R. Lance Manson, RRC, CDT, BSCM, Senior Roof Consultant, Delta Engineering & Inspection, Inc.
The importance of fire rating for roof coverings is not limited to compliance with code: it can save the roof from
catastrophic damage. Recently, I came across two cases which involved a single-ply membrane on combustible
decks that were non-classified assemblies (untested or failed the tests). Both structures on which the roofs were installed were required to have a roof covering with a minimum Class B fire classification. Achieving this fire classification typically starts beneath the membrane with a coverboard or a rigid insulation with board edges staggered from panel edges. Since the roof provides protection from above, it was not possible, unfortunately, to achieve the code-required Class B without removing and replacing the roof membranes.
Why Fire-Rated Roof Coverings?
A roof fire may be the result of:
■ a lightning strike,
■ burning air-borne debris,
■ faulty electrical,
■ mechanical, or photovoltaic components,
■ arson, or
■ improper use of equipment.
An Internet search for "roof fires" reveals multiple recent occurrences in Florida, which were due to one of these causes. The structures included:
■ a high-rise,
■ a church,
■ a nursing home,
■ an aerospace facility,
■ a middle and elementary school, and
■ a large box store.
In October of 2018, the National Fire Protection Association (NFPA) published "Fire Loss in the United States During 2017:' The report stated that 499,000 structure fires occurred in 2017 (five percent increase from 2016), which resulted in $10.7 billion in property damage (structure fires only). There were 3,000 civilian
deaths and 12,160 injured based on NFPA's 2017 National Fire Experience Survey.
What is a Fire Rated Roof Covering?
A fire rated (FR) roof covering provides a degree of fire protection to the roof deck, does not slip from position, and is not expected to produce flying brands. The roof covering includes all the above deck components (i.e. membrane, coverboard, insulation, slip sheet, etc.) whereas a roof assembly includes the deck. To be classified,
the roof system is tested in accordance with UL 790 or ASTM E 108 "Standard Test Methods for Fire Tests of
Roof Coverings;' which simulate fire sources from outside and evaluate the roof covering when installed on combustible (i.e. wood, oriented strand boards or plywood) or noncombustible (i.e. metal, concrete, or poured gypsum) decks. Fire classifications are divided into three classes: A, B, or C; the degree of effectiveness against severe, moderate, or light fire exposure, respectively. There are often limitations for incline; a roof that is steep may permit a fire to spread too quickly.
What Does 2017 Florida Building Code Require?
According to the 2017 Florida Building Code - Building Sixth Edition (FBC), Chapter 15: Roof Assemblies and
Rooftop Structures, §1505 Fire Classification, §1505.1 General: roof assemblies shall be ... tested in accordance with ASTM £108 or UL 790 ... and comply with Table 1505 based on the type of construction of the building. Also, §1505 defines all three classes and non-classified roofing.
Relevant chapters of the FBC include:
■ Chapter 3: Use and Occupancy Classification,
■ Chapter 5: General Building Heights and Areas,
■ Chapter 6: Types of Construction, and
■ Chapter 15: Roof Assemblies and Rooftop Structures.
Chapter 3 provides what occupancy group a structure
belongs to based on the description provided; §302.1 General, lists 10 groups. Chapter 5 provides what type of construction based on occupancy group and building height, refer to Table 504.3 in §504. Chapter 6 defines each of the five construction types, which are based on combustibility of building materials. Additionally, Table 1505.1 in §1505 has three exemptions with two applicable to single-ply roof coverings: a) structures located in a fire district listed in Appendix D of International Wild land-Urban Interface Code (require a Class A rating) and b) non-classified permitted for Group R-3 and Group U when there is a minimum six-foot fire-separation. Contact the project's local authority having jurisdiction (AHJ) for specific project requirements; local ordinance may require more stringent requirements than those listed in Table 1505.1.
Where to Find Classified Roof Coverings?
Classified roof assemblies can be found on UL Online Certifications Directory at
www.ul.com/database. According to UL, only the following categories include products evaluated for Class A, B, and C ratings:
■ Roofing Systems (TGFU),
■ Prepared Roof-covering Materials (TFWZ),
■ Prepared Roof-covering Materials, Formed or Molded Metal, Fiber-Cement, Plastic or Fire-retardant-treated
Wood (TFXX), and
■ Prepared Roofing Accessories (TGDY).
In the classification for the manufacturer of the roof you are proposing to use, a classified system for another
deck construction may be permitted on other deck construction when a gypsum coverboard is added to the
assembly, but only if indicated in the manufacturer's product certification.
Closing Thoughts
In closing, a Class A roof assembly can be installed on all structures to meet applicable code for fire classification. You cannot go wrong with a Class A, but these often include a gypsum coverboard or multiple layers of specialty versions of typical insulations, depending upon the single-ply membrane's burn characteristics. Typically, single-ply membranes that are not self-extinguishing can be further modified to improve fire resistance. These include "FR" in the product name (i.e EPDM FR, FR TPO, etc.). Also, it is important to review all plans and specifications for new construction projects, as specifiers will commonly include a performance requirement for a Class A assembly, which may be located within the summary, product specifications or drawings. If no other local requirements exist and the structure is not exempted from the requirements of Table 1505.1, a Class Bis acceptable in all cases. Do not assume all membranes are the same
even if they are within the same group (i.e. TPO, PVC, etc.). There can be variations between manufacturers'
products: just because one has a classification, others may not. As previously mentioned, contact the project's local authority having jurisdiction (AHJ) for specific project requirements.
FRM
R. Lance Manson, CS/, CDT, RC/ is Project Manager at Delta Engineering. Lance also is a member of FRSA's Codes and Regulatory Compliance, Governmental Affairs Committee and the Young Professionals Council. The author recommends contacting a professional engineer with a background in roof coating applications or a registered roofing consultant for a third-party, non biased opinion prior to any roof coating application.
