CWUIC · California Wildland-Urban Interface Code

How must enclosed and open eaves/soffits be protected?

If your home is in a WUI area, the CWUIC requires the exposed underside of eaves/soffits be built from specified materials (noncombustible, ignition‑resistant, FRT wood of specified thickness, 2‑inch nominal lumber, 1‑hour FRR assemblies) or be a tested boxed assembly (ASTM E2957 or SFM 12‑7A‑3); check **§ 504.3** for enclosed eaves and **§ 504.3.1** for open eaves and provide labels or test reports at plan review.

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Last reviewed: July 6, 2026

What the code requires — 2-4 sentences

The exposed underside of enclosed eaves and soffits must be protected using specified materials or tested assemblies — you must use one of the options listed in § 504.3. For open (unenclosed) eaves the exposed roof deck underside must meet the listed material or assembly options in § 504.3.1. These are prescriptive alternatives (noncombustible, ignition‑resistant, fire‑resistive assemblies, specified lumber sizes, or tested boxed‑in assemblies) intended to reduce ember and flame ignition in Wildland‑Urban Interface areas.

The most important rule: protect the underside of any eave/soffit with one of the exact materials or tested assemblies listed in § 504.3 (for enclosed eaves) or § 504.3.1 (for open eaves) — otherwise the eave is noncompliant.

Requirements in detail

Which items the code accepts (plain list)

For enclosed eaves / soffits the exposed underside must be protected by one or more of the following (as enumerated in § 504.3 — summarized):

  • Noncombustible materials.
  • Ignition‑resistant building materials.
  • Materials that are approved for not less than 1‑hour fire‑resistance‑rated construction on the exterior side (ASTM E119 / UL 263).
  • 2‑inch (51 mm) nominal dimension lumber.
  • 1‑inch (25 mm) nominal fire‑retardant‑treated (FRT) lumber or 3/4‑inch (19.1 mm) nominal FRT plywood, labeled for exterior use and complying with CBC § 2303.2.
  • Boxed‑in soffit assemblies that meet the performance criteria of Section 504.7.2 when tested per ASTM E2957.
  • Boxed‑in soffit assemblies that meet SFM Standard 12‑7A‑3 acceptance criteria.

For open (unenclosed) eaves the exposed roof deck underside must be one or more of the following (per § 504.3.1):

  • Noncombustible material.
  • Ignition‑resistant building material.
  • Fire‑retardant‑treated wood labeled for exterior use and complying with CBC § 2303.2.
  • Materials approved for not less than 1‑hour fire‑resistance on the exterior side (ASTM E119 / UL 263).
  • 2‑inch (51 mm) nominal lumber.
  • One layer of 5/8‑inch (16 mm) Type X gypsum sheathing applied behind an exterior covering on the underside of the roof deck.
  • The exterior portion of a 1‑hour fire‑resistance‑rated exterior assembly (ASTM E119 / UL 263) designed for exterior exposure, including gypsum assemblies listed in the Gypsum Association Fire Resistance Design Manual.

Decision table — quick checklist of options

Decision consideration Acceptable option(s) Code Reference
Enclosed soffit underside — non‑combustibility Noncombustible material § 504.3,
Enclosed soffit — ignition resistance Ignition‑resistant building material § 504.3,
Enclosed soffit — fire‑resistive assembly Exterior side ≥ 1‑hour (ASTM E119 / UL 263) § 504.3,
Enclosed soffit — lumber option 2‑inch (51 mm) nominal lumber § 504.3,
Enclosed soffit — FRT wood option 1‑inch (25 mm) FRT lumber or 3/4‑inch (19.1 mm) FRT plywood, exterior‑labeled, CBC § 2303.2 § 504.3,
Enclosed soffit — tested boxed assembly Meets ASTM E2957 or SFM 12‑7A‑3 acceptance § 504.3 (items 6–7) and referenced standards,
Open eave underside — gypsum option 5/8‑inch (16 mm) Type X gypsum behind exterior covering § 504.3.1,
Open eave underside — 1‑hour exterior assembly Exterior portion of 1‑hour rated assembly (ASTM E119 / UL 263) § 504.3.1,

Notes on defined terms and labeling

  • Fire‑retardant‑treated (FRT) wood must be labeled for exterior use and comply with CBC § 2303.2 — the code treats interior‑only FRT products as unacceptable for these exterior eave applications.
  • Boxed assemblies accepted by test must meet the ASTM E2957 procedures or SFM Standard 12‑7A‑3 acceptance criteria referenced in Chapter 7.

Exceptions & special cases

  • The code provides options; you can satisfy compliance with any one (or combination) of the listed acceptable materials/assemblies in § 504.3 (enclosed) or § 504.3.1 (open). Do not mix and match unless the combination is explicitly allowed or a listed assembly.
  • Boxed‑in soffit assemblies are an accepted path only when the underside meets the ASTM E2957 performance criteria or the SFM 12‑7A‑3 acceptance criteria; a manufacturer’s generic “treated plywood” statement is not equivalent to a tested boxed assembly.
  • The facias (if provided) also have specific material requirements: they must be FRT wood labeled for exterior use, ignition‑resistant materials, materials approved for not less than 1‑hour FRR, or 2‑inch (51 mm) nominal lumber (see related text near § 504.3).

If a requirement you expected is not discussed in the retrieved CWUIC text (for example, prescriptive fastener schedules for soffit panels under wildfire conditions), that specific prescriptive guidance is not present in the cited sections and cannot be inferred from them.

Common mistakes

  • Assuming any “pressure‑treated” or generic “fire retardant” plywood meets the exterior FRT requirement — the code requires FRT labeled for exterior use and compliance with CBC § 2303.2. Check the label and manufacturer data.
  • Installing 1/2‑inch ordinary plywood or interior‑grade gypsum on enclosed soffits thinking it’s acceptable — the code lists 3/4‑inch FRT plywood (enclosed) or 5/8‑inch Type X gypsum (open eaves) as the specified thicknesses/options; do not substitute thinner or unapproved materials.
  • Treating a boxed‑in soffit as compliant solely because it uses noncombustible facing materials — boxed assemblies must meet the specified test methods (ASTM E2957 or SFM 12‑7A‑3) to be accepted.
  • Overlooking that the code requires protection on the exposed underside (not merely the top surface) — compliance is about the underside material/assembly per § 504.3/504.3.1.

Worked example — concrete scenario

Scenario: A single‑family home in a WUI area has an overhang with a boxed‑in enclosed soffit. The soffit will be built from plywood; you must choose materials to comply.

Step 1 — Option check:

  • If you install 3/4‑inch (19.1 mm) FRT plywood, labeled for exterior use and complying with CBC § 2303.2, the soffit underside meets one of the listed alternatives in § 504.3 (item 5). Compliant.

Step 2 — Noncompliant example:

  • If you install 1/2‑inch exterior‑grade plywood (not FRT), that is NOT among the accepted enclosed eave options in § 504.3, so it is noncompliant. You would need to change to a listed option (e.g., 3/4‑inch FRT plywood, 1‑inch FRT lumber, 2‑inch nominal lumber, noncombustible, or a tested boxed assembly per ASTM E2957).

Step 3 — Alternative tested assembly:

  • If you prefer a factory boxed‑in soffit assembly, obtain the manufacturer’s test report showing compliance with ASTM E2957 or SFM Standard 12‑7A‑3 and provide that documentation at plan review/inspection — that satisfies § 504.3 items 6–7.

Related provisions

  • § 504.2 — Roof assembly requirements (Class A roof covering, roof underlayment, bird stops) — relevant because roof covering voids and bird stops affect eave vulnerability.
  • § 504.2.1.1 — Airspace under roof covering (cap sheet, bird stops) — associated details for roof edge protection.
  • § 504.7 — Projections and performance criteria for tested assemblies (504.7.2 referenced by boxed‑in soffit acceptance).
  • SFM Standard 12‑7A‑3 — acceptance standard for soffit assemblies referenced by § 504.3.
  • ASTM E2957 — test method for resistance to wildfire penetration of eaves/soffits (referenced by § 504.3).

Code references

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

  • CWUIC § 504.2.1.1 High relevance — show source text

    504.2.1.1 Airspace under roof covering. Where the roof covering is installed over a combustible deck and the roofing profile creates an airspace under the roof covering, the installation shall comply with the following: 1. A 72 lb. (32.7 kg) cap sheet complying with ASTM D3909 Standard Specification for “Asphalt Rolled Roofing (Glass Felt) Surfaced with Mineral Granules,” shall be installed over the roof deck.

    Exception: Cap sheet is not required where not less than 1 inch of mineral wool board or other noncombustible material is located between the roofing material and wood framing or deck. 2. Bird stops shall be used at the eaves where the profile fits, to prevent the entry of debris at the eave. 3. Hip and ridge caps shall be mudded in to prevent intrusion of fire or embers.

    504.2.1.2 Roof underlayment. A listed and labeled roof underlayment that has been tested as part of the roof assembly in accor- dance with ASTM E108 or UL 790 for Class A fire classification shall be installed in accordance with the underlayment manufacturer’s installation instructions and listing. Bird stops shall be used at the eaves when the profile fits, to prevent the entry of debris at the eave. Hip and ridge caps shall be mudded in to prevent intrusion of fire or embers.

    Exception: Where the roof sheathing is fire-retardant-treated wood labeled for exterior use and complies with Section 2303.2 of the California Building Code, the underlayment shall not be required to comply with a Class A fire classification.

    504.2.2 Roof valleys. Where provided, valley flashings shall be not less than 0.019 inch (0.48 mm) (No. 26 galvanized sheet gage) corrosion-resistant metal installed over a minimum 36-inch-wide (914 mm) underlayment consisting of one layer of 72-pound (32.4 kg) mineral-surfaced, nonperforated cap sheet complying with ASTM D3909 running the full length of the valley.

    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.

  • 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

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

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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 § 5.2.2 High relevance — show source text

    5.2.2_||||||| |504|Ignition-resistant
    construction|Y||704A||||||| |504.1|General|Y||705A.1||||||| |504.2|Roof assembly|Y||705A.2
    1505.2||||||| |504.2.1|Roof covering voids|Y||705A.2||||||| |504.2.1.1|Airspace under roof
    covering|Y||705A.2.1||||||| |504.2.1.2|Roof underlayment|Y||705A.2.2||||||| |504.2.2|Roof valleys|Y||705A.3||||||| |504.3|Protection of
    enclosed eaves|Y||707A.6||||||| |504.3.1|Protection of open
    eaves|Y||707A.5||||||| |504.4|Gutters and
    downspouts|Y||705A.4||||||| |504.5|Exterior walls|Y||707A.4||||||| |504.5.1|Flashing|Y|504.5.1|||||||| |504.5.2|Exterior wall covering|Y||707A.3
    704A.4 #3||||||| |504.5.2.1|Extent of exterior wall
    covering|Y||707A.3.1||||||| |504.6|Underfloor enclosure|Y||707A.9||||||| |504.7|Projections|Y||707A.8||||||| |504.7.1|Underside of
    projections|Y||707A.9,
    707A.10||||||| |504.7.2|Conditions of accep-
    tance for ASTM E2957|Y||707A.11||||||| |504.7.3|Decks|Y||709A.1||||||| |504.7.3.1|Flashing|Y||709A.1.1||||||| |504.7.3.2|Decking surfaces|Y||709A.3||||||| |504.7.3.3|Performance require-
    ments for Section
    504.7.3.2, Item 1|Y||709A.4.2||||||| |504.7.3.3.1|Conditions of accep-
    tance for ASTM E2632|Y||709A.4.1||||||| |504.7.3.3.2|Conditions of accep-
    tance for ASTM E2726|Y||709A.4.2||||||| |504.7.3.4|Performance require-
    ments for Section
    504.7.3.2, Item 7|Y||709A.5||||||| |504.8|Exterior glazing|Y||708A.2.1||||||| |504.8.1|Structural glass
    veneer|Y||708A.2.2||||||| |504.8.2|Operable skylights|Y||708A.2.3||||||| |504.9|Exterior doors|Y||708A.3|||||||

  • CWUIC § 1.5 High relevance — show source text
    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
    503.3.4 Fire-retardant-
    treated wood shin-
    gles and shakes    		 Y 703A.5.2.2
    504 Ignition-resistant
    construction    		 Y 704A
    504.1 General Y 705A.1
    504.2 Roof assembly Y 705A.2
    1505.2
    504.2.1 Roof covering voids Y 705A.2
    504.2.1.1 Airspace under roof
    covering    		 Y 705A.2.1
    504.2.1.2 Roof underlayment Y 705A.2.2
    504.2.2 Roof valleys Y 705A.3
    504.3 Protection of
    enclosed eaves    		 Y 707A.6
    504.3.1 Protection of open
    eaves    		 Y 707A.5
    504.4 Gutters and
    downspouts    		 Y 705A.4
    504.5 Exterior walls Y 707A.4
    504.5.1 Flashing Y 504.5.1
    504.5.2 Exterior wall covering Y 707A.3
    704A.4 #3
    504.5.2.1 Extent of exterior wall
    covering    		 Y 707A.3.1
    504.6 Underfloor enclosure Y 707A.9
    504.
  • CWUIC § 0.42 High relevance — show source text

    Fastener spacing applies where wood exterior soffit framing member-specific gravity is 0.42 or larger. Where the specific gravity of exterior soffit framing members is greater
    than or equal to 0.35 but less than 0.42 in accordance with AWC NDS, the fastener spacing shall be multiplied by 0.67 or the same fastener spacing as prescribed for galvanized
    steel nails shall be permitted to be used where RSRS-01 (2-inch by 0.099-inch by 0.266-inch head) nails replace 6d box nails and RSRS-03 (21/2-inch × 0.131-inch × 0.281-inch
    head) nails replace 8d common nails or 10d box nails. RSRS is a Roof Sheathing Ring Shank nail meeting the specifications in ASTM F1667. Framing members shall be mini-
    mum 2 × 3 nominal with the larger dimension in the cross section aligning with the length of fasteners to provide sufficient embedment depths.
    f. Spacing at intermediate supports shall be not greater than 12 inches on center.|For SI: 1 inch = 25.4 mm, 1 pound per square foot = 0.0479 kPa.
    a. Fasteners shall comply with Sections R703.3.2 and R703.3.3.
    b. Maximum spacing of exterior soffit framing members shall not exceed 24 inches.
    c. Wood structural panels shall be of an exterior exposure grade.
    d. Wood structural panels shall be installed with strength axis perpendicular to supports with not fewer than two continuous spans.
    e. Fastener spacing applies where wood exterior soffit framing member-specific gravity is 0.42 or larger. Where the specific gravity of exterior soffit framing members is greater
    than or equal to 0.35 but less than 0.42 in accordance with AWC NDS, the fastener spacing shall be multiplied by 0.67 or the same fastener spacing as prescribed for galvanized
    steel nails shall be permitted to be used where RSRS-01 (2-inch by 0.099-inch by 0.266-inch head) nails replace 6d box nails and RSRS-03 (21/2-inch × 0.131-inch × 0.281-inch
    head) nails replace 8d common nails or 10d box nails. RSRS is a Roof Sheathing Ring Shank nail meeting the specifications in ASTM F1667. Framing members shall be mini-
    mum 2 × 3 nominal with the larger dimension in the cross section aligning with the length of fasteners to provide sufficient embedment depths.
    f. Spacing at intermediate supports shall be not greater than 12 inches on center.|For SI: 1 inch = 25.4 mm, 1 pound per square foot = 0.0479 kPa.
    a. Fasteners shall comply with Sections R703.3.2 and R703.3.3.
    b. Maximum spacing of exterior soffit framing members shall not exceed 24 inches.
    c. Wood structural panels shall be of an exterior exposure grade.
    d. Wood structural panels shall be installed with strength axis perpendicular to supports with not fewer than two continuous spans.
    e. Fastener spacing applies where wood exterior soffit framing member-specific gravity is 0.42 or larger.

  • CWUIC § 2.1 High relevance — show source text

    2.1 OR R704.3.1|R
    OR
    VINYL AND ALUMINUM
    EXTERIOR SOFFIT
    J-CHANNEL
    UNSUPPORTED SPAN
    LIMITED PER SECTION R704.2.1 OR R704.3.1|R
    OR
    VINYL AND ALUMINUM
    EXTERIOR SOFFIT
    J-CHANNEL
    UNSUPPORTED SPAN
    LIMITED PER SECTION R704.2.1 OR R704.3.1|

    FIGURE R704.2.1(2)—TYPICAL DOUBLE-SPAN VINYL AND ALUMINUM EXTERIOR SOFFIT PANEL SUPPORT

    R704.2.2 Fiber-cement exterior soffit panels. Fiber-cement exterior soffit panels shall be a minimum of [1] / 4 inch (6.4 mm) in thickness and shall comply with the requirements of ASTM C1186, Type A, minimum Grade II, or ISO 8336, Category A, minimum Class 2. Panel joints shall occur over framing or over wood structural panel sheathing. Exterior soffit panels shall be installed with spans and fasteners in accordance with the manufacturer’s installation instructions. R704.2.3 Hardboard exterior soffit panels. Hardboard exterior soffit panels shall be not less than [7] / 16 inch (11.11 mm) in thickness and shall be fastened to framing or nailing strips with 2 [1] / 2 -inch by 0.113-inch (64 mm by 2.9 mm) siding nails spaced not more than 6 inches (152 mm) on center at panel edges and 12 inches (305 mm) on center at intermediate supports.

    R704.2.4 Wood structural panel exterior soffit. The minimum nominal thickness for wood structural panel exterior soffits shall be [3] / 8 inch (9.5 mm) and shall be fastened to framing or nailing strips with 2-inch by 0.099-inch (51 mm by 2.5 mm) nails. Fasteners shall be spaced not less than 6 inches (152 mm) on center at panel edges and 12 inches (305 mm) on center at intermediate supports.

    2025 CALIFORNIA RESIDENTIAL CODE 7-33

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    WALL COVERING

    R704.3 Exterior soffit installation where the design wind pressure exceeds 30 psf. Where the design wind pressure is greater than 30 psf, exterior soffit installation shall comply with Section R704.3.1, R704.3.2, R704.3.3 or R704.3.4. Exterior soffit materials not addressed in Sections R704.3.1 through R704.3.4 shall be in accordance with the manufacturer’s installation instructions.

    R704.3.1 Vinyl exterior soffit panels. Vinyl exterior soffit panels and their attachments shall be capable of resisting wind loads specified in Table R301.2.1(1) for walls using an effective wind area of 10 square feet (0.929 m [2] ) and adjusted for height and exposure in accordance with Table R301.2.1(2). Vinyl exterior soffit panels shall be installed using fasteners specified by the manufacturer and shall be fastened at both ends to a supporting component such as a nailing strip, fascia or subfascia component in accordance with Figure R704.2.1(1).

  • CWUIC § 7-33 High relevance — show source text

    2025 CALIFORNIA RESIDENTIAL CODE 7-33

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

    WALL COVERING

    R704.3 Exterior soffit installation where the design wind pressure exceeds 30 psf. Where the design wind pressure is greater than 30 psf, exterior soffit installation shall comply with Section R704.3.1, R704.3.2, R704.3.3 or R704.3.4. Exterior soffit materials not addressed in Sections R704.3.1 through R704.3.4 shall be in accordance with the manufacturer’s installation instructions.

    R704.3.1 Vinyl exterior soffit panels. Vinyl exterior soffit panels and their attachments shall be capable of resisting wind loads specified in Table R301.2.1(1) for walls using an effective wind area of 10 square feet (0.929 m [2] ) and adjusted for height and exposure in accordance with Table R301.2.1(2). Vinyl exterior soffit panels shall be installed using fasteners specified by the manufacturer and shall be fastened at both ends to a supporting component such as a nailing strip, fascia or subfascia component in accordance with Figure R704.2.1(1). Where the unsupported span of exterior soffit panels is greater than 12 inches (305 mm), intermediate nailing strips shall be provided in accordance with Figure R704.2.1(2). Vinyl exterior soffit panels shall be installed in accordance with the manufacturer’s installation instructions.

    R704.3.2 Fiber-cement exterior soffit panels. F iber-cement exterior soffit panels shall comply with Section R704.2.2 and shall be capable of resisting wind loads specified in Table R301.2.1(1) for walls using an effective wind area of 10 square feet (0.929 m [2] ) and adjusted for height and exposure in accordance with Table R301.2.1(2).

    R704.3.3 Hardboard exterior soffit panels. Hardboard exterior soffit panels shall comply with the manufacturer’s installation instructions and shall be capable of resisting wind loads specified in Table R301.2.1(1) for walls using an effective wind area of 10 square feet (0.929 m [2] ) and adjusted for height and exposure in accordance with Table R301.2.1(2).

    R704.3.4 Wood structural panel exterior soffit. Wood structural panel exterior soffits shall be capable of resisting wind loads specified in Table R301.2.1(1) for walls using an effective wind area of 10 square feet (0.929 m [2] ) and adjusted for height and exposure in accordance with Table R301.2.1(2). Alternatively, wood structural panel exterior soffits shall be installed in accordance with Table R704.3.4.

    |TABLE R704.3.4—PRESCRIPTIVE ALTERNATIVE FOR WOOD STRUCTURAL PANEL EXTERIOR SOFFIT b, c, d,

  • CWUIC § 1409.7.2. High relevance — show source text

    Exceptions:

    Assemblies protected on the outside with one of the following:

    1. A thermal barrier complying with Section 1409.7.2.
    2. Concrete or masonry not less than 1 inch (25 mm) in thickness.
    3. Glass-fiber-reinforced concrete panels not less than [3] / 8 inch (9.5 mm) in thickness.
    4. Metal-faced panels having outer facings not less in thickness than 0.019 inch (0.48 mm) aluminum or 0.016 inch (0.41 mm) corrosion-resistant steel.
    5. Stucco not less than [7] / 8 inch (22.2 mm) in thickness, complying with Section 2510.
    6. Fiber-cement lap, panel or shingle siding complying with Section 1404.17 and Section 1404.17.1 or 1404.17.2, and having a thickness of not less than [1] / 4 inch (6.4 mm).

    14-20 2025 CALIFORNIA BUILDING CODE

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

    EXTERIOR WALLS

    1409.8 Type V construction. IMP shall be permitted for use in Type V construction.

    1409.9 Labeling. Unless otherwise specified, the edge or face of each IMP or package shall bear the label of an approved agency. The label shall contain the manufacturer’s or distributor’s identification, model number, serial number or definitive information describing the product or materials’ performance characteristics and approved agency’s identification.

    1409.9.1 Foam plastic core. IMP having a foam plastic core shall be labeled in accordance with Sections 2603.2 and 2603.5.6, as applicable.

    SECTION 1410—PLASTIC COMPOSITE DECKING

    [BS] 1410.1 Plastic composite decking. Exterior deck boards, stair treads, handrails and guards constructed of plastic composites, including plastic lumber, shall comply with Section 2612.

    SECTION 1411—BUILDING-INTEGRATED PHOTOVOLTAIC (BIPV) SYSTEMS FOR EXTERIOR WALL COVERINGS AND FENESTRATION

    1411.1 Listing required. In addition to complying with other provisions of this code, building-integrated photovoltaic (BIPV) systems used as exterior wall coverings or fenestration shall be listed and labeled in accordance with UL 1703 or both UL 61730-1 and UL 61730-2.

    SECTION 1412—SOFFITS AND FASCIAS AT ROOF OVERHANGS

    1412.1 General. Soffits and fascias at roof overhangs shall be designed and constructed in accordance with the applicable provisions of this section.

    1412.2 General wind requirements. Soffits and fascias shall be capable of resisting the component and cladding loads for walls determined in accordance with Chapter 16 using an effective wind area of 10 square feet (0.93 m [2] ).

    1412.3 Vinyl and aluminum soffit panels. Vinyl and aluminum soffit panels shall comply with Section 1412.2, shall be installed using fasteners specified by the manufacturer and shall be fastened at both ends to a supporting component such as a nailing strip, fascia or subfascia component in accordance with Figure 1412.3(1).

  • CWUIC § 6.3.1. High relevance — show source text

    6.3.1.|The fastening system shall resist the wind forces in Section 1609.6.3.1.| |130|0-60|The fastening system shall resist the wind forces in Section 1609.6.3.1.|The fastening system shall resist the wind forces in Section 1609.6.3.1.|The fastening system shall resist the wind forces in Section 1609.6.3.1.| |All|> 60|The fastening system shall resist the wind forces in Section 1609.6.3.1.|The fastening system shall resist the wind forces in Section 1609.6.3.1.|The fastening system shall resist the wind forces in Section 1609.6.3.1.| |INTERLOCKING CLAY OR CONCRETE ROOF TILE WITH PROJECTING ANCHOR LUGSd, e
    (Installations on spaced/solid sheathing with battens or spaced sheathing)    |INTERLOCKING CLAY OR CONCRETE ROOF TILE WITH PROJECTING ANCHOR LUGSd, e
    (Installations on spaced/solid sheathing with battens or spaced sheathing)    |INTERLOCKING CLAY OR CONCRETE ROOF TILE WITH PROJECTING ANCHOR LUGSd, e
    (Installations on spaced/solid sheathing with battens or spaced sheathing)    |INTERLOCKING CLAY OR CONCRETE ROOF TILE WITH PROJECTING ANCHOR LUGSd, e
    (Installations on spaced/solid sheathing with battens or spaced sheathing)    |INTERLOCKING CLAY OR CONCRETE ROOF TILE WITH PROJECTING ANCHOR LUGSd, e
    (Installations on spaced/solid sheathing with battens or spaced sheathing)    | |Maximum Allow-
    able Stress Design
    Wind Speed,****Vasd
    f
    (mph)    |Mean roof
    height (feet)|Roof slope < 5:12|Roof slope 5:12 < 12:12|Roof slope 12:12 and over| |85|0-60|Fasteners are not required.
    Tiles with installed weight less
    than 9 lbs./sq. ft. require not
    fewer than one fastener per tile.|One fastener per tile every other
    row. Perimeter tiles require one
    fastener. Tiles with installed weight
    less than 9 lbs./sq. ft. require not
    fewer than one fastener per tile.|One fastener required for
    every tile. Tiles with
    installed weight less than 9
    lbs./sq. ft. require not fewer
    than one fastener per tile.| |100|0-40|0-40|0-40|0-40| |100|> 40-60|The head of all tiles shall be nailed. The nose of all eave tiles shall be fastened with approved clips.
    Rake5 tiles shall be nailed with two nails. The nose of all ridge, hip and rake tiles shall be set in a bead
    of roofer’s mastic.|The head of all tiles shall be nailed. The nose of all eave tiles shall be fastened with approved clips.
    Rake5 tiles shall be nailed with two nails.

  • CWUIC § 101.4.7 Medium relevance — show source text

    Existing 101.4.7 Fire walls 706.1 Height (see Height, Building) 502.1, 503, 504, 505, 508, 510 Occupancy classification Chapter 3 Party walls 706.1.1 Relocatable 3113

    Replicable Appendix N Building, Existing 202 Building Department 103 Building Official Duties and powers 103, 104 Qualifications Appendix A Records 104.7

    Termination A101.4 Building-Integrated Photovoltaic (BIPV) (see Photovoltaic) Built-Up Roof 1507.10 Business Occupancy (Group B) 303.1.1, 303.1.2, 304 Alarms and detection 907.2.2 Ambulatory care facilities 304, 422 Area 503, 505, 506, 507, 508 Height 503, 504, 505, 508, 510 Higher education laboratories 428, 2702.2

    Incidental uses 509 Interior finishes Table 803.13, 804 Live load Table 1607.1 Means of egress Aisles 1018.3

    Stairway, exit access 1019 Travel distance 1006.3, 1017.2,

    1006.2.1

    Mixed occupancies 508.2, 508.3, 508.4 Accessory 303.1.2, 508.2 Ambulatory care facilities 422 Assembly 303.1.2

    Assembly spaces 1030 Exit signs 1013.1 Guards 1015.2, 1030.17 Main exit 1030.3

    Open air 1005.3.1, 1005.3.2, 1006.3, 1009.6.4, 1019.3, 1027, 1030.6.2 Panic hardware 1010.2.8, 1010.4.1 Smoke-protected 1005.3.1, 1005.3.2, 1006.3, 1009.6.4, 1019.3, 1027, 1030.6.2 Travel distance 1006.2.1, 1006.3, 1017.2, 1030.7 Mixed occupancies 508.3, 508.4 Accessory 508.2 Education 303.1.3

  • CWUIC § 25.4 Medium relevance — show source text

    Minimum Grade 33 ksi steel shall be used for 33 mil and 43 mil thicknesses. Minimum Grade 50 ksi steel shall be used for 54 and 68 mil thicknesses.
    d. Listed allowable spans are not applicable for 350S162-33, 350S162-43, 550S162-33, 550S162-43 and 800S162-43 continuous joist members.|For SI: 1 inch = 25.4 mm, 1 foot = 304.8 mm, 1 mil = 0.0254 mm, 1 pound per square foot = 0.0479 kPa.
    a. Deflection criterion:L/240 for total loads.
    b. Ceiling deal load = 5 psf.
    c. Minimum Grade 33 ksi steel shall be used for 33 mil and 43 mil thicknesses. Minimum Grade 50 ksi steel shall be used for 54 and 68 mil thicknesses.
    d. Listed allowable spans are not applicable for 350S162-33, 350S162-43, 550S162-33, 550S162-43 and 800S162-43 continuous joist members.|For SI: 1 inch = 25.4 mm, 1 foot = 304.8 mm, 1 mil = 0.0254 mm, 1 pound per square foot = 0.0479 kPa.
    a. Deflection criterion:L/240 for total loads.
    b. Ceiling deal load = 5 psf.
    c. Minimum Grade 33 ksi steel shall be used for 33 mil and 43 mil thicknesses. Minimum Grade 50 ksi steel shall be used for 54 and 68 mil thicknesses.
    d. Listed allowable spans are not applicable for 350S162-33, 350S162-43, 550S162-33, 550S162-43 and 800S162-43 continuous joist members.|For SI: 1 inch = 25.4 mm, 1 foot = 304.8 mm, 1 mil = 0.0254 mm, 1 pound per square foot = 0.0479 kPa.
    a. Deflection criterion:L/240 for total loads.
    b. Ceiling deal load = 5 psf.
    c. Minimum Grade 33 ksi steel shall be used for 33 mil and 43 mil thicknesses. Minimum Grade 50 ksi steel shall be used for 54 and 68 mil thicknesses.
    d. Listed allowable spans are not applicable for 350S162-33, 350S162-43, 550S162-33, 550S162-43 and 800S162-43 continuous joist members.|For SI: 1 inch = 25.4 mm, 1 foot = 304.8 mm, 1 mil = 0.0254 mm, 1 pound per square foot = 0.0479 kPa.
    a. Deflection criterion:L/240 for total loads.
    b. Ceiling deal load = 5 psf.
    c. Minimum Grade 33 ksi steel shall be used for 33 mil and 43 mil thicknesses. Minimum Grade 50 ksi steel shall be used for 54 and 68 mil thicknesses.
    d. Listed allowable spans are not applicable for 350S162-33, 350S162-43, 550S162-33, 550S162-43 and 800S162-43 continuous joist members.|

    |TABLE R804.3.1.1(3)—NUMBER OF

  • CWUIC § 504.7 Medium 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

Frequently asked questions

Can I use untreated plywood on an enclosed soffit if I prime and paint it?

No. For enclosed soffits the code lists specific acceptable materials (for example 3/4‑inch FRT plywood or noncombustible materials). A painted untreated plywood is not listed as an accepted option in § 504.3. Check for FRT labeling or use another accepted material.

Is a boxed‑in soffit automatically compliant if the exterior skin is noncombustible?

No. Boxed‑in assemblies must meet the performance criteria in § 504.7.2 when tested per ASTM E2957 or meet SFM 12‑7A‑3 acceptance criteria to be accepted under § 504.3.

Does 2‑inch nominal lumber really comply for eaves?

Yes — 2‑inch (51 mm) nominal dimension lumber is an explicit prescriptive option for the exposed underside of enclosed eaves in § 504.3.

Can I use 5/8‑inch Type X gypsum for enclosed soffits?

The code lists 5/8‑inch Type X gypsum specifically for open (unenclosed) eave undersides in § 504.3.1, applied behind an exterior covering. For enclosed soffits, the listed gypsum thickness is not the prescriptive item — instead use one of the enumerated § 504.3 options.

Where can I find the standard that tests eave assemblies?

Boxed‑in or tested eave/soffit assemblies are tested under ASTM E2957 or evaluated under SFM Standard 12‑7A‑3, both referenced in Chapter 5 and § 504.3.

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Eaves, Soffits, Gutters, Underfloor Protection and Vents

California Wildland-Urban Interface Code