CSLB General Building (B)Framing and CarpentryHard
A contractor is framing a winder staircase where treads narrow toward the inside of the turn. Per building code, what is the minimum required tread depth at the narrow (walk line inner) end of a winder tread?
- A8 inches
- B6 inches
- C4 inches
- D10 inches
Show answer & explanationAnswer & explanation
Correct answer: B. 6 inches
Building code requires winder treads to have a minimum tread depth of 6 inches at the narrow end, along with a minimum tread depth of 10 inches measured at a point 12 inches from the narrow end, to ensure a safe and stable walking surface throughout the turn.
Why the other options are wrong
- A. 8 inches exceeds the minimum required at the narrow point, though it may occur at other locations.
- C. 4 inches is too narrow and would create an unsafe, unstable stepping surface.
- D. 10 inches is the requirement at the 12-inch walk line point, not at the narrow end.
Winder Tread Minimum Width
Winder stairs must maintain a minimum tread depth of 6 inches at the narrow end and 10 inches at a point 12 inches from the narrow end to ensure safe footing.
- 6-inch minimum at narrowest point
- 10-inch minimum at 12 inches from narrow end
- Applies to curved/turning stair sections
Memory trick: Six at the point, ten a foot in — winders still need room for your feet.