Guardrails must be provided on the open side of a stair where it is more than 30″ above the floor or grade. Stair rails must be at least 34″ high, measured from the nosing of the stair treads. No opening shall allow a 4 3/8″ sphere to pass through with the exception that you are allowed a larger opening provided for the triangle formed between the stair riser, stair tread, and bottom edge of the bottom rail. This open space may not allow a 6” sphere to pass through it.
Be sure to layout the position of your rail posts before installation. This is usually the trickiest part. If the top rail post is set at the rear of the tread, you will want to align the bottom post similarly. Landings and stairs that change directions will often require the thoughtful situating of rail posts to allow for a system that looks and performs well. The handrails are required and must meet specific requirements.