CWUIC · California Wildland-Urban Interface Code

What qualifies as ignition‑resistant building material?

For homeowners: the CWUIC requires materials exposed to wildfire risk to be made of noncombustible materials, properly treated exterior wood, or materials that pass specific face‑to‑face tests (ASTM E84 extended 30‑minute or ASTM E2768), with labeled test results. Panels must be tested with a 1/8‑inch gap unless they have sufficiently thick metal facings. Always request the test report or label showing the CWUIC test method and result when selecting exterior materials.

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Last reviewed: July 6, 2026

What the code requires — 2-4 sentences

Buildings constructed, modified or relocated into Wildland‑Urban Interface areas must use materials that are designed for exterior use and weather exposure and that meet the ignition‑resistant material requirements in § 503.2. Materials qualify by meeting any one of the options in § 503.2.1 through § 503.2.4 (for example: noncombustible, fire‑retardant‑treated wood, certain tested products); the general duty is stated in § 503.1.

The single most important rule: use materials made or tested to resist ignition from embers and small flames — i.e., materials that meet the CWUIC ignition‑resistant criteria in § 503.2.

Requirements in detail

Summary of the paths that make a material “ignition‑resistant” (see § 503.2):

  • Noncombustible material complying with the noncombustibility tests in § 501.4; or
  • Fire‑retardant‑treated wood identified for exterior use that meets CBC Section 2303.2; or
  • Certain other ignition‑resistant building materials that have been tested and labeled per the code (testing details in § 503.2.4).

Key testing and labeling requirements (§ 503.2.4)

  • Materials in the “other ignition‑resistant” category must be tested on both front and back faces using an extended ASTM E84/UL 723 test for a total test period of 30 minutes, or be tested to ASTM E2768. Panel products must be tested with a ripped or cut longitudinal gap of 1/8 inch (3.2 mm). Test results must be shown on the material (label/identification).

  • Exception: materials with a combustible core but a noncombustible exterior covering of at least 0.019 inch (0.48 mm) aluminum or 0.0149 inch (0.38 mm) corrosion‑resistant steel are not required to be tested with the ripped gap.

  • Fire‑retardant‑treated wood roof coverings must meet the CBC roof requirements and be classified Class A when required (see § 503.2.3).

Decision‑relevant dimensions and values

Decision factor Threshold / value to check What to inspect on the product Code Reference
Test method ASTM E84/UL 723 extended — 30 minutes or ASTM E2768 Label or test report; front & back face tests required § 503.2.4
Panel gap for testing 1/8 in (3.2 mm) ripped/cut longitudinal gap Test protocol description in submittal / label § 503.2.4
Metal‑faced composite exception Aluminum ≥ 0.019 in (0.48 mm) or steel ≥ 0.0149 in (0.38 mm) Manufacturer spec sheet showing base metal thickness § 503.2.4 (exception)
Noncombustible acceptance Must pass ASTM E136 (or ASTM E2652 using ASTM E136 acceptance) Lab report / listing that cites test standard § 501.4 / § 503.2.1
Fire‑retardant wood Labeled for exterior use, complies with CBC § 2303.2 Label / treatment certificate § 503.2.2
Labeling requirement Materials shall bear identification showing the fire test results Product label, spec sheet or listed approval § 503.2.4

What “designed for exterior use and weather exposure” means

  • The code explicitly requires ignition‑resistant materials to be designed for exterior use and weather exposure; that expectation is part of § 503.2 and reflected in the testing and labeling requirements (materials must demonstrate performance after exposure or per weathering evaluations where applicable). If a product’s documentation does not claim exterior suitability, it cannot be accepted as ignition‑resistant under § 503.2.

Exceptions & special cases

  • The code gives an explicit exception for metal‑faced composite panels: if the exterior metal is at least 0.019 in (0.48 mm) aluminum or 0.0149 in (0.38 mm) corrosion‑resistant steel, the ripped‑gap test requirement does not apply. Confirm thickness on manufacturer documentation.

  • Materials may qualify by being noncombustible (ASTM E136) or by being fire‑retardant‑treated wood labeled for exterior use (CBC § 2303.2) — either path avoids the § 503.2.4 testing route.

  • Accessory buildings and small structures may still be required to be noncombustible or ignition‑resistant depending on separation distance and size per § 504.11 (which references ignition‑resistant materials described in § 503.2.4). Always check the accessory‑structure rules in Chapter 5.

Common mistakes

  • Assuming a product with a low interior flame‑spread number automatically qualifies — the CWUIC requires the specific face‑to‑face extended tests (ASTM E84/UL 723 for 30 minutes or ASTM E2768) or other recognized paths in § 503.2, not just generic flame spread numbers.

  • Accepting manufacturer marketing claims without a label or test report that specifically states compliance with the listed CWUIC test method and results. § 503.2.4 requires identification showing the fire test results.

  • Forgetting the panel ripped gap requirement: panel products are tested with a 1/8‑inch (3.2 mm) gap unless they meet the metal‑faced exception. Check the test setup in submittals.

  • Using fire‑retardant‑treated wood that is not labeled for exterior use or does not meet CBC Section 2303.2 — the code requires the exterior labeling and compliance for the treatment path.

Worked example — a concrete scenario

Scenario: You specify an insulated metal panel (IMP) with a combustible foam core and an aluminum exterior sheet that the manufacturer lists as 0.018 in (0.46 mm) thickness.

Step 1 — Check the metal thickness exception: the aluminum is 0.018 in, which is below the exception threshold of 0.019 in (0.48 mm), so the exception does not apply. The panel must therefore be tested per § 503.2.4 (both faces) and, for panels, with a ripped longitudinal gap of 1/8 in (3.2 mm).

Step 2 — Specify the test: require an extended ASTM E84/UL 723 report covering 30 minutes or an ASTM E2768 report, showing results for both faces and the ripped gap configuration. Ensure the test report or label is attached to the product submittal. § 503.2.4 requires the test method and identification.

Step 3 — If the manufacturer instead provides an aluminum skin of 0.02 in (0.51 mm), then the panel meets the metal‑faced exception and the ripped‑gap test is not required — but the product still needs identification and appropriate documentation per the code.

Related provisions

  • § 503.1 — General requirement that buildings in WUI areas meet Chapter 5 construction requirements.
  • § 503.2 — Ignition‑resistant building material: design for exterior use and paths to compliance.
  • § 503.2.1 — Noncombustible material acceptance; see § 501.4 for required tests.
  • § 503.2.2 — Fire‑retardant‑treated wood labeled for exterior use (CBC § 2303.2).
  • § 503.2.3 — Fire‑retardant‑treated wood roof coverings; Class A classification where required.
  • § 503.2.4 — Detailed test, gap, labeling and metal‑faced exception rules for “other” ignition‑resistant materials.
  • § 504.11 — Accessory buildings and miscellaneous structures referencing ignition‑resistant materials for certain separations and sizes.

Code references

Grounded in the retrieved California Wildland-Urban Interface Code — click a citation to read the verbatim passage:

  • CWUIC § 504.3 High relevance — show source text

    504.3 Protection of enclosed eaves. The exposed underside of enclosed roof eaves and soffits shall be protected on the exposed underside by one or more of the following:

    1. Noncombustible materials.

    2. Ignition-resistant building materials. 3. Materials approved for not less than 1-hour fire-resistance-rated construction on the exterior side, as tested in accordance with ASTM E119 or UL 263.

    4. 2-inch (51 mm) nominal dimension lumber . 5. 1-inch (25 mm) nominal fire-retardant-treated lumber or [3] / 4 -inch (19.1 mm) nominal fire-retardant-treated plywood, identified for exterior use and complying with Section 2303.2 of the California Building Code . 6. Boxed-in roof eave soffit assemblies with an underside that meets the performance criteria in Section 504.7.2 when tested in accordance with the test procedures set forth in ASTM E2957. 7. Boxed-in roof eave soffit assemblies with an underside that meets the performance criteria in accordance with the test proce- dures set forth in SFM Standard 12-7A-3.

    Facias are required and shall be ignition-resistant building materials , fire-retardant-treated wood labeled for exterior use and complying with Section 2303.2 of the California Building Code, materials approved for not less than 1-hour fire-resistance-rated construction or 2-inch (51 mm) nominal dimension lumber.

    504.3.1 Protection of open eaves. The exposed roof deck on the underside of unenclosed roof eaves shall consist of one or more of the following:

    1. Noncombustible material.

    2. Ignition-resistant building material. 3. Fire-retardant-treated wood labeled for exterior use and complying with Section 2303.2 of the California Building Code. 4. Materials approved for not less than 1-hour fire-resistance-rated construction on the exterior side, as tested in accordance with ASTM E119 or UL 263.

    5. 2-inch (51 mm) nominal dimension lumber. 6. One layer of [5] / 8 -inch (16 mm) Type X gypsum sheathing applied behind an exterior covering on the underside of the roof deck.

    7. The exterior portion of a 1-hour fire-resistance-rated exterior assembly, as tested in accordance with ASTM E119 or UL 263, applied to the underside of the roof deck designed for exterior fire exposure, including assemblies using the gypsum panel and sheathing products listed in the Gypsum Association Fire Resistance Design Manual.

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    SPECIAL BUILDING CONSTRUCTION REGULATIONS

    Facias, if provided, shall be of fire-retardant-treated wood labeled for exterior use and complying with Section 2303.2 of the Cali- fornia Building Code, ignition-resistant building materials, materials approved for not less than 1-hour fire-resistance-rated construction or 2-inch (51 mm) nominal dimension lumber.

  • 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 § 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 § 503.1 High relevance — show source text

    1||||||| |502|RESERVED|N||||||||| |503|Ignition-resistant
    construction and
    material|Y||704A||||||| |503.1|General|Y||701A.3||||||| |503.2|Ignition-resistant
    building material|Y||707A.3 #2||||||| |503.2.1|Noncombustible
    material|Y||704A.4 #1||||||| |503.2.2|Fire-retardant-
    treated wood|Y||704A.4 #2||||||| |503.2.3|Fire-retardant-
    treated wood roof
    coverings|Y||705A.1||||||| |503.2.4|Other ignition-
    resistant building
    material|Y||704A.3||||||| |503.2.4.1|Flame spread|Y||704A.3 #1||||||| |503.2.4.2|Flame front|Y||704A.3 #2||||||| |503.2.4.3|Weathering|Y||703A.5.1||||||| |503.2.4.3.1|Evaluation require-
    ments for weathering|Y||703A.5.2
    703A.5.2.1||||||| |503.2.4.3.2|Wood-plastic
    composite materials|Y||703A.6|||||||

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    APPENDIX H—REFERENCED CALIFORNIA DOCUMENTS

    2025 CWUIC—continued Col2 Adopted
    Yes/No    		 IWUIC
    Section    		 CBC
    Section    		 CFC
    Section    		 Title 14,
    Division 1.5
    Section    		 Title 19,
    Division 1
    Section    		 Gov Code
    Section    		 PRC
    Section    		 HSC
    Section
    Section Title Title Title Title Title Title Title Title Title Title
    Chapter 5 Special building construction regulations Special building construction regulations Special building construction regulations Special building construction regulations Special building construction regulations Special building construction regulations Special building construction regulations Special building construction regulations Special building construction regulations Special building construction regulations
    503.2.4.3.3 Plastic lumber
    materials    		 Y 703A.6
    503.2.5 Surface treatment
    protection    		 Y 703A.5.3
    503.3 Standards of quality Y 703A.1
    503.3.1 Qualification by
    testing    		 Y 703A.2
    503.3.2 Approved agency Y 703A.3
    503.3.3 Labeling Y 703A.4
    _503.3.
  • CWUIC § 2303.2 High relevance — show source text

    1. Noncombustible material.

    2. Ignition-resistant building material. 3. Fire-retardant-treated wood labeled for exterior use and complying with Section 2303.2 of the California Building Code. 4. Materials approved for not less than 1-hour fire-resistance-rated construction on the exterior side, as tested in accordance with ASTM E119 or UL 263.

    5. 2-inch (51 mm) nominal dimension lumber. 6. One layer of [5] / 8 -inch (16 mm) Type X gypsum sheathing applied behind an exterior covering on the underside of the roof deck.

    7. The exterior portion of a 1-hour fire-resistance-rated exterior assembly, as tested in accordance with ASTM E119 or UL 263, applied to the underside of the roof deck designed for exterior fire exposure, including assemblies using the gypsum panel and sheathing products listed in the Gypsum Association Fire Resistance Design Manual.

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    Facias, if provided, shall be of fire-retardant-treated wood labeled for exterior use and complying with Section 2303.2 of the Cali- fornia Building Code, ignition-resistant building materials, materials approved for not less than 1-hour fire-resistance-rated construction or 2-inch (51 mm) nominal dimension lumber.

    504.4 Gutters and downspouts. Gutters and downspouts shall be constructed of noncombustible material. Gutters shall be provided with an approved means to prevent the accumulation of leaves and debris in the gutter.

    504.5 Exterior walls. Exterior walls of buildings or structures shall be constructed with one or more of the following methods, unless they are covered with an exterior wall covering complying with Sections 504.5.2 and 504.5.2.1:

    1. 1-hour fire-resistance-rated construction on the exterior side.

    2. Noncombustible materials.

    3. Heavy timber. Assembly of sawn lumber or glue-laminated wood with the smallest minimum nominal dimension of 4 inches (102 mm). Sawn or glue-laminated planks splined, tongue-and-grove or set close together and well spiked. 4. Log wall construction. 5. Wall assemblies that have been tested in accordance with the test procedures for a 10-minute direct flame contact exposure test set forth in ASTM E2707 with the conditions of acceptance shown in Section 504.9.3. 6. Wall assemblies that meet the performance criteria in accordance with the test procedures for a 10-minute direct flame contact exposure test set forth in SFM Standard 12-7A-1. 7. Wall assemblies suitable for exterior fire exposure containing one layer of [5] / 8 -inch (15.9 mm) Type X gypsum sheathing applied behind the exterior wall covering or cladding on the exterior side of the framing. 8. Wall assemblies suitable for exterior fire exposure with a 1-hour fire-resistance rating, rated from the exterior side, as tested in accordance with ASTM E119 or UL 263.

    9. Fire-retardant-treated wood labeled for exterior use and complying with Section 2303.2 of the California Building Code .

  • CWUIC § 504.5.1 High relevance — show source text

    Such material shall extend from the top of the foundation to the underside of the roof sheathing.

    504.5.1 Flashing. A minimum of 6 inches (152 mm) of metal flashing or noncombustible material applied vertically on the exterior of the wall shall be installed at the ground, decking and roof intersections.

    504.5.2 Exterior wall coverings. Exterior wall coverings shall comply with one or more of the following requirements:

    1. Noncombustible material.

    2. Ignition-resistant building material labeled for exterior use. 3. Fire-retardant-treated wood labeled for exterior use and complying with the requirements of Section 2303.2 of the Califor- nia Building Code. 4. Fire-retardant-treated wood shingles and shakes which have been qualified in accordance with Section 1505.6 of the Cali- fornia Building Code for use as “Class B” roof covering shall be an acceptable alternative wall covering material where installed over solid sheathing.

    Exception: Exterior wall coverings which are a component of an approved wall assembly complying with Section 504.5.

    504.5.2.1 Extent of exterior wall covering. Where provided, exterior wall coverings shall extend from the top of the foundation to the roof, and terminate at 2-inch (50.8 mm) nominal solid wood blocking between rafters at all roof overhangs, or in the case of enclosed eaves, terminate at the enclosure.

    504.6 Underfloor enclosure. Buildings or structures shall have underfloor areas enclosed to the ground with exterior walls in accordance with Section 504.5.

    Exception: Complete enclosure shall not be required where the underside of exposed floors and exposed structural columns, beams and supporting walls are protected as required for exterior 1-hour fire-resistance-rated construction or heavy timber construction or fire-retardant-treated wood. The fire-retardant-treated wood shall be labeled for exterior use and meet the requirements of Section 2303.2 of the California Building Code .

    504.7 Projections . Unenclosed accessory structures attached to buildings with habitable spaces and projections, other than decks, shall be heavy timber construction or constructed of one of the following:

    1. Noncombustible materials.

    2. Fire-retardant-treated wood identified for exterior use and meeting the requirements of Section 2303.2 of the California Building Code .

    3. Ignition-resistant building materials in accordance with Section 503.2. 4. Materials approved for not less than 1-hour fire-resistance-rated construction on the exterior side, as tested in accordance with ASTM E119 or UL 263.

    5. One layer of [5] / 8 -inch (15.9 mm) Type X gypsum sheathing applied behind the exterior covering on the underside of the ceiling. 6. The exterior portion of a 1-hour fire-resistance-rated exterior assembly, as tested in accordance with ASTM E119 or UL 263, applied to the underside of the ceiling assembly, including assemblies using the gypsum panel and sheathing products listed in the Gypsum Association Fire Resistance Design Manual. 7. The underside of a floor projection assembly that meets the performance criteria in Section 504.7.2 when tested in accordance with the test procedures set forth in ASTM E2957.

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  • CWUIC § 504.7.1 High relevance — show source text

    Exception: Structural columns and beams are not required to be protected in accordance with Section 504.7.1 when constructed with sawn lumber or glue-laminated wood with the smallest minimum nominal dimension of 4 inches (102 mm). Sawn or glue- laminated planks shall be splined, tongue-and-groove, or set close together and well spiked.

    504.7.2 Conditions of acceptance for ASTM E2957. The ASTM E2957 test shall be conducted on a minimum of three test specimens and meet the conditions of acceptance in Items 1 through 3. If any one of the three tests does not meet the conditions of acceptance, three additional tests shall be performed. All three additional tests must meet the conditions of acceptance. 1. Absence of flame penetration of the eaves or horizontal projection assembly at any time. 2. Absence of structural failure of the eaves or horizontal projection subassembly at any time. 3. Absence of sustained combustion of any kind at the conclusion of the 40-minute test.

    504.7.3 Decks. The walking surface material of decks, porches, balconies and stairs shall comply with the requirements of Sections 504.7.3.1 through 504.7.3.4.

    504.7.3.1 Flashing. A minimum of a 6-inch (150 mm) metal flashing, applied vertically on the exterior of the wall, shall be installed at all deck-to-wall intersections.

    504.7.3.2 Decking surfaces. The walking surface material of decks, porches, balconies and stairs shall be constructed with any of the following materials: 1. Material that complies with the performance requirements of Section 504.7.3.3 when tested in accordance with ASTM E2632 and ASTM E2726.

    2. Ignition-resistant building material that complies with the performance requirements of Section 503.2.4. 3. Material that complies with the performance requirements of both SFM Standard 12-7A-4 and Section 503.2.4. 4. Fire-retardant-treated wood labeled for exterior use and complying with Section 2303.2 of the California Building Code.

    5. Noncombustible material.

    6. Any material that complies with the performance requirements of SFM Standard 12-7A-4A and any attached exterior wall covering that is noncombustible or ignition-resistant building materials. Exception: Wall material shall be permitted to be of any material that otherwise complies with this chapter when the decking surface material complies with the performance requirements of ASTM E84 or UL 723 with a Class B flame spread index.

    7. Any material that complies with the performance requirements of Section 504.7.3.4 when tested in accordance with ASTM E2632 and any attached exterior wall covering that is noncombustible or ignition-resistant building materials. Exception: Wall material shall be permitted to be of any material that otherwise complies with this chapter when the decking surface material complies with the performance requirements of ASTM E84 or UL 723 with a Class B flame spread index.

  • 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:

    1. The fire-resistance rating of building elements, components or assemblies based on the prescriptive designs prescribed in Section 721 of the California Building Code .
    2. 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 .

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  • CWUIC § 2-4 High relevance — show source text

    HAZARDOUS MATERIALS. As defined in the California Fire Code .

    HEAVY TIMBER CONSTRUCTION. As described in the California Building Code .

    IGNITION-RESISTANT BUILDING MATERIAL. A type of building material that resists ignition or sustained flaming combustion sufficiently so as to reduce losses from wildfire exposure of burning embers and small flames.

    LOCAL RESPONSIBILITY AREA (LRA). Areas of the state in which the financial responsibility of preventing and suppressing fires is the primary responsibility of a city, county, city and county, or district. See also “State Responsibility Area (SRA).”

    LOG WALL CONSTRUCTION. A type of construction in which exterior walls are constructed of solid wood members and where the smallest horizontal dimension of each solid wood member is not less than 6 inches (152 mm).

    MULTILAYERED GLAZED PANELS. Window or door assemblies that consist of two or more independently glazed panels installed parallel to each other, having a sealed air gap in between, within a frame designed to fill completely the window or door opening in which the assembly is intended to be installed.

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    DEFINITIONS

    NONCOMBUSTIBLE ROOF COVERING. A roof covering consisting of any of the following:

    1. Cement shingles or sheets.
    2. Exposed concrete slab roof.
    3. Ferrous or copper shingles or sheets.
    4. Slate shingles.
    5. Clay or concrete roofing tile.
    6. Approved roof covering of noncombustible material. OUTBUILDING (applicable to CCR, Title 14 provisions only). Buildings or structures that are less than 120 square feet (11.15 m2) in size and not used for human habitation. An “Outbuilding” is not a “Building” or “Structure” as defined herein. [CCR Title 14 §1299.02(c)]

    [A] PEER REVIEW. An independent and objective technical review conducted by an approved third party.

    RAFTER TAIL. The portion of roof rafter framing in a sloping roof assembly that projects beyond and overhangs an exterior wall.

    [A] REGISTERED DESIGN PROFESSIONAL. An architect or engineer, registered or licensed to practice professional architecture or engineering, as defined by the statutory requirements of the professional registration laws of the state in which the project is to be constructed.

    RESIDENTIAL UNIT (applicable to CCR, Title 14 provisions only). Any building or portion thereof which contains living facilities including provisions for sleeping, eating, cooking and/or sanitation, for one or more persons. Manufactured homes, mobile homes and factory-built housing are considered residential units. [CCR Title 14 §1270.01(w)]

    RIDGELINE (topography) (applicable to CCR, Title 14 provisions only). The line of intersection of two opposing slope aspects running parallel to the long axis of the highest elevation of land; or an area of higher ground separating two adjacent streams or watersheds. [CCR Title 14 §1270.01(x)]

    ROAD (applicable to CCR, Title 14 provisions only). A public or private vehicular pathway to more than four (4) residential units, or to any industrial or commercial occupancy. [CCR Title 14 §1270.01(y)]

  • 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 § 3.2 High relevance — show source text

    3.2|||||||| |404.4|Hydrants|Y|||507.5|||||| |404.5|Adequate water
    supply|Y|||507.3|1275.02(b)||||| |404.6|Reserved|N||||||||| |404.7|Obstructions|Y|||507.5.4|||||| |404.8|Identification|Y||||1275.04(a)||||| |404.9|Testing and
    maintenance|Y|||507.5.2|||||| |404.10|Reliability|Y|||507.5.2|||||| |404.10.1|Objective|Y|404.10.1|||||||| |404.10.2|Clearance of fuel|Y|||4907.1|||||| |404.10.3|Standby power|Y|||507.5.2|||||| |Chapter 5|Special building construction regulations|Special building construction regulations|Special building construction regulations|Special building construction regulations|Special building construction regulations|Special building construction regulations|Special building construction regulations|Special building construction regulations|Special building construction regulations|Special building construction regulations| |501|General|Y||701A||||||| |501.1|Scope|Y||701A.3||||||| |501.2|Objective|Y||701A.2||||||| |501.3|Fire-resistance-rated
    construction|Y||703.2.1.5||||||| |501.4|Noncombustibility
    tests|Y||703.3||||||| |501.4.1|Noncombustible
    materials|Y||703.3.1||||||| |502|RESERVED|N||||||||| |503|Ignition-resistant
    construction and
    material|Y||704A||||||| |503.1|General|Y||701A.3||||||| |503.2|Ignition-resistant
    building material|Y||707A.3 #2||||||| |503.2.1|Noncombustible
    material|Y||704A.4 #1||||||| |503.2.2|Fire-retardant-
    treated wood|Y||704A.4 #2||||||| |503.2.3|Fire-retardant-
    treated wood roof
    coverings|Y||705A.1||||||| |503.2.4|Other ignition-
    resistant building
    material|Y||704A.3||||||| |503.2.4.1|Flame spread|Y||704A.3 #1||||||| |503.2.4.2|Flame front|Y||704A.3 #2||||||| |503.2.4.3|Weathering|Y||703A.5.1||||||| |503.2.4.3.1|Evaluation require-
    ments for weathering|Y||703A.5.2
    703A.5.2.1||||||| |503.2.4.3.2|Wood-plastic
    composite materials|Y||703A.6|||||||

    APPENDIX H-28 2025 CALIFORNIA WILDLAND-URBAN INTERFACE CODE

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    APPENDIX H—REFERENCED CALIFORNIA DOCUMENTS

  • CWUIC § 3-3 High relevance — show source text

    301 General . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .3-3

    302 Wildland-Urban Interface Area Designations . . . . . .3-3

    CHAPTER 4 WILDLAND-URBAN INTERFACE AREA

    REQUIREMENTS . . . . . . . . . . . . . . . . . . . . . . 4-3

    401 General . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .4-3

    402 Applicability . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .4-3

    403 Access . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .4-3

    404 Water Supply . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .4-7

    CHAPTER 5 SPECIAL BUILDING CONSTRUCTION

    REGULATIONS . . . . . . . . . . . . . . . . . . . . . . . . 5-3

    501 General . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .5-3

    502 Reserved . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .5-3

    503 Ignition-Resistant Construction and Material. . . . . .5-3

    504 Ignition-Resistant Construction. . . . . . . . . . . . . . . . . .5-4

    505 Reserved . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .5-9

    506 Reserved . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .5-9

    507 Replacement or Repair of Roof Coverings. . . . . . . . .5-9

    CHAPTER 6 FIRE PROTECTION REQUIREMENTS. . . . . . .6-3

    601 General. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6-3

    602 Fire Protection Plans . . . . . . . . . . . . . . . . . . . . . . . . . . . 6-3

    603 Vegetation Plan . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6-4

    604 Maintenance of Defensible Space . . . . . . . . . . . . . . . 6-5

Frequently asked questions

What test report language should I look for to prove compliance?

Look for an identification or lab report stating compliance with ASTM E84/UL 723 (extended 30‑minute) or ASTM E2768, with tests on both faces and, for panels, performed with a 1/8 in (3.2 mm) ripped/cut longitudinal gap unless the metal‑faced exception applies (see § 503.2.4).

Does “noncombustible” mean the same as “ignition‑resistant”?

Noncombustible materials are an accepted path to being ignition‑resistant under § 503.2.1, but the material must pass the noncombustibility tests in § 501.4 (ASTM E136 or equivalent) — so noncombustible is a qualifying category within the ignition‑resistant definitions.

Can I use fire‑retardant‑treated wood?

Yes — if it is labeled for exterior use and complies with CBC Section 2303.2, it satisfies the fire‑retardant‑treated wood path in § 503.2.2.

Do product marketing claims alone prove compliance?

No. § 503.2.4 requires identification showing the specific fire test results; accept only labeled products or test reports that cite the required ASTM/UL standards.

If my panel has a metal skin, when is the ripped‑gap test not required?

If the panel has a combustible core but an exterior metal covering of at least 0.019 in (0.48 mm) aluminum or 0.0149 in (0.38 mm) corrosion‑resistant steel, the ripped‑gap test is not required (exception in § 503.2.4).

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