Minimum Inside Radius For Circular Stairs

The minimum inside radius for circular stairs is double the distance of the tread width.

Example: If the stair tread width is 4 feet, then the inside radius can't be less than 8 feet. From the center point of the circular stairs, to the inside of the circular stairway (distance between two arrows in illustration above) couldn't be less than 8 feet.

Attention: Don't forget to check with your local building department to verify any building codes on this website. This information could be incorrect or outdated. Building codes are updated regularly and to some building departments have different interpretations for certain building codes.

Acceptable Circular Stair Design

Circular Stair Design That Doesn't Meet This Particular Building Code