TL;DR
- IBHS research shows approximately 90% of structure losses in WUI wildfires result from ember intrusion, not direct flame contact
- Class A fire-rated roofing is required by California Building Code in all Very High Fire Hazard Severity Zones (VHFHSZ) — roughly half of San Diego County falls in these designations
- Concrete and clay tile, metal, and Class A-rated asphalt shingles all qualify; wood shake does not without an added fire-resistant underlayment treatment — and even treated shake loses its rating over time
- California FAIR Plan data and the Insurance Information Institute both document that insurers are withdrawing from WUI markets across San Diego County at rates that make roofing quality a direct factor in insurability
- Some insurers now offer 5–15% premium discounts for Class A roofing combined with ember-resistant venting in fire-zone properties
Why ember intrusion, not flames, is the primary threat
The popular image of wildfire destroying a home involves wall-to-wall flames engulfing the structure. That’s not typically what the research shows.
The Insurance Institute for Business and Home Safety (IBHS) has conducted post-fire assessments across major California wildfires — Paradise (Camp Fire), Sonoma (Tubbs Fire), and the San Diego region’s Cedar and Witch Creek events. Their findings are consistent: ember intrusion accounts for approximately 90% of structure losses in wildland-urban interface zones.
How does that happen? During an active fire, firebrands — burning debris from trees, brush, and neighboring structures — travel ahead of the fire front. Wind-driven embers have been documented traveling 1–2 miles in front of active fire lines. These embers land on roofs, collect in gutters, and enter structures through:
- Open or underscreened ridge vents
- Standard box-style gable vents without 1/16-inch corrosion-resistant mesh
- Exposed rafter tails under open eaves
- Gaps around pipe boots, vent penetrations, and skylight frames
- Deteriorated bird-stop mortar on tile roofs, which creates open cavities
The fire doesn’t have to reach your property line to destroy your home. This is why California’s WUI construction standards focus so heavily on hardening the building envelope against ember intrusion — and why roofing material and installation quality are directly tied to fire survivability.
What the CAL FIRE and Insurance Information Institute data show
CAL FIRE’s structure loss reports for major Southern California wildfires consistently find that homes with Class A roofing have substantially lower rates of total loss compared to homes with Class B, Class C, or unrated roofing.
In the 2003 Cedar Fire, which burned through portions of El Cajon, Santee, Lakeside, and Ramona, CAL FIRE’s post-event analysis identified that many destroyed structures had wood shake or aged composition roofing that had lost its original fire-resistant treatment. Treated wood shake products carry a Class A rating when new — but the treatment degrades. The California Building Code now requires fire-retardant-treated wood shakes to be re-treated or replaced when the treatment is no longer effective, typically within 10–15 years.
The Insurance Information Institute (III) publishes annual data on wildfire insured losses. Their 2024 data shows:
- Wildfire insured losses in California averaged $8.3 billion per year from 2017–2023, the highest concentrated period in state history
- San Diego County insurers filed the highest per-policy premium increases in California from 2020–2024 for wildland-adjacent properties
- Major carriers — State Farm, Allstate, Farmers — have non-renewed or paused new policy issuance in VHFHSZ areas across the county, pushing homeowners toward the California FAIR Plan
That last point has direct consequences for San Diego homeowners. The FAIR Plan is the insurer of last resort — policies are more expensive and provide less coverage than standard market policies. And the FAIR Plan itself has tightened inspection requirements, including roof age and condition thresholds. A roof over 20 years old in a VHFHSZ zone may trigger a required inspection before coverage is issued.
Class A, B, and C fire ratings — what each means
Fire ratings for roofing materials are established through ASTM testing standards and are required to appear on material documentation:
| Rating | What it means | Common materials |
|---|---|---|
| Class A | Highest resistance. Withstands severe fire exposure — large, wind-driven flame spread. Required in California VHFHSZ zones. | Concrete tile, clay tile, standing seam metal, stone-coated steel, Class A-rated asphalt shingles (most modern architectural shingles with qualifying underlayment) |
| Class B | Moderate resistance. Withstands moderate fire exposure. | Some treated wood products, some built-up roofing systems |
| Class C | Light resistance. Withstands light fire exposure. | Basic roll roofing, some older single-ply products |
| Unrated | No fire rating. Not permitted in fire zones. | Original untreated wood shake, untreated cedar shingles |
Key nuance for asphalt shingles: The shingle itself and the underlayment system together determine the fire rating. A qualifying Class A shingle installed over a non-rated underlayment may not achieve the Class A rating for the roof assembly. California C-39 licensed contractors who work in VHFHSZ zones should be specifying both shingle and underlayment to the correct assembly rating.
Key nuance for tile: Concrete and clay tile are inherently Class A, but the underlayment beneath the tile determines fire performance at penetrations and at the eave. Tile with an open eave and unprotected underlayment at the leading edge is still vulnerable to ember intrusion even though the tile itself won’t burn.
California’s VHFHSZ requirement — what applies in San Diego County
California Government Code § 51182 and California Building Code (CBC) Chapter 7A require Class A roofing for new construction and reroofing in VHFHSZ zones. San Diego County has significant VHFHSZ coverage:
- El Cajon, La Mesa (eastern portions) — fire hazard designations in hillside areas
- Lakeside, Santee, Alpine — large VHFHSZ coverage
- Ramona, Poway, Rancho Bernardo (eastern) — most of these communities fall in VHFHSZ
- Escondido (inland and eastern zones) — VHFHSZ coverage increases toward the eastern boundary
- Julian, Pine Valley, Descanso, Campo — mountain and backcountry zones, all VHFHSZ
- Oceanside, Carlsbad, Vista (eastern portions) — fire designation in canyon-adjacent areas
Homeowners can verify their property’s fire hazard designation using CAL FIRE’s online FHSZ map or through the San Diego County planning portal. When a reroofing permit is pulled in a VHFHSZ area, the building department requires documentation that the proposed materials meet the Class A assembly requirement.
What this means practically: If you’re reroofing in a fire zone and a contractor proposes anything other than concrete tile, clay tile, metal, stone-coated steel, or a documented Class A shingle assembly, that’s a code compliance issue — not just a preference issue.
Which roofing materials perform best against ember intrusion?
IBHS wildfire research includes ember resistance testing, which differs somewhat from the standard ASTM fire rating tests. Ember resistance measures how well a material — and the system it’s part of — resists ignition from small burning debris landing on and around it.
Best overall ember resistance:
- Clay and concrete tile — noncombustible surface, high thermal mass. Primary vulnerability is open eaves, unscreened vents, and gaps in bird-stop mortar. The tile itself performs extremely well.
- Standing seam metal — noncombustible. Continuous seam eliminates gap intrusion at field seams. Excellent ember resistance when eaves are enclosed and vents are screened.
- Stone-coated steel — similar to standing seam in ember resistance; stone coating adds fire resistance beyond the substrate.
Good ember resistance with proper assembly:
- Class A asphalt shingles with qualifying underlayment — the granule surface provides some resistance, but the seams between shingles and at penetrations are higher-vulnerability points. Modern architectural shingles with proper installation perform well; older shingles with dried and cracked sealant strips perform significantly worse.
Higher vulnerability:
- Fire-retardant-treated wood shake — Class A when new and treatment is intact. Treatment degrades in 10–15 years in San Diego’s UV environment. In the Cedar Fire assessment, a disproportionate share of wood shake homes with aged roofing were total losses.
- Old-generation asphalt shingles (pre-2000) — inconsistent fire ratings, less robust sealant technology, high vulnerability at deteriorated edges and valleys.
The ember-resistant vent gap — where Class A roofing isn’t enough
IBHS’s post-fire research identified a consistent pattern: Class A roofs still burned when vents were unprotected. The material rating covers the field of the roof. It doesn’t address what happens when embers enter through a standard box vent or gable vent.
The IBHS Wildfire Prepared Home standard — now a recognized designation in California insurance markets — specifies:
- Ridge vents: Must use products designed to block ember penetration (mesh size ≤ 1/16 inch). Standard continuous ridge vents lack adequate ember blocking.
- Soffit and eave vents: Must be metal mesh with ≤ 1/16 inch openings. Vinyl vents melt in fire conditions, opening large gaps for ember entry.
- Gable vents: Should be protected with compliant mesh or replaced with baffle-type systems.
- Turbine and power vents: Require closeable dampers or ember-resistant shrouds.
California’s 2023 Building Code update added ember-resistant venting requirements to the Chapter 7A WUI standards for new construction. Existing homes aren’t required to upgrade unless reroofing — but insurance carriers and the FAIR Plan are increasingly using vent hardening as an inspection criterion.
What fire-resistant roofing does to insurance premiums
The data on premium discounts for fire-resistant roofing is less systematic than the loss data — discount availability varies by carrier, property location, and underwriting program. That said, several documented patterns hold across the California market:
Documented discount structures:
- The Insurance Information Institute confirms that Class A roofing combined with ember-resistant venting qualifies for premium credits with most carriers that still write WUI policies in California. The III cites a typical range of 5–15% annual premium reduction for properties meeting both criteria.
- The IBHS Wildfire Prepared Home designation — which requires Class A roofing, ember-resistant vents, enclosed eaves, and defensible space — can qualify for 15–25% reductions with carriers that recognize the program (currently a growing list including several regional California carriers).
- Some carriers apply a rating surcharge for wood shake roofing regardless of fire-retardant treatment status — effectively making Class A non-wood materials less expensive to insure by comparison.
FAIR Plan considerations: The FAIR Plan doesn’t offer a named discount for Class A roofing — it’s a minimum requirement, not a credit. However, a roof that fails the FAIR Plan’s inspection criteria can result in non-renewal. Meeting the standards keeps you in the pool and eligible for coverage.
The insurance math in practice: If a WUI-zone home in Ramona or Poway pays $3,200/year for homeowner’s insurance and qualifies for a 10% Class A discount, that’s $320/year — $3,200 over a decade. A full Class A reroof in San Diego runs $14,000–$30,000 depending on size and material. The insurance discount alone doesn’t pay for the roof, but it offsets a meaningful portion and is additive to the fire safety benefit and the expanded market of insurers willing to write the property.
Frequently asked questions
Is Class A roofing required in San Diego?
It depends on the property’s fire hazard designation. California Building Code requires Class A roofing for all new construction and reroofing in VHFHSZ (Very High Fire Hazard Severity Zone) areas. Many San Diego communities — including Poway, Ramona, Lakeside, Alpine, Santee, and portions of El Cajon and Escondido — have VHFHSZ designations. Verify your property’s designation through the CAL FIRE FHSZ map or the San Diego County planning portal.
Do I need to replace my roof to qualify for a fire insurance discount?
Not necessarily — carriers vary in their requirements. Some offer ember-resistant vent hardening credits without requiring a full reroof. However, if your existing roof is wood shake or aged asphalt with deteriorated sealant, the combination of a Class A reroof and vent hardening produces the largest insurance premium benefit and the greatest actual fire resistance improvement.
Does concrete tile need ember-resistant venting to be fire-safe?
Yes. Concrete tile itself is noncombustible and performs well in IBHS testing. But tile roofs with open eaves, unscreened ridge vents, or gaps in bird-stop mortar at hips and ridges are still vulnerable to ember entry into the attic space. The tile and the vent system together determine actual fire survivability.
How long does fire-retardant treatment on wood shake last in San Diego?
Typically 10–15 years. San Diego’s UV intensity degrades fire-retardant treatments faster than the national average. When treated shake loses its rating, it becomes essentially unrated wood — a high fire risk in WUI zones. California code requires the treatment to be maintained — either re-treatment or replacement. Most roofers recommend full replacement rather than re-treatment, as the aging substrate typically has other issues by year 12–15.
What’s the difference between a Class A shingle and a regular architectural shingle?
Many modern architectural shingles are classified as Class A — the difference is the specific shingle-plus-underlayment assembly used. The Class A rating is typically achieved with a qualifying fiberglass-mat shingle installed over a rated underlayment. Not all architectural shingles achieve Class A without the right underlayment system. Ask your contractor to confirm the full assembly rating, not just the shingle rating.
Considering a reroof in a San Diego fire zone? Our roof inspection service includes a fire hazard assessment and current material rating documentation. See how each roofing type performs over time in our San Diego roof lifespan guide, or compare materials cost and performance in our metal vs. shingle breakdown.
Service area
Top Pro Roofing SD serves all of San Diego County — including communities in fire hazard zones: Poway, Ramona, El Cajon, Escondido, Lakeside, Santee, and Alpine. Call (858) 808-6055 for a free roof and fire-hazard assessment.