Understanding flame spread index, smoke developed index, and what fire resistant fence classifications mean for San Diego, Orange County, and Los Angeles wildfire zone compliance.
ASTM E84 Standard
The Steiner Tunnel Test (ASTM E84) is the industry standard for measuring surface burning characteristics of building materials. A 24-foot sample is placed in a tunnel and exposed to a controlled flame for 10 minutes.
The test measures two critical factors: how far flames spread across the material surface (Flame Spread Index) and how much smoke is produced (Smoke Developed Index).
Flame Spread Index
The Flame Spread Index (FSI) indicates how quickly fire spreads across a material's surface under ASTM E84. It can be one part of a broader fire-aware perimeter plan. Documented classifications by material are collected in our technical data.
Fire Classifications
ASTM E136 documentation may be requested or required depending on jurisdiction, parcel conditions, and AHJ review.
The most restrictive ASTM E84 category for combustible materials. It may be requested or required depending on jurisdiction, parcel conditions, and AHJ review.
Moderate flame spread. Product documentation, assembly details, and local AHJ review determine suitability.
Higher flame spread rate. May not be accepted in many wildfire zones. Confirm with your local AHJ for allowable materials.
Fencing Materials
See how common fencing materials used in San Diego, Orange County, and Los Angeles compare on the fire resistance scale.
Material Comparison
Southern California properties often need perimeter materials selected with wildfire exposure, maintenance, and local defensible-space expectations in mind. Fire-performance documentation can be one part of a broader fire-aware perimeter plan, alongside site cleanup, spacing, access, and AHJ review.
Aluminum fencing is commonly used as a non-combustible material option in fire-aware perimeter planning. Product documentation, assembly details, and local AHJ review determine suitability for a specific parcel.
Steel fencing is commonly used as a non-combustible material option in fire-aware perimeter planning. Project acceptance depends on the specific product documentation, assembly details, and local AHJ review.
Composite fencing may have ASTM E84 documentation depending on the product line. Because composite assemblies are product-specific, product documentation, assembly details, and local AHJ review determine suitability before installation near structures.
Wood and standard vinyl fencing are combustible materials that need careful review near structures. Cedar and pine typically fall into Class C or remain unrated entirely, and standard vinyl can melt or deform under heat. For properties in high-risk areas, pairing a documented non-combustible fence with landscape rock as non-combustible ground cover can support defensible-space planning when local requirements and AHJ review align.
Local Regulatory Status
Yes — the City of San Diego has already adopted Zone 0, ahead of the state. The city's requirement lives in San Diego Municipal Code (SDMC) §512.0604, the San Diego Wildland Urban Interface (SDWUI) Code. It applies to structures in a Very High Fire Hazard Severity Zone within the City of San Diego and took effect for new structures on February 28, 2026, and applies to existing structures beginning February 28, 2027 (subject to change at the discretion of the Fire Code Official).
The statewide Zone 0 rule is separate: the California Board of Forestry released an updated draft on April 17, 2026 (workshop April 23, 2026) and it is still a draft, not final law — the original December 31, 2025 deadline passed without adoption. That draft traces to AB 3074 (2020) and PRC §4291, and its fence and gate language is draft §1298.04(b)(8)–(9).
San Diego's adopted rule includes specific exceptions. Existing vinyl fencing may be allowed within 5 feet if it runs parallel to the wall, sits no less than 4 feet from the structure, is kept clear of debris, and has no vegetation between the fence and the structure. New parallel wood fencing is permitted only if it is Fire Retardant Treated Wood (FRTW), meets the vinyl conditions, and is on the California OSFM Wildland Urban Interface (WUI) Products Handbook and approved for exterior use. Your insurer or the IBHS may not allow vinyl or FRTW within 5 feet even where code does.
| Rule | Status | Key dates |
|---|---|---|
| City of San Diego — SDMC §512.0604 (SDWUI Code) | Adopted | New: Feb 28, 2026 · Existing: Feb 28, 2027 |
| Statewide — Board of Forestry (PRC §4291 / AB 3074) | Draft (April 2026) | Not yet final; comment period open |
Sources: City of San Diego Zone 0 Guidelines for Existing Structures (rev. 4/22/2026); California Board of Forestry Zone 0 draft rule text (April 2026). Confirm current status with your AHJ before final design decisions.
Common Questions
Fire ratings depend on the specific product and test reports. Ask for ASTM E84 or E136 documentation and confirm acceptance with your local AHJ.
Fire ratings depend on the specific product and test reports. Ask for ASTM E84 or E136 documentation and confirm acceptance with your local AHJ.
Fire hazard zones and requirements vary by neighborhood and jurisdiction. Check local hazard maps and confirm local requirements with your AHJ. We can help interpret requirements for your property.
Fire hazard zones and requirements vary by neighborhood and jurisdiction. Check local hazard maps and confirm local requirements with your AHJ. We can help interpret requirements for your property.
Fire ratings depend on the specific product and test reports. Ask for ASTM E84 or E136 documentation and confirm acceptance with your local AHJ.
Aluminum and steel are commonly used as non-combustible material options in fire-aware perimeter planning. Product documentation, assembly details, and local AHJ review determine suitability for a specific parcel.
Aluminum fences are commonly used as non-combustible material options for fire-aware perimeter planning. Product documentation, assembly details, and local AHJ review determine whether a specific installation is acceptable for a given parcel.
ASTM E84 Class A means a material has a Flame Spread Index between 0 and 25 and a Smoke Developed Index of 450 or less under that test method. It may be requested or required depending on jurisdiction, parcel conditions, and AHJ review.
Some composite fencing products have ASTM E84 documentation, while others do not. Product documentation, assembly details, and local AHJ review determine suitability before installation in a California fire hazard zone.
Non-combustible material options such as aluminum, steel, masonry, and stone can support Zone 0 planning, but requirements vary by jurisdiction, parcel, connection detail, and AHJ review. Wood, vinyl, and composite products need product-specific review before being used near structures.
Yes. The City of San Diego adopted Zone 0 through San Diego Municipal Code (SDMC) §512.0604, the San Diego Wildland Urban Interface (SDWUI) Code, effective for new structures on February 28, 2026 and for existing structures beginning February 28, 2027. The statewide Board of Forestry Zone 0 rule remains a draft (April 2026) and is not yet final law. Confirm current requirements with your AHJ.
We install aluminum, steel, and gabion systems across San Diego, Orange County, and Los Angeles with fire-performance documentation available by product. Requirements vary by jurisdiction and AHJ review.
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