UL 790 Standard Test Procedures for Fire Testing of Roofing Coatings

The “UL 790 Standard Test Methods for Fire Testing of Roofing Coverings” standard, developed by Underwriters Laboratories (UL), describes the requirements for measuring the relative fire properties of roofing coverings exposed to simulated fire sources originating from the outside of the building where they are installed. These requirements apply to roofing coverings intended to be installed on combustible or non-combustible roof decking, as intended.

The UL 790 standard defines the following test methods:

• Intermittent flame exposure test
• Flame spread test
• Burning part test
• Flying piece test
• rain test

This standard defines three fire exposure classes:

• Class A represents the highest level of fire protection. Its characteristics include:
  • Effective against severe fires.
  • Excellent resistance to flame spread.
  • High level of protection of the roof surface.
  • Minimum burnt particle formation.
  • It is commonly preferred for commercial, industrial, and fire-prone buildings.
• Class B roofing systems provide moderate fire protection. They offer the following:
  • Moderate flame resistance
  • Good protection against burning particles.
  • Lower performance compared to Class A.
• Class C systems are designed for light fire exposure. They provide the following:
  • Basic fire protection
  • Limited resistance to external fire spread.
  • Suitable only where permitted by the relevant building regulations.

These classifications allow designers and regulators to select roofing systems that are suitable for the fire hazards associated with a particular building location.

Tests conducted in accordance with these requirements aim to demonstrate the performance of roofing materials over the types and durations of fire exposure in question, but do not aim to determine the acceptability of roofing materials for use after fire exposure. These fire testing methods do not provide a baseline for comparing expected performance under all real fire conditions, but they do provide a baseline for comparing the response of roofing materials when exposed to the fire sources described herein.

These test methods address roofing materials used on both combustible and non-combustible decking. Combustible decking is typically constructed using materials that do not meet the ASTM E136 standard requirements. These include wood sheathing, oriented strand board (OSB), or plywood. Non-combustible decking, on the other hand, is typically constructed entirely from materials that fully meet the ASTM E136 standard requirements. These include metal, concrete, or cast plaster.

The UL 790 standard is one of the most widely recognized fire safety standards for evaluating the external fire performance of roof systems. This standard establishes laboratory test methods to determine how roof coverings react when exposed to fire sources originating from outside the building, such as burning embers, flames from adjacent structures, or wind-borne fire fragments.

The UL 790 standard is widely referenced by building codes, roofing manufacturers, architects, and certification bodies throughout North America. It provides a standardized method for comparing the fire performance of different roofing materials and installations.

The primary purpose of the UL 790 standard is to evaluate the relative fire performance of roofing materials when subjected to simulated external fire exposures. This standard helps determine whether a roofing system can:

• Resistance to ignition from external fire sources.
• Limiting flame spread on the roof surface.
• Preventing fire from penetrating through the roof structure.
• Resistance to burning embers and flying sparks.
• Continuing to protect the building structure during fire exposure.

The UL 790 standard, rather than measuring the fire resistance of an entire building, specifically evaluates the performance of roofing systems installed on combustible or non-combustible roof decking.

This standard applies to numerous roofing products, including:

• Asphalt tiles
• Metal roofing systems
• Clay and concrete roof tiles
• Slate roof
• Layered roof
• Modified bitumen roofing
• Single-layer membrane roof
• Synthetic roofing materials
• Composite roofing systems

This standard evaluates complete roof systems, including roofing, underlayment, fastening system, and support decking, as all components affect overall fire performance.

The UL 790 standard includes various standardized fire exposure tests:

• Intermittent flame exposure test: This test involves subjecting the roofing material to repeated flame exposure to determine its ability to withstand direct flame without excessive damage or fire penetration.
• Flame spread test: The flame spread test measures how quickly flames spread across the roof surface. Roof systems that limit flame spread receive higher ratings.
• Burning piece test: One of the best-known UL 790 assessments, this test places burning pieces of wood of specific size and weight on the roof surface to simulate embers carried by the wind during a fire.
• Flying debris assessment: This assessment determines whether burning pieces of roofing material detaching from the roof ignite nearby combustible materials, creating additional fire hazards.
• Rain test: Some roofing systems are exposed to water before fire testing to simulate weather conditions and verify that moisture does not significantly reduce fire performance.

The UL 790 standard plays a vital role in modern building safety because roof systems are often the first building component to be exposed to external fires. This standard helps to:

• Enhancing user security
• To reduce the spread of fire between buildings.
• Protecting structural roof components.
• To support reducing insurance risk.
• Demonstrating compliance with building regulations.
• Increasing confidence in the performance of roofing products.

Many building codes require roof systems to meet specific UL 790 standard classifications, depending on the type of use, roof structure, and regional fire risk.

The UL 790 standard is widely used in the following areas:

• Housing construction
• commercial buildings
• Industrial plants
• Warehouses
• Hospitals
• Educational institutions
• Government buildings
• Data centers
• Renewable energy projects with rooftop solar energy installations

Roofing manufacturers also rely on UL 790 certification when marketing their products in North America.

The UL 790 standard is technically compatible with the ASTM E108 Standard Test Methods for Fire Testing of Roofings standard. Both standards use essentially equivalent fire testing procedures and are often used interchangeably by building codes and certification bodies.

Compliance with the UL 790 standard offers manufacturers several advantages:

• Easier acceptance in construction projects.
• Proven fire safety performance.
• Higher market competitiveness
• Support for product certification
• Increased customer confidence
• Compliance with legal regulatory requirements.

Manufacturers typically conduct UL 790 standard testing during product development to optimize roof system design before commercial release.

For many years, our organization, with its competent and experienced team, has been understanding the needs of its clients, providing the advanced testing services they require, and assisting them in the establishment, implementation, and improvement of management systems. Within this framework, we also provide testing services compliant with the UL 790 standard.