The Basics of Fire Ratings
One of the primary responsibilities an Architect must fulfill on every project, is to protect the Health, Safety and Welfare (HSW) of everyone using, or occupying, a building. This is achieved through various strategies including the use of fire alarms, automatic sprinkler systems, and fire-resistance-rated assemblies. These are employed to ensure occupants sufficient time to exit the building should a catastrophic event take place, such as a building fire.
Fire-resistance-rated elements are floors, walls, or roofs, comprised of multiple components that when tested together form an assembly that resists the spread of fire. These assemblies are identified to resist the spread of fire for a designated length of time while remaining intact. Fire-ratings vary in hourly increments from 1-hour up to 4-hours, but in rare instances can be as low as 30-minutes. The required fire ratings as determined by the International Building Code (IBC) are largely dependent on the building’s type of construction (masonry, metal, wood, etc.), the building’s use (activities taking place within), as well as the flammability of the building’s anticipated contents. To be effective, fire-rated assemblies must be installed continuously, without interruption, and any openings in fire-rated assemblies, such as doors, windows, etc. must also be either fire-rated themselves or protected by a fire-rated device, such as a damper or fire shutter.
In multi-use buildings, fire-rated (demising) walls separate tenant spaces, to allow time for firefighters to extinguish a fire before it spreads to adjacent tenant spaces. And, when in close proximity to one another, exterior fire-rated assemblies can delay and/or prevent the spread of fire to adjacent buildings.
Typically, multiple strategies are employed in tandem, which consists of an advance warning system (fire alarm), an automatic extinguishing system (fire sprinklers), and use of fire-resistance-rated assemblies; all with the ultimate goal of preserving human life.