Fire damage to a commercial roof

Your commercial roofing system does more than simply keep your business dry. Your roof (along with fire-resistant building materials, sprinkler systems, extinguishers etc.), is part of your building’s overall fire protection.

Do you know what fire rating your commercial roof has? Do you know if your roof is adequately protecting your business, equipment, and employees? It’s valuable knowledge for any building owner or facility manager to have, so let’s look at the differences, what they mean, and the tests used to determine a roof’s fire resistance.

Standard Test Methods for Fire Classification

The International Building Code makes it clear that all roof coverings must be tested and meet class requirements outlined by ASTM (American Society for Testing and Materials), specifically ASTM E108 or UL 790. (These tests are conducted at UL (Underwriters Laboratories) or another certified testing location.)

These fire tests consist of the following areas:

Spread of Flame Test

Spread of flame tests are usually performed in a device called a Steiner tunnel, where flame is allowed to spread on the underside of a horizontally-cut specimen of material.

The maximum spread of flame permitted is six feet for Class A testing, eight feet for Class B testing, and thirteen feet for Class C testing. The slope of the material is determined before the test. The spread of flame test is only performed on roof systems with non-combustible decks.

Intermittent Flame Test

The intermittent flame test involves a gas flame being applied to a test specimen. The gas flame is turned on and off for a predetermined number of cycles. In order to meet Class A requirements, the material being tested must stand up to fifteen cycles. Class B requires the material to survive eight cycles, and Class C requires three cycles.

Burning Brand Test

A burning brand test subjects a roof sample to a burning piece of wood, called a brand.

The brands are placed on the roof sample and left until either the brand has been completely consumed, or failure of the roof sample occurs (meaning the roof material catches fire).

The brands are different sizes for different class tests. Class A tests are performed with a brand weighing 2,000 grams, Class B tests with a brand weighing 500 grams, and Class C tests with a brand weighing 9 ¼ grams.

Class A Roofing

Roofing material with a Class A fire rating means that it has been approved for severe fire exposure. Many architects specify Class A roof coverings even when the building doesn’t necessarily need one, just so a structure is assured to have a high degree of fire resistance.

Class A materials are non-combustible or extremely fire retardant and include materials like clay tiles, slate roof tiles, or metal roofs. Additionally, single ply roofs (like TPO and PVC roofing materials) are also available with Class A ratings as are some asphalt shingles.

Keep in mind that some of these materials are assembly-rated, meaning that they are tested as part of a roof assembly. The term “roof assembly” includes all portions that make up the commercial roof – the outermost roof material, underlayment, insulation, and roof deck.

Class A roofs are especially important in areas of the country that are prone to wildfires and high winds that have the potential to spread those wildfires.

Class B Roofing

A Class B rating is for roofing material that is rated against moderate fire exposure. Materials that fall under Class B are typically pressure-treated shakes and shingles, neither of which are common commercial roofing materials.

Class C Roofing

Roofing materials with a Class C rating include untreated wood shakes, particle board, and plywood. None of these materials are recommended for use as roofing material, either for commercial or residential properties.

Unrated Roofing

Unrated roofing material provides little (or no) fire resistance and should be avoided. Commercial building codes typically do not accommodate unrated roofing material.

Class 1

In addition to the above ratings, there is also a special rating known as Class 1. This rating is only awarded by FM Global, and means that an entire roof assembly has passed a series of tests known as FM 4470. FM Global is an insurance company that specializes in providing services to large corporations in the HPR, or Highly Protected Risk category.

The FM 4470 tests include:

  • Internal fire
  • External fire (ASTM E108)
  • Simulated wind uplift
  • Metal component corrosion resistance
  • Hail damage
  • Water leakage
  • Foot traffic resistance

Just because a roof meets the Class A rating does not necessarily mean that it will meet the Class 1 rating, due to the fact that the entire roof assembly must be tested. However, all Class 1 systems meet Class A ratings.

What’s the Difference Between Class 1 and Class A Roofs?

If you’re a professional roofer, you know the difference between Class 1 and Class A. But for the typical business owner, the terminology might get a little confusing. Long story short, all systems with a Class 1 designation are also Class A roofs, but not vice versa.

Class 1 systems take into account the entire roof assembly and undergo a multitude of tests to ensure that no combustible materials are used. Class A materials, by comparison, are considered to be “effective against severe fire exposure,” but may be installed over a roof deck that is considered combustible.

Building Codes in Your Area

The local building codes in your state, city, or jurisdiction will specify the fire class rating that your commercial building requires. The fire class rating requirement is largely determined by the natural fire hazard risk in your area of the country. Building owners can find out more about their area’s building codes by contacting either their local government or fire department.

TEMA Roofing Protects Your Business

Is your commercial roof’s fire resistance up to code? If you aren’t sure, contact the expert commercial roofing contractors at TEMA Roofing Services. Our professionals understand commercial roof fire ratings better than anyone, and will give you the straight scoop about whether or not your commercial building’s roof is giving you the right amount of fire protection.

Don’t take chances and don’t sit around believing that the unthinkable will never happen to your business. Contact TEMA Roofing Services today!