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Thermal splitting of fiberglass-based asphalt roof shingles was particularly common for product manufactured in the early 1990's. Asphalt Shingle & Other Roofing Materials Fire Rating Tests & Standards

This article describes testing and standards for fire ratings and fire resistance of asphalt shingles and other roofing materials.

Readers should see our complete list of standards for roofing and roofing products.

We include a list of roof testing services and laboratories. Our page top photo shows remains of roofing materials found on a buildings following a roof fire ignited by a chimney fire that spread out of the chimney and into the roof structure.

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- Daniel Friedman, Publisher/Editor/Author - See WHO ARE WE?

Definitions of Fire Ratings for Asphalt Shingle & Other Roofing Materials

Chimney fire burns through roof (C) Daniel Friedman

[Click to enlarge any image]

As stated in Best Practices Guide to Residential Construction (Steve Bliss, J Wiley & Sons) in that book's chapter on BEST ROOFING PRACTICES,

Keep in mind that the purposes of roof covering fire ratings (to desribe the fire resistance of a roofing material), and the intent of roof fire resistance in general are to allow building occupants more time to escape in event of a fire, not to guarantee that the building nor its ocupants will be unharmed in the event of a fire.

A table of roof fire ratings and details about the applicable standards is at FIRE RATINGS for ROOF SURFACES.

All roofing materials that carry any fire rating (A, B, or C - see "Table of Roof Covering Fire Ratings & Standards" below) must:

Watch out: if a roofing shingle or other roof covering material is not installed exactly according to the manufacturer's recommendations its fire rating may be compromised and reduced, as may the roof warranty too. Also, a roof that has resisted a fire successfully, and thus helped protect the building from a fire, is likely to need to be replaced after a fire or after exposure to high heat from a nearby fire. Also watch for discount-grade roof shingles that may carry no fire rating whatsoever.

Also see these roofing material articles where we describe fire ratings:

Both UL 790 and ASTM E 108 fire classification tests discussed below use the same test methods. These standards include

How these standard fire rating tests are applied will vary, however, for each type of roof covering product and roof assembly or structure.

For example as NRCA (Kirby) points out, a roof system whose application is restricted to use on noncombustible decks (such as a steel or concrete or gypsum surface), only the spread-of-flame test will be required, while a roof system that is applied over a combustible roof deck (a wood-framed building with plywood roof sheathing for example), the tests for fire resistance of that product will include spread-of flame as well as intermittent flame and burning brand tests.

Keep in mind that the purposes of roof covering fire ratings (to describe the fire resistance of a roofing material), and the intent of roof fire resistance in general are to allow building occupants more time to escape in event of a fire, not to guarantee that the building nor its occupants will be unharmed in the event of a fire. Our table of roof fire ratings is given below.

Table of Roof Covering Fire Ratings & Standards: UL 790 & ASTM E-108
Roof Fire Rating Fire Rating Properties 
Roof coverings with Class A, B, or C fire ratings must all have these properties

Apply to fires originating from outside the building.

During or after a fire the roof materials will not:

Blow off or fall off of the roof deck as flaming or glowing brands (burning embers that might further spread fire)

Break, slide, crack, or warp to expose the underlying roof deck

Allow the roof deck to fall away as glowing particles

Allow sustained flaming of the underside of the roof deck
Class A Fire Protection

Highest fire resistance: the roof can withstand severe exposure to fire
See ASTM E-108

According to the NRCA (Kirby) who referred to ASTM E 108 and ANSI/UL 790, "Class A roof coverings are not readily flammable, are effective against moderate fire exposures, and do not carry or communicate (i.e. spread) the fire. "

Example test process for Class A Fire Protection Rating: A 12" x 12" x 2-1/4" gridded configuration of 3 tiers of 12 12-inch wood strips are placed on a test sample while air is forced over the brand and the brand is allowed to burn up to 1 1/2 hours until it extinguishes itself or the roof assembly fails.

Class B Fire Protection

Moderate fire resistance

NRCA (Kirby): "Class B roof coverings are not readily flammable, are effective against moderate fire exposures, and do not readily cary or communicate fire."

Example test process for Class B Fire Protection Rating: similar to Class A above, but the fire test configuration is smaller: 6" x 6" x 2 1/4-" grid using 3 tiers of six six-inch long wood strips is used.
Class C Fire Protection

Light fire resistance

NRCA (Kirby): "Class C roof coverings are not readily flammable, are effective against light fire exposures, and do not readily carry or communicate fire."

Example test process for Class C Fire Protection Rating: similar to Class A and B above, but a still smaller fire test configuration is used: 1 1/2" c 1 1/2" x 25/32" block of wood with one saw kerf on the wood block's top and bottom faces is used to conduct the fire resistance test.

Note1: External Building Fire Resistance vs. Internal Building Fire Resistance

Chimney fire burns through roof (C) Daniel Friedman

External fires refers to fires that originate outside of the building rather than within the structure. Examples are nearby forest or brush fires, or other nearby building fires.

As Kirby points out, because these fire ratings evaluate the resistance to external fires, they do not bear on building hourly fire ratings for roofs or ceilings.

Building hourly fire resistance ratings pertain to fires that originate inside the building.

Our house fire photo (left) shows the attic view of a section of plywood-sheathed asphalt-shingled roof that burned through when a 2004 chimney fire spread to the building structure in this New York Home.

Here is an outdoor view of the building [image] exterior wall where the fire occurred, starting in a first-floor family room woodstove.

This fire originated in the woodstove or metal chimney flue and spread from this "external" chimney to the roof and roof structure at the lower edge of the hipped roof visible in the outdoor photo. There were no injuries.

[Click to enlarge any image]

Roof Fire Rating Standards & Requirements

The U.S. Federal Housing Administration (FHA) and other lenders require that building roofing materials conform to these standards. Various U.S. national or model building codes & state & Canadian Provincial building codes or fire codes require that roofs must carry at least a Class C fire rating or better.

The tests described by ANSI/UL 790 and ASTM E 108 fire resistance evaluation for roofs are used by model building codes such as the Uniform Building Code (Table 15-A "Minimum Roof Classes"). Roof classifications with respect to fire resistance are A, B, C, and "non-rated".

The BOCA (Building Code Officials and Code Administrators International, Inc.) National Building Code [using 1999 as an example] describes roof classifications in BOCA section 1505, "Fire Classification" and uses Class A, B, and C roofs tested according to the two fire resistance test standards we discuss here.

UL 790 - Underwriters Laboratories Roof Fire Ratings A B C Tests

ASTM/UL 790 "Tests for Fire Resistance of Roof Covering Materials"

Underwriters Laboratories has defined the UL 790 Standard Tests of roofing material fire resistance to external fire sources: fires that originate outside of the structure itself. Roof covering packaging that encloses shingles or other roofing that have a fire rating will display the level of fire or wind resistance rating of the materials. UL 790 is a quality assurance service listing.

The UL tests under UL 790 evaluate the behavior of a roof covering under three fire hazards

  1. Exposure of the roof to intermittent flame
  2. Flame spread in the roofing material
  3. Ignition of the roof covering from burning brands (say an ember or burning branch from a nearby brush fire)

ASTM E-108 - Standard Test Methods for Fire Tests of Roof Coverings

ASTM E 108 "Standard Test Methods for Fire Tests of Roof COverings" is the second widely-accepted fire-resistance capacity test used to determine a product or in this case a roof assembly's fire classification.

ABSTRACT: This specification covers mineral granule-surfaced asphalt roofing shingles. Covered here are the self-sealing (Type I) and non-self-sealing (Type II) types of shingles.

The shingles shall consist of organic felt or glass mat(s) saturated or impregnated, and coated on both sides with a hot asphaltic material and completely surfaced on the weather side with mineral granules embedded in the coating.

The reverse side of the shingles shall be covered with a suitable material to prevent the shingles from sticking together in the package, causing possible damage upon being unpacked at ambient temperatures.

Type I shingles shall have a factory-applied adhesive that will seal the shingles together after application. Both types shall meet the conditions for Class A fire exposure, and loss and behaviour on heating tests. Type I shingles shall pass an additional wind resistance test.

Watch out: if a roofing shingle or other roof covering material is not installed exactly according to the manufacturer's recommendations its fire rating may be compromised and reduced, as may the roof warranty too.

Also, a roof that has resisted a fire successfully, and thus helped protect the building from a fire, is likely to need to be replaced after a fire or after exposure to high heat from a nearby fire. Also watch for discount-grade roof shingles that may carry no fire rating whatsoever.

Roofing material articles where we describe fire ratings:

UL Underwriters Laboratories: Standards Pertaining to Roofing Systems

Directory of Roofing Shingle Testing Laboratories

See TEST LABS - ROOF SHINGLE for our complete directory of companies offering various types of testing for roofing materials, including roof shingles and other roof surfaces.

Testing Laboratory Serving a Wider Audience than Roofing Products & Roofing Industry Manufacturers

Applied Technical Services

http://www.atslab1.com/

Chemir Analytical Services
http://www.chemir.com/

EMS Lab, the megalith of testing in the U.S.: materialstestinglaboratory.com/


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