The fire performance of building products has always come under close scrutiny — and for good reason. The structures where people live and work must be safe. It is for this reason that building codes exist, to provide a means to safeguard life and protect the private and public welfare through regulating the design, construction practices, construction material quality, location, occupancy and maintenance of buildings and structures. When regulating materials, many of the model building codes refer to performance standards developed by standard development organizations such as the American Society for Testing and Materials (ASTM). Some building codes and insurance rating organizations also rely on test information from Factory Mutual Research Corporation (FMRC) and Underwriters Laboratories Inc. (UL).
Fire Tests for Roof Systems
Many fire tests evaluate performance of complete roof systems, from the roof deck through the roof coverings. These tests measure:
- Resistance of a roof system to external fire exposure;
- Roof/Ceiling resistance to an internal fire exposure;
- Resistance to interior fire spread; and
- A roof assembly fuel contribution rate.
Many of these tests involve testing the entire roof assembly, while some focus on the individual components.
Factory Mutual Roof Tests:
FM Calorimeter (FM 4450/4470/4471) and ASTM E108
FM Approvals Global, established to assess product or material risk and system performance for specific insurance underwriters of property, liability and casualty policies, approves roof assemblies based upon a comprehensive series of tests outlined in FM Standards 4450, 4470 and 4471. This series of tests evaluates materials for their ability to resist fire, wind, hail, durability and corrosion of metal parts. Roofing assemblies that successfully pass all tests in Standard 4450 are given an FM Class 1 rating. Other assemblies are rated Class 2.
FM classifies roof decks into two categories:
- Noncombustible Rated
- Class 1 Rated
Noncombustible Rated decks are cementitious decks such as structural concrete, fiber reinforced cement, gypsum and certain lightweight insulating concretes. Class 1 Rated Decks may be steel, fire-retardant-treated wood, cementitious woodfiber, fiber reinforced plastic and certain lightweight insulating concretes.
FM fire performance tests are the FM Calorimeter (FM Standard 4450/4470/4471), used to assess the fuel contribution rate of a roof assembly and the Exterior combustibility test, conducted in accordance with ASTM E108. Insulation products are evaluated in roof assemblies for fire performance using the FM Calorimeter, which in turn qualifies them to be included in assemblies meeting FM 4450/4470/4471 standards. Exterior combustibility is determined in accordance with ASTM E108 and involves all components of the roof assembly to be tested together. The test includes three parts:
- Spread of flame
- Intermittent flame
- Burning brand
The spread of flame is the only test conducted on roof assemblies with concrete, steel or gypsum decks, while all three tests performed on assemblies incorporating combustible (wood, plank, plywood, T&G plank) roof decks. The slope of the roof and maximum insulation thickness are both factors as well.
Underwriters Laboratories Inc. Roof Tests:
UL 790, ANSI/UL 1256 and UL 263
Underwriters Laboratories Inc. (UL) is an independent testing organization established to evaluate products for public safety. UL conducts three basic fire tests for roofing assemblies: Roof resistance to External Fire Exposure (UL Standard 790, ASTM E108, or UBC 15-2), Resistance to Interior Fire Spread, (ANSI/UL 1256), and Roof/Ceiling Fire Resistance Rating (UL 263, ASTM E119, NFPA 251 or UBC 7-1). The UL version of ASTM E108 as previously described is UL 790. As such, three test procedures are included in UL 790: Spread of Flame, Intermittent Flame and the Burning Brand. Since this test evaluates the performance of a roof assembly, all components of the roof system are tested together. With ANSI/UL 1256, the entire roof assembly including deck, adhesives, vapor retarders, insulation and roof membrane is tested in a 25-foot long tunnel for 30 minutes. The test uses an open flame with prescribed airflow in the tunnel. Ratings derived from the test are reported in the UL Roofing Materials and Systems Directory under the Roof Deck Constructions category (TGKX).
The UL version of ASTM E119 is UL 263 and is used to determine the fire resistance of a complete assembly.
Importance of FM 4450 Calorimeter Test and ANSI/UL 1256 Resistance to Interior Fire Spread Test
The spread of fire on the underside of a roof deck is a concern when buildings have large, open interior space, such as a warehouse or manufacturing facility. The two fire tests used by code bodies to evaluate the spread of fire in this manner are FM 4450, also called the FM Calorimeter Test and ANSI/UL 1256 also known as the Resistance to Interior Fire Spread Test. While both tests evaluate the entire roof assembly from deck to roof covering, the test conditions and test pass criteria are very different Only roof assemblies that pass FM 4450 may be used in FM insured buildings.