What are the design criteria such as deflection limits and strength for wood guard rails or hand rails?
The International Building Code (available from ICC) requires handrails and guards be designed to resist a load of 50 plf applied in any direction at the top of the handrail or guard, a single concentrated load of 200 lbs applied in any direction at the top, and a 50 lb. load applied horizontally over a one square foot area of the plane of the intermediate rails or balusters (applied normally), transferring these loads through supports to the structural elements of the building. These loads need not be assumed to act concurrently. In addition, there is a provision that when using allowable stress design (working stress design), the allowable stress for members and their attachments are permitted to be increased by one-third.

Most rail systems are hardwoods and need a different set of design values (Note that most of the hardwoods used typically do not have a grade stamp, they would have to be graded in some way to determine design values, assuming they are in the NDS Supplement). Furthermore, no criteria for deflection exists for this application. The test criteria are commonly interpreted to mean ultimate load at failure.