Final answer:
Guardrails on stairs are typically required if there are more than four risers, according to the International Residential Code; however, local building codes may vary and should be consulted for specific requirements.
Step-by-step explanation:
The requirement for guardrails on stairs depends on the building codes applicable in the area, which are typically based on the model building codes like the International Building Code (IBC) or the International Residential Code (IRC). For example, the IBC requires guardrails on open-sided walking surfaces, mezzanines, industrial equipment platforms, stairways, ramps, and landings that are more than 30 inches above the floor or grade below. The IRC requires guardrails if the stairs have more than four risers. However, it is important to check the local building codes for the exact requirements as they can vary from one place to another and may have been updated or amended locally.