CWUIC · California Wildland-Urban Interface Code

When does roof replacement or repair trigger ignition‑resistant requirements?

Q: How do I know whether my roof work will trigger the rule?

If the building is an existing structure and you will replace the roof covering or replace 50% or more of it in any 12‑month period , the rule in § 507.1 applies. Otherwise, ensure any portion installed during a repair or addition is at least Class A .

Q: Does the Code say how to measure the “50 percent” (area vs. cost)?

No — § 507.1 states the 50% / 12‑month threshold but does not define the method of measurement in the text provided. You must confirm with the authority having jurisdiction how they calculate percent replaced (the Code text available here does not specify).

Q: If I re‑cover only part of the roof now and finish later, can I avoid the requirement?

If the cumulative work reaches 50% or more within 12 months , the trigger applies and the replacement must comply with new‑construction roof covering requirements per § 507.1 . Plan repair phasing with your local code official if you are trying to avoid triggering the threshold.

Q: If only the underlayment or flashing is replaced, does that count toward 50%?

The Code language refers to roof covering replacement; § 507.1 does not detail whether underlayment or flashing alone count toward the 50% calculation. That level of interpretation is not in the retrieved text and should be clarified with the local code official.

If you replace a roof on a pre‑existing building or replace **50% or more of the roof covering in any 12‑month period**, the California Wildland‑Urban Interface Code requires the roof to be replaced to the same ignition‑resistant standard used for new construction (see **§ 507.1**), and any portion added or repaired during work must be **Class A** at minimum; confirm measurement details (how “50%” is calculated) with your local code official.

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Last reviewed: July 6, 2026

What the code requires — 2-4 sentences

When the roof covering on a building in existence before this Code is replaced or 50 percent or more replaced within a 12‑month period, the roof must be replaced with the roof covering required for new construction (i.e., ignition‑resistant materials and assemblies required for new buildings). This rule is stated in § 507.1 and directs compliance with the roof requirements for new construction in § 504.2 and § 504.2.1 . In addition, any portion of a roof covering installed as part of an addition, alteration, or repair to an existing structure must meet at least a Class A fire classification (also in § 507.1).

The single most important rule: if you replace a whole roof or 50% or more of the roof area within 12 months, the entire roof covering must meet the new‑construction ignition‑resistant roof requirements (see § 507.1).

Requirements in detail

Which buildings and work are affected

Existing buildings (those in existence prior to adoption of the Code): replacement or large repairs to the roof covering are covered by § 507.1.
New construction is already required to meet ignition‑resistant roof requirements per § 504.2 / § 504.2.1; when the threshold in § 507.1 is met for an existing building, the replacement roof must meet those new‑construction requirements.

Key thresholds and actions (decision table)

Decision dimension	Trigger / value	Required outcome	Code Reference
Building status	Existing building (built before Code adoption)	Apply § 507.1 test	§ 507.1
Extent of replacement	50 percent or more of the roof covering replaced within a 12‑month period	Entire roof must be replaced with roof covering required for new construction	§ 507.1
Time window	12‑month period	Used to measure the 50% replacement threshold	§ 507.1
Minimum classification for repairs/additions	Any roof portion applied during an addition/alteration/repair must be Class A at a minimum	Install materials/assemblies meeting Class A	§ 507.1
Standard to follow for replacement	Follow roof covering requirements for new construction (airspaces, underlayment, etc.)	See § 504.2 and § 504.2.1 for roof assembly and void requirements	§ 507.1 → § 504.2 / § 504.2.1

What “replace” and “portion applied” mean in the Code text

The Code uses the phrase “replaced or have 50 percent or more replaced in a 12‑month period” to establish the threshold; that phrase is the controlling trigger in § 507.1. The section also states “All portions of a roof covering applied during an addition, alteration or repair … shall meet at least a Class A fire classification.”

Exceptions & special cases

The text of § 507.1 itself contains no listed exceptions to the 50% / 12‑month rule; it simply mandates replacement to meet new‑construction roof requirements and the Class A minimum for portions applied during repairs.
The Code cross‑references the new‑construction roof requirements (for assembly, underlayment, and roof‑covering voids) in § 504.2 and § 504.2.1; any specific permitted alternatives or tested assemblies would be those allowed under those sections.
The Code extract available here does not define how to calculate “50 percent” (area, square footage, number of roof planes, or cost). The Code text in § 507.1 does not specify the calculation method — local code officials typically determine the measuring method or reference local guidance. The document provided does not include a rule for that calculation.

Common mistakes

Mistake: Assuming the rule applies only to complete tear‑offs. Reality: The trigger is extent of replacement (50% or more in 12 months), not whether the work is a full tear‑off or a partial; measure extent before deciding compliance. § 507.1 is explicit on the percent/time trigger.
Mistake: Believing a small patch or isolated repair is always exempt. Reality: Multiple repairs that cumulatively replace 50% or more within 12 months will trigger the new‑construction requirement. § 507.1.
Mistake: Using a non‑Class A product for a repair because “only a portion” is being replaced. Reality: All portions of a roof covering applied during an addition, alteration or repair must be at least Class A per § 507.1.
Mistake: Relying on cost of work instead of area to compute the 50% threshold. The Code text does not state whether percent is measured by area, cost, or another metric — that method is not specified in the retrieved text and should be verified with the authority having jurisdiction.

Worked example — concrete scenario

Scenario: A homeowner has a 2,000 ft² roof on a house that predates the CWUIC. Over 10 months the owner replaces roof covering on the south and west slopes totaling 1,100 ft².

Threshold test: 1,100 ft² replaced / 2,000 ft² = 55% replaced within 12 months → meets the 50 percent or more within a 12‑month period trigger. Result: The entire roof covering must be replaced with the roof covering required for new construction in accordance with § 504.2 and § 504.2.1. Also, the portions installed for the repairs/additions must be Class A at minimum as they were applied during repair/alteration. Code: § 507.1 (replacement threshold and Class A requirement) and follow § 504.2 / § 504.2.1 for the required assemblies.

If instead only 900 ft² (45%) were replaced in the same 12‑month period, the 50% trigger would not be met by the plain reading of § 507.1; however, the work performed during the repair would still have to meet the minimum Class A requirement for portions applied during the repair/addition.

Related provisions (CWUIC sections)

§ 507.1 — Replacement or repair threshold and Class A minimum (controlling)
§ 507 — Section heading and scope for Replacement or Repair of Roof Coverings (see section text and context)
§ 504.2 — Roof assembly requirements for ignition‑resistant construction (referenced by § 507.1)
§ 504.2.1 — Roof covering voids / specific roof covering provisions (referenced by § 507.1)
§ 503.2 / § 503.2.3 — Definitions and standards for ignition‑resistant building materials and fire‑retardant treated wood roof coverings (materials referenced by Chapter 5 requirements)
§ 504.3 — Protection of enclosed and open eaves (related roof detail requirements)

Code references

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

CWUIC § 504.11.3 High relevance — show source text
504.11.3 Accessory buildings greater than 120 square feet, located 3 feet or more but less than 50 feet. Accessory buildings that are greater than 120 square feet (11.15 m2) in size and separated from an applicable building on the same lot by a distance of 3 feet (914 mm) or more but less than 50 feet (15 240 mm) shall be constructed of noncombustible materials or of ignition-resistant building materials as described in Section 503.2.4.

504.11.4 Accessory buildings 120 square feet or less, located 3 feet or more but less than 50 feet. Where required by the code offi- cial, accessory buildings 120 square feet (11.15 m2) or less and separated from an applicable building on the same lot by a distance of 3 feet (914 mm) or more but less than 50 feet (15 240 mm) shall be constructed of noncombustible materials or of ignition-resistant building materials as described in Section 503.2.4.

504.11.5 Miscellaneous structures located 3 feet or more but less than 50 feet. Where required by the code official, miscellaneous structures that require a permit and are separated from an applicable building on the same lot by a distance of 3 feet (914 mm) or more but less than 50 feet (15 240 mm) shall be constructed of noncombustible materials or of ignition-resistant building materials as described in Section 503.2.4.

504.11.6 Roof construction. Roof assemblies and roof coverings of accessory buildings required to be constructed entirely of noncombustible materials or of ignition-resistant building materials shall comply with Sections 504.2 and 504.2.1. Roofs shall have a roofing assembly installed in accordance with its listing and the manufacturer’s installation instructions. Roof assemblies in Fire Hazard Severity Zones shall comply with a Class A fire classification when tested in accordance with ASTM E108 or UL 790.

SECTION 505— RESERVED

SECTION 506— RESERVED

SECTION 507—REPLACEMENT OR REPAIR OF ROOF COVERINGS

507.1 General. The roof covering on buildings or structures in existence prior to the adoption of this code that are replaced or have 50 percent or more replaced in a 12-month period shall be replaced with a roof covering required for new construction in accordance with Sections 504.2 and 504.2.1. All portions of a roof covering applied during an addition, alteration or repair to an existing structure shall meet at least a Class A fire classification.

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CALIFORNIA WILDLAND-URBAN INTERFACE CODE – MATRIX ADOPTION TABLE

CHAPTER 6 – FIRE PROTECTION REQUIREMENTS

(Matrix Adoption Tables are nonregulatory, intended only as an aid to the code user. See Chapter 1 for state agency authority and building applications.)
CWUIC § 3-3 High relevance — show source text
301 General . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .3-3

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

CHAPTER 4 WILDLAND-URBAN INTERFACE AREA

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

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

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

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

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

CHAPTER 5 SPECIAL BUILDING CONSTRUCTION

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

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

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

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

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

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

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

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

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

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

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

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

604 Maintenance of Defensible Space . . . . . . . . . . . . . . . 6-5
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 § 5-3 Medium relevance — show source text
502 Reserved . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .5-3

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

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

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

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

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

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

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

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

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

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

605 Spark Arrestors. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6-5

606 Liquefied Petroleum Gas Installations . . . . . . . . . . . 6-5

607 Storage of Firewood and Combustible Materials . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6-5

608 Building Siting and Setbacks . . . . . . . . . . . . . . . . . . . . 6-5

609 Ridgelines, Fuel Breaks and Greenbelts . . . . . . . . . . . 6-6

610 Fire Safe Development Regulations . . . . . . . . . . . . . . 6-7

611 Subdivision Review Survey . . . . . . . . . . . . . . . . . . . . . . 6-7

612 General Plan Safety Element . . . . . . . . . . . . . . . . . . . . 6-7

CHAPTER 7 REFERENCED STANDARDS . . . . . . . . . . . . . .7-3

APPENDIX A GENERAL REQUIREMENTS . . . . APPENDIX A-3

A101 General. . . . . . . . . . . . . . . . . . . . . . . . . . . . . APPENDIX A-3

A102 Vegetation Control. . . . . . . . . . . . . . . . . . . APPENDIX A-3

CWUIC § 507.1 Medium relevance — show source text

SECTION 505— RESERVED

SECTION 506— RESERVED

SECTION 507—REPLACEMENT OR REPAIR OF ROOF COVERINGS

507.1 General. The roof covering on buildings or structures in existence prior to the adoption of this code that are replaced or have 50 percent or more replaced in a 12-month period shall be replaced with a roof covering required for new construction in accordance with Sections 504.2 and 504.2.1. All portions of a roof covering applied during an addition, alteration or repair to an existing structure shall meet at least a Class A fire classification.

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CALIFORNIA WILDLAND-URBAN INTERFACE CODE – MATRIX ADOPTION TABLE

CHAPTER 6 – FIRE PROTECTION REQUIREMENTS

(Matrix Adoption Tables are nonregulatory, intended only as an aid to the code user. See Chapter 1 for state agency authority and building applications.)

Adopting Agency	BSC	BSC- CG	SFM	Col5	HCD	Col7	Col8	DSA	Col10	OSHPD	Col12	Col13	Col14	Col15	Col16	BSCC	DPH	AGR	DWR	CEC	CA	SL	SLC
Adopting Agency	BSC	BSC- CG	T-24	T-19*	1	2	1/AC	AC	SS	1	1R	2	3	4	5	5	5	5	5	5	5	5	5
Adopt Entire Chapter
Adopt Entire Chapter as amended (amended sections listed below)			X
Adopt only those sections that are listed below
[California Code of Regulations, Title 19, Division 1]
Chapter / Section
601.1			X
601.2			X
601.3			X
602.1 –602.3.2			X
603.1 –603.4.2.1			X
604.1			X
604.2 –604.4			X
606.1			X
606.3			X
607.

CWUIC § 504.3 Medium relevance — show source text
504.3 Protection of enclosed eaves. The exposed underside of enclosed roof eaves and soffits shall be protected on the exposed underside by one or more of the following:

1. Noncombustible materials.

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

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

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

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

1. Noncombustible material.

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

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

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

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SPECIAL BUILDING CONSTRUCTION REGULATIONS

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

CWUIC § 503.1 Medium relevance — show source text

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

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APPENDIX H—REFERENCED CALIFORNIA DOCUMENTS

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

CWUIC § 4902.1 Medium relevance — show source text

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

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APPENDIX H—REFERENCED CALIFORNIA DOCUMENTS

2025 CWUIC—continued	Col2	Adopted Yes/No	IWUIC Section	CBC Section	CFC Section	Title 14, Division 1.5 Section	Title 19, Division 1 Section	Gov Code Section	PRC Section	HSC Section
Section	Title	Title	Title	Title	Title	Title	Title	Title	Title	Title
Chapter 2	Definitions	Definitions	Definitions	Definitions	Definitions	Definitions	Definitions	Definitions	Definitions	Definitions
	Multilayered glazed panels	Y
	Noncombustible roof covering	Y
	Outbuilding (T14)	Y				1299.02(c)
	Peer review	Y
	Rafter tail	Y		702A
	Registered design professional	Y
	Residential unit (T14)	Y				1270.01(w)
	Ridgeline (topography) (T14)	Y				1270.01(x)
	Road (T14)	Y				1270.

CWUIC § 1.5 Medium relevance — show source text

2025 CALIFORNIA WILDLAND-URBAN INTERFACE CODE APPENDIX H-29

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APPENDIX H—REFERENCED CALIFORNIA DOCUMENTS

2025 CWUIC—continued	Col2	Adopted Yes/No	IWUIC Section	CBC Section	CFC Section	Title 14, Division 1.5 Section	Title 19, Division 1 Section	Gov Code Section	PRC Section	HSC Section
Section	Title	Title	Title	Title	Title	Title	Title	Title	Title	Title
Chapter 5	Special building construction regulations	Special building construction regulations	Special building construction regulations	Special building construction regulations	Special building construction regulations	Special building construction regulations	Special building construction regulations	Special building construction regulations	Special building construction regulations	Special building construction regulations
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 § 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 § 0.125 Medium relevance — show source text
Exception: Materials having a structural base of noncombustible material as determined in accordance with ASTM E136, or with ASTM E2652 using the acceptance criteria prescribed by ASTM E136, and a surfacing of not more than 0.125 inch (3.18 mm) in thick- ness having a flame spread index not greater than 50 when tested in accordance with ASTM E84 or UL 723 shall be acceptable as noncombustible.

SECTION 502— RESERVED

SECTION 503—IGNITION-RESISTANT CONSTRUCTION AND MATERIAL

503.1 General. Buildings and structures hereafter constructed, modified or relocated into or within wildland-urban interface areas shall meet the construction requirements in accordance with Chapter 5 . Materials required to be ignition-resistant building materials shall comply with the requirements of Section 503.2.

Exceptions:

1. New accessory buildings and miscellaneous structures complying with Section 504.11. 2. Additions to and remodels of buildings originally constructed prior to July 1, 2008. 3. Group C occupancy special buildings conforming to the limitations specified in Section 450.4.1 of the California Building Code.

503.2 Ignition-resistant building material. Ignition-resistant building materials shall be designed for exterior use and weather expo- sure and shall comply with any one of the requirements in Section 503.2.1 through 503.2.4.3.3 .

503.2.1 Noncombustible material. Noncombustible material shall comply with the requirements in Section 501.4 .

2025 CALIFORNIA WILDLAND-URBAN INTERFACE CODE 5-3

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

SPECIAL BUILDING CONSTRUCTION REGULATIONS

503.2.2 Fire-retardant-treated wood. Fire-retardant-treated wood shall be identified for exterior use and shall meet the requirements of Section 2303.2 of the California Building Code .

503.2.3 Fire-retardant-treated wood roof coverings. Roof assemblies containing fire-retardant-treated wood shingles and shakes shall comply with the requirements of Section 1505.6 of the California Building Code and shall be classified as Class A roof assemblies as required in Section 1505.2 of the California Building Code .

503.2.4 Other ignition-resistant building material. Material shall be tested on the front and back faces in accordance with the extended ASTM E84 or UL 723 test, for a total test period of 30 minutes, or with the ASTM E2768 test. The materials shall bear identification showing the fire test results. Panel products shall be tested with a ripped or cut longitudinal gap of [1] / 8 inch (3.2 mm). The materials, when tested in accordance with the test procedures set forth in ASTM E84 or UL 723 for a test period of 30 minutes, or with ASTM E2768, shall comply with Sections 503.2.4.1 through 503.2.4.3.

Exception: Materials composed of a combustible core and a noncombustible exterior covering made from either aluminum at a minimum 0.019 inch (0.48 mm) thickness or corrosion-resistant steel at a minimum 0.0149 inch (0.38 mm) thickness shall not be required to be tested with a ripped or cut longitudinal gap.

CWUIC § 0.099 Medium relevance — show source text

3(1)—continued	Col2	Col3	Col4
NOMINAL MATE- RIAL THICKNESS (inches)	DESCRIPTIONa, b OF FASTENER AND LENGTH (inches)	SPACINGc OF FASTENERS	SPACINGc OF FASTENERS
NOMINAL MATE- RIAL THICKNESS (inches)	DESCRIPTIONa, b OF FASTENER AND LENGTH (inches)	Edges (inches)	Body of paneld (inches)
Floor underlayment; plywood-hardboard-particleboardf-fiber-cementh	Floor underlayment; plywood-hardboard-particleboardf-fiber-cementh	Floor underlayment; plywood-hardboard-particleboardf-fiber-cementh	Floor underlayment; plywood-hardboard-particleboardf-fiber-cementh
Fiber-cement	Fiber-cement	Fiber-cement	Fiber-cement
1/4	11/4 long × 0.099″ corrosion-resistant, ring shank nails (finished flooring other than tile)	3	6
1/4	Staple 18 ga.7/8 long,1/4 crown (finished flooring other than tile)	3	6
1/4	11/4 long × .121 shank × .375 head diameter corrosion-resistant (galvanized or stainless steel) roofing nails (for tile finish)	8	8
1/4	11/4 long, No. 8 × .375 head diameter, ribbed wafer-head screws (for tile finish)	8	8
Plywood	Plywood	Plywood	Plywood
1/4 and5/16	11/4 ring or screw shank nail-minimum 121/2 ga. (0.099″) shank diameter	3	6
1/4 and5/16	Staple 18 ga.,7/8, 3/16 crown width	2	5
11/32, 3/8, 15/32 and1/2	11/4 ring or screw shank nail-minimum 121/2 ga. (0.099″) shank diameter	6	8e
19/32, 5/8, 23/32 and3/4	11/2 ring or screw shank nail-minimum 121/2 ga. (0.099″) shank diameter	6	8
19/32, 5/8, 23/32 and3/4	Staple 16 ga.

Frequently asked questions

How do I know whether my roof work will trigger the rule?

If the building is an existing structure and you will replace the roof covering or replace 50% or more of it in any 12‑month period, the rule in § 507.1 applies. Otherwise, ensure any portion installed during a repair or addition is at least Class A.

Does the Code say how to measure the “50 percent” (area vs. cost)?

No — § 507.1 states the 50% / 12‑month threshold but does not define the method of measurement in the text provided. You must confirm with the authority having jurisdiction how they calculate percent replaced (the Code text available here does not specify).

If I re‑cover only part of the roof now and finish later, can I avoid the requirement?

If the cumulative work reaches 50% or more within 12 months, the trigger applies and the replacement must comply with new‑construction roof covering requirements per § 507.1. Plan repair phasing with your local code official if you are trying to avoid triggering the threshold.

If only the underlayment or flashing is replaced, does that count toward 50%?

The Code language refers to roof covering replacement; § 507.1 does not detail whether underlayment or flashing alone count toward the 50% calculation. That level of interpretation is not in the retrieved text and should be clarified with the local code official.

What classification is required for portions applied during an addition or repair?

Any portion of roof covering installed during an addition, alteration, or repair must meet at least a Class A fire classification, per § 507.1.

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