CWUIC · California Wildland-Urban Interface Code

What are the requirements for gutters, downspouts and roof valleys?

In CWUIC areas the code mandates **noncombustible** gutters and downspouts and requires gutters to have an approved leaf/debris control (see **§ 504.4**). Roof valleys are addressed by **§ 504.2.2** (CWUIC cross‑references the applicable valley‑lining rules); the detailed valley dimensions and materials are specified in the California Building/Residential Code (e.g., metal valley lining **≥ 24 in**, roll roofing ply sizes, closed valley **≥ 36 in**) — consult CBC §1507.2.8.2 / CRC §R905.2.8.2 and your local authority for enforcement and installation details.

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Last reviewed: July 6, 2026

What the code requires — 2-4 sentences

The California Wildland‑Urban Interface Code (CWUIC) explicitly requires that gutters and downspouts be made of noncombustible material and that gutters be provided with an approved means to prevent the accumulation of leaves and debris (§ 504.4) . Roof valleys are addressed by CWUIC § 504.2.2, which points to the valley‑lining/roof assembly requirements the code references (see mapping to 705A.3 in the CWUIC index) — the CWUIC text in the provided files points to that cross‑reference but does not reproduce the full valley lining text verbatim in § 504.2.2 itself . Where the CWUIC defers to the California Building/Residential Code for valley lining details, the commonly used provisions are § 1507.2.8.2 (CBC) / § R905.2.8.2 (CRC) — these specify valley lining materials and minimum widths (see citations below) .

The single most important rule: gutters and downspouts in WUI areas must be noncombustible, and gutters must be protected from leaf/debris accumulation — see § 504.4.

Requirements in detail

Gutters and downspouts (CWUIC)

  • Material: Gutters and downspouts shall be constructed of noncombustible material — § 504.4. Noncombustible is a defined acceptance class in Chapter 5 (test criteria in § 501.4.1) .
  • Debris control: Gutters shall be provided with an approved means to prevent the accumulation of leaves and debris in the gutter (for example: gutter covers, screens, leaf guards) — § 504.4 .
  • CWUIC guidance (informational): Appendix G recommends noncombustible gutters and gutter covers as a home‑hardening measure (informational, not a substitute for § 504.4) .

Roof valleys (CWUIC + referenced codes)

  • CWUIC identifies roof valleys as a regulated element under § 504.2.2 and points to the referenced valley rules (705A.3) — the CWUIC index shows this cross‑reference but the detailed text for valley lining is found in the adopted building/residential code provisions that the CWUIC incorporates by reference .
  • Practical, decision‑relevant valley lining dimensions/materials are specified in the California Building Code and California Residential Code. Typical permissive options in those provisions include:
    • Open valleys (metal lined): metal valley lining not less than 24 inches (610 mm) wide (CBC § 1507.2.8.2, Residential § R905.2.8.2) .
    • Open valleys (roll roofing): two‑ply mineral‑surfaced roll roofing — bottom ply 18 inches (457 mm), top ply 36 inches (914 mm) (CBC/CRC) .
    • Closed valleys (shingle covered): single ply smooth roll roofing or self‑adhering polymer‑modified bitumen underlayment not less than 36 inches (914 mm) wide (CBC/CRC) .
  • Note: valley linings must be installed in accordance with the manufacturer’s instructions and the applicable roofing code section cited above (CBC/CRC) — CWUIC defers to those installation standards via the cross‑reference .

Quick reference table (decision‑relevant values)

Item Requirement / value Code reference
Gutter & downspout material Noncombustible § 504.4
Gutter debris protection Approved means to prevent accumulation of leaves/debris (e.g., covers/screens) § 504.4; Appendix G recommendation
Open valley — metal lining width ≥ 24 in (610 mm) CBC § 1507.2.8.2 / CRC § R905.2.8.2
Open valley — roll roofing plies Bottom 18 in (457 mm); Top 36 in (914 mm) CBC § 1507.2.8.2 / CRC § R905.2.8.2
Closed valley — lining width ≥ 36 in (914 mm) or self‑adhering ASTM D1970 underlayment 36 in CBC § 1507.2.8.2 / CRC § R905.2.8.2

Exceptions & special cases

  • The CWUIC text reproduced in the provided files does not include an alternate numeric valley‑lining specification inside § 504.2.2 itself; instead it cross‑references the applicable referenced provision (705A.3). The detailed valley lining prescriptions are found in the California Building Code / Residential Code sections cited above; where local adoption differs, the local authority having jurisdiction enforces the adopted text (CWUIC index and cross‑references) .
  • Appendix G of the CWUIC lists gutter covers and noncombustible gutters as a recommended home‑hardening measure (informational) — recommendations in Appendix G are not mandatory requirements but support the mandatory language in § 504.4 .
  • Manufacturer’s instructions: valley linings must be installed per the manufacturer’s instructions and the roofing code section; CWUIC relies on those instructions via its cross‑references .

Common mistakes

  • Installing combustible gutters (PVC, vinyl) or using combustible downspout material — CWUIC requires noncombustible gutters and downspouts (§ 504.4) .
  • Not providing a means to prevent leaf/debris accumulation (leaving gutters open and clogged) — that defeats the purpose of § 504.4 and is cited as a primary risk factor in WUI areas .
  • Assuming CWUIC valley requirements are “the same as any roof”: CWUIC points to valley requirements by cross‑reference; you must check the referenced CBC/CRC valley lining rules (widths and material) rather than rely on informal practice (§ 504.2.2 mapping) .
  • Using undersized valley lining (e.g., metal lining narrower than 24 in) or improper layering for roll roofing — follow CBC/CRC valley widths and ply instructions exactly .
  • Installing gutter screens that trap debris (they can block flow) — the code requires an approved means to prevent accumulation; selection/installation must allow drainage while excluding debris (§ 504.4) .

Worked example — applying the rule with numbers

Scenario: a typical house in a WUI area has an open metal valley where two roof planes meet and a conventional aluminum gutter system.

  1. Gutters/downspouts: Select gutters and downspouts manufactured from noncombustible material (e.g., aluminum). Install leaf guards or other approved covers so leaves/debris cannot accumulate in the gutter (this satisfies § 504.4) .
  2. Valley lining: Because the valley is an open valley, specify a metal valley lining with a minimum width of 24 in (610 mm). Confirm the lining material meets the corrosion‑resistant metal criteria called out in CBC/CRC valley provisions and install per manufacturer instructions (see CBC § 1507.2.8.2 / CRC § R905.2.8.2) .
  3. Inspection: On completion, verify gutters are noncombustible and have functioning leaf guards; verify the valley lining width and installation match the specified 24 in minimum and that flashing/attachment follows the roofing code instructions (CBC/CRC) .

Related provisions

  • § 504.2.2 — Roof valleys (CWUIC cross‑reference to valley requirements / 705A.3)
  • § 504.4 — Gutters and downspouts (material and debris control)
  • CBC § 1507.2.8.2 — Valley linings (materials and minimum widths) — referenced by roofing standards
  • CRC § R905.2.8.2 — Valley linings in the Residential Code (same dimensional rules)
  • CWUIC Appendix G (G101.2.1) — Home‑hardening recommendations (noncombustible gutters, gutter covers) — informational only

Code references

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

  • 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 § 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.

    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.

    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 § 1507.2.8.1 High relevance — show source text

    1507.2.8.1 Base and cap flashing. Base and cap flashing shall be installed in accordance with the manufacturer’s instructions. Base flashing shall be of either corrosion-resistant metal of minimum nominal 0.019-inch (0.483 mm) thickness or mineralsurfaced roll roofing weighing not less than 77 pounds per 100 square feet (3.76 kg/m [2] ). Cap flashing shall be corrosion-resistant metal of minimum nominal 0.019-inch (0.483 mm) thickness.

    1507.2.8.2 Valleys. Valley linings shall be installed in accordance with the manufacturer’s instructions before applying shingles. Valley linings of the following types shall be permitted:

    1. For open valleys (valley lining exposed) lined with metal, the valley lining shall be not less than 24 inches (610 mm) wide and of any of the corrosion-resistant metals in Table 1507.2.8.2.
    2. For open valleys, valley lining of two plies of mineral-surfaced roll roofing complying with ASTM D3909 or ASTM D6380 shall be permitted. The bottom layer shall be 18 inches (457 mm) and the top layer not less than 36 inches (914 mm) wide.
    3. For closed valleys (valleys covered with shingles), valley lining of one ply of smooth roll roofing complying with ASTM D6380 and not less than 36 inches (914 mm) wide or types as described in Item 1 or 2 above shall be permitted. Selfadhering polymer modified bitumen underlayment bearing a label indicating compliance with ASTM D1970 and not less than 36 inches (914 mm) wide shall be permitted in lieu of the lining material.
    TABLE 1507.2.8.2—VALLEY LINING MATERIAL Col2 Col3 Col4
    MATERIAL MINIMUM THICKNESS GAGE WEIGHT
    Aluminum 0.024 in. — —
    Cold-rolled copper 0.0216 in. — ASTM B370, 16 oz. per square ft.
    Copper — — 16 oz.
    Galvanized steel 0.0179 in. 26 (zinc-coated G90) —
    High-yield copper 0.0162 in. — ASTM B370, 12 oz. per square ft.
    Lead — — 2.5 pounds
    Lead-coated copper 0.0216 in. — ASTM B101, 16 oz. per square ft.
    Lead-coated high-yield copper 0.0162 in. — ASTM B101, 12 oz.
  • CWUIC § 2.1 High relevance — show source text

    This appendix is for informational purposes and is not intended for adoption.

    User notes:

    About this appendix: Appendix G is an information appendix that provides discussion of some elements of the proposed self-defense mechanisms and their role in enhancing the protection of exposed structures in the wildland-urban interface. The items provided in this appendix provide owners with suggestions for increasing the survivability of their structure. These items are not mandatory but can be considered by owners to increase the safety of structures.

    SECTION G101—GENERAL

    G101.1 Identification of the problem. The California Wildland-Urban Interface Code establishes a set of minimum standards to reduce the loss of property from wildfire. The purpose of these standards is to prevent wildfire spreading from vegetation to a building. Many homes were built in the wildland-urban interface areas prior to the implementation of provisions found in this code. As a result, many homes are lacking in their ability to survive an approaching wildfire. Many of the features discussed in this appendix are designed as low- cost features to retrofit existing homes. Additionally, recommendations are provided beyond the minimum code requirements for those homeowners who desire to increase the survivability of their home. This appendix chapter provides a discussion of some possible self- defense features to enhance survivability and harden the structure against an approaching wildfire.

    G101.2 Structural survivability. The home-hardening features listed in Section G101.2.1 were developed as a best practices guide to assist homeowners in increasing the ignition resistance of their homes from wildfires. Some of these items are based on upgrading to more stringent building materials when that building component is due for replacement as part of its normal maintenance or lifespan, such as the roof covering.

    G101.2.1 Home-hardening features. If homes are not already provided with the suggested protection, the following items should be considered in hardening a home against wildfire. 1. When it is time to replace your roof, replace it with roof assembly classified as Class A when tested in accordance with ASTM E108 or UL 790.

    2. Block any spaces at the eaves between your roof covering and sheathing with noncombustible materials (bird stops). 3. Install a noncombustible rain gutter and downspouts. Install rain gutter covers to prevent the accumulation of leaves and debris in the gutters. 4. Cover your chimney and stovepipe outlets with a noncombustible, corrosion-resistant metal mesh screen (spark arrestor), with [3] / 8 -inch (9.5 mm) to [1] / 2 -inch (12.7 mm) openings. 5. Install ember- and flame-resistant vents. Choose products that have been approved and labeled as OSFM Wildland-Urban Interface (WUI) Products. A temporary solution is to cover the vent openings with a noncombustible and corrosion-resistant mesh with [1] / 16 -inch (1.6 mm) to [1] / 8 -inch (3.2 mm) openings. 6. Caulk and plug gaps greater than [1] / 8 inch (3.2 mm) around exposed rafters and blocking to prevent ember intrusion into the attic or other enclosed spaces. 7. _Inspect exterior siding for dry rot, gaps, cracks and warping.

  • CWUIC § 1507.2.4 High relevance — show source text

    1507.2.4 Asphalt shingles. Asphalt shingles shall comply with ASTM D3462.

    1507.2.5 Fasteners. Fasteners for asphalt shingles shall be galvanized, stainless steel, aluminum or copper roofing nails, minimum 12-gage [0.105 inch (2.67 mm)] shank with a minimum [3] / 8 -inch-diameter (9.5 mm) head, of a length to penetrate through the roofing materials and not less than [3] / 4 inch (19.1 mm) into the roof sheathing. Where the roof sheathing is less than [3] / 4 inch (19.1 mm) thick, the nails shall penetrate through the sheathing. Fasteners shall comply with ASTM F1667.

    15-10 2025 CALIFORNIA BUILDING CODE

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

    ROOF ASSEMBLIES AND ROOFTOP STRUCTURES

    1507.2.6 Attachment. Asphalt shingles shall have the minimum number of fasteners required by the manufacturer, but not less than four fasteners per strip shingle or two fasteners per individual shingle. Where the roof slope exceeds 21 units vertical in 12 units horizontal (21:12), shingles shall be installed as required by the manufacturer.

    1507.2.7 Ice barrier. Where required, ice barriers shall comply with Section 1507.1.2.

    1507.2.8 Flashings. Flashing for asphalt shingles shall comply with this section. Flashing shall be applied in accordance with this section and the asphalt shingle manufacturer’s instructions.

    1507.2.8.1 Base and cap flashing. Base and cap flashing shall be installed in accordance with the manufacturer’s instructions. Base flashing shall be of either corrosion-resistant metal of minimum nominal 0.019-inch (0.483 mm) thickness or mineralsurfaced roll roofing weighing not less than 77 pounds per 100 square feet (3.76 kg/m [2] ). Cap flashing shall be corrosion-resistant metal of minimum nominal 0.019-inch (0.483 mm) thickness.

    1507.2.8.2 Valleys. Valley linings shall be installed in accordance with the manufacturer’s instructions before applying shingles. Valley linings of the following types shall be permitted:

    1. For open valleys (valley lining exposed) lined with metal, the valley lining shall be not less than 24 inches (610 mm) wide and of any of the corrosion-resistant metals in Table 1507.2.8.2.
    2. For open valleys, valley lining of two plies of mineral-surfaced roll roofing complying with ASTM D3909 or ASTM D6380 shall be permitted. The bottom layer shall be 18 inches (457 mm) and the top layer not less than 36 inches (914 mm) wide.
    3. For closed valleys (valleys covered with shingles), valley lining of one ply of smooth roll roofing complying with ASTM D6380 and not less than 36 inches (914 mm) wide or types as described in Item 1 or 2 above shall be permitted. Selfadhering polymer modified bitumen underlayment bearing a label indicating compliance with ASTM D1970 and not less than 36 inches (914 mm) wide shall be permitted in lieu of the lining material.
  • CWUIC § 2.8.2 Medium relevance — show source text
    1. For open valleys, valley lining of two plies of mineral-surfaced roll roofing, complying with ASTM D3909 or ASTM D6380 Class M, shall be permitted. The bottom layer shall be 18 inches (457 mm) and the top layer not less than 36 inches (914 mm) wide.
    2. For closed valleys (valley covered with shingles), valley lining of one ply of smooth roll roofing complying with ASTM D6380 and not less than 36 inches wide (914 mm) or valley lining as described in Item 1 or 2 shall be permitted. Selfadhering polymer-modified bitumen underlayment complying with ASTM D1970 and not less than 36 inches (914 mm) wide shall be permitted in lieu of the lining material.
    TABLE R905.2.8.2—VALLEY LINING MATERIAL Col2 Col3 Col4
    ** MATERIAL** ** MINIMUM THICKNESS (inches)** ** GAGE** ** WEIGHT (pounds)**
    Aluminum 0.024 — —
    Cold-rolled copper 0.0216 nominal — ASTM B370, 16 oz. per square foot
    Galvanized steel 0.0179 26 (zinc-coated G90) —
    High-yield copper 0.0162 nominal — ASTM B370, 12 oz. per square foot
    Lead — — 21/2
    Lead-coated copper 0.0216 nominal — ASTM B101, 16 oz. per square foot
    Lead-coated high-yield copper 0.0162 nominal — ASTM B101, 12 oz. per square foot
    Painted terne — — 20
    Stainless steel — 28 —
    Zinc alloy 0.027 — —
    For SI: 1 inch = 25.4 mm, 1 pound = 0.454 kg, 1 square foot = 0.93 m2. For SI: 1 inch = 25.4 mm, 1 pound = 0.454 kg, 1 square foot = 0.93 m2. For SI: 1 inch = 25.4 mm, 1 pound = 0.454 kg, 1 square foot = 0.93 m2. For SI: 1 inch = 25.4 mm, 1 pound = 0.454 kg, 1 square foot = 0.93 m2.

    R905.2.8.3 Sidewall flashing. Base flashing against a vertical sidewall shall be continuous or step flashing and shall be not less than 4 inches (102 mm) in height and 4 inches (102 mm) in width and shall direct water away from the vertical sidewall onto the roof or into the gutter. Where siding is provided on the vertical sidewall, the vertical leg of the flashing shall be continuous under the siding. Where anchored masonry veneer is provided on the vertical sidewall, the base flashing shall be provided in accordance with this section and counterflashing shall be provided in accordance with Section R703.8.2.2. Where exterior plaster or adhered masonry veneer is provided on the vertical sidewall, the base flashing shall be provided in accordance with this section and Section R703.7.3.

  • CWUIC § 2.1 Medium relevance — show source text

    G101.2.1 Home-hardening features. If homes are not already provided with the suggested protection, the following items should be considered in hardening a home against wildfire. 1. When it is time to replace your roof, replace it with roof assembly classified as Class A when tested in accordance with ASTM E108 or UL 790.

    2. Block any spaces at the eaves between your roof covering and sheathing with noncombustible materials (bird stops). 3. Install a noncombustible rain gutter and downspouts. Install rain gutter covers to prevent the accumulation of leaves and debris in the gutters. 4. Cover your chimney and stovepipe outlets with a noncombustible, corrosion-resistant metal mesh screen (spark arrestor), with [3] / 8 -inch (9.5 mm) to [1] / 2 -inch (12.7 mm) openings. 5. Install ember- and flame-resistant vents. Choose products that have been approved and labeled as OSFM Wildland-Urban Interface (WUI) Products. A temporary solution is to cover the vent openings with a noncombustible and corrosion-resistant mesh with [1] / 16 -inch (1.6 mm) to [1] / 8 -inch (3.2 mm) openings. 6. Caulk and plug gaps greater than [1] / 8 inch (3.2 mm) around exposed rafters and blocking to prevent ember intrusion into the attic or other enclosed spaces. 7. Inspect exterior siding for dry rot, gaps, cracks and warping. Caulk or plug gaps greater than [1] / 8 inch (3.2 mm) in siding and replace any damaged boards, including those with dry rot. 8. Install weather stripping to fill gaps greater than [1] / 8 inch (3.2 mm) between garage doors and door frames to prevent ember intrusion. The weather stripping must be compliant with UL Standard 10C. 9. When it’s time to replace your windows, replace them with multipaned windows that have at least one pane of tempered glass. Choose products that have been approved and labeled as OSFM Wildland-Urban Interface (WUI) Products. 10. When it’s time to replace your siding or deck, use noncombustible, ignition-resistant, or other OSFM-approved Wildland- Urban Interface (WUI) Products. 11. Cover openings to operable skylights with noncombustible metal mesh screen with openings in the screen not to exceed [1] / 8 inch (3.2 mm). 12. Install a minimum 6-inch metal flashing, applied vertically on the exterior of the wall at the deck-to-wall intersection to protect the combustible siding material. 13. _Enclose openings beneath decks or cantilevered construction with one of the materials required in Section 504.5.

  • 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 § 405.4 Medium relevance — show source text

    **Not less than a 10 percent recycled content value.
    **Tier 2.**Not less than a 15 percent recycled content value.||2
    |2
    |
    |
    |
    | |A4.405.4Renewable source building products are used.||||||| |Enhanced Durability and Reduced Maintenance||||||| |4.406.1 Annular spaces around pipes, electric cables, conduits or
    other openings in plates at exterior walls shall be protected against
    the passage of rodents by closing such openings with cement mortar,
    concrete masonry or similar method acceptable to the enforcing
    agency.||||||| |Water Resistance and Moisture Management||||||| |A4.407.1Install foundation and landscape drains.||||||| |A4.407.2Install gutter and downspout systems to route water at least
    5 feet away from the foundation or connect to landscape drains which
    discharge to a dry well, sump, bioswale, rainwater capture system or
    other approved on-site location.||||||| |A4.407.3 Provide flashing details on the building plans and comply
    with accepted industry standards or manufacturer’s instructions.||||||| |A4.407.4 Protect building materials delivered to the construction site
    from rain and other sources of moisture.||||||| |A4.407.5In Climate Zone 16 an ice/water barrier is installed at roof
    valleys, eaves and wall to roof intersections.||||||| |A4.407.6Exterior doors to the dwelling are protected to prevent
    water intrusion.||||||| |A4.407.7 A permanent overhang or awning at least 2 feet in depth is
    provided.|||||||

    2025 CALIFORNIA GREEN BUILDING STANDARDS CODE APPENDIX A4-27

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

    APPENDIX A4 — RESIDENTIAL VOLUNTARY MEASURES

    SECTION A4.602—RESIDENTIAL OCCUPANCIES APPLICATION CHECKLIST—continued

  • CWUIC § 0.0254 Medium relevance — show source text

    Minimum Grade 50 ksi steel shall be used for 54 and 68 mil thicknesses.|For SI: 1 mil = 0.0254 mm, 1 inch = 25.4 mm, 1 foot = 304.8 mm, 1 pound per square foot = 0.0479 kPa, 1 pound per square inch = 6.895 kPa, 1 ksi = 1,000 psi = 6.895 MPa.
    a. Deflection criteria:L/360 for live loads,L/240 for total loads.
    b. Design load assumptions:
    Roof/ceiling dead load is 12 psf.
    Attic dead load is 10 psf.
    c. Building width is in the direction of horizontal framing members supported by the header.
    d. 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.|For SI: 1 mil = 0.0254 mm, 1 inch = 25.4 mm, 1 foot = 304.8 mm, 1 pound per square foot = 0.0479 kPa, 1 pound per square inch = 6.895 kPa, 1 ksi = 1,000 psi = 6.895 MPa.
    a. Deflection criteria:L/360 for live loads,L/240 for total loads.
    b. Design load assumptions:
    Roof/ceiling dead load is 12 psf.
    Attic dead load is 10 psf.
    c. Building width is in the direction of horizontal framing members supported by the header.
    d. 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.|For SI: 1 mil = 0.0254 mm, 1 inch = 25.4 mm, 1 foot = 304.8 mm, 1 pound per square foot = 0.0479 kPa, 1 pound per square inch = 6.895 kPa, 1 ksi = 1,000 psi = 6.895 MPa.
    a. Deflection criteria:L/360 for live loads,L/240 for total loads.
    b. Design load assumptions:
    Roof/ceiling dead load is 12 psf.
    Attic dead load is 10 psf.
    c. Building width is in the direction of horizontal framing members supported by the header.
    d. 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.|

    6-78 2025 CALIFORNIA RESIDENTIAL CODE

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

    WALL CONSTRUCTION

    TABLE R603.6(2)—BOX-BEAM AND BACK-TO-BACK HEADER SPANS
    (HEADERS SUPPORTING ROOF AND CEILING ONLY)a, b, d    		 Col2 Col3 Col4 Col5 Col6 Col7 Col8 Col9 Col10 Col11
    MEMBER
    DESIGNATION    		 GROUND SNOW LOAD
    (50 psf)    		 GROUND SNOW LOAD
    **(50
  • CWUIC § 1602.6 Medium relevance — show source text

    The test shall be ruled successful by the Authority Having Jurisdiction before final approval is granted. 1602.6 Sizing. The design and size of rainwater drains, gutters, conductors, and leaders shall comply with Chapter 11 of this code.

    328 2025 CALIFORNIA PLUMBING CODE

    ), Copyright © 2025 IAPMO, and may not be used for any other purpose or distributed to any other persons or parties.

    NONPOTABLE RAINWATER CATCHMENT SYSTEMS

    1602.7 Rainwater Catchment System Materials. Rain- 1603.3 Rainwater Catchment Collection Surfaces. water catchment system materials shall comply with Section Rainwater shall be collected from roof surfaces or other 1602.7.1 through Section 1602.7.3 . impervious manmade, aboveground collection surfaces. 1602.7.1 Water Supply and Distribution Materi- 1603.3.1 Other Surfaces. Natural precipitation colals. Rainwater catchment water supply and distribution lected from surface water runoff, vehicular parking surmaterials shall comply with the requirements of this code faces, or manmade surfaces at or below grade shall be in for potable water supply and distribution systems unless accordance with the water quality requirements for onotherwise provided for in this section. site treated nonpotable gray water systems in Section

    1506.0.

    1602.7.2 Rainwater Catchment System Drainage Materials. Materials used in rainwater catchment Exception: Collected rainwater or storm water used

    exclusively for subsurface landscape irrigation.

    drainage systems, including gutters, downspouts, conductors, and leaders shall be in accordance with the 1603.3.2 Prohibited Discharges. Overflows and requirements of this code for storm drainage. bleed-off pipes from roof-mounted equipment and appli ances shall not discharge onto roof surfaces that are

    1602.7.3 Storage Tanks. Rainwater storage tanks shall

    intended to collect rainwater without prior approval from

    comply with Section 1603.5.

    the Authority Having Jurisdiction.

    1602.8 Rainwater Catchment System Color and

    1603.4 Minimum Water Quality. The minimum water

    Marking Information. Rainwater catchment systems shall

    quality for harvested rainwater shall meet the applicable water

    have a colored background in accordance with Section 601.3.

    quality requirements for the intended applications as deter Rainwater catchment systems shall be marked, in lettering in

    mined by the Authority Having Jurisdiction. In the absence of

    accordance with Section 601.3.3, with the words: “CAU water quality requirements determined by the Authority Hav TION: NONPOTABLE RAINWATER, DO NOT DRINK.”

    ing Jurisdiction, the minimum treatment and water quality

  • CWUIC § 5-1 Medium relevance — show source text

    2025 CALIFORNIA WILDLAND-URBAN INTERFACE CODE 5-1

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    5-2 2025 CALIFORNIA WILDLAND-URBAN INTERFACE CODE

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    5 SPECIAL BUILDING CONSTRUCTION REGULATIONS

    User notes:

    About this chapter: Chapter 5 provides regulations that establish minimum standards for the location, design and construction of buildings and structures based on construction within a Fire Hazard Severity Zone or a Wildland-Urban Interface (WUI) Area.

    The construction provisions of Chapter 5 are intended to supplement the requirements of the California Building Code and California Residential Code and address mitigation of the unique hazards posed to buildings by wildfire and to reduce the hazards of building fires spreading to wildland fuels. This is accomplished by requiring ignition-resistant construction materials. Construction features regulated include underfloor areas; roof coverings; eaves and soffits; gutters and downspouts; exterior walls, doors and windows; ventilation openings and accessory structures.

    SECTION 501—GENERAL

    501.1 Scope. Buildings and structures in a wildland-urban interface area shall be constructed in accordance with the California Build- ing Code and this code.

    Exceptions:

    1. Group U accessory structures not exceeding 120 square feet (11 m [2] ) in floor area where located not less than 50 feet (15 240 mm) from applicable buildings.
    2. Group U agricultural buildings not less than 50 feet (15 240 mm) from applicable buildings.

    501.2 Objective. The objective of this chapter is to establish minimum standards to locate, design and construct buildings and structures or portions thereof for the protection of life and property, to resist damage from wildfires, and to mitigate building and structure fires from spreading to wildland fuels.

    501.3 Fire-resistance-rated construction. Where this code requires 1-hour fire-resistance-rated construction, the fire-resistance rating of building elements, components or assemblies shall be determined in accordance with the test procedures set forth in ASTM E119 or UL 263.

    Exceptions:

    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.

  • CWUIC § 8.1 Medium relevance — show source text

    8.1_ –504.8.2|||X||||||||||||||||||||| |504.9|||X||||||||||||||||||||| |504.9.1 –504.9.3|||X||||||||||||||||||||| |504.10.1 – 504.10.3|||X||||||||||||||||||||| |504.11 – 504.11.1|||X||||||||||||||||||||| |504.11.2 –504.11.6|||X||||||||||||||||||||| |505 – 506_Reserved_|||X||||||||||||||||||||| |507.1|||X|||||||||||||||||||||

    • The California Code of Regulations (CCR), Title 19, Division 1 provisions that are found in the California Wildland-Urban Interface Code are a reprint from the current CCR, Title 19, Division 1 text for the code user’s convenience only. The scope, applicability and appeals procedures of CCR, Title 19, Division I remain the same. The state agency does not adopt sections identified by the following symbol: The Office of the State Fire Marshal’s adoption of this chapter or individual sections is applicable to structures regulated by other state agencies pursuant to Section 1.11.

    The California Code of Regulations (CCR), Title 14, Division 1.5 provisions that are found in the California Wildland-Urban Interface Code are not listed in the Matrix Adoption Tables as they are not within the State Fire Marshal’s authority to adopt. These provisions are a reprint from the current CCR, Title 14, Division 1.5 text for the code user’s convenience only and are identified in the body of the code by square brackets containing references to applicable Title 14 sections.

    2025 CALIFORNIA WILDLAND-URBAN INTERFACE CODE 5-1

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    5-2 2025 CALIFORNIA WILDLAND-URBAN INTERFACE CODE

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

    5 SPECIAL BUILDING CONSTRUCTION REGULATIONS

    User notes:

    About this chapter: Chapter 5 provides regulations that establish minimum standards for the location, design and construction of buildings and structures based on construction within a Fire Hazard Severity Zone or a Wildland-Urban Interface (WUI) Area.

    The construction provisions of Chapter 5 are intended to supplement the requirements of the California Building Code and California Residential Code and address mitigation of the unique hazards posed to buildings by wildfire and to reduce the hazards of building fires spreading to wildland fuels. This is accomplished by requiring ignition-resistant construction materials. Construction features regulated include underfloor areas; roof coverings; eaves and soffits; gutters and downspouts; exterior walls, doors and windows; ventilation openings and accessory structures.

    SECTION 501—GENERAL

    501.1 Scope. Buildings and structures in a wildland-urban interface area shall be constructed in accordance with the California Build- ing Code and this code.

    Exceptions:

    1. Group U accessory structures not exceeding 120 square feet (11 m [2] ) in floor area where located not less than 50 feet (15 240 mm) from applicable buildings.
    2. Group U agricultural buildings not less than 50 feet (15 240 mm) from applicable buildings.
  • 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

  • CWUIC § 1.5 Medium relevance — show source text

    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 1270.01(y)
    Roof assembly Y
    Roof covering Y
    Roof covering system Y
    Roof deck Y
    Roof eave Y 702A
    Roof eave soffit Y 702A
    Slope Y
    State Responsibility
    Area (SRA)    		 Y 702A 4902.1
    Strategic
    ridgeline (T14)    		 Y 1270.01(dd)
    Structure Y 202 1270.01(ee)
    Subdivision Y
    Tree crown Y
    Undeveloped
    ridgeline (T14)    		 Y 1270.01(ii)
    Unenclosed acces-
    sory structure    		 Y
    Vertical curve (T14) Y 1270.01(k)
    Wildfire Y 702A 4902.1
    Wildfire exposure Y 702A 4902.1
    Wildland Y
    Wildland-urban inter-
    face area    		 Y 702A 4902.1
    Chapter 3 Wildland-urban interface areas Wildland-urban interface areas Wildland-urban interface areas Wildland-urban interface areas Wildland-urban interface areas Wildland-urban interface areas Wildland-urban interface areas Wildland-urban interface areas Wildland-urban interface areas Wildland-urban interface areas
    301 General Y
    301.1 Scope Y 4201
    301.
  • CWUIC § 17.75 Medium relevance — show source text

    30|17.75|20.83|24.16|27.73|31.55|8.00| |60|45|< 1:12|3.55|3.87|4.54|5.27|6.05|6.88|4.03| |60|45|5:12|4.94|5.37|6.31|7.31|8.40|9.55|6.34| |60|45|7:12|11.71|12.75|14.97|17.36|19.93|22.67|7.39| |60|45|12:12|22.70|24.71|29.00|33.64|38.62|43.94|10.29| |60|60|< 1:12|3.68|4.01|4.71|5.46|6.27|7.13|4.23| |60|60|5:12|5.11|5.57|6.54|7.58|8.70|9.90|7.31| |60|60|7:12|14.38|15.66|18.37|21.31|24.46|27.83|8.71| |60|60|12:12|29.30|31.90|37.44|43.42|49.85|56.72|12.57| |For SI: 1 inch = 25.4 mm, 1 foot = 304.8 mm, 1 mile per hour = 0.447 m/s, 1 pound-force per linear foot = 0.146 kN/m, 1 pound per square foot = 47.88 Pa.
    a. Tabulated lengths were derived by calculating design wind pressures in accordance with Figure 28.4-1 of ASCE 7 for a building with a mean roof height of 35 feet, topographic
    factor,Kzt, equal to 1.0, and Risk Category II. For wind perpendicular to the ridge, the effects of a 2-foot overhang on each endwall are included. The design pressures were
    used to calculate forces to be resisted by solid wall segments in each. The forces to be resisted by each wall line were then divided by the default design strength of 840
    pounds per linear foot of length to determine the unreduced length,UR, of solid wall length required in each endwall. The actual mean roof height of the building shall not
    exceed the least horizontal dimension of the building.
    b. Tabulated lengths in the “minimum” column are based on the requirement of Section 28.4.4 of ASCE 7 that the main windforce-resisting system be designed for a minimum
    pressure of 16 psf multiplied by the wall area of the building and 8 psf multiplied by the roof area of the building projected onto a vertical plane normal to the assumed wind
    direction. Tabulated lengths in shaded cells are less than the “minimum” value. Where the minimum controls, it is permitted to be reduced in accordance with Notes c, d and
    e. See Section R608.7.1.1.
    c. For buildings with a mean roof height of less than 35 feet, tabulated lengths are permitted to be reduced by multiplying by the appropriate factor,_R_1, from Table R608.7.1.1(4).
    The reduced length shall be not less than the “minimum” value shown in the table.
    d.

  • CWUIC § 7.1.1 Medium relevance — show source text

    Tabulated lengths for “one story or top story of two story” are based on a floor-to-ceiling height of 10 feet. Tabulated lengths for “first story of two story” are based on floor-
    to-ceiling heights of 10 feet each for the first and second story. For floor-to-ceiling heights less than assumed, use the lengths in this table or Table R608.7.1.1(1) or Table
    R608.7.1.1(2), or multiply the value in the table by the reduction factor,_R_2, from Table R608.7.1.1(5).
    e. Tabulated lengths are based on the default design shear strength of 840 pounds per linear foot of solid wall segment. The tabulated lengths are permitted to be reduced by
    multiplying by the applicable reduction factor for design strength,_R_3, from Table R608.7.1.1(6).
    f. The reduction factors,_R_1, _R_2 and_R_3, in Table R608.7.1.1(4), Table R608.7.1.1(5), and Table R608.7.1.1(6), respectively, are permitted to be compounded, subject to the limita-
    tions of Note b. However, the minimum number and minimum length of solid walls segments in each wall line shall comply with Sections R608.7.1 and R608.7.2.1,
    respectively.
    g. For intermediate values of sidewall length, endwall length, roof slope and basic wind speed, use the next higher value, or determine by interpolation.|For SI: 1 inch = 25.4 mm, 1 foot = 304.8 mm, 1 mile per hour = 0.447 m/s, 1 pound force per linear foot = 0.146 kN/m, 1 pound per square foot = 47.88 Pa.
    a. Tabulated lengths were derived by calculating design wind pressures in accordance with Figure 28.4-1 of ASCE 7 for a building with a mean roof height of 35 feet, topographic
    factor,Kzt, equal to 1.0, and Risk Category II. The design pressures were used to calculate forces to be resisted by solid wall segments in each sidewall. The forces to be resisted
    by each wall line were then divided by the default design strength of 840 pounds per linear foot of length to determine the unreduced length,UR, of solid wall length required
    in each sidewall. The actual mean roof height of the building shall not exceed the least horizontal dimension of the building.
    b. Tabulated lengths in the “minimum” column are based on the requirement of Section 28.4.4 of ASCE 7 that the main windforce-resisting system be designed for a minimum
    pressure of 16 psf multiplied by the wall area of the building and 8 psf multiplied by the roof area of the building projected onto a vertical plane normal to the assumed wind
    direction. Tabulated lengths in shaded cells are less than the “minimum” value. Where the minimum controls, it is permitted to be reduced in accordance with Notes c, d and
    e. See Section R608.7.1.1.
    c. For buildings with a mean roof height of less than 35 feet, tabulated lengths are permitted to be reduced by multiplying by the appropriate factor,_R_1, from Table R608.7.1.1(4).
    The reduced length shall be not less than the “minimum” value shown in the table.
    d.

Frequently asked questions

Do gutters really have to be noncombustible in WUI areas?

Yes. The CWUIC requires gutters and downspouts to be constructed of noncombustible material — § 504.4. The code treats combustible gutters as an ignition hazard in WUI settings .

Does CWUIC specify exact valley lining widths?

CWUIC § 504.2.2 points to the referenced valley rules (705A.3); the detailed valley lining widths are provided in the California Building/Residential Code (typical values: 24 in, 36 in, 18 in plies) — see CBC § 1507.2.8.2 / CRC § R905.2.8.2 .

Are gutter covers required or just recommended?

CWUIC § 504.4 requires “an approved means to prevent the accumulation of leaves and debris” (this is mandatory). Appendix G also recommends gutter covers as a best practice but Appendix G itself is informational, not the source of the mandatory requirement .

If my valley is closed (shingle‑covered), what lining is required?

For closed valleys the CBC/CRC allow a single ply of smooth roll roofing or a self‑adhering polymer‑modified bitumen underlayment not less than 36 inches (914 mm) wide; follow the roofing code section and the manufacturer’s instructions (CBC § 1507.2.8.2 / CRC § R905.2.8.2) .

Who enforces these requirements?

The local Authority Having Jurisdiction enforces the CWUIC and the referenced building/residential code provisions; check local adoption/interpretations and plan review requirements since CWUIC cross‑references other code sections for valley lining details .

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