Framing & StructuralQuestion 452 of 700

On a stairway that turns using winder treads, what is the MINIMUM tread depth measured at the walk line, and the MINIMUM depth at any point of the narrow end?

a.12 inches at the walk line and 8 inches at the narrow end
b.10 inches at the walk line and 6 inches at the narrow end
c.11 inches at the walk line and 10 inches at the narrow end
d.7 inches at the walk line and 4 inches at the narrow end

Explanation

Winder treads must provide at least 10 inches of depth at the walk line (typically 12 inches from the narrow side) and never less than 6 inches at any point. The other options either overstate the required depths or allow a dangerously narrow 4-inch section at the inside of the turn.

Law Reference: 2025 CA Residential Code §R311.7.5.2.1

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