Overview of UL 790: Fire Tests of Roof Coverings
Roofs play a significant factor in fire resistance—that’s a fact—and If you've looked at roofing systems or materials in the past, you’ve probably come across the term: UL 790 ratings.
What do these ratings mean, and why should you care? That’s what we’re going to explore in this article—and a whole lot more!
Let’s get started.
What Is UL 790?
UL 790 is a widely-used and recognized fire rating system that was developed to help measure and assess the fire-resistance of roofing materials. Here’s how it works:
Each roof material is exposed to fire, and is then assigned a rating based on its resistance to the flames.
This resistance rating is then used to determine whether or not the roofing material meets safety standards for commercial and residential buildings and is provided a rating of A, B, or C.
The Three UL 790 Fire Ratings
Roofing materials tested under UL 790 receive one of three ratings. Let’s take a look at all three:
UL 790 Class A
UL 790 Class A fire ratings are the highest rating a roofing product can achieve.
The rating means that the material provides the best protection and resistance to fire and significantly reduces the possibility and risk of flames spreading.
Class A-rated roofs are best used in areas that are prone to wildfires—or where wildfires and other fire safety measures are a concern.
UL 790 Class B
Although a step down from Class A fire rating, these materials offer a decent and moderate amount of fire resistance.
But keep in mind: although they have some level of protection, they don’t perform as well under prolonged exposure to fire.
UL 790 Class C
Typically, UL 790 C fire ratings are applied to materials with minimal fire resistance. They provide a limited amount of fire resistance. In other words, roofing materials exposed to fire for a prolonged period of time with this fire rating will not hold up as well as Class A or Class B-rated materials.
How Are the UL 790 Fire Ratings Determined
To establish UL 790 fire ratings, roofing materials undergo a series of tests that evaluate how well wood resists fire under different conditions, measuring the following components:
Flame Spread
Intermittent Flame Exposure
Burning Brand
Once these factors are tested, the material is assigned a rating of Class A, B, or C.
1. Flame Spread
The goal of measuring flame spread is to determine how quickly—and at which rate—flames can move across a surface when exposed to a direct fire source.
How is Flame Spread Measured?
A test flame is applied to the roofing material, and its progression is monitored over a set period of time.
Class C-rated materials will typically allow fire to spread rapidly, which makes them less suitable for areas with high risk, while Class B and Class A rated materials will not allow the frames to spread much—or even at all.
2. Intermittent Flame Exposure
The intermittent flame exposure test evaluated how a roofing material will respond to recurring fire threats—not direct flames.
Unlike the flame spread test, where fire is applied continuously, this method involves alternating between flame application and cooling periods.
How is Intermittent Flame Exposure Measured?
Intermittent flame exposure is measured by submitting a roofing material to flames for a specific duration, removing it, and then reapplying those flames.
The process continues multiple times, and the material is observed for any signs of ignition, structure damage, or prolonged, burning.
Lower rated materials, such as UL 790 Class C, typically catch fire after the repeated exposure, whereas UL 790 Class B may only endure minor damages.
Class A rated materials, on the other hand, will be able to withstand multiple attempts and show limited amounts—if any—damage.
3. Burning Brand Test
The burning brand test evaluates how well a roofing material resists catching fire when exposed to burning embers, firebrands, or debris that often float or sit on rooftop surfaces.
How is Burning Brand Measured?
To measure this accurately, a piece of burning wood (the "brand") is placed on the roof material surface and left there to determine:
Whether or not the material catches fire
Whether or not the fire spread
How long the wood burns
While Class C rated materials catch and spread the fire, Class B rated materials will catch fire but not spread. Class A rated materials will neither catch fire nor spread the fire.
Benefits of Installing UL 790 Class A Roofing
Now that we see how UL 790 class ratings are determined, let’s take a look at some of the benefits of choosing a roofing material that is UL 790 Class A-rated. To name few, you have:
Increased Home Safety:
Because a home with Class A fire rated roofs are extremely resistant to fire, your home carries an added level of protection that other homes don’t have.
Potential Insurance Benefits
And because many other homes do not always have this extra layer of protection, it’s possible that insurance companies will offer you lower premiums for property.
Compliance with Building Codes
Another benefit to consider is that many areas prone to wildfires tend to require homes to be built with roofs that have Class A fire ratings.
By choosing roofing materials with Class A Fire ratings—such as CeDUR’s shiloh roofing—you no longer have to worry about your roof being compliant with residential or commercial building standards.
CeDUR Roofing and UL 790 Class A Ratings
CeDUR roofing products are designed to meet the highest standards in both design and durability. And one of their most recognized features is their UL 790 Class A fire rating.
Unlike some traditional roofing materials, which typically require chemical treatments or additional layers, CeDUR shakes naturally provide top-tier fire resistance.
Comparing CeDUR to Other Roofing Materials
So how does CeDUR stack up against other roofing materials exactly? Let’s take a look:
Wood Shakes
Unlike CeDUR, Natural wood is highly flammable and requires chemical treatments to achieve a Class A rating. Simply put, CeDUR shakes are more durable and resistant and require less maintenance.
Asphalt Shingles
Although asphalt shingles have Class A ratings, it’s important to note that their fire resistance degrades over time, whereas CeDUR shake roofing does not. This means that CeDUr roofing is a better option in terms of longevity.
Metal Roofing
Many consider metal roofing to be a great option for both homes and commercial buildings. But metal roofs can heat up and, as a result, damage other structural components of your home or commercial business.
Clay Tiles
Compared to almost all other materials, clay roof tiles provide some of the best fire resistance. However, they are also incredibly heavy and tend to require additional structural support to be used. In other words, you may have to purchase new roofing materials and structural support.
Use CeDUR for Class A Fire Rated Roofing
More often than not, choosing the right roofing material involves balance. You have to find the right design with the best durability and safety.
And this includes finding a roofing material with a UL 790 Class A rating.
With CeDUR, you can gain access to the roofing products that not only have beautiful aesthetic designs but also have exceptional durability and fire resistance.
Whether you’re a commercial property or a residential homeowner, your home should have a reliable option above its foundation.
Interested in installing a UL 790 Class A-rated roof? Find a contractor?
View our gallery or contact us today to learn more!