Per ADA, stairways must have handrails on both sides, mounted 34–38 inches above the stair tread nosing, with a minimum of 1.5 inches of clearance from walls. Handrails must be continuous along the full flight, extending at least 12 inches beyond the top and bottom risers, and have a graspable, smooth surface with rounded edges. They must be securely mounted to support at least 250 pounds of force.
Additional Information: https://www.ada.gov/law-and-regs/design-standards/standards-guidance/#top