Metal Roof Fire Rating: What Homeowners Need to Know

The fire resistance of a roof affects insurance, building codes, and safety. This article explains metal roof fire rating classifications, testing standards, material differences, installation factors that influence performance, and practical steps homeowners can take to improve fire protection. Understanding how metal roofs earn Class A, B, or C ratings helps make safer choices.

Rating	Performance	Typical Metal Assembly
Class A	Best – Withstands severe exposures	Metal panel + noncombustible deck + rated underlayment
Class B	Moderate – Withstands moderate exposures	Metal panel with certain underlayments
Class C	Basic – Withstands light exposures	Thin metal panels or less protective assemblies

What Is A Metal Roof Fire Rating

A metal roof fire rating is an industry classification that describes how well a roofing system resists flame spread and burning embers during a fire. Ratings are commonly expressed as Class A, Class B, or Class C based on standard laboratory tests that simulate burning conditions and ember exposure.

Fire Rating Classes And What They Mean

Listing the classes clarifies expectations. Class A offers the highest protection against severe fire exposures, including burning embers and flame spread. Class B provides moderate protection, while Class C is the minimum protection, suitable for areas with limited exposure risk. Building codes and insurance policies often specify minimum classes for different wildfire or urban fire risk zones.

Relevant Testing Standards

Recognized standards determine fire ratings. The main tests for roofing materials include UL 790 (ASTM E108) for fire tests of roof coverings and ASTM E108 for built-up roof systems. These tests evaluate flame spread, burning brand exposure, and sometimes embers to assign Class A/B/C.

How Metal Roofs Typically Perform

Metal roofs are inherently noncombustible, which helps many metal roof assemblies achieve at least a Class A or B rating. Performance depends on the entire assembly—metal panels, underlayment, deck type, and fasteners. Properly designed metal roofs commonly meet Class A standards.

Material Differences And Their Impact

Not all metal roofing performs identically. Steel, aluminum, copper, and zinc are noncombustible, but thickness, coatings, and profiles matter. Thicker gauges and standing seam profiles often provide better barrier integrity. Paint systems and coatings do not significantly alter noncombustibility but can affect thermal performance and longevity.

Role Of Underlayment And Decking

Underlayment and roof deck are critical to achieving a fire rating. Noncombustible decks (metal or gypsum) and fire-rated underlayments help assemblies earn higher classes. Organic or combustible underlayments and wooden decks reduce overall fire resistance. Selecting noncombustible or fire-retardant underlayment significantly improves the roof’s rating.

Installation Factors That Influence Fire Rating

Correct installation preserves the tested assembly characteristics required for a rating. Factors include fastener type and placement, ventilation openings, roof penetrations, and sealing at ridges and eaves. Modifications without re-testing can reduce the rated performance. Installation deviations from the tested configuration may void the stated fire class.

Wildfire Considerations And Ember Resistance

Wildfire exposure focuses on embers and spot fires rather than direct flame contact. Metal roofs with tight seams, minimal gaps, and noncombustible flashings reduce ember entry. Adding ember-resistant accessories, like boxed eaves and spark-arresting vents, enhances protection. Ember resistance is a practical complement to lab-based fire ratings in wildfire-prone areas.

Building Codes, Local Regulations, And Insurance

Local jurisdictions and insurance companies often reference fire ratings when setting requirements or offering discounts. Areas with high wildfire risk may mandate Class A roofs or specific ember-resistant features. Documented rated assemblies can lead to insurance credits. Checking local code language and insurer policies before replacing a roof ensures compliance and potential savings.

Upgrades To Improve Fire Performance

Existing metal roofs can be upgraded to improve performance. Options include replacing combustible underlayment with fire-rated materials, sealing gaps at penetrations, and installing ember-resistant vents. In some cases, adding a fire-rated board over the deck and beneath new metal panels will raise the assembly class. Upgrades should follow manufacturer guidelines or tested assembly details to preserve a valid fire rating.

Cost Considerations And Lifespan

Metal roofs with higher fire ratings often cost more due to thicker panels, noncombustible decks, and specialized underlayments. However, metal roofs typically offer long lifespans and lower maintenance, which offset initial costs. The long-term benefits include improved safety, potential insurance discounts, and reduced replacement frequency.

Comparing Metal To Other Roof Materials

Compared to wood shakes or asphalt shingles, metal roofs usually provide superior fire performance. Wood shakes are combustible and struggle to meet high fire-class ratings, while some treated or specially installed asphalt systems can achieve Class A. Metal roofs often provide the best combination of noncombustibility and ember resistance among common roofing choices.

Documentation And Certification

When selecting a metal roof for fire safety, request the manufacturer’s UL or ASTM test report and the specific assembly details used for the rating. Documentation should list the exact panel profile, underlayment type, deck construction, and installation method. Retain these documents for code inspections and insurance verification.

Maintenance Best Practices To Preserve Fire Rating

Regular maintenance retains the protective characteristics of a metal roof. Tasks include cleaning gutters and valleys to prevent debris accumulation, inspecting and sealing penetrations, and replacing degraded underlayment when needed. Keeping the roof free of combustible materials near eaves is essential. Routine maintenance helps ensure the rated performance remains effective over the roof’s service life.

How To Choose A Metal Roof For Fire Safety

Homeowners should prioritize assemblies with documented Class A or Class B ratings for higher-risk zones. Confirm that the installed system exactly matches the tested assembly, including underlayment and deck materials. Use accredited contractors experienced with rated metal roof installations. Verification of certified assemblies and professional installation minimizes surprises during inspections or insurance reviews.

Frequently Asked Questions

Can A Metal Roof Catch Fire?

Metal itself does not ignite, but internal components like underlayment or adjacent combustible materials could burn. Proper assembly and noncombustible underlayments greatly reduce this risk. Metal roofs are far less likely to contribute to roof fires than combustible options.

Does Paint Or Coating Affect The Fire Rating?

Typical paint and protective coatings do not change the noncombustible nature of metal panels. However, thick intumescent coatings would be part of a tested assembly and must be documented to affect ratings. Relying on standard paint systems alone is not a substitute for rated assemblies.

Will A Metal Roof Lower Insurance Premiums?

Insurers sometimes offer discounts for Class A roofs or roofs with confirmed ember-resistant features, especially in wildfire-prone regions. Discounts vary by insurer and region. Providing certified test reports to the insurer can support eligibility for discounts.

Key Takeaways For Decision Makers

Metal roof fire rating depends on the entire roof assembly—metal panels, underlayment, deck, and installation details. Prioritize documented Class A or B rated assemblies in areas with fire risk, verify manufacturer test reports, use experienced contractors, and maintain the roof to preserve performance. These steps help maximize safety, meet code requirements, and potentially reduce insurance costs.