CWUIC · California Wildland-Urban Interface Code
When must accessory buildings and miscellaneous structures use ignition‑resistant construction?
If a shed, gazebo, patio cover or other permit‑required outbuilding is close to your house (especially under **3 feet**, or **3–50 feet** and the building is over **120 sq ft**), the CWUIC generally requires it to be built with **noncombustible** or **ignition‑resistant** materials and its roof to meet the roof‑assembly rules—see **§ 504.11**, **§ 504.11.1** and **§ 504.11.6**; check material tests in **§ 503.2.4** and ask your code official for any local discretion.
Last reviewed: July 6, 2026
What the code requires — 2–4 sentences
Accessory buildings and miscellaneous structures in WUI areas that can create a significant exterior fire exposure hazard must meet the ignition‑resistance rules of § 504.11. The code applies these rules to accessory buildings and permit‑required miscellaneous structures (trellises, arbors, patio covers, gazebos, etc.) and sets different requirements keyed to separation distance, size and whether a building permit is required — see § 504.11.1. Roof assemblies for accessory buildings that must be ignition‑resistant or noncombustible must also meet roof requirements in § 504.11.6 and the referenced roof sections.
If an accessory building or permit‑required miscellaneous structure is close to an applicable building (especially less than 3 feet or 3–50 feet and larger than 120 square feet), it generally must be built of noncombustible or ignition‑resistant materials.
Requirements in detail
Scope and applicability (who/what this covers)
- Applies to accessory buildings and attached or detached miscellaneous structures that require a building permit, including trellises, arbors, patio covers, gazebos and similar structures — § 504.11.1. Decks, awnings, and canopies are handled elsewhere by the code (deck rules at § 504.7.3; awnings/canopies per CBC § 3105).
Decision dimensions you must check
- Three decision‑relevant dimensions: separation distance from the applicable building, floor area (size) of the accessory building, and whether the structure requires a permit. The table below summarizes the prescriptive outcomes and the code reference to check.
| Situation (decision inputs) | Construction required | Code Reference |
|---|---|---|
| Separated by less than 3 feet from an applicable building — accessory buildings of any size, and miscellaneous structures that require a permit | Construct of noncombustible materials or ignition‑resistant building materials | § 504.11.2 |
| Separated 3 feet or more but less than 50 feet — accessory building greater than 120 sq ft | Construct of noncombustible materials or ignition‑resistant building materials | § 504.11.3 |
| Separated 3 feet or more but less than 50 feet — accessory building 120 sq ft or less | Construct of noncombustible or ignition‑resistant where required by the code official (local enforcement discretion) | § 504.11.4 |
| Separated 3 feet or more but less than 50 feet — miscellaneous structures that require a permit | Construct of noncombustible or ignition‑resistant where required by the code official | § 504.11.5 |
| Roof assemblies and coverings of accessory buildings that are required to be noncombustible or ignition‑resistant | Comply with § 504.2 and § 504.2.1; assemblies installed per listing/manufacturer; in Fire Hazard Severity Zones, roofing assemblies must meet Class A per ASTM E108 or UL 790 | § 504.11.6 (references § 504.2 / § 504.2.1) |
Note: “Ignition‑resistant building materials” are defined/tested in Chapter 503 (see § 503.2.4 and related subsections) — always check the material acceptance criteria there when you specify or accept a product.
Material standard to meet
- When the code requires ignition‑resistant construction, the acceptable approaches are: using noncombustible materials, fire‑retardant‑treated wood where allowed, or other materials tested and listed as ignition‑resistant in § 503.2 (notably § 503.2.4). Always use the test/listing required by Chapter 503 for exterior, weather‑exposed materials.
Exceptions & special cases
- Decks: excluded from § 504.11 and must follow § 504.7.3 instead (see the exceptions in § 504.11.1).
- Awnings and canopies: regulated by the California Building Code (CBC § 3105), not § 504.11.
- Group U accessory buildings (outbuildings) located at least 50 feet from an applicable building may be excepted from many Chapter 5 requirements (see the general exceptions at § 101.3.1 and § 501.1). If your accessory building is ≥50 feet from the applicable building, confirm the specific exception language that applies to your occupancy/classification.
- Small detached outbuildings: even small Group U structures can be covered by § 504.11 if they are closer than the exceptions allow or if local code official requires it — always confirm permit triggers with the enforcing agency.
Common mistakes
- Assuming any small shed is exempt. Mistake: size alone doesn’t rule out § 504.11 — distance and permit requirement matter. Check 120 sq ft, 3 ft, and 50 ft thresholds.
- Measuring from the wrong reference point. Mistake: measure the shortest horizontal separation between the accessory/misc structure and the applicable building on the same lot (confirm local measuring practice with the code official).
- Treating “ignition‑resistant” as interchangeable with “Class A roofing.” “Ignition‑resistant” is a broader material classification (see § 503.2.4); roof assemblies have their own performance and installation requirements and may additionally require Class A in Fire Hazard Severity Zones per § 504.11.6.
- Ignoring code official discretion. For accessory buildings ≤120 sq ft or miscellaneous structures between 3 and 50 feet, the code official may require ignition‑resistant construction — don’t assume “no” just because your structure is small. § 504.11.4 and § 504.11.5 make this explicit.
Worked example
Scenario: You plan to install a detached storage building that is 200 sq ft (floor area) and will sit 10 feet from your house in a WUI area.
- Which rule applies? The building is greater than 120 square feet and is 3 feet or more but less than 50 feet from the applicable building — see § 504.11.3.
- Construction requirement: The storage building must be constructed of noncombustible materials or ignition‑resistant building materials (as described in § 503.2.4).
- Roof requirement: Because the building is required to be noncombustible or ignition‑resistant, its roof assembly and roof covering must comply with § 504.2 and § 504.2.1, and you must follow the roofing assembly listing/manufacturer instructions; if the site is in a Fire Hazard Severity Zone, the roof assembly must be Class A per ASTM E108 or UL 790 per § 504.11.6.
Conclusion: For this 200‑sq‑ft shed at 10 ft, you will specify an ignition‑resistant or noncombustible exterior product, and you must ensure the roof meets the stated roof assembly requirements (Class A if in a FHSZ).
Related provisions
- § 504.11 — Accessory buildings and miscellaneous structures (general rule and thresholds).
- § 504.11.1 — Applicability (what kinds of accessory/misc structures are covered; decks/awnings exceptions).
- § 504.11.6 — Roof construction requirements for accessory buildings required to be noncombustible/ignition‑resistant (references § 504.2/§ 504.2.1 and Class A roofing tests).
- § 504.11.2 – § 504.11.5 — Specific distance/size permutations (see the table above for how these apply).
- § 503.2.4 — Definition and test/listing requirements for ignition‑resistant building materials (material acceptance criteria).
- § 504.2 / § 504.2.1 — Roof assembly and roof covering installation and void protection requirements referenced by § 504.11.6.
Code references
Grounded in the retrieved California Wildland-Urban Interface Code — click a citation to read the verbatim passage:
CWUIC § 504.11.3 High relevance — show source text
504.11.3 Accessory buildings greater than 120 square feet, located 3 feet or more but less than 50 feet. Accessory buildings that are greater than 120 square feet (11.15 m2) in size and separated from an applicable building on the same lot by a distance of 3 feet (914 mm) or more but less than 50 feet (15 240 mm) shall be constructed of noncombustible materials or of ignition-resistant building materials as described in Section 503.2.4.
504.11.4 Accessory buildings 120 square feet or less, located 3 feet or more but less than 50 feet. Where required by the code offi- cial, accessory buildings 120 square feet (11.15 m2) or less and separated from an applicable building on the same lot by a distance of 3 feet (914 mm) or more but less than 50 feet (15 240 mm) shall be constructed of noncombustible materials or of ignition-resistant building materials as described in Section 503.2.4.
504.11.5 Miscellaneous structures located 3 feet or more but less than 50 feet. Where required by the code official, miscellaneous structures that require a permit and are separated from an applicable building on the same lot by a distance of 3 feet (914 mm) or more but less than 50 feet (15 240 mm) shall be constructed of noncombustible materials or of ignition-resistant building materials as described in Section 503.2.4.
504.11.6 Roof construction. Roof assemblies and roof coverings of accessory buildings required to be constructed entirely of noncombustible materials or of ignition-resistant building materials shall comply with Sections 504.2 and 504.2.1. Roofs shall have a roofing assembly installed in accordance with its listing and the manufacturer’s installation instructions. Roof assemblies in Fire Hazard Severity Zones shall comply with a Class A fire classification when tested in accordance with ASTM E108 or UL 790.
SECTION 505— RESERVED
SECTION 506— RESERVED
SECTION 507—REPLACEMENT OR REPAIR OF ROOF COVERINGS
507.1 General. The roof covering on buildings or structures in existence prior to the adoption of this code that are replaced or have 50 percent or more replaced in a 12-month period shall be replaced with a roof covering required for new construction in accordance with Sections 504.2 and 504.2.1. All portions of a roof covering applied during an addition, alteration or repair to an existing structure shall meet at least a Class A fire classification.
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CALIFORNIA WILDLAND-URBAN INTERFACE CODE – MATRIX ADOPTION TABLE
CHAPTER 6 – FIRE PROTECTION REQUIREMENTS
(Matrix Adoption Tables are nonregulatory, intended only as an aid to the code user. See Chapter 1 for state agency authority and building applications.)
CWUIC § 504.10.3 High relevance — show source text
2. The vent and mesh material shall be noncombustible.
3. The vent and mesh material shall be corrosion resistant.
504.10.3 Vent locations. Gable-end and dormer vents shall be located not less than 10 feet (3048 mm) from lot lines. Underfloor ventilation openings shall be located as close to grade as practical.
504.11 Accessory buildings and miscellaneous structures. Accessory buildings and miscellaneous structures that have the potential to pose a significant exterior fire exposure hazard during wildfires shall be constructed to conform to the ignition-resistance require- ments of this section.
504.11.1 Applicability . Sections 504.11.2 through 504.11.6 apply to buildings accessory to an applicable building on the same lot, and attached or detached miscellaneous structures that require a building permit, including but not limited to trellises, arbors, patio covers, gazebos and similar structures.
Exceptions: 1. Decks shall comply with the requirements of Section 504.7.3. 2. Awnings and canopies shall comply with the requirements of Section 3105 of the California Building Code.
504.11.2 Miscellaneous structures and accessory buildings within 3 feet. Miscellaneous structures that require a permit, and accessory buildings of any size, when separated from an applicable building on the same lot by a distance of less than 3 feet (914 mm), shall be constructed of noncombustible materials or ignition-resistant building materials as described in Section 503.2.4.
504.11.3 Accessory buildings greater than 120 square feet, located 3 feet or more but less than 50 feet. Accessory buildings that are greater than 120 square feet (11.15 m2) in size and separated from an applicable building on the same lot by a distance of 3 feet (914 mm) or more but less than 50 feet (15 240 mm) shall be constructed of noncombustible materials or of ignition-resistant building materials as described in Section 503.2.4.
504.11.4 Accessory buildings 120 square feet or less, located 3 feet or more but less than 50 feet. Where required by the code offi- cial, accessory buildings 120 square feet (11.15 m2) or less and separated from an applicable building on the same lot by a distance of 3 feet (914 mm) or more but less than 50 feet (15 240 mm) shall be constructed of noncombustible materials or of ignition-resistant building materials as described in Section 503.2.4.
504.11.5 Miscellaneous structures located 3 feet or more but less than 50 feet. Where required by the code official, miscellaneous structures that require a permit and are separated from an applicable building on the same lot by a distance of 3 feet (914 mm) or more but less than 50 feet (15 240 mm) shall be constructed of noncombustible materials or of ignition-resistant building materials as described in Section 503.2.4.
CWUIC § 504.10.1 High relevance — show source text
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SPECIAL BUILDING CONSTRUCTION REGULATIONS
lation, foundations and crawl spaces, or any other opening intended to permit ventilation, either in a horizontal or vertical surface, shall be in accordance with Section 504.10.1 or Section 504.10.2 to resist building ignition from the intrusion of burning embers and flame through the ventilation openings.
504.10.1 Performance requirements. Ventilation openings shall be fully covered with Wildfire Flame and Ember Resistant vents approved and listed by the California State Fire Marshal, or WUI vents, tested in accordance with ASTM E2886, to demonstrate compliance with all the following requirements:
- There shall be no flaming ignition of the cotton material during the Ember Intrusion Test.
- There shall be no flaming ignition during the Integrity Test portion of the Flame Intrusion Test.
- The maximum temperature of the unexposed side of the vent shall not exceed 662°F (350°C).
504.10.2 Off ridge and ridge vents. Vents that are installed on a sloped roof, such as dormer vents, shall comply with all of the following: 1. Vents shall be covered with a mesh where the dimensions of the mesh therein shall be a minimum of [1] / 16 inch (1.6 mm) and shall not exceed [1] / 8 inch (3.2 mm) in diameter.
2. The vent and mesh material shall be noncombustible.
3. The vent and mesh material shall be corrosion resistant.
504.10.3 Vent locations. Gable-end and dormer vents shall be located not less than 10 feet (3048 mm) from lot lines. Underfloor ventilation openings shall be located as close to grade as practical.
504.11 Accessory buildings and miscellaneous structures. Accessory buildings and miscellaneous structures that have the potential to pose a significant exterior fire exposure hazard during wildfires shall be constructed to conform to the ignition-resistance require- ments of this section.
504.11.1 Applicability . Sections 504.11.2 through 504.11.6 apply to buildings accessory to an applicable building on the same lot, and attached or detached miscellaneous structures that require a building permit, including but not limited to trellises, arbors, patio covers, gazebos and similar structures.
Exceptions: 1. Decks shall comply with the requirements of Section 504.7.3. 2. Awnings and canopies shall comply with the requirements of Section 3105 of the California Building Code.
504.11.2 Miscellaneous structures and accessory buildings within 3 feet. Miscellaneous structures that require a permit, and accessory buildings of any size, when separated from an applicable building on the same lot by a distance of less than 3 feet (914 mm), shall be constructed of noncombustible materials or ignition-resistant building materials as described in Section 503.2.4.
CWUIC § 5-1 High relevance — show source text
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5 SPECIAL BUILDING CONSTRUCTION REGULATIONS
User notes:
About this chapter: Chapter 5 provides regulations that establish minimum standards for the location, design and construction of buildings and structures based on construction within a Fire Hazard Severity Zone or a Wildland-Urban Interface (WUI) Area.
The construction provisions of Chapter 5 are intended to supplement the requirements of the California Building Code and California Residential Code and address mitigation of the unique hazards posed to buildings by wildfire and to reduce the hazards of building fires spreading to wildland fuels. This is accomplished by requiring ignition-resistant construction materials. Construction features regulated include underfloor areas; roof coverings; eaves and soffits; gutters and downspouts; exterior walls, doors and windows; ventilation openings and accessory structures.
SECTION 501—GENERAL
501.1 Scope. Buildings and structures in a wildland-urban interface area shall be constructed in accordance with the California Build- ing Code and this code.
Exceptions:
- Group U accessory structures not exceeding 120 square feet (11 m [2] ) in floor area where located not less than 50 feet (15 240 mm) from applicable buildings.
- Group U agricultural buildings not less than 50 feet (15 240 mm) from applicable buildings.
501.2 Objective. The objective of this chapter is to establish minimum standards to locate, design and construct buildings and structures or portions thereof for the protection of life and property, to resist damage from wildfires, and to mitigate building and structure fires from spreading to wildland fuels.
501.3 Fire-resistance-rated construction. Where this code requires 1-hour fire-resistance-rated construction, the fire-resistance rating of building elements, components or assemblies shall be determined in accordance with the test procedures set forth in ASTM E119 or UL 263.
Exceptions:
- The fire-resistance rating of building elements, components or assemblies based on the prescriptive designs prescribed in Section 721 of the California Building Code .
- The fire-resistance rating of building elements, components or assemblies based on the calculation procedures in accordance with Section 722 of the California Building Code .
501.4 Noncombustibility tests. The tests indicated in Section 501.4.1 shall serve as criteria for acceptance of noncombustible building materials. The term “noncombustible” does not apply to the flame spread characteristics of interior finish or trim materials. A material shall not be classified as a noncombustible building construction material if it is subject to an increase in combustibility or flame spread beyond the limitations herein established through the effects of age, moisture or other atmospheric conditions.
501.4.1 Noncombustible materials. Materials required to be noncombustible shall be tested in accordance with ASTM E136 and pass the test. Alternately, materials required to be noncombustible shall be tested in accordance with ASTM E2652 using the accep- tance criteria prescribed by ASTM E136.
CWUIC § 0.125 High relevance — show source text
Exception: Materials having a structural base of noncombustible material as determined in accordance with ASTM E136, or with ASTM E2652 using the acceptance criteria prescribed by ASTM E136, and a surfacing of not more than 0.125 inch (3.18 mm) in thick- ness having a flame spread index not greater than 50 when tested in accordance with ASTM E84 or UL 723 shall be acceptable as noncombustible.
SECTION 502— RESERVED
SECTION 503—IGNITION-RESISTANT CONSTRUCTION AND MATERIAL
503.1 General. Buildings and structures hereafter constructed, modified or relocated into or within wildland-urban interface areas shall meet the construction requirements in accordance with Chapter 5 . Materials required to be ignition-resistant building materials shall comply with the requirements of Section 503.2.
Exceptions:
1. New accessory buildings and miscellaneous structures complying with Section 504.11. 2. Additions to and remodels of buildings originally constructed prior to July 1, 2008. 3. Group C occupancy special buildings conforming to the limitations specified in Section 450.4.1 of the California Building Code.
503.2 Ignition-resistant building material. Ignition-resistant building materials shall be designed for exterior use and weather expo- sure and shall comply with any one of the requirements in Section 503.2.1 through 503.2.4.3.3 .
503.2.1 Noncombustible material. Noncombustible material shall comply with the requirements in Section 501.4 .
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SPECIAL BUILDING CONSTRUCTION REGULATIONS
503.2.2 Fire-retardant-treated wood. Fire-retardant-treated wood shall be identified for exterior use and shall meet the requirements of Section 2303.2 of the California Building Code .
503.2.3 Fire-retardant-treated wood roof coverings. Roof assemblies containing fire-retardant-treated wood shingles and shakes shall comply with the requirements of Section 1505.6 of the California Building Code and shall be classified as Class A roof assemblies as required in Section 1505.2 of the California Building Code .
503.2.4 Other ignition-resistant building material. Material shall be tested on the front and back faces in accordance with the extended ASTM E84 or UL 723 test, for a total test period of 30 minutes, or with the ASTM E2768 test. The materials shall bear identification showing the fire test results. Panel products shall be tested with a ripped or cut longitudinal gap of [1] / 8 inch (3.2 mm). The materials, when tested in accordance with the test procedures set forth in ASTM E84 or UL 723 for a test period of 30 minutes, or with ASTM E2768, shall comply with Sections 503.2.4.1 through 503.2.4.3.
Exception: Materials composed of a combustible core and a noncombustible exterior covering made from either aluminum at a minimum 0.019 inch (0.48 mm) thickness or corrosion-resistant steel at a minimum 0.0149 inch (0.38 mm) thickness shall not be required to be tested with a ripped or cut longitudinal gap.
CWUIC § 102.4 High relevance — show source text
Chapter 5 Special Building Construction Regulations.
The regulations in Chapter 5 establish minimum standards for the location, design and construction of buildings and structures based on construction within a Fire Hazard Severity Zone or a Wildland-Urban Interface (WUI) Area.
The construction provisions of Chapter 5 are intended to supplement the requirements of the California Building Code and Califor- nia Residential Code and address mitigation of the unique hazards posed to buildings by wildfire and to reduce the hazards of building fires spreading to wildland fuels. This is accomplished by requiring ignition-resistant construction materials.
Chapter 6 Fire Protection Requirements.
Chapter 6 contains additional requirements for development and construction in Local Responsibility Areas (LRA) designated as Very High Fire Hazard Severity Zones and areas designated by the State Fire Marshal as State Responsibility Areas (SRA). While many of these provisions are found in Title 14 and Title 19 of the California Code of Regulations, they are replicated here for the code user. The local jurisdiction has the authority to apply the same regulations to LRA when the regulations are adopted by local ordinance.
The requirements in this chapter reference the process for adoption of Very High Fire Hazard Severity Zones in the LRA; criteria for evaluating existing subdivisions that are at significant fire risk and are without an adequate secondary egress; and criteria for fire safety provisions required in the Safety Element of a city or county General Plan.
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The chapter includes mitigation strategies to reduce the hazards of fire originating within a structure spreading to wildland and fire originating in wildland spreading to structures.
Chapter 7 Referenced Standards.
Chapter 7 lists all of the product and installation standards and codes that are referenced throughout Chapters 1 through 6 and includes identification of the promulgators and the section numbers in which the standards and codes are referenced. As stated in Section 102.4, these standards and codes become an enforceable part of the code (to the prescribed extent of the reference) as if printed in the body of the code.
Appendix A General Requirements.
Appendix A, while not part of the code, can become part of the code when specifically included in the adopting ordinance. Its purpose is to provide fire-protection measures supplemental to those found in Chapter 6 to reduce the threat of wildfire in a wildland-urban interface area and improve the capability for controlling such fires. This appendix includes detailed requirements for vegetation control; the code official’s authority to close wildland-interface areas in times of high fire danger; control of fires, fireworks usage and other sources of ignition; storage of hazardous materials and combustibles; bans on the dumping of waste materials and ashes and coals in wildlandurban interface areas; protection of pumps and water supplies; and limits on temporary uses within the wildland-urban interface area.
Appendix B Vegetation Management Plan.
Appendix B, while not part of the code, can become part of the code when specifically included in the adopting ordinance. Its purpose is to provide criteria for submitting vegetation management plans, specifying their content and establishing a criterion for considering vegetation management as being a fuel modification.
Appendix C Community Wildland-Urban Interface (WUI) Fire Hazard Evaluation Framework.
CWUIC § 8.1 High relevance — show source text
8.1_ –504.8.2|||X||||||||||||||||||||| |504.9|||X||||||||||||||||||||| |504.9.1 –504.9.3|||X||||||||||||||||||||| |504.10.1 – 504.10.3|||X||||||||||||||||||||| |504.11 – 504.11.1|||X||||||||||||||||||||| |504.11.2 –504.11.6|||X||||||||||||||||||||| |505 – 506_Reserved_|||X||||||||||||||||||||| |507.1|||X|||||||||||||||||||||
- The California Code of Regulations (CCR), Title 19, Division 1 provisions that are found in the California Wildland-Urban Interface Code are a reprint from the current CCR, Title 19, Division 1 text for the code user’s convenience only. The scope, applicability and appeals procedures of CCR, Title 19, Division I remain the same. The state agency does not adopt sections identified by the following symbol: The Office of the State Fire Marshal’s adoption of this chapter or individual sections is applicable to structures regulated by other state agencies pursuant to Section 1.11.
The California Code of Regulations (CCR), Title 14, Division 1.5 provisions that are found in the California Wildland-Urban Interface Code are not listed in the Matrix Adoption Tables as they are not within the State Fire Marshal’s authority to adopt. These provisions are a reprint from the current CCR, Title 14, Division 1.5 text for the code user’s convenience only and are identified in the body of the code by square brackets containing references to applicable Title 14 sections.
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5 SPECIAL BUILDING CONSTRUCTION REGULATIONS
User notes:
About this chapter: Chapter 5 provides regulations that establish minimum standards for the location, design and construction of buildings and structures based on construction within a Fire Hazard Severity Zone or a Wildland-Urban Interface (WUI) Area.
The construction provisions of Chapter 5 are intended to supplement the requirements of the California Building Code and California Residential Code and address mitigation of the unique hazards posed to buildings by wildfire and to reduce the hazards of building fires spreading to wildland fuels. This is accomplished by requiring ignition-resistant construction materials. Construction features regulated include underfloor areas; roof coverings; eaves and soffits; gutters and downspouts; exterior walls, doors and windows; ventilation openings and accessory structures.
SECTION 501—GENERAL
501.1 Scope. Buildings and structures in a wildland-urban interface area shall be constructed in accordance with the California Build- ing Code and this code.
Exceptions:
- Group U accessory structures not exceeding 120 square feet (11 m [2] ) in floor area where located not less than 50 feet (15 240 mm) from applicable buildings.
- Group U agricultural buildings not less than 50 feet (15 240 mm) from applicable buildings.
CWUIC § 501.2 High relevance — show source text
501.2 Objective. The objective of this chapter is to establish minimum standards to locate, design and construct buildings and structures or portions thereof for the protection of life and property, to resist damage from wildfires, and to mitigate building and structure fires from spreading to wildland fuels.
501.3 Fire-resistance-rated construction. Where this code requires 1-hour fire-resistance-rated construction, the fire-resistance rating of building elements, components or assemblies shall be determined in accordance with the test procedures set forth in ASTM E119 or UL 263.
Exceptions:
- The fire-resistance rating of building elements, components or assemblies based on the prescriptive designs prescribed in Section 721 of the California Building Code .
- The fire-resistance rating of building elements, components or assemblies based on the calculation procedures in accordance with Section 722 of the California Building Code .
501.4 Noncombustibility tests. The tests indicated in Section 501.4.1 shall serve as criteria for acceptance of noncombustible building materials. The term “noncombustible” does not apply to the flame spread characteristics of interior finish or trim materials. A material shall not be classified as a noncombustible building construction material if it is subject to an increase in combustibility or flame spread beyond the limitations herein established through the effects of age, moisture or other atmospheric conditions.
501.4.1 Noncombustible materials. Materials required to be noncombustible shall be tested in accordance with ASTM E136 and pass the test. Alternately, materials required to be noncombustible shall be tested in accordance with ASTM E2652 using the accep- tance criteria prescribed by ASTM E136.
Exception: Materials having a structural base of noncombustible material as determined in accordance with ASTM E136, or with ASTM E2652 using the acceptance criteria prescribed by ASTM E136, and a surfacing of not more than 0.125 inch (3.18 mm) in thick- ness having a flame spread index not greater than 50 when tested in accordance with ASTM E84 or UL 723 shall be acceptable as noncombustible.
SECTION 502— RESERVED
SECTION 503—IGNITION-RESISTANT CONSTRUCTION AND MATERIAL
503.1 General. Buildings and structures hereafter constructed, modified or relocated into or within wildland-urban interface areas shall meet the construction requirements in accordance with Chapter 5 . Materials required to be ignition-resistant building materials shall comply with the requirements of Section 503.2.
Exceptions:
1. New accessory buildings and miscellaneous structures complying with Section 504.11. 2. Additions to and remodels of buildings originally constructed prior to July 1, 2008. 3. Group C occupancy special buildings conforming to the limitations specified in Section 450.4.1 of the California Building Code.
503.2 Ignition-resistant building material. Ignition-resistant building materials shall be designed for exterior use and weather expo- sure and shall comply with any one of the requirements in Section 503.2.1 through 503.2.4.3.3 .
503.2.1 Noncombustible material. Noncombustible material shall comply with the requirements in Section 501.4 .
2025 CALIFORNIA WILDLAND-URBAN INTERFACE CODE 5-3
CWUIC § 101.1 High relevance — show source text
PART 1—GENERAL PROVISIONS
SECTION 101—SCOPE AND GENERAL REQUIREMENTS
[A] 101.1 Title. These regulations shall be known as the California Wildland-Urban Interface Code of [ NAME OF JURISDICTION ], hereinafter referred to as “this code.”
[A] 101.2 Scope. This code applies to building materials, systems and/or assemblies used in the exterior design and construction of new buildings located within a wildland-urban interface (WUI) area and contains minimum requirements to mitigate conditions that might cause a fire originating in a structure to ignite vegetation in the wildland-urban interface (WUI) area, and conversely, a wildfire burning in vegetative fuels to transmit fire to buildings and threaten to destroy life, overwhelm fire suppression capabilities or result in large property losses.
[A] 101.2.1 Appendices. Provisions in the appendices shall not apply unless specifically adopted.
[A] 101.3 Purpose. The purpose of this code is to establish minimum regulations for the safeguarding of life and for property protection. Regulations in this code are intended to mitigate the risk to life and structures from intrusion of fire from wildland fire exposures and fire exposures from adjacent structures and to mitigate structure fires from spreading to wildland fuels. The extent of this regulation is intended to be tiered commensurate with the relative level of hazard present.
The unrestricted use of property in wildland-urban interface areas is a potential threat to life and property from fire and resulting erosion. Safeguards to prevent the occurrence of fires and to provide adequate fire protection facilities to control the spread of fire in wildland-urban interface areas shall be in accordance with this code.
This code shall supplement the jurisdiction’s building and fire codes, if such codes have been adopted, to provide for special regulations to mitigate the fire- and life-safety hazards of the wildland-urban interface areas.
101.3.1 Application. New buildings located in any Fire Hazard Severity Zone or Wildland-Urban Interface (WUI) Fire Area designated by the enforcing agency constructed after the application date shall comply with the provisions of this code. This shall include all new buildings with residential, commercial, educational, institutional or similar occupancy type use, which shall be referred to in this code as “applicable buildings,” as well as new buildings and structures accessory to those applicable buildings.
Exceptions: 1. Group U occupancy accessory buildings of any size located at least 50 feet (15 240 mm) from an applicable building on the same lot.
2. Group U occupancy agricultural buildings, as defined in Section 202 of the California Building Code of any size located at least 50 feet (15 240 mm) from an applicable building. 3. Group C occupancy special buildings conforming to the limitations specified in Section 450.4.1 of the California Building Code. 4. New accessory buildings and miscellaneous structures specified in Section 504.11 shall comply only with the requirements of that section.
5. Additions to and remodels of buildings originally constructed prior to July 1, 2008.
101.3.1.1 Application date and where required. New buildings for which an application for a building permit is submitted on or after July 1, 2008, located in any Fire Hazard Severity Zone or Wildland-Urban Interface Area shall comply with this code, including all of the following areas:
CWUIC § 101.3.1 High relevance — show source text
This code shall supplement the jurisdiction’s building and fire codes, if such codes have been adopted, to provide for special regulations to mitigate the fire- and life-safety hazards of the wildland-urban interface areas.
101.3.1 Application. New buildings located in any Fire Hazard Severity Zone or Wildland-Urban Interface (WUI) Fire Area designated by the enforcing agency constructed after the application date shall comply with the provisions of this code. This shall include all new buildings with residential, commercial, educational, institutional or similar occupancy type use, which shall be referred to in this code as “applicable buildings,” as well as new buildings and structures accessory to those applicable buildings.
Exceptions: 1. Group U occupancy accessory buildings of any size located at least 50 feet (15 240 mm) from an applicable building on the same lot.
2. Group U occupancy agricultural buildings, as defined in Section 202 of the California Building Code of any size located at least 50 feet (15 240 mm) from an applicable building. 3. Group C occupancy special buildings conforming to the limitations specified in Section 450.4.1 of the California Building Code. 4. New accessory buildings and miscellaneous structures specified in Section 504.11 shall comply only with the requirements of that section.
5. Additions to and remodels of buildings originally constructed prior to July 1, 2008.
101.3.1.1 Application date and where required. New buildings for which an application for a building permit is submitted on or after July 1, 2008, located in any Fire Hazard Severity Zone or Wildland-Urban Interface Area shall comply with this code, including all of the following areas:
All unincorporated lands designated by the State Board of Forestry and Fire Protection as State Responsibility Area (SRA) including:
Moderate Fire Hazard Severity Zones.
High Fire Hazard Severity Zones.
Very High Fire Hazard Severity Zones.
Land designated as a Very High Fire Hazard Severity Zone by cities and other local agencies.
2025 CALIFORNIA WILDLAND-URBAN INTERFACE CODE 1-15
on Jul 18, 2025 11:14 AM (CDT) THEREUNDER.
ADMINISTRATION
Land designated as a wildland-urban interface area by cities and other local agencies.
Exceptions: 1. New buildings located in any Fire Hazard Severity Zone within a State Responsibility Area, for which an application for a building permit is submitted on or after January 1, 2008, shall comply with this code. 2. New buildings located in any Fire Hazard Severity Zone within a State Responsibility Area or any wildland-urban interface area designated by cities and other local agencies for which an application for a building permit is submit- ted on or after December 1, 2005, but prior to July 1, 2008, shall only comply with the following sections of this chapter: 2.1. Section 507 – Replacement or Repair of Roof Coverings.
2.2. Section 504.10 – Vents.
[A] 101.4 Retroactivity. The provisions of the code shall apply to conditions arising after the adoption thereof, conditions not legally in existence at the adoption of this code and conditions that, in the opinion of the code official, constitute a distinct hazard to life or property.
Exception: Provisions of this code that specifically apply to existing conditions are retroactive.
CWUIC § 504.7 High relevance — show source text
Ignition Source Control Appendix A, A104 Ignition-Resistant Building Material 202, 503 Ignition-Resistant Construction 504 Appendages 504.7 Detached accessory structures 504.11 Eaves 504.3
Exterior doors 504.9
Exterior walls 504.5
Gutters and downspouts 504.4 Protection of eaves 504.3 Roof covering 504.2 Underfloor protection 504.6 Vents 504.10
Windows 504.8 Ignition-Resistant Construction and Material 503 Inspection and Enforcement 109 Abatement 109.3.8 Authority to inspect 109.1.2 Citations 109.3.4
Enforcement 109.2 Placarding 109.3.5.3 Prosecution 109.3.6
Reinspections 109.1.3 Right of entry 104.4 Testing 109.1.4 Unsafe conditions 109.3.5
Key Box 403.1
Land Use Limitations Appendix A, A108 Legal Defense of the Code Official 104.8.1 Liability of the Code Official 104.8
Log Wall Construction 202 LP-Gas Installations 606
Maintenance 101.6 Maintenance of Defensible Space 604 Modified area 604.2 Responsibility 604.3 Trees 604.4 Mapping of Wildland-Urban Interface Area 302.2 Multilayered Glazed Panels 202
Noncombustible Roof Covering 202
Outbuilding 202
Peer Review 104.2.2.7, 202 Permits
Application 105.4 Approval 105.5 Expiration 105.8 Issuance 105.6 Preliminary inspection 105.4.1 Refusal to issue 105.6.1
Required 105.2 Retention 105.9
Revocation 105.10 Validity 105.7 Work exempt from permit 105.3 Placarding as Unsafe 109.3.5.3 Powers and Duties of the Code
Official 104.1
Practical Difficulties 104.2.3 Protection of Pumps and Water Storage Facilities Appendix A, A107
Rafter Tail 202 Referenced Standards 102.4, Chapter 7 Registered Design Professional 104.2.1.2, 104.2.2.6.2, 106.1, 202 Residential Unit 202 Retroactivity 101.4 Ridgelline 202 Road 202 Roof Covering 202 Roof Covering System 202 Roof Coverings, Replacement or Repair of 507
Roof Deck 202
Scope 101 Self-Defense Mechanism Appendix G Service Utilities 111
Slope 202 Spark Arrestors 605 Stop Work Order 113 Storage of Firewood and Combustible Materials 607 Strategic Ridgeline 202 Structure 202
Subdivision 202
CWUIC § 601.3 Medium relevance — show source text
Dead-end Road 202 Defensible Space 403, 601.3 Vegetation Plan 603 Definitions 202 Designation of Wildland-Urban Interface Area 302.1
Director 202 Driveway 202 Dumping Appendix A, A106 Dwelling 202
Exterior Covering 202
INDEX
Fees 109 Findings of Fact Appendix E Fire Chief 202 Fire Danger Rating System Appendix D Fire Flow Calculation Area Application 404.5 Defined 202 Fire Hazard Severity Zones 1.1.2, 202, 302.1, 302.2, Appendix D, Appendix H Fire Protection Plans 602
Fire Weather 202
Fire-Resistance-Rated Construction 501.3 Fire-Resistive Vegetation Appendix F Fire-Retardant-Treated Lumber or
Wood 503.2, 504.5, 504.7, 504.11 Flame Spread Index 202 Flashing 504.2.1, 504.5.1 Fuel Break 202, 609 Fuel Models Appendix D Fuel Modification 202
Fuel Modification Distance 603.2
Fuel Mosaic 202 Fuel-Loading 202
General Requirements Appendix A Green Belt 202
Greenways 202
Hammerhead/T 202 Hazardous Land Use 202
Hazardous Materials 202 Heavy Timber Construction 202
Ignition Source Control Appendix A, A104 Ignition-Resistant Building Material 202, 503 Ignition-Resistant Construction 504 Appendages 504.7 Detached accessory structures 504.11 Eaves 504.3
Exterior doors 504.9
Exterior walls 504.5
Gutters and downspouts 504.4 Protection of eaves 504.3 Roof covering 504.2 Underfloor protection 504.6 Vents 504.10
Windows 504.8 Ignition-Resistant Construction and Material 503 Inspection and Enforcement 109 Abatement 109.3.8 Authority to inspect 109.1.2 Citations 109.3.4
Enforcement 109.2 Placarding 109.3.5.3 Prosecution 109.3.6
Reinspections 109.1.3 Right of entry 104.4 Testing 109.1.4 Unsafe conditions 109.3.5
Key Box 403.1
Land Use Limitations Appendix A, A108 Legal Defense of the Code Official 104.8.1 Liability of the Code Official 104.8
Log Wall Construction 202 LP-Gas Installations 606
Maintenance 101.6 Maintenance of Defensible Space 604 Modified area 604.2 Responsibility 604.3 Trees 604.4 Mapping of Wildland-Urban Interface Area 302.2 Multilayered Glazed Panels 202
Noncombustible Roof Covering 202
Outbuilding 202
Frequently asked questions
When does a structure “require a permit” for purposes of § 504.11?
If local building code or the enforcing agency requires a building permit for the accessory or miscellaneous structure, it falls under the “requires a permit” category in § 504.11; check with the local building department to confirm permit triggers.
Is a 100 sq ft shed always exempt from ignition‑resistant construction?
No. A 100 sq ft accessory building may still be subject to § 504.11 if it is located less than 3 feet from an applicable building or if the code official requires ignition‑resistant construction when it’s located 3–50 feet away. Check § 504.11.2 and § 504.11.4.
What does “ignition‑resistant material” mean in practice?
It means materials that meet the testing and listing criteria in Chapter 503 (notably § 503.2.4 and allied subsections) for exterior, weather‑exposed use; accepted options include noncombustible materials and certain tested panel products or fire‑retardant‑treated wood where permitted.
Do roof coverings for accessory buildings always need to be Class A?
Not always — but if the accessory building is required to be noncombustible or ignition‑resistant, its roof must comply with § 504.2 / § 504.2.1, and in Fire Hazard Severity Zones, roof assemblies must be Class A (ASTM E108 or UL 790) per § 504.11.6.
Who decides whether small accessory buildings between 3–50 ft must be ignition‑resistant?
The code official (local enforcement) has discretion to require ignition‑resistant construction for accessory buildings 120 sq ft or less and for miscellaneous permit‑required structures located 3–50 feet, as stated in § 504.11.4 and § 504.11.5.
More in California Wildland-Urban Interface Code
- Administration and Definitions
- Board of Appeals, Administration & Enforcement (permits, code official duties, appeals process)
- Wildland‑Urban Interface Area Designation & Mapping
- Fire Service Access & Water Supply (fire apparatus roads, driveways, hydrants, draft sites, standby power)
- Wildland‑Urban Interface Area Requirements (access, water, premises identification, key boxes)
- Referenced Standards & Test Methods
- Special Building Construction Regulations (ignition‑resistant construction, roof/vent/assembly requirements)
- Appendices and Model Ordinances (vegetation plans, severity‑zone adoption, home‑hardening guidance)
- Fire Protection Requirements (fire protection plans, systems, safety element provisions)
- Referenced California Documents & Matrix (CCR/Title 14 & 19 cross‑references, statutory references)
- Vegetation Management & Defensible Space (vegetation plans, maintenance, fire‑smart characteristics)
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