Fire and Wind Safety for Commercial Roofs: Important Considerations
A commercial building’s roofing system plays a critical role in its performance and longevity while protecting interior building components and ensuring that occupants stay safe. Building performance is based on a structure’s ability to “tolerate specified magnitudes of events within tolerable limits of damage,” states the ICC Performance Code for Buildings and Facilities (ICCPC). These ‘events’ can be natural (expected) or technological hazards. Expected events include wind, rain, ice, snow, and thermal loads, while technological hazards range from fires and explosions to exposure to corrosive and toxic materials.
Roof damage typically occurs because of roof system abuse, material deterioration, inferior design, or inadequate roofing application. Safely-designed and regularly maintained commercial roofs offer the necessary fire safety and wind load resistance to protect commercial buildings and tenants from catastrophic roof failures.
Fire Ratings and Fire Resistance
“It is easier to design a roof that will resist penetration and fire spread than to ensure that a roof will not cause this problem.”
Fire safety is a top life-safety consideration for any commercial roof. Commercial roof assemblies must have built-in safeguards against spreading fire to prevent building damage, loss of property, or severe or fatal injury to occupants from fire, smoke, or toxic fumes. This is especially true in built-up cities or industrial or manufacturing districts, where buildings are positioned closely together, and fires can spread rapidly.
Several fire ratings have been developed to rate the fire resistance of various roof coverings and materials to encourage increased fire safety in a commercial building’s design and construction. Class A is the highest fire rating possible, providing the best performance, while Class C and ‘unrated’ are the lowest.
Standard fire tests establish a roof cover’s performance (or rating) when exposed to fire. Materials are tested to see how easily and quickly flames take to spread across the roof’s surface or penetrate through the roofing material. How rapidly a roofing membrane loses its integrity is also a testing criterion.
Critical considerations for fire-resistant commercial roofs include their system type and slope
While noncombustible roof coverings like slate, concrete, and clay tiles, asphalt/glass fiber composition shingles, and metal panels generally offer Class A or B fire resistance when tested, a roof assembly is always the sum of its parts. As a 2010 NRCA tech article highlights, even if roof membranes are Class A-rated, underlayment sheets and roof decks selected for use in a roof system may not offer a Class A or B fire rating.
Changes in the 2009 International Building Codes (IBC) now make it mandatory for all roof coverings to undergo a standard fire test to determine their performance when exposed to fire. Only coverings installed over a noncombustible roof deck or on noncombustible framing are exempt from fire testing. Roof coverings made from recycled plastic and rubber, some wood shake products, and aluminum require additional materials to be used between the roof covering and sheathing to attain a Class A rating.
Another key consideration for fire-rated roof coverings is that, if used on steep-slope roofs, they offer less fire resistance than when applied to low-slope roofs. In this case, contractors must take additional precautions to increase a roof structure’s fire-resistant properties.
Wind Uplift Ratings and Wind Load Resistance
Several factors impact how wind interacts with a building, including the structure’s height and its exposure to or protection from high-speed winds. For example, buildings in urban and suburban areas enjoy greater protection from strong winds. Conversely, facilities near flat and unobstructed surfaces (such as large bodies of water or open tracts of land) are subject to greater wind loads and uplift pressures. Tall buildings also experience faster wind speeds, which in turn increases wind loads.
Wind uplift occurs when the air pressure below a roof assembly exceeds the air pressure above it. Various wind uplift ratings are used to test the uplift resistance of roof structures and coverings. The highest wind uplift occurs at roof corners and edges. It’s here that strong winds can often wreak havoc on buildings, leading to damaged roof covers, roof deck blow-offs, or even roof structure collapse.
Roofing contractors must pay special attention to the design selection of a commercial roof to mitigate wind uplift or wind force damage. Correctly attaching roof systems to the substrate and using appropriate wind-uplift compliant roofing materials is critical for ensuring adequate wind resistance.
For example, fasteners are often required at the perimeter and corners of roof membranes to meet various wind uplift loads. For commercial buildings in areas where basic wind speeds increase beyond 90 mph, various “design, construction, and maintenance enhancements” are also advised.
Wind and Fire Safety Concerns for Building Managers
If you don’t know enough about roofing products, safety specifications, codes, and requirements, ensuring that the appropriate fire- and wind-resistant roofing systems and materials are used for your commercial roof installation or repair project can be challenging.
RoofSource can assist. As a building products manufacturer representative in the Southwestern United States, we can inspect your commercial roof to confirm your roofing project’s scope of work. We can also set the parameters for the warranties, roof system type, and the quality of the materials needed so that roofing contractors quoting on the work can use this data to comply with local and state building codes.
We have established relationships with reputable product manufacturers and contractors and can help recommend the right contractors for the job. You can rest assured that any roof system specified and installed on your commercial building will provide long-term performance while keeping occupants safe.
Contact us today to talk to a specialist about your commercial roofing project needs.