Brunette Girl Wearing Erotic Outfit On The Stairs With Iron Handrails

Codes also generally require that there be a 1½" clearance between the underside of the handrail and any obstruction -- including the horizontal bracket arm. There is an allowance however for variations in the handrail size -- for every 1/2" of additional perimeter dimension over 4", 1/8" may be subtracted from the clearance requirement.
Handrail strength (USA)
Handrails and railings are to support a continuous load of 50 plf(75 kg-m) or a concentrated load of 200 pounds (90 kg). While most steel and aluminum members are adequate to accommodate those loads, decorative wood balusters generally fail under the required loads.