CRC · California Residential Code
When does flood‑resistant construction apply and what sections govern it?
If any part of a residence is in a mapped flood hazard area, CRC **§ R306** requires using the design flood elevation to set elevation, foundation, opening, materials and equipment protection rules; coastal/V‑zone sites and floodways have stricter rules and ASCE 24 applies in certain cases; the text for **§ R301.6** (deflection) was referenced in the CRC index but its full wording was not available in the retrieved files. file
Last reviewed: July 6, 2026
What the code requires — 2–4 sentences
Buildings and structures located in whole or in part in flood hazard areas must be designed and built to resist flood damage in accordance with § R306 of the California Residential Code (CRC) . The CRC uses the design flood elevation (the higher of the base‑flood elevation or a legally adopted local design flood) to define flood hazard areas and set elevation/protection requirements . Where applicable, coastal high‑hazard and V/Coastal A Zones have additional rules (see § R306.3) and buildings in floodways must meet ASCE 24 . The user‑requested structural deflection provision, § R301.6, was referenced in the CRC index but the full text for § R301.6 was not included in the retrieved files, so that specific text could not be quoted here .
The single most important rule: if any part of a building is in a mapped flood hazard area, the structure and any substantial improvements must meet the elevation, materials and anchoring requirements in § R306 (use the design flood elevation to determine those requirements) .
Requirements in detail
Scope / triggers
- Applies to:
- New buildings and structures constructed in whole or in part in flood hazard areas established by Table R301.2 (CRC) — see § R306.1 .
- Substantial improvement or repair of substantial damage for buildings located in whole or in part in flood hazard areas — see § R306.1 .
- If a building lies in multiple flood zones, it must comply with the provisions for the most restrictive zone (A, Coastal A, V zones) — § R306.1 .
- Design of structures in identified floodways must comply with ASCE 24 (per § R306.1 and related notes) .
Key defined terms (first mention bolded)
- Design flood elevation — the elevation used to define flood hazard areas; at minimum the higher of: (1) the base flood elevation for the 1‑percent (100‑year) event (including wave height), or (2) the elevation specified on an adopted flood hazard map — § R306.1.4 .
- Lowest floor — the lowest floor of the lowest enclosed area (including basement) but excluding certain unfinished flood‑resistant enclosures used only for parking, access or limited storage (if those enclosures meet the section’s limits) — § R306.1.5 .
What you must do (high‑level)
- Determine whether the site is in a FEMA/locally adopted flood hazard area (Table R301.2 / community maps) and establish the design flood elevation — § R306.1.4 .
- Elevate the building or design floodproofing/structural resistance per the zone‑specific rules in § R306.2 (general A zones) and § R306.3 (coastal high‑hazard / V and Coastal A zones) .
- Protect or locate mechanical, plumbing and electrical systems at or above the required elevation (or design them to ASCE 24 criteria) — § R306.1.6 .
- Use flood‑damage‑resistant materials below the required elevation — § R306.1.8 .
- Provide required documentation (as‑built elevations sealed by an RDP) and inspection submittals (elevation verification at placement of lowest floor) — § R306.1.10 and § R109.1.3 file.
Decision‑relevant dimensions / values (table)
| Decision question | Key value / threshold | Code Reference |
|---|---|---|
| What defines the hazard area? | Use the design flood elevation (higher of base‑flood or adopted design flood) | § R306.1.4 |
| Maximum allowed increase in design flood elevation from a project in riverine areas (when no floodway designated) | 1 foot (305 mm) maximum cumulative increase | § R306.1.4.2 |
| Elevation requirement for coastal high‑hazard / V & Coastal A zones | Bottom of lowest horizontal structural member (except piling, pile caps, columns, grade beams and bracing) elevated to base flood elevation + 1 foot (305 mm) or the design flood elevation, whichever is higher | § R306.3.2(1) |
| How to treat enclosed areas below the required elevation | Enclosed areas below required elevation permitted only for vehicle parking, access or storage and must meet breakaway/opening rules or be constructed per ASCE 24 | § R306.2 and § R306.3.6 file |
| Flood openings (automatic) for enclosed areas | Bottom of each opening ≤ 1 foot (305 mm) above the higher of final interior floor grade or finished exterior grade under the opening; at least two openings on different sides of each enclosed area | § R306.2.2.1 |
| Protection of services (electrical/HVAC/plumbing) | Locate at or above elevation required in § R306.2 or § R306.3, or design per ASCE 24 to resist flood effects | § R306.1.6 |
| Definition of lowest floor for elevation measurement | Lowest floor includes basement and lowest enclosed area but excludes certain unfinished flood‑resistant enclosures used only for parking, access or storage (if compliant) | § R306.1.5 |
| Reference for foundation and anchoring in flood hazard areas | Foundations must meet Chapter 4 and flood provisions in § R306.2.3; floodway designs require ASCE 24 | § R401.1 and § R306.2.3 file |
| Note about structural deflection requirement (user‑requested § R301.6) | Full text for § R301.6 was not present in retrieved CRC excerpts; the index shows the entry Deflection R301.6 but the section text could not be located in the provided files |
Construction details (high level)
- Breakaway walls, vents/openings and foundation design rules for enclosed areas are set out in § R306.2 (A zones) and § R306.3.5 (coastal systems) — use the table above for openings limits and expected uses file.
- Coastal high‑hazard areas require elevating structural members above wave runup and may prohibit stem wall/enclosed foundations except where specifically allowed — see § R306.3.2 and related subsections .
- Documentation and RDP sealings are required for elevations in § R306.1.10 and construction documents per § R306.3.9 file.
Exceptions & special cases
- Alternative compliance: ASCE 24 is permitted as an alternative to the prescriptive CRC flood requirements where appropriate — § R306.1.1 .
- If design flood elevations are not specified on maps, the building official may require the applicant to use available federal/state data or obtain a registered design professional’s hydrologic/hydraulic study — § R306.1.4.1 .
- In riverine areas without designated floodways, applicants must demonstrate their development will not increase the design flood elevation by more than 1 foot (305 mm) — § R306.1.4.2 .
- Exception for locating equipment below required elevation is allowed only if systems are designed to prevent water entry/accumulation and meet ASCE 24 criteria; electrical wiring may be allowed below if compliant with the California Electrical Code for wet locations — § R306.1.6 .
- Manufactured‑home specific language in Appendix G (Building Code) applies for manufactured homes; note the CRC text marks manufactured‑home provisions “not adopted in CA” in § R306.1.9 — § R306.1.9 and Appendix G references file.
Common mistakes
- Treating the FEMA FIRM zone alone as sufficient — you must use the design flood elevation (higher of mapped base flood or locally adopted design flood) as required in § R306.1.4 .
- Measuring elevation to the wrong datum or to the bottom of a breakaway wall rather than the lowest floor; use the definition in § R306.1.5 and provide RDP‑sealed as‑built elevations per § R306.1.10 and § R109.1.3 file.
- Installing mechanical/electrical equipment below required elevation without ASCE 24 design or proper wet‑location provisions — § R306.1.6 explains the limited exception and ASCE 24 requirements .
- Confusing “enclosed area” permitted uses — enclosed spaces below required elevation are limited to vehicle parking, access or limited storage and must meet opening/breakaway rules — § R306.3.6 and § R306.2 file.
Worked example — concrete scenario with numbers
Scenario: New single‑family home on a lot mapped as Zone AE (riverine) with a community base flood elevation (BFE) of +8.0 ft NAVD. The community also has a locally adopted design flood elevation of +9.0 ft NAVD at this site.
- Determine the design flood elevation: higher of BFE (+8.0 ft) and locally adopted (+9.0 ft) → +9.0 ft NAVD (per § R306.1.4) .
- Lowest floor elevation requirement:
- If in a standard A zone (not coastal high‑hazard), elevate the lowest floor to at or above the design flood elevation → lowest floor ≥ +9.0 ft NAVD (see § R306.2 and definition § R306.1.5) file.
- If the lot were in a Coastal A or V zone with required freeboard, you might need design flood elevation + 1 ft (coastal rule) — e.g., bottom of lowest horizontal member ≥ +10.0 ft NAVD — per § R306.3.2 for coastal high‑hazard areas .
- Mechanical and electrical equipment must be at or above +9.0 ft NAVD unless designed per ASCE 24 (see § R306.1.6) .
- At placement of the lowest floor (including basement, if any) the building official will require an RDP‑sealed elevation certificate documenting that the lowest floor meets the required elevation — § R109.1.3 and § R306.1.10 file.
This concrete set of steps follows the procedural and measurement requirements in § R306 (and inspection submittals in § R109.1.3) file.
Related provisions
- § R306.1 — General scope and application (flood hazard areas, ASCE 24 reference)
- § R306.1.4 / R306.1.4.1 / R306.1.4.2 — Design flood elevation and determination; 1‑foot cumulative increase limit in riverine areas file
- § R306.1.5 — Definition of lowest floor
- § R306.1.6 — Protection/placement of mechanical, plumbing and electrical systems
- § R306.2 — General A‑zone requirements, openings and foundations (including opening height ≤ 1 ft above grade)
- § R306.3 — Coastal high‑hazard (V) and Coastal A Zone special requirements (elevation + freeboard, breakaway, etc.)
- § R306.3.9 — Construction documents and RDP documentation requirements
- § R109.1.3 — Floodplain inspection and elevation verification at placement of lowest floor
- ASCE 24 — referenced as the alternative/required standard for floodway and some coastal designs (see § R306.1.1 and related CRC references) file
Note about § R301.6: the CRC index shows the entry Deflection R301.6, but the actual text for § R301.6 was not available in the retrieved CRC excerpts. I could not locate or quote the provision text for § R301.6 in the provided files; if you need R301.6’s exact wording or how deflection limits interact with flood loads, I can retrieve that section if you upload the relevant CRC pages or allow me to search additional files .
Code references
Grounded in the retrieved California Residential Code — click a citation to read the verbatim passage:
CRC § 3-35 High relevance — show source text
Exceptions:
Buildings where the structural members of walls, floors, ceilings and roofs are entirely of noncombustible materials or pressure-preservative-treated wood.
Where in addition to the requirements of Section R305.1, an approved method of protecting the foam plastic and structure from subterranean termite damage is used.
On the interior side of basement walls.
2025 CALIFORNIA RESIDENTIAL CODE 3-35
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BUILDING PLANNING
FIGURE R305.4—TERMITE INFESTATION PROBABILITY MAP
Note: Lines defining areas are approximate only. Local conditions may be more or less severe than indicated by the region classification.
SECTION R306—FLOOD-RESISTANT CONSTRUCTION
R306.1 General. Buildings and structures constructed in whole or in part in flood hazard areas established in Table R301.2, and substantial improvement and repair of substantial damage of buildings and structures located in whole or in part in flood hazard areas, shall be designed and constructed in accordance with the provisions contained in this section. Buildings and structures that are located in more than one flood hazard area, including A Zones, Coastal A Zones and V Zones, shall comply with the provisions associated with the most restrictive flood hazard area. Buildings and structures located in whole or in part in identified floodways shall be designed and constructed in accordance with ASCE 24.
R306.1.1 Alternative provisions. As an alternative to the requirements in Section R306, ASCE 24 is permitted subject to the limitations of this code and the limitations therein.
R306.1.2 Structural systems. Structural systems of buildings and structures shall be designed, connected and anchored to resist flotation, collapse or permanent lateral movement due to structural loads and stresses from flooding equal to the design flood elevation.
R306.1.3 Flood-resistant construction. Buildings and structures erected in areas prone to flooding shall be constructed by methods and practices that minimize flood damage.
R306.1.4 Establishing the design flood elevation. The design flood elevation shall be used to define flood hazard areas. At a minimum, the design flood elevation shall be the higher of the following:
- The base flood elevation at the depth of peak elevation of flooding, including wave height, that has a 1-percent (100-year flood) or greater chance of being equaled or exceeded in any given year.
- The elevation of the design flood associated with the area designated on a flood hazard map adopted by the community, or otherwise legally designated.
R306.1.4.1 Determination of design flood elevations. If design flood elevations are not specified, the building official is authorized to require the applicant to comply with either of the following:
- Obtain and reasonably use data available from a federal, state or other source.
- Determine the design flood elevation in accordance with accepted hydrologic and hydraulic engineering practices used to define special flood hazard areas. Determinations shall be undertaken by a registered design professional who shall document that the technical methods used reflect currently accepted engineering practice. Studies, analyses and computations shall be submitted in sufficient detail to allow thorough review and approval.
CRC § 1.1 High relevance — show source text
R306.1.1 Alternative provisions. As an alternative to the requirements in Section R306, ASCE 24 is permitted subject to the limitations of this code and the limitations therein.
R306.1.2 Structural systems. Structural systems of buildings and structures shall be designed, connected and anchored to resist flotation, collapse or permanent lateral movement due to structural loads and stresses from flooding equal to the design flood elevation.
R306.1.3 Flood-resistant construction. Buildings and structures erected in areas prone to flooding shall be constructed by methods and practices that minimize flood damage.
R306.1.4 Establishing the design flood elevation. The design flood elevation shall be used to define flood hazard areas. At a minimum, the design flood elevation shall be the higher of the following:
- The base flood elevation at the depth of peak elevation of flooding, including wave height, that has a 1-percent (100-year flood) or greater chance of being equaled or exceeded in any given year.
- The elevation of the design flood associated with the area designated on a flood hazard map adopted by the community, or otherwise legally designated.
R306.1.4.1 Determination of design flood elevations. If design flood elevations are not specified, the building official is authorized to require the applicant to comply with either of the following:
- Obtain and reasonably use data available from a federal, state or other source.
- Determine the design flood elevation in accordance with accepted hydrologic and hydraulic engineering practices used to define special flood hazard areas. Determinations shall be undertaken by a registered design professional who shall document that the technical methods used reflect currently accepted engineering practice. Studies, analyses and computations shall be submitted in sufficient detail to allow thorough review and approval.
R306.1.4.2 Determination of impacts. In riverine flood hazard areas where design flood elevations are specified but floodways have not been designated, the applicant shall demonstrate that the effect of the proposed buildings and structures on design flood elevations, including fill, when combined with other existing and anticipated flood hazard area encroachments, will not increase the design flood elevation more than 1 foot (305 mm) at any point within the jurisdiction.
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BUILDING PLANNING
R306.1.5 Lowest floor. The lowest floor shall be the lowest floor of the lowest enclosed area, including basement, and excluding any unfinished flood-resistant enclosure that is useable solely for vehicle parking, building access or limited storage provided that such enclosure is not built so as to render the building or structure in violation of this section.
R306.1.6 Protection of mechanical, plumbing and electrical systems. Electrical systems, equipment and components; heating, ventilating, air-conditioning; plumbing appliances and plumbing fixtures; duct systems; and other service equipment shall be located at or above the elevation required in Section R306.2 or R306.3. If replaced as part of a substantial improvement, electrical systems, equipment and components; heating, ventilating, air-conditioning and plumbing appliances and plumbing fixtures; duct systems; and other service equipment shall meet the requirements of this section. Systems, fixtures, and equipment and components shall not be mounted on or penetrate through walls intended to break away under flood loads.
CRC § 304.3.1 High relevance — show source text
Exceptions:
- Buildings of Group R occupancy with not more than five dwelling or sleeping units used solely for residential purposes where the existing building and the addition comply with the conventional light-frame construction methods of the Cali- fornia Building Code or the provisions of the California Residential Code .
- Any existing lateral load-carrying structural element whose demand-capacity ratio with the addition considered is not more than 10 percent greater than its demand-capacity ratio with the addition ignored shall be permitted to remain unaltered. For purposes of calculating demand-capacity ratios, the demand shall consider applicable load combinations with design lateral loads or forces in accordance with Section 1609 of the California Building Code and Section 304.3.1 of this code . For purposes of this exception, comparisons of demand-capacity ratios and calculation of design lateral loads, forces and capacities shall account for the cumulative effects of additions and alterations since original construction.
When calculating demand-capacity ratios for wind, the date of original construction shall be permitted to be taken as the date of completion of a prior addition, alteration or repair in compliance with Section 1609 of the California Building Code or the code wind forces in effect at the time. When calculating demand-capacity ratios for earthquake, the date of original construction shall be permitted to be taken as the date of completion of a prior addition, alteration or repair in compliance with Section 304.3.1 or the full seismic forces in effect at the time.
[BS] 1103.3 Flood hazard areas. Additions and foundations in flood hazard areas shall comply with the following requirements:
- For horizontal additions that are structurally interconnected to the existing building: 1.1. If the addition and all other proposed work, when combined, constitute substantial improvement, the existing building and the addition shall comply with Section 1612 of the California Building Code, or Section R306 of the California Residential Code, as applicable. 1.2. If the addition constitutes substantial improvement, the existing building and the addition shall comply with Section 1612 of the California Building Code, or Section R306 of the California Residential Code, as applicable. 1.3. If the addition does not constitute substantial improvement, the addition is not required to comply with the flood design requirements for new construction, provided that both of the following apply: 1.3.1. The addition shall not create or extend any nonconformity of the existing building with the flood-resistant construction requirements. 1.3.2. The lowest floor of the addition shall be at or above the lower of the lowest floor of the existing building or the lowest floor elevation required in Section 1612 of the California Building Code, or Section R306 of the California Residential Code, as applicable.
- For horizontal additions that are not structurally interconnected to the existing building: 2.1. The addition shall comply with Section 1612 of the California Building Code, or Section R306 of the California Resi- dential Code, as applicable. 2.2. If the addition and all other proposed work, when combined, constitute substantial improvement, the existing building and the addition shall comply with Section 1612 of the California Building Code, or Section R306 of the California Residential Code, as applicable.
- For vertical additions and all other proposed work that, when combined, constitute substantial improvement, the existing building shall comply with Section 1612 of the California Building Code, or Section R306 of the California Residential Code, as applicable.
CRC § 1612.3 High relevance — show source text
For buildings and structures in flood hazard areas established in Section 1612.3 of the California Building Code, or Section R322 of the California Residential Code, as applicable, any additions that do not constitute substantial improvement of the existing structure are not required to comply with the flood design requirements for new construction, provided that both of the following apply:
- The addition shall not create or extend a nonconformity of the existing building or structure with the flood-resistant construction requirements.
- The lowest floor of the addition shall be at or above the lower of the lowest floor of the existing building or structure or the lowest floor elevation required in Section 1612 of the California Building Code or Section R306 of the California Residential Code, as applicable.
[BS] 502.3 Existing structural elements carrying gravity load. Any existing gravity load-carrying structural element for which an addition and its related alterations cause an increase in design dead, live or snow load, including snow drift effects, of more than 5 percent shall be replaced or altered as needed to carry the gravity loads required by the California Building Code for new structures. Any existing gravity load-carrying structural element whose vertical load-carrying capacity is decreased as part of the addition and its related alterations shall be considered to be an altered element subject to the requirements of Section 503.3. Any existing element that will form part of the lateral load path for any part of the addition shall be considered to be an existing lateral load-carrying structural element subject to the requirements of Section 502.3.
Exception: Buildings of Group R occupancy with not more than five dwelling or sleeping units used solely for residential purposes where the existing building and the addition together comply with the conventional light-frame construction methods of the Cali- fornia Building Code or the provisions of the California Residential Code .
[BS] 502.4 Existing structural elements carrying lateral load. Where the addition is structurally independent of the existing structure, existing lateral load-carrying structural elements shall be permitted to remain unaltered. Where the addition is not structurally independent of the existing structure, the lateral force-resisting system of the existing structure and its addition acting together as a single structure shall comply with Section 1609 of the California Building Code and with Section 304.3.1 of this code.
Exceptions:
- Any existing lateral load-carrying structural element whose demand-capacity ratio with the addition considered is not more than 10 percent greater than its demand-capacity ratio with the addition ignored shall be permitted to remain unaltered. For purposes of calculating demand-capacity ratios, the demand shall consider applicable load combinations with design lateral loads or forces in accordance with Sections 1609 and 1613 of the California Building Code . For purposes of this exception, comparisons of demand-capacity ratios and calculation of design lateral loads, forces and capacities shall account for the cumulative effects of additions and alterations since original construction. When calcu
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PRESCRIPTIVE COMPLIANCE METHOD
CRC § G109 High relevance — show source text
G108.4 Water facilities. All new or replacement water facilities shall be designed in accordance with the provisions of Chapter 7, ASCE 24, to minimize or eliminate infiltration of floodwaters into the systems.
G108.5 Storm drainage. Storm drainage shall be designed to convey the flow of surface waters to minimize or eliminate damage to persons or property.
G108.6 Streets and sidewalks. Streets and sidewalks shall be designed to minimize potential for increasing or aggravating flood levels.
SECTION G109—MANUFACTURED HOMES
G109.1 Elevation. All new and replacement manufactured homes to be placed or substantially improved in a flood hazard area shall be elevated such that the top of the foundation for the manufactured home is at or above the design flood elevation.
G109.2 Foundations. All new and replacement manufactured homes, including substantial improvement of existing manufactured homes, shall be placed on a permanent, reinforced foundation that is designed in accordance with Section R306 of the California Residential Code .
G109.3 Anchoring. All new and replacement manufactured homes to be placed or substantially improved in a flood hazard area shall be installed using methods and practices that minimize flood damage. Manufactured homes shall be securely anchored to an adequately anchored foundation system to resist flotation, collapse and lateral movement. Methods of anchoring are authorized to include, but are not limited to, use of over-the-top or frame ties to ground anchors. This requirement is in addition to applicable state and local anchoring requirements for resisting wind forces.
G109.4 Protection of mechanical equipment and outside appliances. Mechanical equipment and outside appliances shall be elevated to or above the design flood elevation.
Exception: Where such equipment and appliances are designed and installed to prevent water from entering or accumulating within their components and the systems are constructed to resist hydrostatic and hydrodynamic loads and stresses, including the effects of buoyancy, during the occurrence of flooding up to the elevation required by Section R306 of the California Residen- tial Code, the systems and equipment shall be permitted to be located below the elevation required by Section R306 of the California Residential Code . Electrical wiring systems shall be permitted below the design flood elevation provided that they conform to the provisions of the California Electrical Code.
G109.5 Enclosures. Fully enclosed areas below elevated manufactured homes shall comply with the requirements of Section R306 of the California Residential Code .
SECTION G110—RECREATIONAL VEHICLES
G110.1 Placement prohibited. The placement of recreational vehicles shall not be authorized in coastal high-hazard areas and in floodways.
G110.2 Temporary placement. Recreational vehicles in flood hazard areas shall be fully licensed and ready for highway use, or shall be placed on a site for less than 180 consecutive days.
G110.3 Permanent placement. Recreational vehicles that are not fully licensed and ready for highway use, or that are to be placed on a site for more than 180 consecutive days, shall meet the requirements of Section G109 for manufactured homes.
SECTION G111—TANKS
G111.1 Tanks. Underground and above-ground tanks shall be designed, constructed, installed and anchored in accordance with ASCE 24.
APPENDIX G-6 2025 CALIFORNIA BUILDING CODE
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APPENDIX G—FLOOD-RESISTANT CONSTRUCTION
SECTION G112—OTHER BUILDING WORK
CRC § 2.1 High relevance — show source text
Chemical termiticide treatment in accordance with Section R305.2.
Termite-baiting system installed and maintained in accordance with the label.
Pressure-preservative-treated wood in accordance with the provisions of Section R304.1.
Naturally durable termite-resistant wood.
Physical barriers in accordance with Section R305.3 and used in locations as specified in Section R304.1.
Cold-formed steel framing in accordance with Sections R505.2.1 and R603.2.1.
R305.1.1 Quality mark. Lumber and plywood required to be pressure-preservative treated in accordance with Section R305.1 shall bear the quality mark of an approved inspection agency that maintains continuing supervision, testing and inspection over the quality of the product and that has been approved by an accreditation body that complies with the requirements of the American Lumber Standard Committee treated wood program.
R305.1.2 Field treatment. Field-cut ends, notches and drilled holes of pressure-preservative-treated wood shall be retreated in the field in accordance with AWPA M4.
R305.2 Chemical termiticide treatment. Chemical termiticide treatment shall include soil treatment or field-applied wood treatment. The concentration, rate of application and method of treatment of the chemical termiticide shall be in strict accordance with the termiticide label.
R305.3 Barriers. Approved physical barriers, such as metal or plastic sheeting or collars specifically designed for termite prevention, shall be installed in a manner to prevent termites from entering the structure. Shields placed on top of an exterior foundation wall shall be used only if in combination with another method of protection.
R305.4 Foam plastic protection. In areas where the probability of termite infestation is “very heavy” as indicated in Figure R305.4, extruded and expanded polystyrene, polyisocyanurate and other foam plastics shall not be installed on the exterior face or under interior or exterior foundation walls or slab foundations located below grade. The clearance between foam plastics installed above grade and exposed earth shall be not less than 6 inches (152 mm).
Exceptions:
Buildings where the structural members of walls, floors, ceilings and roofs are entirely of noncombustible materials or pressure-preservative-treated wood.
Where in addition to the requirements of Section R305.1, an approved method of protecting the foam plastic and structure from subterranean termite damage is used.
On the interior side of basement walls.
2025 CALIFORNIA RESIDENTIAL CODE 3-35
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BUILDING PLANNING
FIGURE R305.4—TERMITE INFESTATION PROBABILITY MAP
Note: Lines defining areas are approximate only. Local conditions may be more or less severe than indicated by the region classification.
SECTION R306—FLOOD-RESISTANT CONSTRUCTION
R306.1 General. Buildings and structures constructed in whole or in part in flood hazard areas established in Table R301.2, and substantial improvement and repair of substantial damage of buildings and structures located in whole or in part in flood hazard areas, shall be designed and constructed in accordance with the provisions contained in this section. Buildings and structures that are located in more than one flood hazard area, including A Zones, Coastal A Zones and V Zones, shall comply with the provisions associated with the most restrictive flood hazard area. Buildings and structures located in whole or in part in identified floodways shall be designed and constructed in accordance with ASCE 24.
CRC § 1.4.2 High relevance — show source text
R306.1.4.2 Determination of impacts. In riverine flood hazard areas where design flood elevations are specified but floodways have not been designated, the applicant shall demonstrate that the effect of the proposed buildings and structures on design flood elevations, including fill, when combined with other existing and anticipated flood hazard area encroachments, will not increase the design flood elevation more than 1 foot (305 mm) at any point within the jurisdiction.
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BUILDING PLANNING
R306.1.5 Lowest floor. The lowest floor shall be the lowest floor of the lowest enclosed area, including basement, and excluding any unfinished flood-resistant enclosure that is useable solely for vehicle parking, building access or limited storage provided that such enclosure is not built so as to render the building or structure in violation of this section.
R306.1.6 Protection of mechanical, plumbing and electrical systems. Electrical systems, equipment and components; heating, ventilating, air-conditioning; plumbing appliances and plumbing fixtures; duct systems; and other service equipment shall be located at or above the elevation required in Section R306.2 or R306.3. If replaced as part of a substantial improvement, electrical systems, equipment and components; heating, ventilating, air-conditioning and plumbing appliances and plumbing fixtures; duct systems; and other service equipment shall meet the requirements of this section. Systems, fixtures, and equipment and components shall not be mounted on or penetrate through walls intended to break away under flood loads.
Exception: Locating electrical systems, equipment and components; heating, ventilating, air-conditioning; plumbing appliances and plumbing fixtures; duct systems; and other service equipment is permitted below the elevation required in Section R306.2 or R306.3 provided that they are designed and installed to prevent water from entering or accumulating within the components and to resist hydrostatic and hydrodynamic loads and stresses, including the effects of buoyancy, during the occurrence of flooding to the required elevation in accordance with ASCE 24. Electrical wiring systems are permitted to be located below the required elevation provided that they conform to the provisions of the California Electrical Code for wet locations.
R306.1.7 Protection of water supply and sanitary sewage systems. Water supply systems shall be designed to minimize or elim- inate infiltration of floodwaters into the water supply and distribution systems. Sanitary sewage systems shall be designed to minimize or eliminate infiltration of floodwaters into sanitary drainage systems and discharges from sanitary drainage systems into floodwaters.
R306.1.8 Flood-resistant materials. Building materials and installation methods used for flooring and interior and exterior walls and wall coverings below the elevation required in Section R306.2 or R306.3 shall be flood damage-resistant materials that conform to the provisions of FEMA TB-2.
R306.1.9 Manufactured homes. (Not adopted in CA)
R306.1.10 As-built elevation documentation. A registered design professional shall prepare and seal documentation of the elevations specified in Section R306.2 or R306.3.
CRC § G115 High relevance — show source text
G114.4 Enclosures below design flood elevation. Fully enclosed areas below the design flood elevation shall be constructed in accordance with ASCE 24.
G114.5 Flood-damage-resistant materials. Flood-damage-resistant materials shall be used below the design flood elevation.
G114.6 Protection of mechanical, plumbing and electrical systems. Mechanical, plumbing and electrical systems, including plumbing fixtures, shall be elevated to or above the design flood elevation.
Exception: Electrical systems, equipment and components; heating, ventilating, air conditioning and plumbing appliances; plumbing fixtures, duct systems and other service equipment shall be permitted to be located below the design flood elevation provided that they are designed and installed to prevent water from entering or accumulating within the components and to
2025 CALIFORNIA BUILDING CODE APPENDIX G-7
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APPENDIX G—FLOOD-RESISTANT CONSTRUCTION
resist hydrostatic and hydrodynamic loads and stresses, including the effects of buoyancy, during the occurrence of flooding to the design flood elevation in compliance with the flood-resistant construction requirements of this code. Electrical wiring systems shall be permitted to be located below the design flood elevation provided that they conform to the provisions of the California Electrical Code.
SECTION G115—REFERENCED STANDARDS
G115.1 General. See Table G115.1 for standards that are referenced in various sections of this appendix. Standards are listed by the standard identification with the effective date, standard title, and the section or sections of this appendix referenced in the standard.
TABLE G115.1—REFERENCED STANDARDS Col2 Col3 STANDARD ACRONYM STANDARD NAME SECTIONS HEREIN REFERENCED ASCE 24—14 Flood Resistant Design and Construction G104.1, G108.3, G108.4, G111.1, G112.1,
G112.5, G112.6, G112.7, G113.1, G114.4HUD 24 CFR Part 3285 (2008) Manufactured Home Construction and Safety Standards G102 CBC_—25_ California Building Code G103.2, G114.1, G114.3 CRC_—25_ California Residential Code G109.2, G109.4, G109.5 CEC_—25_ California Electrical Code G109.4, G114.6 APPENDIX G-8 2025 CALIFORNIA BUILDING CODE
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CALIFORNIA BUILDING CODE – MATRIX ADOPTION TABLE
APPENDIX H – SIGNS
(Not adopted by state agencies)
CRC § 916-574 High relevance — show source text
Note: Contact information for the California Department of Water Resources and the Department’s Directory of Flood Officials, which includes levee and reclamation district boundary maps, is available on-line at the following website: www.water.ca.gov/ BuildingCodes. The Department of Water Resources Building Code Project Engineer can be contacted at 916-574-1451. The Central Valley Flood Control Board Chief Engineer can be contacted at 916-574-0609. The California Emergency Management Agency Inland Region Program Manager can be contacted at 916-845-8488.
CK109.2 Appeals. When a request for an alternate means of protection has been denied by the building official, the applicant may file a written appeal with the board of appeals. In considering such appeal, the board of appeals may provide additional information to, and request additional written statements from the Central Valley Flood Protection Board, the California Department of Water Resources and the California Emergency Management Agency. If such additional written statements are provided, the board of appeals shall consider those statements.
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APPENDIX CK — AREAS PROTECTED BY THE FACILITIES OF THE CENTRAL VALLEY FLOOD PROTECTION PLAN
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APPENDIX CK — AREAS PROTECTED BY THE FACILITIES OF THE CENTRAL VALLEY FLOOD PROTECTION PLAN
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APPENDIX NA-2 2025 CALIFORNIA RESIDENTIAL CODE
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Concrete Capillary break R506.2.3.1 Compressive strength R402.2 Floors (on ground) R506 Tile (roof) R905.3 Weathering Figure R301.2(1), R402.2 Construction
3D-printed Appendix BM Cavity wall masonry R608 Cob Appendix BK Extended plate walls Appendix BN Flood-resistant R306
Floors Chapter 5 Footings R403 Foundation material R402
Foundation walls R404
Foundations Chapter 4 Hemp-lime Appendix BL Masonry R606, R607, R608, R610 Pollutant control R340 Roofs Chapter 8 Steel framing R505, R603, R804 Strawbale Appendix BJ Straw-clay Appendix BI Walls Chapter 6 Waste R334.1 Wood framing R502, R602, R802 Construction Documents R106, R306.3.9
CRC § 1.2. High relevance — show source text
1.2. If the addition constitutes substantial improvement, the existing building and the addition shall comply with Section 1612 of the California Building Code, or Section R306 of the California Residential Code, as applicable. 1.3. If the addition does not constitute substantial improvement, the addition is not required to comply with the flood design requirements for new construction, provided that both of the following apply: 1.3.1. The addition shall not create or extend any nonconformity of the existing building with the flood-resistant construction requirements. 1.3.2. The lowest floor of the addition shall be at or above the lower of the lowest floor of the existing building or the lowest floor elevation required in Section 1612 of the California Building Code, or Section R306 of the California Residential Code, as applicable. 2. For horizontal additions that are not structurally interconnected to the existing building: 2.1. The addition shall comply with Section 1612 of the California Building Code, or Section R306 of the California Resi- dential Code, as applicable. 2.2. If the addition and all other proposed work, when combined, constitute substantial improvement, the existing building and the addition shall comply with Section 1612 of the California Building Code, or Section R306 of the California Residential Code, as applicable. 3. For vertical additions and all other proposed work that, when combined, constitute substantial improvement, the existing building shall comply with Section 1612 of the California Building Code, or Section R306 of the California Residential Code, as applicable. 4. For a new foundation, replacement foundation or a foundation raised or extended upward, the foundation shall comply with Section 1612 of the California Building Code, or Section R306 of the California Residential Code, as applicable.
SECTION 1104—ENERGY CONSERVATION
1104.1 Minimum requirements. Additions to existing buildings shall comply with applicable provisions of the California Energy Code (Part 6, Title 24, C.C.R).
11-4 2025 CALIFORNIA EXISTING BUILDING CODE
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12 HISTORIC BUILDINGS
Chapter 12 is not adopted by the State of California.
Historic buildings and structures shall comply with Part 8, Title 24, California Code of Regulations.
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CALIFORNIA EXISTING BUILDING CODE – MATRIX ADOPTION TABLE
CHAPTER 13 – PERFORMANCE COMPLIANCE METHODS
Not adopted by the State of California (May be available for adoption by local ordinance. See Section 1.1.11.) (See Section 104.11 for consideration of alternative means of compliance.)
CRC § 3-33 Medium relevance — show source text
R304 Protection of Wood and Wood-Based Products
Against Decay . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-33
R305 Protection Against Subterranean Termites. . . . . . . 3-35
R306 Flood-Resistant Construction. . . . . . . . . . . . . . . . . . . 3-36
R307 Storm Shelters . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-40
R308 Site Address . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-40
R309 Automatic Sprinkler Systems . . . . . . . . . . . . . . . . . . . 3-41
R310 Smoke Alarms. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-54
R311 Carbon Monoxide Alarms. . . . . . . . . . . . . . . . . . . . . . . 3-58
R312 Minimum Room Areas . . . . . . . . . . . . . . . . . . . . . . . . . 3-59
R313 Ceiling Height . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-59
R314 Mezzanines . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-60
R315 Sleeping Lofts. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-60
R316 Habitable Attics . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-61
R317 Garages and Carports. . . . . . . . . . . . . . . . . . . . . . . . . . 3-61
R318 Means of Egress . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-62
R319 Emergency Escape and Rescue Openings . . . . . . . . 3-65
R320 Handrails . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-67
R321 Guards and Window Fall Protection . . . . . . . . . . . . . 3-67
R322 Accessibility . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-68
R323 Elevators and Platform Lifts . . . . . . . . . . . . . . . . . . . . 3-68
R324 Glazing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-68
CRC § 2.2 Medium relevance — show source text
Wind-loading values shall be those required by this code. 5. Walls intended to break away under flood loads as specified in Item 3 or 4 have flood openings that meet the criteria in Section R306.2.2, Item 2.
Exceptions: The following shall not be required to comply with this section:
Elevator shafts.
Utility chases that protect utility lines from freezing, provided that the utility chases are the minimum size necessary to protect the utility lines and do not provide access for a person to enter the space.
R306.3.6 Enclosed areas below required elevation. Enclosed areas below the elevation required in Section R306.3.2 shall be used solely for parking of vehicles, building access or storage.
R306.3.6.1 Protection of building envelope. An exterior door that meets the requirements of Section R609 shall be installed at the top of stairs that provide access to the building and that are enclosed with walls designed to break away in accordance with Section R306.3.5.
R306.3.7 Stairways and ramps. Stairways and ramps that are located below the lowest floor elevations specified in Section R306.3.2 shall comply with one or more of the following:
- Be designed and constructed with open or partially open risers and guards.
- Stairways and ramps not part of the required means of egress shall be designed and constructed to break away during design flood conditions without causing damage to the building or structure, including foundation.
- Be retractable, or able to be raised to or above the lowest floor elevation, provided that the ability to be retracted or raised prior to the onset of flooding is not contrary to the means of egress requirements of the code.
- Be designed and constructed to resist flood loads and minimize transfer of flood loads to the building or structure, including foundation.
Areas below stairways and ramps shall not be enclosed with walls below the elevation required in Section R306.3.2 unless such walls are constructed in accordance with Section R306.3.5.
R306.3.8 Decks and porches. Attached decks and porches shall meet the elevation requirements of Section R306.3.2 and shall either meet the foundation requirements of this section or shall be cantilevered from or knee braced to the building or structure. Self-supporting decks and porches that are below the elevation required in Section R306.3.2 shall not be enclosed by solid, rigid walls, including walls designed to break away. Self-supporting decks and porches shall be designed and constructed to remain in place during base flood conditions or shall be frangible and break away under base flood conditions.
R306.3.9 Construction documents. The construction documents shall include documentation that is prepared and sealed by a registered design professional that the design and methods of construction to be used meet the applicable criteria of this section.
R306.3.10 Tanks. Underground tanks shall be anchored to prevent flotation, collapse and lateral movement under conditions of the base flood. Above-ground tanks shall be installed at or above the elevation required in Section R306.3.2. Where elevated on platforms, the platforms shall be cantilevered from or knee braced to the building or shall be supported on foundations that conform to the requirements of Section R306.3.
SECTION R307—STORM SHELTERS
CRC § 2-5 High relevance — show source text
Part II—Definitions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .2-5
CHAPTER 2 DEFINITIONS. . . . . . . . . . . . . . . . . . . . . . . . . . . .2-5
R201 General. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-5
R202 Definitions. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-5
Part III—Building Planning and Construction . . . . . . . . . . . .3-5
CHAPTER 3 BUILDING PLANNING . . . . . . . . . . . . . . . . . . . . .3-5
R300 Site Drainage . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-5
R301 Design Criteria . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-5
R302 Fire-Resistant Construction . . . . . . . . . . . . . . . . . . . . 3-23
R303 Foam Plastic . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-31
R304 Protection of Wood and Wood-Based Products
Against Decay . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-33
R305 Protection Against Subterranean Termites. . . . . . . 3-35
R306 Flood-Resistant Construction. . . . . . . . . . . . . . . . . . . 3-36
R307 Storm Shelters . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-40
R308 Site Address . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-40
R309 Automatic Sprinkler Systems . . . . . . . . . . . . . . . . . . . 3-41
R310 Smoke Alarms. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-54
R311 Carbon Monoxide Alarms. . . . . . . . . . . . . . . . . . . . . . . 3-58
R312 Minimum Room Areas . . . . . . . . . . . . . . . . . . . . . . . . . 3-59
R313 Ceiling Height . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-59
CRC § 2.3.1 Medium relevance — show source text
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APPENDIX CK-8 2025 CALIFORNIA RESIDENTIAL CODE
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APPENDIX NA-2 2025 CALIFORNIA RESIDENTIAL CODE
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Concrete Capillary break R506.2.3.1 Compressive strength R402.2 Floors (on ground) R506 Tile (roof) R905.3 Weathering Figure R301.2(1), R402.2 Construction
3D-printed Appendix BM Cavity wall masonry R608 Cob Appendix BK Extended plate walls Appendix BN Flood-resistant R306
Floors Chapter 5 Footings R403 Foundation material R402
Foundation walls R404
Foundations Chapter 4 Hemp-lime Appendix BL Masonry R606, R607, R608, R610 Pollutant control R340 Roofs Chapter 8 Steel framing R505, R603, R804 Strawbale Appendix BJ Straw-clay Appendix BI Walls Chapter 6 Waste R334.1 Wood framing R502, R602, R802 Construction Documents R106, R306.3.9
Court Emergency escape and rescue openings R319.1, R319.2.4 Means of egress R318.1 Natural light R325.1.1 Covering Exterior R703
Interior R702 Roof Chapter 9 Wall Chapter 7 Crawl Space R408
Access R408.4
Damper Fireplace R1001.7.1 Dampproofing R406 Day Care Appendix BD Defined R202 Large family day-care homes R336 Dead Loads R301.4
Decay Protection against R304 Deck
Attachment R318.5 Supported by exterior wall R507 Wood/plastic composite boards R507.2.2
Definitions Building R202 Mechanical system R202 Plumbing R202 Design Criteria R301 Alternative provisions R301.1.1 Application R301.1 Climatic and geographic R301.2 Dead load R301.4
Deflection R301.6 Engineered design R301.1.3
Accessibility R322 Accessory Dwelling Unit R202 Authority to Enforce Automatic Fire Sprinkler Systems 1.8.9.1, R313.2 Accessory Structure Elevations R306.3.2
Energy R330.5 Exterior walls R302.1
Scope R101.2 Addition (see also Existing Buildings) Carbon monoxide alarms R311.2.2 Change of occupancy R110.1 Construction R302.2.3
CRC § 7.1 Medium relevance — show source text
Covering R703 Insulation finish systems R703.9 Lath R703.7.1
Plaster R703.7 Exterior Insulation and Finish Systems (EIFS) 703.9
Exterior Wall
Construction R302.1
Fire-resistance rating R302.1
Factory Built Chimneys R1005 Fireplace stoves R1005.3 Fireplaces R1004 Fastening Table R602.3(1) Fees, Permit R108 Finishes Flame spread and smoke density R302.9 For ceilings R805 Interior R302.9, R311, R702 Fire Sprinkler System (see Automatic Sprinkler System) Ceiling configurations R309.3.4.1.1, R309.3.4.1.2, R309.3.4.1.3 Flow rate R309.3.4.1 Fireblocking Barrier between stories R302.11,
R602.8 Chimney R1003.19 Fireplace R1001.12 Fireplaces Chapter 10 Clearance R1001.11 Corbeling R1001.8 Factory-built R1004 Fireblocking R1001.12 Walls R1001.5
Fire-Resistant Construction R302 Draftstopping R302.2 Dwelling-garage fire separation R302.6 Dwelling-garage opening and penetration R302.5 Exterior walls R302.1 Fireblocking R302.11 Floors R302.13
Foam plastics R302.8 Insulation R302.10, R302.14 Penetrations R302.4
Townhouse separation R302.2 Two-family dwellings R302.3 Under-stair protection R302.7 Wall and ceiling finishes R302.9 Fire-Separation Distance Exterior walls and wall projections R302.1 Ground-mounted photovoltaic systems R329.7, R329.8 Fixtures
Clearance R327.1
Flood protection R306.1.6 Plumbing fixture, general R326, R327 Flame Spread Index R302.10, R302.9 Flashing R703.4, R703.8.5, R903.2, R905 Flood Protection Plan Areas protected by the facilities of Central Valley Appendix CK Flood-Resistant Construction
General and structural R301.2.4, R306 Floors
Bathtub and shower R327.2 Concrete (on ground) R506 Loads R301, R501.2 Steel framing R505 Treated wood (on ground) R504
Wood framing R502 Flue
Area R1003.14, R1003.15 Lining R1003.11, R1003.12 Multiple R1003.13 Foam Plastics R303 Footings R403 Foundations Chapter 4 Cripple walls R602.10.9, R602.11.2, R602.9
Frost protection R403.1.4.1 Inspection R109.1.1 Walls R404
Frame
CRC § 1.6 Medium relevance — show source text
Foam plastics R302.8 Insulation R302.10, R302.14 Penetrations R302.4
Townhouse separation R302.2 Two-family dwellings R302.3 Under-stair protection R302.7 Wall and ceiling finishes R302.9 Fire-Separation Distance Exterior walls and wall projections R302.1 Ground-mounted photovoltaic systems R329.7, R329.8 Fixtures
Clearance R327.1
Flood protection R306.1.6 Plumbing fixture, general R326, R327 Flame Spread Index R302.10, R302.9 Flashing R703.4, R703.8.5, R903.2, R905 Flood Protection Plan Areas protected by the facilities of Central Valley Appendix CK Flood-Resistant Construction
General and structural R301.2.4, R306 Floors
Bathtub and shower R327.2 Concrete (on ground) R506 Loads R301, R501.2 Steel framing R505 Treated wood (on ground) R504
Wood framing R502 Flue
Area R1003.14, R1003.15 Lining R1003.11, R1003.12 Multiple R1003.13 Foam Plastics R303 Footings R403 Foundations Chapter 4 Cripple walls R602.10.9, R602.11.2, R602.9
Frost protection R403.1.4.1 Inspection R109.1.1 Walls R404
Frame
Inspection R109.1.4 Frost Protection R507.3, R507.3.3, R1001.2 Fuel Cell Power System, Stationary R322 Fuel-Burning Appliances (see Appliances)
Garbage Disposal (see Food-Waste Disposers) Garages R317, R330.8.1 Electric vehicle charging infrastructure R317.6 Protection of Energy Storage Systems R330.8
Generators R331
Girders R502.5 Glazing Aggregate area R325.1 Greenhouses R324.6.6 Protection of openings R301.2.1.2 Safety glazing at hazardous locations R324
Site-built R324.5 Skylights and sloped glazing R324.6 Grade
Of lumber R502.1.1, R602.1.1, R802.1.1 Grade Plane R101.2, R301.2.2.7, R316.3 Ground Floors (on ground) R504, R506 Guards or Guardrail R321, R324.4.4 Exterior R507.10 Guestroom (see Lodging House) Gypsum Board and Gypsum Panel Products R702.3
Hallways R318.6 Hand Shower (see Shower) Handrails R318.7.8, R318.8.3, R320, R324.4.4 Alternating tread devices R318.7.12.2 Ship’s ladders R318.7.13.2 Hazardous Location R324
Headers
SIP R610.8
Steel R603.6
Wood R602.7
CEC § G114 Medium relevance — show source text
G113.3 Floodway encroachment. Temporary structures and temporary storage in floodways shall meet the requirements of G104.5.
SECTION G114—UTILITY AND MISCELLANEOUS GROUP U
G114.1 Utility and miscellaneous Group U. Utility and miscellaneous Group U includes buildings that are accessory in character and miscellaneous structures not classified in any specific occupancy in this code, including, but not limited to, agricultural buildings, aircraft hangars (accessory to a one- or two-family residence), barns, carports, fences more than 6 feet (1829 mm) high, grain silos (accessory to a residential occupancy), greenhouses, livestock shelters, private garages, retaining walls, sheds, stables and towers.
G114.2 Flood loads. Utility and miscellaneous Group U buildings and structures, including substantial improvement of such buildings and structures, shall be anchored to prevent flotation, collapse or lateral movement resulting from flood loads, including the effects of buoyancy, during conditions of the design flood.
G114.3 Elevation. Utility and miscellaneous Group U buildings and structures, including substantial improvement of such buildings and structures, shall be elevated such that the lowest floor, including basement, is elevated to or above the design flood elevation in accordance with Section 1612 of this code.
G114.4 Enclosures below design flood elevation. Fully enclosed areas below the design flood elevation shall be constructed in accordance with ASCE 24.
G114.5 Flood-damage-resistant materials. Flood-damage-resistant materials shall be used below the design flood elevation.
G114.6 Protection of mechanical, plumbing and electrical systems. Mechanical, plumbing and electrical systems, including plumbing fixtures, shall be elevated to or above the design flood elevation.
Exception: Electrical systems, equipment and components; heating, ventilating, air conditioning and plumbing appliances; plumbing fixtures, duct systems and other service equipment shall be permitted to be located below the design flood elevation provided that they are designed and installed to prevent water from entering or accumulating within the components and to
2025 CALIFORNIA BUILDING CODE APPENDIX G-7
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APPENDIX G—FLOOD-RESISTANT CONSTRUCTION
resist hydrostatic and hydrodynamic loads and stresses, including the effects of buoyancy, during the occurrence of flooding to the design flood elevation in compliance with the flood-resistant construction requirements of this code. Electrical wiring systems shall be permitted to be located below the design flood elevation provided that they conform to the provisions of the California Electrical Code.
SECTION G115—REFERENCED STANDARDS
G115.1 General. See Table G115.1 for standards that are referenced in various sections of this appendix. Standards are listed by the standard identification with the effective date, standard title, and the section or sections of this appendix referenced in the standard.
Frequently asked questions
When exactly do I have to follow § R306?
Follow § R306 whenever any part of the building is located in a mapped flood hazard area (per Table R301.2) or when work qualifies as a substantial improvement or repair of substantial damage to a building in a flood hazard area .
How do I determine the design flood elevation to use?
Use the higher of the base flood elevation for the 1‑percent event (including wave height) or the locally adopted design flood elevation; if not specified, obtain federal/state data or have an RDP perform accepted hydrologic/hydraulic analysis per § R306.1.4 / R306.1.4.1 .
Can I put HVAC equipment below the required elevation if I waterproof it?
Only if the equipment and systems are designed and installed to prevent water entry and to resist hydrostatic/hydrodynamic loads (ASCE 24 criteria) — otherwise they must be located at or above the elevation required in § R306.2 or § R306.3 .
What documentation will the building official require?
An RDP‑sealed as‑built elevation of the lowest floor per § R306.1.10, and elevation verification at placement of the lowest floor (inspection requirement § R109.1.3) file.
Is ASCE 24 allowed instead of CRC flood provisions?
Yes — ASCE 24 is permitted as an alternative to § R306 requirements subject to code limitations; floodways and some coastal situations require ASCE 24 design anyway (see § R306.1.1 and § R306.1) .
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