Shatterproof safety glass is required on all windows when the house wall acts as a barrier to adjacent stairs, landings or areas at the top and bottom of stairs. If a window or a portion of a window falls within the zone shown in the image below, the window must be safety glazed. This rule is designed to prevent injuries due to accidental impact from falls. The application of safety glazing film to glass that was not originally treated is acceptable. You also can install a guardrail at least 18" from the glass to satisfy the requirement.