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A 101 Guide to Fire Ratings and Highly Rated Materials

A 101 Guide to Fire Ratings and Highly Rated Materials

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If you’re starting a new building project, you’ll need to consider fire rating guidelines.  Fire ratings are used to ensure newly constructed buildings are compliant with ASTM, IBC, UL, and other relevant standards.

We’ll look at ASTM E-84 and ASTM E-119 in particular, since these are the most relevant fireproofing standards. 

ASTM E-84 and E-119

ASTM E-84 and the ASTM E-119 are tests that measure distinct aspects of burning behavior.

ASTM E-84 is the “Standard Test Method for Surface Burning Characteristics of Building Materials,” and ASTM E-119 is the “Standard Test Methods for Fire Tests of Building Construction and Materials.”

ASTM E-84 is almost identical to UL 723, and ASTM E-119 is almost identical to UL 263; the standards are technically different, but the methods of testing are essentially the same. 

In plain English, ASTM E-84 tests characteristics of flame and smoke of a material, and ASTM E-119 measures the fire resistance of a material. With the right intumescent or cementitious coating, your project can exceed the requirements for both tests.

What are ASTM E-84 flame spread ratings?

The ASTM E-84 measures burn behavior against a flame spread index and smoke development index. The flame spread index is a measure of how quickly the flame travels after making contact with the substrate, and the smoke development rating measures how much smoke is produced from the fire. 

ASTM E-84 testing is conducted via a Steiner Tunnel, which is a 24 x 24-inch steel box. The sample material is placed in the Steiner Tunnel and exposed to two burners. The controlled burn is monitored, and the flame spread and smoke development are analyzed with a specialized software. 

Typically, the sample material will also be coated with a specialized coating known as an intumescent paint. Based on how much the fire spreads and smoke develops, the material will receive a class rating. 

These metrics are rated in three different classes:

  • Class A has a Flame Spread Index of 0 – 25 
  • Class B has a Flame Spread Index of 26 – 75
  • Class B has a Flame Spread Index of 76 – 200

Flame Spread Rating by Material

Different materials have higher and lower flame spread ratings. The chart below provides the flame spread rating and respective class of various building materials.

Note how treating plywood (and other materials) with a fire resistant paint can improve its flame spread rating from a Class III to Class I. Additionally, reinforcing walls, structural steel, and other areas of a new build with fire resistant materials can improve your fire rating. 

We’ll cover more of those materials below, but first let’s talk more about ASTM E-119 standards. 

What are ASTM E-119 fire ratings?

Unlike ASTM E-84, ASTM E-119 measures the time a building material can withstand persistent exposure to fire without structural failure. In other words, ASTM E-119 is a “time test” of sorts. This standard is incredibly important for structural steel and other critical infrastructure.

The ASTM E-119 test is performed by placing a sample material into a furnace. The material is left in the furnace for a pre-specified amount of time and temperature based on the rating the material needs to meet.  At the end of the test, the material is tested for its structural integrity.

Fire ratings for the ASTM E-119 typically fall between 1 to 4 hours. Longer times indicate better fire resistance.

Depending on the IBC code that applies to your particular material and the way it’s been applied, a fire rating of 1 to 4 hours might be required. For example, fire walls in Type II construction require at least a 2 hour fire rating. 

What are the most fire resistant materials?

Building with the right materials can help builders meet the standards set forward by ASTM E-119 and ASTM E-84. The following materials are worth considering in areas of a new construction that require fireproofing

  • Concrete: Concrete has low thermal conductivity and is non-combustible, making it naturally resistant to fire. However, concrete is also mixed with “aggregate material” which can include gravel, stone, and other material which might not be as resistant. As a result, concrete with a lower aggregate-to-concrete ratio should be purchased when fire resistance is important. 
  • Stucco: Stucco is a type of plaster that’s made from Portland cement, sand, and limestone. It can be used to strengthen the fire rating of materials like wood, brick, and other masonry. Stucco typically adds a 1-hour fire rating to whatever material you’re reinforcing. 
  • Brick: Bricks are forged in fire kilns, making them naturally resistant to fire. Specifically, there are UL certified brick walls that add incredible fire resistance. U302 brick veneers can add up to 2-hours of fire rating, and U902 veneers have a 4-hour fire rating. These assemblies can add extra fire resistance to your build. 
  • Gypsum (or drywall): With gypsum, i.e., drywall, you’re looking for a Type X board. Type X is specially treated with fire resistant, non-combustible fibers. Most Type X drywall has a 1-hour fire rating. 
  • Fire resistant windows: There are two types of fire resistant glass; polished wire glass and ceramic glass. Polished wire glass is reinforced with wire, while ceramic glass has been made with a fire resistant glaze. Both are worth considering for your next build. 



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