All stairways shall have a rise of not over eight inches to a step, and not less than nine inches tread, exclusive of the nosing. All stairways and all hallways must be not less than three feet in width in houses containing less than fifteen rooms; not less than three feet six inches in width in houses containing not less than fifteen rooms and not more than twenty-five rooms; and not less than four feet in width in houses containing twenty-five or more rooms.