CWUIC · California Wildland-Urban Interface Code

What are the vent performance requirements and rules for off‑ridge/ridge vents?

Your vents must follow one of two CWUIC paths: install a CSFM‑listed WUI vent tested to ASTM E2886 (no flaming in tests; unexposed side ≤662°F) or, for off‑ridge/ridge (sloped‑roof) vents, use mesh with openings between 1/16" and 1/8" that is noncombustible and corrosion‑resistant, per §§ 504.10, 504.10.1 and 504.10.2.

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Last reviewed: July 6, 2026

What the code requires — 2-4 sentences

Ventilation openings must meet one of two CWUIC paths: either be fully covered by Wildfire Flame and Ember Resistant vents (WUI vents) listed by the California State Fire Marshal and tested to ASTM E2886 or—where the opening is an off‑ridge / ridge (sloped‑roof) vent such as a dormer vent—comply with specific mesh size and material requirements. The controlling provisions are § 504.10, § 504.10.1, and § 504.10.2 of the CWUIC.

Either use a listed WUI vent that passes the ASTM E2886 ember/flame tests (and the unexposed‑side temperature limit), or for vents on sloped roofs use mesh that is no smaller than 1/16" (1.6 mm) and no larger than 1/8" (3.2 mm) and is noncombustible and corrosion‑resistant (the choice is set out in the code).

Requirements in detail

Which ventilation openings are covered

The CWUIC applies these rules to ventilation openings for enclosed attics, gable ends, ridge ends, under eaves and cornices, enclosed eave soffit spaces, enclosed rafter spaces, underfloor ventilation, foundations and crawl spaces, and other ventilation openings. Compliance must follow either § 504.10.1 or § 504.10.2. § 504.10.

Option A — Listed WUI vents / performance path (use this if you install a listed product)

Key requirements (from § 504.10.1):

Ventilation openings must be fully covered with Wildfire Flame and Ember Resistant vents approved and listed by the California State Fire Marshal (referred to as WUI vents) and tested in accordance with ASTM E2886. § 504.10.1.
To pass, the listed vent must meet all of these test acceptance criteria:
1. No flaming ignition of the cotton material during the Ember Intrusion Test. § 504.10.1(1).
2. No flaming ignition during the Integrity Test portion of the Flame Intrusion Test. § 504.10.1(2).
3. The maximum temperature of the unexposed side of the vent shall not exceed 662°F (350°C). § 504.10.1(3).

Notes: ASTM E2886 testing and California listing are required for this path; the code ties compliance to the listed product performance (not simply to “close mesh”).

Option B — Off‑ridge / ridge vents (specific construction path)

When the vent is installed on a sloped roof (examples: dormer vents, ridge vents), the code provides specific requirements in § 504.10.2:

The vent shall be covered with a mesh whose openings are a minimum of 1/16 inch (1.6 mm) and shall not exceed 1/8 inch (3.2 mm) in diameter. § 504.10.2(1).
The vent and mesh material shall be noncombustible. § 504.10.2(2).
The vent and mesh material shall be corrosion resistant. § 504.10.2(3).

Summary: For off‑ridge/ridge vents you may follow the mesh/material rules in § 504.10.2 instead of using a listed ASTM E2886 WUI vent, but you must meet all three items in § 504.10.2.

Quick decision table (decision‑relevant dimensions / values)

Decision point	Required value / limit	Code reference
Listed WUI vent test standard	ASTM E2886	§ 504.10.1
Ember Intrusion Test — flaming on cotton	No flaming ignition allowed	§ 504.10.1(1)
Integrity (Flame Intrusion) Test — flaming	No flaming ignition allowed	§ 504.10.1(2)
Temperature — unexposed side	≤ 662°F (350°C)	§ 504.10.1(3)
Off‑ridge / ridge vent mesh minimum opening	1/16 inch (1.6 mm)	§ 504.10.2(1)
Off‑ridge / ridge vent mesh maximum opening	1/8 inch (3.2 mm)	§ 504.10.2(1)
Off‑ridge / ridge vent material combustibility	Noncombustible	§ 504.10.2(2)
Off‑ridge / ridge vent material durability	Corrosion resistant	§ 504.10.2(3)

Exceptions & special cases

The three cited sections (§ 504.10, § 504.10.1, § 504.10.2) set out the two compliance paths and the off‑ridge/ridge vent specifics; those sections do not list additional exceptions for off‑ridge/ridge vents within the text of those three sections. The code does, elsewhere, regulate vent locations and other details (for example § 504.10.3 addresses vent locations), but those are outside the three controlling subsections you asked to focus on.
If you rely on a product listed by the California State Fire Marshal, confirm the product listing covers the specific vent type and application you plan to use; the listing is the basis of compliance under § 504.10.1.

Common mistakes

Assuming any fine‑mesh screen is acceptable: the mesh limits (1/16"–1/8") in § 504.10.2 are specific — too large (≥ 1/4") fails the maximum opening requirement; too fine (smaller than 1/16") is not permitted by that subsection.
Using combustible or non‑corrosion‑resistant mesh on a sloped‑roof vent. § 504.10.2(2) and (3) require noncombustible and corrosion resistant materials.
Installing a vent claimed to be "ember‑resistant" without checking for a California State Fire Marshal listing or ASTM E2886 test evidence — § 504.10.1 requires a CSFM‑listed WUI vent tested to ASTM E2886.
Confusing the temperature limit: the 662°F (350°C) unexposed‑side limit applies to the tested/listed WUI vent acceptance criteria in § 504.10.1(3), not to the mesh diameter rules in § 504.10.2.

Worked example — concrete scenario

Scenario: You are replacing two dormer vents on a sloped roof. Manufacturer A offers a stainless‑steel mesh insert with opening diameter 1/16" (1.6 mm); Manufacturer B offers aluminum mesh with 1/4" (6.4 mm) openings. Which complies?

Path analysis:
- Manufacturer A mesh = 1/16", stainless steel (noncombustible) and stainless is corrosion‑resistant → meets all three items of § 504.10.2 (mesh within 1/16"–1/8", noncombustible, corrosion resistant). Use of that mesh would comply with the off‑ridge/ridge vent rules.
- Manufacturer B mesh = 1/4" (6.4 mm) openings → exceeds the maximum 1/8" (3.2 mm) diameter allowed in § 504.10.2(1) and therefore does not comply with the off‑ridge/ridge vent path.
Alternative: If you instead install a CSFM‑listed WUI vent tested to ASTM E2886, verify the product listing and test results meet § 504.10.1 (no flaming ignition in the listed tests; unexposed side ≤ 662°F / 350°C). A properly listed product under § 504.10.1 would also be compliant.

Related provisions

§ 504.10 — Vents (general requirement: ventilation openings shall comply with § 504.10.1 or § 504.10.2).
§ 504.10.1 — Performance requirements for listed WUI vents (ASTM E2886 acceptance criteria).
§ 504.10.2 — Off‑ridge and ridge vents: mesh size, noncombustible and corrosion‑resistant materials.
(Related/nearby) § 504.10.3 — Vent locations (e.g., gable‑end and dormer vents location requirements). This section addresses placement and is useful when planning vent location but is outside the three controlling subsections you asked about.

Code references

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

CWUIC § 504.10.1 High relevance — show source text
on Jul 18, 2025 11:14 AM (CDT) THEREUNDER.

SPECIAL BUILDING CONSTRUCTION REGULATIONS

lation, foundations and crawl spaces, or any other opening intended to permit ventilation, either in a horizontal or vertical surface, shall be in accordance with Section 504.10.1 or Section 504.10.2 to resist building ignition from the intrusion of burning embers and flame through the ventilation openings.

504.10.1 Performance requirements. Ventilation openings shall be fully covered with Wildfire Flame and Ember Resistant vents approved and listed by the California State Fire Marshal, or WUI vents, tested in accordance with ASTM E2886, to demonstrate compliance with all the following requirements:
1. There shall be no flaming ignition of the cotton material during the Ember Intrusion Test.
2. There shall be no flaming ignition during the Integrity Test portion of the Flame Intrusion Test.
3. The maximum temperature of the unexposed side of the vent shall not exceed 662°F (350°C).
504.10.2 Off ridge and ridge vents. Vents that are installed on a sloped roof, such as dormer vents, shall comply with all of the following: 1. Vents shall be covered with a mesh where the dimensions of the mesh therein shall be a minimum of [1] / 16 inch (1.6 mm) and shall not exceed [1] / 8 inch (3.2 mm) in diameter.

2. The vent and mesh material shall be noncombustible.

3. The vent and mesh material shall be corrosion resistant.

504.10.3 Vent locations. Gable-end and dormer vents shall be located not less than 10 feet (3048 mm) from lot lines. Underfloor ventilation openings shall be located as close to grade as practical.

504.11 Accessory buildings and miscellaneous structures. Accessory buildings and miscellaneous structures that have the potential to pose a significant exterior fire exposure hazard during wildfires shall be constructed to conform to the ignition-resistance require- ments of this section.

504.11.1 Applicability . Sections 504.11.2 through 504.11.6 apply to buildings accessory to an applicable building on the same lot, and attached or detached miscellaneous structures that require a building permit, including but not limited to trellises, arbors, patio covers, gazebos and similar structures.

Exceptions: 1. Decks shall comply with the requirements of Section 504.7.3. 2. Awnings and canopies shall comply with the requirements of Section 3105 of the California Building Code.

504.11.2 Miscellaneous structures and accessory buildings within 3 feet. Miscellaneous structures that require a permit, and accessory buildings of any size, when separated from an applicable building on the same lot by a distance of less than 3 feet (914 mm), shall be constructed of noncombustible materials or ignition-resistant building materials as described in Section 503.2.4.
CWUIC § 504.9.3 High relevance — show source text
Gaps between doors and door openings_ shall be controlled by one or more of the following methods: 1. Weather-stripping products constructed of materials that which comply with both of the following: 1.1. The tensile strength of the material shall be tested in accordance with ASTM D638 before and after exposure to ASTM G155 for a period of 2,000 hours, and the maximum allowable difference in tensile strength values between exposed and nonexposed samples shall not exceed 10 percent. 1.2. When tested to UL 94, the materials shall have a flammability rating of V-2 or better. 2. Door overlaps onto jambs and headers. 3. Garage door jambs and headers covered with metal flashing.

504.9.3 Conditions of acceptance for ASTM E2707. The ASTM E2707 test shall be conducted on a minimum of three test specimens and meet the conditions of acceptance in Items 1 and 2. If any one of the three tests do not meet the conditions of acceptance, three additional tests shall be performed. All three additional tests must meet the conditions of acceptance. 1. Absence of flame penetration through the wall assembly at any time. 2. Absence of evidence of glowing combustion on the interior surface of the assembly at the end of the 70-minute test.

504.10 Vents. Where provided, ventilation openings for enclosed attics, gable ends, ridge ends, under eaves and cornices, enclosed eave soffit spaces, enclosed rafter spaces formed where ceilings are applied directly to the underside of roof rafters, underfloor venti

5-8 2025 CALIFORNIA WILDLAND-URBAN INTERFACE CODE

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

SPECIAL BUILDING CONSTRUCTION REGULATIONS

lation, foundations and crawl spaces, or any other opening intended to permit ventilation, either in a horizontal or vertical surface, shall be in accordance with Section 504.10.1 or Section 504.10.2 to resist building ignition from the intrusion of burning embers and flame through the ventilation openings.

504.10.1 Performance requirements. Ventilation openings shall be fully covered with Wildfire Flame and Ember Resistant vents approved and listed by the California State Fire Marshal, or WUI vents, tested in accordance with ASTM E2886, to demonstrate compliance with all the following requirements:
1. There shall be no flaming ignition of the cotton material during the Ember Intrusion Test.
2. There shall be no flaming ignition during the Integrity Test portion of the Flame Intrusion Test.
3. The maximum temperature of the unexposed side of the vent shall not exceed 662°F (350°C).
504.10.2 Off ridge and ridge vents. Vents that are installed on a sloped roof, such as dormer vents, shall comply with all of the following: 1. Vents shall be covered with a mesh where the dimensions of the mesh therein shall be a minimum of [1] / 16 inch (1.6 mm) and shall not exceed [1] / 8 inch (3.2 mm) in diameter.

2. The vent and mesh material shall be noncombustible.

3. The vent and mesh material shall be corrosion resistant.

CWUIC § 1.5 High relevance — show source text

2025 CALIFORNIA WILDLAND-URBAN INTERFACE CODE APPENDIX H-29

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 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
504.9.1	Garage doors	Y
504.9.2	Garage door perimeter gap	Y		708A.4
504.9.3	Conditions of accep- tance for ASTM E2707	Y		707A.4.1
504.10	Vents	Y		706A.1
504.10.1	Performance requirements	Y		706A.2
504.10.2	Off ridge and ridge vents	Y		706A.2.1
504.10.3	Vent locations	Y
504.11	Accessory buildings and miscellaneous structures	Y		710A.1
504.11.1	Applicability	Y		710A.2
504.11.2	Miscellaneous struc- tures and accessory buildings within 3 feet	Y		710A.3.1
504.11.3	Accessory buildings greater than 120 square feet, located 3 feet or more but less than 50 feet	Y		710A.3.2
504.11.4	Accessory buildings 120 square feet or less, located 3 feet or more but less than 50 feet	Y		710A.3.3
504.11.5	Miscellaneous struc- tures located 3 feet or more but less than 50 feet	Y		710A.3.4
504.11.6	Roof construction			710A.4
505	RESERVED	N
506	RESERVED	N
507	Replacement or repair of roof coverings	Y		705A.1 1505.1.1
507.1	General	Y		705A.1 1505.1.

CWUIC § 1.1 Medium relevance — show source text
Openings in roof framing members shall conform to the requirements of Section R802.7. Required ventilation openings shall open directly to the outside air and shall be protected to prevent the entry of birds, rodents, snakes and other similar creatures.

R806.1.1 Vents in the Wildland Urban Interface (WUI). Where provided, ventilation openings for enclosed attics, gable ends, ridge ends, under eaves and cornices, enclosed eave soffit spaces, enclosed rafter spaces formed where ceilings are applied directly to the underside of roof rafters, underfloor ventilation, foundations and crawl spaces, or any other opening intended to permit ventilation, either in a horizontal or vertical plane, shall be in accordance with Part 7, California Wildland-Urban Interface Code to resist building ignition from the intrusion of burning embers and flame through the ventilation openings. R806.2 Minimum vent area. The minimum net free ventilating area shall be [1] / 150 of the area of the vented space. Exception: The minimum net free ventilation area shall be [1] / 300 of the vented space provided both of the following conditions are met:
1. In Climate Zones 6, 7 and 8, a Class I or II vapor retarder is installed on the warm-in-winter side of the ceiling.
2. Not less than 40 percent and not more than 50 percent of the required ventilating area is provided by ventilators located in the upper portion of the attic or rafter space. Upper ventilators shall be located not more than 3 feet (914 mm) below the ridge or highest point of the space, measured vertically. The balance of the required ventilation provided shall be located in the bottom one-third of the attic space. Where the location of wall or roof framing members conflicts with the installation of upper ventilators, installation more than 3 feet (914 mm) below the ridge or highest point of the space shall be permitted.
R806.3 Vent and insulation clearance. Where eave or cornice vents are installed, blocking, bridging and insulation shall not block the free flow of air. Not less than a 1-inch (25 mm) space shall be provided between the insulation and the roof sheathing and at the location of the vent.

R806.4 Installation and weather protection. Ventilators shall be installed in accordance with manufacturer’s instructions. Installation of ventilators in roof systems shall be in accordance with the requirements of Section R903. Installation of ventilators in wall systems shall be in accordance with the requirements of Section R703.1.

R806.5 Unvented attic and unvented enclosed rafter assemblies. Unvented attics and unvented enclosed roof framing assemblies created by ceilings that are applied directly to the underside of the roof framing members and structural roof sheathing applied directly to the top of the roof framing members/rafters, shall be permitted where all the following conditions are met:
1. The unvented attic space is completely within the building thermal envelope.
2. Interior Class I vapor retarders are not installed on the ceiling side (attic floor) of the unvented attic assembly or on the ceiling side of the unvented enclosed roof framing assembly.
3. Where wood shingles or shakes are used, a minimum [1] / 4 -inch (6.4 mm) vented airspace separates the shingles or shakes and the roofing underlayment above the structural sheathing.

CWUIC § 3.4.2 Medium relevance — show source text

Add 5 gpm to the flow rate required by Section_R309.3.4.2_ where the water service pipe supplies more than one dwelling.|For SI: 1 inch = 25.4 mm, 1 foot = 304.8 mm, 1 gallon per minute = 0.063 L/s, 1 pound per square inch = 6.895 kPa.
NP = Not Permitted. Pressure loss exceeds reasonable limits.
a. Values are applicable for underground piping materials listed in_ the California Plumbing Code_ and are based on an SDR of 11 and a Hazen Williams C Factor of 150.
b. Values include the following length allowances for fittings: 25-percent length increase for actual lengths up to 100 feet and 15-percent length increase for actual lengths over
100 feet.
c. Flow rate from Section P2904.4.2. Add 5 gpm to the flow rate required by Section_R309.3.4.2_ where the water service pipe supplies more than one dwelling.|For SI: 1 inch = 25.4 mm, 1 foot = 304.8 mm, 1 gallon per minute = 0.063 L/s, 1 pound per square inch = 6.895 kPa.
NP = Not Permitted. Pressure loss exceeds reasonable limits.
a. Values are applicable for underground piping materials listed in_ the California Plumbing Code_ and are based on an SDR of 11 and a Hazen Williams C Factor of 150.
b. Values include the following length allowances for fittings: 25-percent length increase for actual lengths up to 100 feet and 15-percent length increase for actual lengths over
100 feet.
c. Flow rate from Section P2904.4.2. Add 5 gpm to the flow rate required by Section_R309.3.4.2_ where the water service pipe supplies more than one dwelling.|

TABLE R309.3.6.2(2)—MINIMUM WATER METER PRESSURE LOSS (PL )a m	Col2	Col3	Col4
FLOW RATE (gallons per minute, gpm)b	5/8-INCH METER PRESSURE LOSS (pounds per square inch, psi)	3/4-INCH METER PRESSURE LESS (pounds per square inch, psi)	1-INCH METER PRESSURE LOSS (pounds per square inch, psi)
8	3	3	1
10	3	3	1
12	4	3	1
14	6	5	1
16	7	6	1
18	9	7	2
20	11	9	2
23	14	11	3
26	18	14	3
31	26	22	4
39	38	35	6
52	NP	NP	10
For SI: 1 inch = 25.4 mm, 1 pound per square inch = 6.895 kPa, 1 gallon per minute = 0.063 L/s. NP = Not permitted unless the actual water meter pressure loss is known. a. Table P2904.6.2(2) establishes conservative values for water meter pressure loss or installations where the water meter loss is unknown. Where the actual water meter pres- sure loss is published and available from the meter manufacturer,PLm shall be the published pressure loss for the selected meter. b.

CWUIC § 3.8 Medium relevance — show source text
on Jul 18, 2025 11:14 AM (CDT) THEREUNDER.

ROOF-CEILING CONSTRUCTION

R804.3.8 Roof tie-down. Roof assemblies shall be connected to walls below in accordance with Table R804.3. A continuous load path shall be provided to transfer uplift loads to the foundation.

SECTION R805—CEILING FINISHES

R805.1 Ceiling installation. Ceilings shall be installed in accordance with the requirements for interior wall finishes as provided in Sections R702.1 through R702.6.

SECTION R806—ROOF VENTILATION

Note: The IECC climate zones used by this section differ from those used by the California Energy Code to determine applicability of energy efficiency measures. Comparison of IECC and California Energy Code climate zones is shown in Table R702.7.3.

R806.1 Ventilation required. Enclosed attics and enclosed rafter spaces formed where ceilings are applied directly to the underside of roof rafters shall have cross ventilation for each separate space by ventilating openings protected against the entrance of rain or snow. Ventilation openings shall have a least dimension of [1] / 16 inch (1.6 mm) minimum and [1] / 4 inch (6.4 mm) maximum. Ventilation openings having a least dimension larger than [1] / 4 inch (6.4 mm) shall be provided with corrosion-resistant wire cloth screening, hardware cloth, perforated vinyl or similar material with openings having a least dimension of [1] / 16 inch (1.6 mm) minimum and [1] / 4 inch (6.4 mm) maximum. Openings in roof framing members shall conform to the requirements of Section R802.7. Required ventilation openings shall open directly to the outside air and shall be protected to prevent the entry of birds, rodents, snakes and other similar creatures.

R806.1.1 Vents in the Wildland Urban Interface (WUI). Where provided, ventilation openings for enclosed attics, gable ends, ridge ends, under eaves and cornices, enclosed eave soffit spaces, enclosed rafter spaces formed where ceilings are applied directly to the underside of roof rafters, underfloor ventilation, foundations and crawl spaces, or any other opening intended to permit ventilation, either in a horizontal or vertical plane, shall be in accordance with Part 7, California Wildland-Urban Interface Code to resist building ignition from the intrusion of burning embers and flame through the ventilation openings. R806.2 Minimum vent area. The minimum net free ventilating area shall be [1] / 150 of the area of the vented space. Exception: The minimum net free ventilation area shall be [1] / 300 of the vented space provided both of the following conditions are met:
1. In Climate Zones 6, 7 and 8, a Class I or II vapor retarder is installed on the warm-in-winter side of the ceiling.
2. Not less than 40 percent and not more than 50 percent of the required ventilating area is provided by ventilators located in the upper portion of the attic or rafter space. Upper ventilators shall be located not more than 3 feet (914 mm) below the ridge or highest point of the space, measured vertically. The balance of the required ventilation provided shall be located in the bottom one-third of the attic space.
CWUIC § 25.4 Medium relevance — show source text
|17′-7″| |800S162-68|12′-10″|11′-6″|18′-6″|16′-7″|19′-11″|18′-11″| |1000S162-43|—|—|—|—|—|—| |1000S162-54|12′-10″|11′-7″|18′-5″|16′-6″|19′-8″|18′-8″| |1000S162-68|13′-8″|12′-3″|19′-8″|17′-9″|21′-1″|20′-1″| |1200S162-43|—|—|—|—|—|—| |1200S162-54|—|—|—|—|—|—| |1200S162-68|14′-5″|12′-11″|20′-9″|18′-7″|22′-0″|21′-0″| |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.
CWUIC § 2-1000 Medium relevance — show source text
|7′-10″|6′-10″|6′-1″|5′-6″|5′-0″|6′-11″|6′-1″|5′-5″|4′-11″|4′-6″| |2-1000S162-54|12′-3″|11′-5″|10′-9″|10′-2″|9′-6″|11′-6″|10′-9″|10′-1″|9′-5″|8′-9″| |2-1000S162-68|14′-5″|13′-5″|12′-8″|12′-0″|11′-6″|13′-6″|12′-8″|12′-0″|11′-5″|10′-10″| |2-1200S162-54|12′-11″|11′-3″|10′-0″|9′-0″|8′-2″|11′-5″|10′-0″|9′-0″|8′-1″|7′-4″| |2-1200S162-68|15′-11″|14′-10″|14′-0″|13′-4″|12′-8″|15′-0″|14′-0″|13′-3″|12′-7″|11′-11″| |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.
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 § 304.8 Medium relevance — show source text

or heavy timber, or fire-retardant-treated wooda, b|≥ 2 feet to < 5 feet| |Projections|Not fire-resistance rated|0 hours|≥ 5 feet| |Openings in
walls|Not allowed|NA|< 3 feet| |Openings in
walls|25% maximum of wall area|0 hours|3 feet| |Openings in
walls|Unlimited|0 hours|5 feet| |Penetrations|All|Comply with Section R302.4|< 3 feet| |Penetrations|All|None required|3 feet| |For SI: 1 foot = 304.8 mm.
NA = Not Applicable.
a. The fire-resistance rating shall be permitted to be reduced to 0 hours on the underside of the eave overhang if fireblocking is provided from the wall top plate to the underside
of the roof sheathing.
b. The fire-resistance rating shall be permitted to be reduced to 0 hours on the underside of the rake overhang where vent openings that communicate with the attic are not
installed in the overhang or gable wall.|For SI: 1 foot = 304.8 mm.
NA = Not Applicable.
a. The fire-resistance rating shall be permitted to be reduced to 0 hours on the underside of the eave overhang if fireblocking is provided from the wall top plate to the underside
of the roof sheathing.
b. The fire-resistance rating shall be permitted to be reduced to 0 hours on the underside of the rake overhang where vent openings that communicate with the attic are not
installed in the overhang or gable wall.|For SI: 1 foot = 304.8 mm.
NA = Not Applicable.
a. The fire-resistance rating shall be permitted to be reduced to 0 hours on the underside of the eave overhang if fireblocking is provided from the wall top plate to the underside
of the roof sheathing.
b. The fire-resistance rating shall be permitted to be reduced to 0 hours on the underside of the rake overhang where vent openings that communicate with the attic are not
installed in the overhang or gable wall.|For SI: 1 foot = 304.8 mm.
NA = Not Applicable.
a. The fire-resistance rating shall be permitted to be reduced to 0 hours on the underside of the eave overhang if fireblocking is provided from the wall top plate to the underside
of the roof sheathing.
b. The fire-resistance rating shall be permitted to be reduced to 0 hours on the underside of the rake overhang where vent openings that communicate with the attic are not
installed in the overhang or gable wall.|

TABLE R302.1(2)—EXTERIOR WALLS—DWELLINGS, TOWNHOUSES AND ACCESSORY BUILDINGS WITH AUTOMATIC RESIDENTIAL FIRE SPRINKLER PROTECTION	Col2	Col3	Col4
EXTERIOR WALL ELEMENT	EXTERIOR WALL ELEMENT	MINIMUM FIRE-RESISTANCE RATING	MINIMUM FIRE SEPARATION DISTANCE
Walls	Fire-resistance rated	1 hour—tested in accordance with ASTM E119, UL 263 or Section 703.2.

CWUIC § 1.5 Medium 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 § 504.9 Medium relevance — show source text
504.9 Exterior doors. Exterior doors shall be constructed in accordance with any of the following:

1. Noncombustible construction .

2. Solid-core wood not less than 1 [3] / 4 inches thick (44 mm) . 3. The exterior door shall be constructed of solid core wood that complies with the following requirements: 3.1. Stiles and rails shall not be less than 1 3/8 inches (35 mm) thick. 3.2. Raised panels shall not be less than 11/4 inches (32 mm) thick, except for the exterior perimeter of the raised panel that shall be permitted to taper to a tongue not less than 3/8 inch (10 mm) thick. 4. Have a fire protection rating of not less than 20 minutes when tested according to NFPA 252, UL 10B or UL 10C . 5. The exterior surface or cladding meeting the performance requirements of Section 504.9.3 when tested in accordance with ASTM E2707.

6. The exterior surface or cladding shall be tested to meet the performance requirements of SFM Standard 12-7A-1.

Windows within doors and glazed doors shall be in accordance with Section 504.8.

504.9.1 Garage doors. Automatic garage door openers for vehicle doors serving a residential building shall be equipped with a battery backup function.

504.9.2 Garage door perimeter gap. Exterior garage doors shall resist the intrusion of embers by preventing gaps between doors and door openings, at the bottom, sides and tops of doors, from exceeding [1] / 8 inch (3.2 mm). Gaps between doors and door openings shall be controlled by one or more of the following methods: 1. Weather-stripping products constructed of materials that which comply with both of the following: 1.1. The tensile strength of the material shall be tested in accordance with ASTM D638 before and after exposure to ASTM G155 for a period of 2,000 hours, and the maximum allowable difference in tensile strength values between exposed and nonexposed samples shall not exceed 10 percent. 1.2. When tested to UL 94, the materials shall have a flammability rating of V-2 or better. 2. Door overlaps onto jambs and headers. 3. Garage door jambs and headers covered with metal flashing.

504.9.3 Conditions of acceptance for ASTM E2707. The ASTM E2707 test shall be conducted on a minimum of three test specimens and meet the conditions of acceptance in Items 1 and 2. If any one of the three tests do not meet the conditions of acceptance, three additional tests shall be performed. All three additional tests must meet the conditions of acceptance. 1. Absence of flame penetration through the wall assembly at any time. 2. Absence of evidence of glowing combustion on the interior surface of the assembly at the end of the 70-minute test.

504.10 Vents. Where provided, ventilation openings for enclosed attics, gable ends, ridge ends, under eaves and cornices, enclosed eave soffit spaces, enclosed rafter spaces formed where ceilings are applied directly to the underside of roof rafters, underfloor venti

5-8 2025 CALIFORNIA WILDLAND-URBAN INTERFACE CODE

Frequently asked questions

Can I use a standard attic ridge vent if it's covered with 1/8" mesh?

Yes — if the vent installed on the sloped roof meets all three items in § 504.10.2: mesh no smaller than 1/16" and no larger than 1/8", the vent and mesh are noncombustible, and the materials are corrosion resistant.

Is a CSFM listing required for every vent?

No — the code offers two compliance paths. A CSFM‑listed WUI vent tested to ASTM E2886 satisfies § 504.10.1, or you may meet the off‑ridge/ridge construction requirements in § 504.10.2 for sloped‑roof vents. Choose one path and meet its full requirements.

Does the 662°F (350°C) limit apply to mesh vents under § 504.10.2?

No — the 662°F (350°C) unexposed‑side temperature limit is part of the ASTM E2886/listed‑vent acceptance criteria in § 504.10.1(3). The mesh‑size and material rules in § 504.10.2 do not include that temperature test.

If a product is labeled "ember resistant," is that enough?

Not by itself. For the ASTM E2886 path you need a California State Fire Marshal listing and the test acceptance results required by § 504.10.1. For off‑ridge/ridge venting, product labeling must match the mesh and material criteria in § 504.10.2.

Where can I confirm a vent product is listed?

Check the California State Fire Marshal product listings and the manufacturer’s test documentation confirming ASTM E2886 testing and the acceptance criteria required under § 504.10.1.

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How must enclosed and open eaves/soffits be protected?

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Eaves, Soffits, Gutters, Underfloor Protection and Vents

California Wildland-Urban Interface Code