Hi Chris,
The key is this:
chris mc wrote:IRC.
In dwelling units only one handrail is required and on only one side: (bold is mine)
R311.5.6 Handrails. Handrails shall be provided on at least one side of each continuous run of treads or flight with four or more risers.
You are thinking of the IBC and intermediate handrails, which is often misapplied anyway as the requirement is for 'the required width' and not 'the actual width' - i.e., the required width may be 60 inches with a handrail required on each side, while the actual width may be 60 feet ... and still only those two handrails are required. Intermediate handrails are only required if the required width is greater than 60 inches (which leaves a handrail within 30 inches). If the required width was 120 inches, and the actual width was 60 feet, only one intermediate handrail would be required - the two side handrails would account for the first 60 inches of required width and the intermediate handrail would account for the second 60 inches of required width (30 inches to each side of the intermediate handrail): (bold is mine)
1012.8 Intermediate handrails. Stairways shall have intermediate handrails located in such a manner so that all portions of the stairway width required for egress capacity are within 30 inches (762 mm) of a handrail. On monumental stairs, handrails shall be located along the most direct path of egress travel.