CWUIC · California Wildland-Urban Interface Code

What are the testing, labeling and weathering requirements for 'other' ignition‑resistant materials?

Materials labeled as “other ignition‑resistant” must be tested front and back (extended ASTM E84/UL 723 for 30 minutes or ASTM E2768), meet flame and flame‑front limits, pass specified weathering/retention procedures (including the ≤10% post‑weathering peak heat release limit for WPC/plastic lumber), and carry a label showing test results and pretest weathering per CWUIC §§ 503.2.4, 503.2.4.1, 503.2.4.3.

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Last reviewed: July 6, 2026

What the code requires — 2-4 sentences

The California Wildland‑Urban Interface Code requires that other ignition‑resistant building material be fire‑tested on both front and back faces using the extended ASTM E84 / UL 723 procedure for a total test period of 30 minutes, or be tested under ASTM E2768, and that the product bear identification showing the fire test results (the controlling rule is § 503.2.4) . Panel products must be tested with a ripped or cut longitudinal gap of 1/8 inch (3.2 mm) unless they meet the exception for specified metal coverings (see Exceptions) (§ 503.2.4) . The materials must meet the flame spread and flame front limits in § 503.2.4.1 and § 503.2.4.2, and must demonstrate durability through the weathering requirements in § 503.2.4.3 .

The single most important rule: any material claiming to be an “other ignition‑resistant building material” must be tested to the specified fire test(s), labeled with the results, and meet the stated flame, flame‑front and weathering performance limits in § 503.2.4 and its subsections.

Requirements in detail

Scope and test methods (what tests are allowed)

  • Test on front and back faces using:

    • Extended ASTM E84 (also shown as UL 723) for a 30‑minute total test period, or
    • ASTM E2768.
      These requirements are specified in § 503.2.4 .

  • Panel products: test with a ripped/cut longitudinal gap of 1/8 inch (3.2 mm) unless the product qualifies for the metal‑covering exception in § 503.2.4 .

Performance limits required after testing

  • Flame spread index: not to exceed 25 (see § 503.2.4.1) .
  • Flame front: flame front shall not progress more than 10 feet 6 inches (3200 mm) beyond the burner centerline at any time during the test (see § 503.2.4.2) .

Weathering / durability requirements

  • Materials must maintain the required performance under expected temperature, moisture and ultraviolet exposure; see § 503.2.4.3 .
  • Specific weathering evaluation procedures:
    • Fire‑retardant‑treated wood, wood‑plastic composite (WPC) materials and plastic lumber: evaluate after weathering in accordance with Method A in ASTM D2898 (see § 503.2.4.3.1) .
    • Wood‑plastic composite materials: must be tested in this sequence: (1) ASTM E1354 at an incident heat flux of 50 kW/m² in horizontal orientation, (2) weather per ASTM D7032, then (3) retest with ASTM E1354 and show an increase of no more than 10% in peak rate of heat release compared to the non‑weathered specimen (see § 503.2.4.3.2) .
    • Plastic lumber materials: same sequence but weathering per ASTM D6662 and the same ≤ 10% allowable increase in peak heat release (see § 503.2.4.3.3) .

Labeling and product identification

  • Materials and assemblies tested per Chapter 5 must bear an identification label showing the fire test results. The label must be issued by a testing/inspecting agency approved by the State Fire Marshal and include: agency identification mark, manufacturer contact, model/product ID, pretest weathering specified in this chapter, and the compliance standard per Chapter 7 (see § 503.3.3) .

Quick reference table (decision‑relevant dimensions / values)

Dimension / value Requirement Code Reference
Test methods allowed Extended ASTM E84/UL 723 (30 min) or ASTM E2768 § 503.2.4
Panel gap for test 1/8 inch (3.2 mm) ripped/cut longitudinal gap (unless exception) § 503.2.4
Flame spread index ≤ 25 § 503.2.4.1
Flame front progression ≤ 10 ft 6 in (3200 mm) beyond burner centerline § 503.2.4.2
Weathering method — FRT wood / WPC / plastic lumber ASTM D2898 (Method A) § 503.2.4.3.1
Weathered retest protocol — WPC ASTM E1354 @ 50 kW/m², weather ASTM D7032, retest ≤ 10% increase in peak HRR § 503.2.4.3.2
Weathered retest protocol — plastic lumber ASTM E1354 @ 50 kW/m², weather ASTM D6662, retest ≤ 10% increase in peak HRR § 503.2.4.3.3
Label contents (selected) Agency ID, manufacturer contact, model no., pretest weathering, compliance standard § 503.3.3

Exceptions & special cases

  • Metal‑covered panels: Materials that are a combustible core with a noncombustible exterior covering of aluminum ≥ 0.019 inch (0.48 mm) or corrosion‑resistant steel ≥ 0.0149 inch (0.38 mm) are not required to be tested with the ripped/cut longitudinal gap (exception in § 503.2.4) .
  • If a product is listed/approved by the State Fire Marshal per the product evaluation rules, use of that listing follows § 503.3.1 / § 503.3.2 (qualification by testing and approved agency) — tested products must meet conditions of the test as reported (§ 503.3.1 and § 503.3.2) .
  • Surface treatments (paint, stain, coatings) are explicitly not an approved method to meet ignition‑resistant requirements (§ 503.2.5) — do not rely on coatings to qualify a product unless the coating itself is part of the tested assembly and the test conditions reflect real‑world exposure) .

Common mistakes

  • Assuming a single‑face E84 test is adequate. The code requires front and back face testing or ASTM E2768 for 30 minutes (§ 503.2.4) .
  • Forgetting the 1/8 inch longitudinal gap requirement for panel testing — many lab reports use solid specimens; the CWUIC requires the ripped/cut gap for panels unless the metal‑covering exception applies (§ 503.2.4) .
  • Overlooking weathering: some manufacturers provide only initial fire test results but do not provide pretest weathering or post‑weathering retest data required by § 503.2.4.3 and labeling rules in § 503.3.3 .
  • Misreading the 10% allowance: the code permits no more than a 10% increase in peak heat release after the specified weathering/retest sequence for WPC and plastic lumber — exceedance means the product fails the requirement (§ 503.2.4.3.2, § 503.2.4.3.3) .
  • Relying on surface coatings alone to achieve compliance — § 503.2.5 disallows paints/coatings/stains as the approved method of protection unless the entire assembly, including coating, was tested appropriately .

Worked example — applying the rule with numbers

Scenario: A manufacturer produces a wood‑plastic composite (WPC) deck plank and submits test data.

  1. Initial fire test: ASTM E1354 (horizontal) at 50 kW/m² on the unweathered WPC shows a peak heat release rate (PHRR) of 300 kW. (Initial test required by § 503.2.4.3.2) .
  2. Weathering: The manufacturer subjects samples to ASTM D7032 weathering per § 503.2.4.3.2 .
  3. Retest: After weathering, ASTM E1354 horizontal test yields a PHRR of 325 kW. Percentage increase = (325 − 300)/300 = 8.33%.
  4. Result: Because the post‑weathering increase (8.33%) is ≤ 10%, the WPC meets the weathering‑retention performance requirement in § 503.2.4.3.2 .
  5. Labeling: The product label must show the fire test results, pretest weathering method used, manufacturer contact and compliance standard per § 503.3.3 .

If the post‑weathering PHRR had been 335 kW the increase would be 11.7% and the material would fail the weathering requirement (§ 503.2.4.3.2) .

Related provisions

  • § 503.2.4 — Other ignition‑resistant building material (tests required; panel gap; general)
  • § 503.2.4.1 — Flame spread limit (≤ 25)
  • § 503.2.4.2 — Flame front progression limit (≤ 10 ft 6 in / 3200 mm)
  • § 503.2.4.3 — Weathering requirements (overall) and its subsections § 503.2.4.3.1, § 503.2.4.3.2, § 503.2.4.3.3 (D2898; E1354 at 50 kW/m²; ASTM D7032 / D6662; ≤ 10% peak HRR increase)
  • § 503.3.1 — Qualification by testing (acceptance when test results/conditions met)
  • § 503.3.2 — Approved agency requirements for product evaluation testing (CBC Section 1703 scope)
  • § 503.3.3 — Labeling requirements and required label contents (including pretest weathering)
  • § 503.2.5 — Prohibition on relying on paints/coatings/stains as the approved protective method

Code references

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

  • CWUIC § 503.2.2 High relevance — show source text

    on Jul 18, 2025 11:14 AM (CDT) THEREUNDER.

    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.

    503.2.4.1 Flame spread. The material shall exhibit a flame spread index not exceeding 25.

    503.2.4.2 Flame front. The material shall exhibit a flame front that does not progress more than 10 feet 6 inches (3200 mm) beyond the centerline of the burner at any time during the test.

    503.2.4.3 Weathering. Ignition-resistant building materials shall maintain their performance in accordance with this section under conditions of use. The materials shall meet the performance requirements for weathering (including exposure to temperature, moisture and ultraviolet radiation) contained in Sections 503.2.4.3.1 through 503.2.4.3.3, as applicable to the materials and conditions of use.

    503.2.4.3.1 Evaluation requirements for weathering. Fire-retardant-treated wood, wood-plastic composite materials and plastic lumber materials shall be evaluated after weathering in accordance with Method A “Test Method for Accelerated Weathering of Fire-Retardant-Treated Wood for Fire Testing” in ASTM D2898.

    503.2.4.3.2 Wood-plastic composite materials. Wood-plastic composite materials shall also demonstrate acceptable fire performance after weathering by the following procedure: first testing in accordance with ASTM E1354 at an incident heat flux of 50 kW/m [2] in the horizontal orientation, then weathering in accordance with ASTM D7032 and then retesting in accordance with ASTM E1354 and exhibiting an increase of no more than 10 percent in peak rate of heat release when compared to the peak heat release rate of the nonweathered material.

  • CWUIC § 503.2.4.1 High relevance — show source text

    503.2.4.1 Flame spread. The material shall exhibit a flame spread index not exceeding 25.

    503.2.4.2 Flame front. The material shall exhibit a flame front that does not progress more than 10 feet 6 inches (3200 mm) beyond the centerline of the burner at any time during the test.

    503.2.4.3 Weathering. Ignition-resistant building materials shall maintain their performance in accordance with this section under conditions of use. The materials shall meet the performance requirements for weathering (including exposure to temperature, moisture and ultraviolet radiation) contained in Sections 503.2.4.3.1 through 503.2.4.3.3, as applicable to the materials and conditions of use.

    503.2.4.3.1 Evaluation requirements for weathering. Fire-retardant-treated wood, wood-plastic composite materials and plastic lumber materials shall be evaluated after weathering in accordance with Method A “Test Method for Accelerated Weathering of Fire-Retardant-Treated Wood for Fire Testing” in ASTM D2898.

    503.2.4.3.2 Wood-plastic composite materials. Wood-plastic composite materials shall also demonstrate acceptable fire performance after weathering by the following procedure: first testing in accordance with ASTM E1354 at an incident heat flux of 50 kW/m [2] in the horizontal orientation, then weathering in accordance with ASTM D7032 and then retesting in accordance with ASTM E1354 and exhibiting an increase of no more than 10 percent in peak rate of heat release when compared to the peak heat release rate of the nonweathered material.

    503.2.4.3.3 Plastic lumber materials. Plastic lumber materials shall also demonstrate acceptable fire performance after weathering by the following procedure: first testing in accordance with ASTM E1354 at an incident heat flux of 50 kW/m [2] in the horizontal orientation, then weathering in accordance with ASTM D6662 and then retesting in accordance with ASTM E1354 and exhibiting an increase of no more than 10 percent in peak rate of heat release when compared to the peak heat release rate of the nonweathered material.

    503.2.5 Surface treatment protection. Use of paints, coatings, stains or other surface treatments are not an approved method of protection as required in this chapter.

    503.3 Standards of quality. Building material, systems, assemblies and methods of construction shall be tested in accordance with the standards specified in Chapter 5.

    503.3.1 Qualification by testing. Material and material assemblies tested in accordance with the requirements of Section 503 shall be accepted for use when the results and conditions of those tests are met. Product evaluation testing of material and material assemblies shall be approved or listed by the State Fire Marshal or identified in a current report issued by an approved agency.

    503.3.2 Approved agency. Product evaluation testing shall be performed by an approved agency in accordance with Section 1703 of the California Building Code. The scope of accreditation for the approved agency shall include building product compliance with this code.

    503.3.3 Labeling. Material and material assemblies tested in accordance with the referenced standards shall bear an identification label showing the fire test results. That identification label shall be issued by a testing and/or inspecting agency approved by the State Fire Marshal.

    1. Identification mark of the approved testing and/or inspecting agency.

    2. Contact and identification information of the manufacturer.

  • 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 § 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 § 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|||||||

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    APPENDIX H—REFERENCED CALIFORNIA DOCUMENTS

  • 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.

    2025 CALIFORNIA WILDLAND-URBAN INTERFACE CODE 5-5

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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 § 504.11.3 Medium 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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    5-10 2025 CALIFORNIA WILDLAND-URBAN INTERFACE CODE

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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 § 4902.1 Medium relevance — show source text

    01(i)||||| ||Exterior wall assembly|Y||702A||||||| ||Exterior wall covering|Y||702A||||||| ||Fire chief|Y||||||||| ||Fire code official|Y|||202|||||| ||Fire flow calculation
    area|Y||||||||| ||Fire hazard severity
    zones|Y||702A|4902.1|||2201||| ||Fire protection plan|Y||702A|4902.1|||||| ||Fire weather|Y||||||||| ||Fire-resistance-rated
    construction|Y||||||||| ||Fire-smart vegetation|Y|||4902.1|1271.01||||| ||Flame spread index|Y||||||||| ||Fuel|Y||||||||4291(a)(1)(A)| ||Fuel break_(T14)|Y||||1270.01(n)||||| ||Fuel modification|Y||||||||| ||Fuel mosaic|Y||||||||| ||Fuel-loading|Y||||||||| ||Green belt(T14)|Y||||1270.01(o)||||| ||Greenways (T14)|Y||||1270.01(p)||||| ||Hammerhead/T (T14)|Y||||1270.01(q)||||| ||Hazardous land use
    (T14)_|Y||||1270.01(r)||||| ||Hazardous materials|Y||||||||| ||Heavy timber
    construction|Y||||||||| ||Ignition-resistant
    building material|Y||||||||| ||Local responsibility
    area (LRA)|Y||702A|4902.1|||||| ||Log wall construction|Y|||||||||

    2025 CALIFORNIA WILDLAND-URBAN INTERFACE CODE APPENDIX H-25

    on Jul 18, 2025 11:14 AM (CDT) THEREUNDER.

    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 2 Definitions Definitions Definitions Definitions Definitions Definitions Definitions Definitions Definitions Definitions
    Multilayered glazed
    panels    		 Y
    Noncombustible roof
    covering    		 Y
    Outbuilding (T14) Y 1299.02(c)
    Peer review Y
    Rafter tail Y 702A
    Registered design
    professional    		 Y
    Residential unit (T14) Y 1270.01(w)
    Ridgeline
    (topography) (T14)    		 Y 1270.01(x)
    Road (T14) Y 1270.
  • CWUIC § 503.2.5 Medium relevance — show source text

    503.2.5 Surface treatment protection. Use of paints, coatings, stains or other surface treatments are not an approved method of protection as required in this chapter.

    503.3 Standards of quality. Building material, systems, assemblies and methods of construction shall be tested in accordance with the standards specified in Chapter 5.

    503.3.1 Qualification by testing. Material and material assemblies tested in accordance with the requirements of Section 503 shall be accepted for use when the results and conditions of those tests are met. Product evaluation testing of material and material assemblies shall be approved or listed by the State Fire Marshal or identified in a current report issued by an approved agency.

    503.3.2 Approved agency. Product evaluation testing shall be performed by an approved agency in accordance with Section 1703 of the California Building Code. The scope of accreditation for the approved agency shall include building product compliance with this code.

    503.3.3 Labeling. Material and material assemblies tested in accordance with the referenced standards shall bear an identification label showing the fire test results. That identification label shall be issued by a testing and/or inspecting agency approved by the State Fire Marshal.

    1. Identification mark of the approved testing and/or inspecting agency.

    2. Contact and identification information of the manufacturer.

    3. Model number or identification of the product or material. 4. Pretest weathering specified in this chapter. 5. Compliance standard as described under Chapter 7.

    503.3.4 Fire-retardant-treated wood shingles and shakes. Fire-retardant-treated wood shingles and shakes shall be approved and listed by the State Fire Marshal in accordance with Section 208(c), Title 19 California Code of Regulations.

    � SECTION 504—IGNITION-RESISTANT CONSTRUCTION

    504.1 General. Ignition-resistant construction shall be in accordance with Sections 504.2 through 504.11.6 .

    5-4 2025 CALIFORNIA WILDLAND-URBAN INTERFACE CODE

    on Jul 18, 2025 11:14 AM (CDT) THEREUNDER.

    SPECIAL BUILDING CONSTRUCTION REGULATIONS

    504.2 Roof assembly. Roofs shall have a roof assembly that complies with a Class A fire classification when tested in accordance with ASTM E108 or UL 790.

    Exceptions: The following assemblies are exempt from testing and shall be considered as equivalent to the Class A fire classification:

    1. Roof assemblies with coverings of brick, masonry or an exposed concrete roof deck.
    2. Roof assemblies with ferrous or copper shingles or sheets, metal sheets and shingles, clay or concrete roof tile or slate installed on noncombustible decks or ferrous, copper or metal sheets installed without a roof deck on noncombustible framing.
    3. Roof assemblies with minimum 16 oz/sq ft (0.0416 kg/m [2] ) copper sheets installed over combustible roof decks. 4. Roof assemblies of slate roof covering installed over ASTM D226, Type II underlayment over combustible decks.

    504.2.1 Roof covering voids. Where there is a void under the roof covering it shall comply with Section 504.2.1.1 or 504.2.1.2.

  • CWUIC § 501.2 Medium 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 .

    2025 CALIFORNIA WILDLAND-URBAN INTERFACE CODE 5-3

  • 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

  • CWUIC § 19-1 Medium relevance — show source text

    000|19-1|21-6|16-5|17-1|15-1|14-0|12-6|9-11|9-7| |24|2-#6|40,000|17-7|21-1|14-1|14-10|12-8|11-9|10-8|8-7|8-4| |24|2-#6|60,000|DR|DR|DR|DR|DR|DR|DR|DR|DR| |24|Center distance_A_k, l|Center distance_A_k, l|3-3|4-1|2-5|2-7|2-1|1-11|1-7|1-2|1-1| |For SI: 1 inch = 25.4 mm, 1 foot = 304.8 mm, 1 pound per square inch = 6.895 kPa, 1 pound per square foot = 0.0479 kPa, Grade 40 = 280 MPa, Grade 60 = 420 MPa.
    a. See Table R608.3 for tolerances permitted from nominal thickness.
    b. Table values are based on concrete with a minimum specified compressive strength of 2,500 psi. See Note j.
    c. Table values are based on uniform loading. See Section R608.8.2 for lintels supporting concentrated loads.
    d. Deflection criterion is_L_/240, where_L_ is the clear span of the lintel in inches, or1/2-inch, whichever is less.
    e. Linear interpolation is permitted between ground snow loads and between lintel depths.
    f. DR indicates design required.
    g. Lintel depth,D, is permitted to include the available height of wall located directly above the lintel, provided that the increased lintel depth spans the entire length of the
    lintel.
    h. Stirrups shall be fabricated from reinforcing bars with the same yield strength as that used for the main longitudinal reinforcement.
    i. Allowable clear span without stirrups applicable to all lintels of the same depth,D. Top and bottom reinforcement for lintels without stirrups shall be not less than the least
    amount of reinforcement required for a lintel of the same depth and loading condition with stirrups. All other spans require stirrups spaced at not more than_d_/2.
    j. Where concrete with a minimum specified compressive strength of 3,000 psi is used, clear spans for lintels without stirrups shall be permitted to be multiplied by 1.05. If the
    increased span exceeds the allowable clear span for a lintel of the same depth and loading condition with stirrups, the top and bottom reinforcement shall be equal to or
    greater than that required for a lintel of the same depth and loading condition that has an allowable clear span that is equal to or greater than that of the lintel without stir-
    rups that has been increased.
    k. Center distance,A, is the center portion of the clear span where stirrups are not required. This is applicable to all longitudinal bar sizes and steel yield strengths.
    l. Where concrete with a minimum specified compressive strength of 3,000 psi is used, center distance,A, shall be permitted to be multiplied by 1.10.
    m.The maximum clear opening width between two solid wall segments shall be 18 feet. See Section R608.7.2.1.

Frequently asked questions

What test report elements are required on the product label?

The label must be issued by an approved testing/inspecting agency and include the agency identification mark, manufacturer contact, product/model ID, the pretest weathering used, and the compliance standard (see § 503.3.3) .

Are single‑face E84 tests acceptable?

No. Both front and back faces must be tested using the extended ASTM E84/UL 723 for a 30‑minute period (or ASTM E2768) per § 503.2.4 .

If my panel has a metal skin, do I still need the ripped gap in testing?

If the product has a combustible core with an exterior covering of aluminum ≥ 0.019 inch or corrosion‑resistant steel ≥ 0.0149 inch, you are not required to test with the ripped/cut 1/8 inch gap (exception in § 503.2.4) .

How is the 10% limit for post‑weathering measured?

For WPC and plastic lumber, test initial PHRR with ASTM E1354 at 50 kW/m², weather per the referenced ASTM (D7032 for WPC, D6662 for plastic lumber), retest with ASTM E1354 and confirm the peak heat release increase is no more than 10% over the non‑weathered specimen (see § 503.2.4.3.2 and § 503.2.4.3.3) .

Can surface coatings be used to meet ignition‑resistant requirements?

No. Use of paints, coatings, stains or other surface treatments is not an approved method of protection to meet these Chapter 5 requirements (see § 503.2.5) .

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California Wildland-Urban Interface Code