
b.Each tread provides a minimum run at a defined walk-line point (about 12 inches from the narrow edge) and headroom is at least 6 feet 6 inches
c.Risers may be any height with no limit
d.No center column is allowed
Explanation
Spiral stairs are allowed with special geometry: the tread depth is measured at a walk line roughly 12 inches from the narrower edge and must meet a minimum there, with reduced but defined headroom of at least 6 feet 6 inches. Uniform 11-inch treads, unlimited risers, and a no-center-column rule do not describe a spiral stair.
Law Reference: 2025 CA Residential Code §R311.7.10.1Practice all 700 questions free — no signup required.
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