CRC · California Residential Code
What foundations and foundation spaces does the CRC chapter cover?
Chapter 4 of the California Residential Code (beginning with **§ R401.1**) governs what kinds of foundations and foundation spaces are covered (footings, foundation walls, basements, crawl/under‑floor spaces, slab foundations, wood/masonry/concrete and precast systems) and prescribes how they must be designed, drained and protected from moisture, frost and pests; it requires foundations to transmit loads per **§ R301**, mandates grading away from the foundation, perimeter drains for below‑grade habitable spaces (with limited soil exceptions), and specific vapor/ drainage details for basement and wood foundations (see **§ R401.1**, **§ R401.2**, **§ R401.3**, **§ R403**, **§ R405**, **§ R406**).
Last reviewed: July 6, 2026
What the code requires — 2-4 sentences
The California Residential Code (CRC) Chapter 4 controls the design and construction of foundations and foundation spaces (basements, crawl/under-floor spaces, footings and foundation walls) and requires that foundations transmit design loads to supporting soil while addressing drainage, waterproofing, frost protection and material-specific rules — see § R401.1. § R401.2 requires foundation construction to accommodate all loads per § R301 and that fills supporting foundations be designed and tested as appropriate. § R401.3 requires surface drainage away from foundations (grade fall or drains) to protect foundation performance.
The bottom line: Chapter 4 is the CRC’s rulebook for what kinds of foundations and foundation spaces are covered, how they must be supported, drained and protected from moisture, frost and pests (see § R401.1).
Requirements in detail
Scope — what is covered (high level)
- The chapter governs the foundation structure and the supporting soil for: footings, foundation walls, basements, crawl spaces / under‑floor spaces, slab‑on‑grade foundations, wood foundations, masonry foundations, concrete foundations, and precast concrete foundations — established in § R401.1 and the chapter intro.
- Design must also comply with flood provisions when applicable (see Table R301.2 and Section R306 referenced in § R401.1).
Foundation design and soils
- Foundations must be capable of carrying and transmitting all imposed loads in accordance with § R301; § R401.2 requires fill soils that support footings to be designed, installed and tested in accordance with accepted engineering practice.
Drainage and moisture control
- Surface grading: the finish grade must fall not less than 6 inches (152 mm) within the first 10 feet (3048 mm) away from the foundation; if that is not possible, approved drains or swales must be provided. § R401.3.
- For concrete or masonry foundations that retain earth and enclose habitable/usable spaces below grade, perimeter drains (tile, perf pipe, gravel drains or other approved systems) at or below the top of footing (or below slab) are required, and must discharge to daylight or an approved system; gravel drains must extend not less than 1 foot (305 mm) beyond the outside edge of the footing and 6 inches (152 mm) above the top of the footing. § R405.1.
- Exception: a drainage system is not required where the foundation is installed on well‑drained Group I soils per Table R401.4.1(2) — see the exception to § R405.1.
Basements and wood foundations (moisture / vapor control)
- Wood foundations enclosing habitable or usable spaces below grade require drainage and dampproofing in accordance with §§ R405.2 and R406; specific subrequirements include a minimum 4‑inch (102 mm) porous base under a basement floor and a 6‑mil (0.15 mm) polyethylene vapor retarder over that base. §§ R405.2.1–R405.2.2.
- Where soils other than Group I exist, a sump is required to drain the porous layer and footings: the sump must be not less than 24 inches (610 mm) in diameter or 20 inches square and shall extend not less than 24 inches (610 mm) below the bottom of the basement floor; discharge must be by gravity or mechanical means to an approved system. § R405.2.3.
Footings and foundation walls (material specific)
- Footings for exterior walls must be continuous and supported on undisturbed natural soil or engineered fill; concrete footings are to be designed per § R403 (or ACI 332). § R403.1.
- Prescriptive minimum footing sizes for light‑frame construction are given in Table R403.1(1) (see § R403). § R403.
- Frost‑protected shallow foundations (FPSF) are permitted where applicable; FPSF rules (minimum footing depth, R‑values and insulation placement) and limitations (not for unheated porches/garages, and must be for spaces maintained at a monthly mean temperature of not less than 64°F (18°C)) are in § R403.3 and its tables/figures. § R403.3.
- Precast concrete foundation walls that retain earth and enclose habitable spaces must have perforated drainage pipe below base and must meet design/manufacturing requirements in § R404.5 (including design drawings and third‑party labeling). § R404.5.
Under‑floor / crawl spaces
- Under‑floor and crawl space requirements (ventilation, ground cover, passive sub‑membrane depressurization, sealing penetrations, duct/air‑handler rules) are addressed in § R408 and related appendices/energy/sealing rules; BE103 supplements specific crawl space air sealing and vapor‑retarder requirements (e.g., 6‑mil soil‑gas‑retarder and venting rules). See § R408 and BE103 references.
Markdown table — decision‑relevant dimensions / values
| Item | Control / Value | Code Reference |
|---|---|---|
| Minimum grade fall away from foundation | 6 in (152 mm) within first 10 ft (3048 mm) (or provide drains/swales) | § R401.3 |
| Impervious surfaces within 10 ft of foundation slope | Not less than 2% away from building (if impervious) | § R401.3 (Exception) |
| Gravel base under wood foundation basement floor | 4 in (102 mm) minimum porous layer | § R405.2.1 |
| Vapor retarder under basement floor | 6‑mil (0.15 mm) polyethylene | § R405.2.2 |
| Sump size (where required) | ≥ 24 in (610 mm) diameter or 20 in square; extends ≥ 24 in (610 mm) below basement floor bottom | § R405.2.3 |
| Perimeter drain position (concrete/masonry) | At or below top of footing or below the bottom of slab; gravel drain extends ≥ 1 ft (305 mm) beyond footing and 6 in (152 mm) above top of footing | § R405.1 |
| Wood foundation allowance (when prescriptive rules apply) | Permitted only in buildings not more than two floors and a roof and interior basement/foundation walls spaced ≤ 50 ft (15 240 mm) — with seismic limitations | § R401.1 (Exception) |
| Heated‑space minimum for FPSF use | Monthly mean temp not less than 64°F (18°C) | § R403.3 |
| Precast concrete min. concrete strength for panels | See § R402.3.1 (panels: 5,000 psi min in manufacture) | § R402.3.1 |
Exceptions & special cases
- The chapter expressly allows its prescriptive provisions to be used for wood foundations only for small buildings (buildings with no more than two floors and a roof) and where interior basement/foundation walls are at intervals not exceeding 50 feet; wood foundations in Seismic Design Categories D0, D1 or D2 require accepted engineering practice (see § R401.1, Exception).
- Drainage systems around concrete/masonry foundations are not required on Group I soils (well‑drained sand/gravel mixtures) per the exception to § R405.1 (see Table R401.4.1(2)).
- Frost‑protected shallow foundations have specific insulation and depth requirements and are not permitted for unheated spaces (porches, garages) or for slabs not maintained at the required monthly mean temperature — see § R403.3.
- Precast foundation panels require design drawings and third‑party identification prior to installation — see § R404.5.2–R404.5.3.
If a CRC text excerpt needed to answer a very specific construction method (for example the full numeric values in Table R403.1(1) for every footing scenario or the full R‑values in Table R403.3(1)) is not included in the retrieved snippets above, that specific table or figure should be consulted directly in the CRC for the exact prescriptive values (the files retrieved include the tables but the excerpts shown here do not reproduce every table cell).
Common mistakes
- Assuming Chapter 4 replaces the need to follow § R301 (loads) or accepted engineering practice — § R401.2 requires foundations to accommodate all loads per § R301.
- Omitting perimeter drains for habitable below‑grade spaces — § R405.1 is explicit for concrete/masonry foundations.
- Using frost‑protection details for unheated slabs or porches — § R403.3 forbids FPSF use for unheated spaces.
- Forgetting vapor control under basement slabs for wood foundations (need 6‑mil vapor retarder) — § R405.2.2.
- Misapplying the wood‑foundation allowance beyond the limits of the exception in § R401.1 (size and seismic limits).
Worked example — concrete basement that encloses habitable space (numbers)
Scenario: A single‑family home with a below‑grade finished basement on typical (non‑Group I) soil.
Steps and applicable code items:
- Confirm scope: Chapter 4 applies to the foundation and foundation spaces — § R401.1.
- Design loads and bearing: Design foundation to carry and transmit loads per § R301; ensure soils/fill are designed/tested (per § R401.2).
- Site grading: final grade must drop 6 in within 10 ft from foundation; if impossible, provide drains/swales (§ R401.3).
- Perimeter drainage: provide a perforated drain or tile at or below the top of footing (or below slab), surrounded by washed gravel; the gravel drain must extend ≥ 1 ft beyond the footing and 6 in above the footing; drain must discharge to daylight or an approved system — § R405.1.
- Basement floor base and vapor retarder: place a 4 in porous gravel base under the basement floor and cover it with 6‑mil polyethylene before casting floor — §§ R405.2.1–R405.2.2.
- Sump (non‑Group I soils): provide a sump ≥ 24 in diameter (or 20 in square) extending ≥ 24 in below bottom of basement floor and sized to permit gravity or mechanical removal of accumulated water — § R405.2.3.
- Footing dimensions: use the prescriptive footing widths/thicknesses in Table R403.1(1) unless a design per § R403 or engineered design is required. § R403.
Related provisions (select list)
- § R401.1 — General application/scope for foundations and foundation spaces.
- § R401.2 — Foundation construction must accommodate loads per § R301; fill soils design/testing.
- § R401.3 — Surface drainage and grading away from foundations.
- § R403 — Footings (general, frost‑protected shallow foundation rules and Table R403.1(1)).
- § R404 — Foundation and retaining walls (wood, masonry, precast requirements).
- § R405 — Foundation drainage (perimeter drains, gravel, exceptions for Group I soils).
- § R406 — Foundation waterproofing and dampproofing requirements.
- § R408 — Under‑floor (crawl) spaces — ventilation, ground cover and related rules.
- § R402.3 / R402.3.1 — Precast concrete foundation material and manufacture requirements.
Code references
Grounded in the retrieved California Residential Code — click a citation to read the verbatim passage:
CRC § 4.1.1 High relevance — show source text
2||||X|||||||||||||||||||| |R401.4.1.1 through
R401.4.1.1.5||||X|||||||||||||||||||| |R404.5.1||||X|||||||||||||||||||| |R408.3||||X|||||||||||||||||||| |R408.4||||X|||||||||||||||||||| |R408.8||||||||||||||||||||X||||The state agency does not adopt sections identified with the following symbol: †
2025 CALIFORNIA RESIDENTIAL CODE 4-1
on Jul 18, 2025 11:14 AM (CDT) THEREUNDER.
4-2 2025 CALIFORNIA RESIDENTIAL CODE
on Jul 18, 2025 11:14 AM (CDT) THEREUNDER.
4 FOUNDATIONS
User notes:
About this chapter: Chapter 4 provides requirements for constructing footings and walls for foundations of wood, masonry, concrete and precast concrete. In addition to a foundation’s ability to support the required design loads, this chapter addresses several other factors that can affect foundation performance. These include controlling surface water and subsurface drainage, requiring soil tests where conditions warrant and evaluating proximity to slopes and minimum depth requirements. This chapter also provides requirements to minimize adverse effects of moisture, decay and pests in basements and crawl spaces.
SECTION R401—GENERAL
R401.1 Application. The provisions of this chapter shall control the design and construction of the foundation and foundation spaces for buildings. In addition to the provisions of this chapter, the design and construction of foundations in flood hazard areas as established by Table R301.2 shall meet the provisions of Section R306. Wood foundations shall be designed and installed in accordance with AWC PWF.
Exception: The provisions of this chapter shall be permitted to be used for wood foundations only in the following situations:
- In buildings that have not more than two floors and a roof.
- Where interior basement and foundation walls are constructed at intervals not exceeding 50 feet (15 240 mm) .
Wood foundations in Seismic Design Category D 0, D 1 or D 2 shall be designed in accordance with accepted engineering practice.
R401.2 Requirements. Foundation construction shall be capable of accommodating all loads in accordance with Section R301 and of transmitting the resulting loads to the supporting soil. Fill soils that support footings and foundations shall be designed, installed and tested in accordance with accepted engineering practice.
Note: See Section R301.1.1.1 for limited-density owner-built rural dwellings.
R401.3 Drainage. Surface drainage shall be diverted to a storm sewer conveyance or other approved point of collection that does not create a hazard. Lots shall be graded to drain surface water away from foundation walls. The grade shall fall not fewer than 6 inches (152 mm) within the first 10 feet (3048 mm).
Exception: Where lot lines, walls, slopes or other physical barriers prohibit 6 inches (152 mm) of fall within 10 feet (3048 mm), drains or swales shall be constructed to ensure drainage away from the structure. Impervious surfaces within 10 feet (3048 mm) of the building foundation shall be sloped not less than 2 percent away from the building.
**R401.4 Soil tests.
CRC § 25.4 High relevance — show source text
CONCRETE OR MASONRY FOUNDATION PER SECTION R401
FRAMING FASTENERS PER TABLE R602.3(1)
For SI: 1 inch = 25.4 mm.
APPENDIX BI-4 2025 CALIFORNIA RESIDENTIAL CODE
on Jul 18, 2025 11:14 AM (CDT) THEREUNDER.
APPENDIX BI — LIGHT STRAW-CLAY CONSTRUCTION
FIGURE BI103.2.4(2)—LIGHT STRAW-CLAY WALL, SINGLE STUD WIDTH
DOUBLE TOP PLATE
FLAT SOLID BLOCKING
WOOD METAL STRAP BRACING (LIB) PER TABLE R602.10.4 WHERE APPLICABLE PER SECTION R602.10
2X STUDS PER SECTION BI103.2.4, ITEM 1
1x1 CLEAT CENTERED ON EACH STUD FACE BETWEEN HORIZONTAL STABILIZATION
HORIZONTAL STABILIZATION OF LIGHT STRAW-CLAY PER SECTION BI103.2.4, ITEM 2
LIGHT STRAY-CLAY INFILL
ANCHORAGE PER SECTION R403.1.6
2X SILL PLATE
CONCRETE OR MASONRY FOUNDATION PER SECTION R401
FRAMING FASTENERS PER TABLE R602.3(1)
FIGURE BI103.2.4(3)—LIGHT STRAW-CLAY WALL WITH BLIND STUDS
DOUBLE TOP PLATES
2X LET-IN PLATE
WOOD METAL BRACING (LIB) PER TABLE R602.10.4 WHERE APPLICABLE PER SECTION R602.10
2x6 MINIMUM STUDS PER SECTION BI103.2.4, ITEM 1
LIGHT STRAW-CLAY INFILL
HORIZONTAL STABILIZATION PER SECTION BI103.2.4, ITEM 2
2X BOTTOM PLATE
2X SILL PLATE
ANCHORAGE PER SECTION R403.1.6
CONCRETE OR MASONRY FOUNDATION PER SECTION R401
FRAMING FASTENERS PER TABLE R602.3(1)
2025 CALIFORNIA RESIDENTIAL CODE APPENDIX BI-5
on Jul 18, 2025 11:14 AM (CDT) THEREUNDER.
APPENDIX BI — LIGHT STRAW-CLAY CONSTRUCTION
BI103.3 Materials. The materials used in light straw-clay construction shall be in accordance with Sections BI103.3.1 through BI103.3.3.
BI103.3.1 Straw requirements. Straw shall be stems of wheat, rye, oats, rice or barley, and shall be free of visible decay, insects and green plant material.
BI103.3.2 Clay subsoil requirements. Suitability of clay subsoil shall be determined in accordance with Table BI103.2.3.
BI103.3.3 Light straw-clay mixture. A light straw-clay mixture shall consist of loose straw mixed and coated with clay slip such that there is not more than 5 percent uncoated straw, and shall be in accordance with Table BI103.2.3.
BI103.4 Wall construction. Light straw-clay wall construction shall be in accordance with the requirements of Sections BI103.4.1 through BI103.4.7.
BI103.4.1 Light straw-clay maximum thickness. The maximum thickness of light straw-clay shall be in accordance with Table BI103.2.3.
CRC § 305.2 High relevance — show source text
A4.305.2 Recycled water piping. Based on projected availability, dual water piping is installed for future use of recycled water at the following locations:
- Interior piping for the use of recycled water is installed to serve all water closets, urinals and floor drains.
- Exterior piping is installed to transport recycled water from the point of connection to the structure. Recycled water systems shall be designed and installed in accordance with the California Plumbing Code.
A4.305.3 Recycled water for landscape irrigation. Recycled water is used for landscape irrigation.
2025 CALIFORNIA GREEN BUILDING STANDARDS CODE APPENDIX A4-13
on Jul 18, 2025 11:14 AM (CDT) THEREUNDER.
APPENDIX A4 — RESIDENTIAL VOLUNTARY MEASURES
SECTION A4.306 —INNOVATIVE CONCEPTS AND LOCAL ENVIRONMENTAL CONDITIONS
A4.306.1 Innovative concepts and local environmental conditions. The provisions of this code are not intended to prevent the use of any alternate material, appliance, installation, device, arrangement, method, design or method of construction not specifically prescribed by this code. This code does not limit the authority of city, county, or city and county government to make necessary changes to the provisions contained in this code pursuant to Section 101.7.1.
APPENDIX A4-14 2025 CALIFORNIA GREEN BUILDING STANDARDS CODE
on Jul 18, 2025 11:14 AM (CDT) THEREUNDER.
A4 RESIDENTIAL VOLUNTARY MEASURES
DIVISION A4.4 – MATERIAL CONSERVATION AND RESOURCE EFFICIENCY
SECTION A4.401—GENERAL (RESERVED)
SECTION A4.402—DEFINITIONS
A4.402.1 Definitions. The following terms are defined in Chapter 2.
ASSEMBLY (ASSEMBLY PRODUCT).
POSTCONSUMER CONTENT.
PRECONSUMER (OR POSTINDUSTRIAL) CONTENT.
PROPORTIONAL RECYCLED CONTENT (PRC M ).
RECYCLED CONTENT (RC).
RECYCLED CONTENT VALUE (RCV).
Assembly products (RCV A ). Materials (RCV M ).
SECTION A4.403—FOUNDATION SYSTEMS
A4.403.1 Frost protected foundation systems. As allowed by local conditions, utilize a Frost-Protected Shallow Foundation (FPSF) in compliance with the California Residential Code (CRC). When an FPSF foundation system is installed, the manual required by Section 4.410.1 shall include instructions to the owner or occupant regarding the necessity for heating the structure as required in Section R403.3 of the California Residential Code.
A4.403.2 Reduction in cement use. As allowed by the enforcing agency, cement used in foundation mix design shall be reduced as follows:
Tier 1. Not less than a 20 percent reduction in cement use.
Tier 2. Not less than a 25 percent reduction in cement use.
Note: Products commonly used to replace cement in concrete mix designs include, but are not limited to:
Fly ash.
Slag.
Silica fume.
Rice hull ash.
SECTION A4.404—EFFICIENT FRAMING TECHNIQUES
CRC § 3-82 High relevance — show source text
R336 Large Family Day-Care Homes . . . . . . . . . . . . . . . . . . . 3-82
R337 Materials and Construction Methods for Exterior
Wildfire Exposure . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-83
R338 Electric Vehicle . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-83
2025 CALIFORNIA RESIDENTIAL CODE xxi
on Jul 18, 2025 11:14 AM (CDT) THEREUNDER.
CONTENTS
R339 Reserved . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-84
R340 Pollutant Control . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-84
CHAPTER 4 FOUNDATIONS . . . . . . . . . . . . . . . . . . . . . . . . . 4-3
R401 General . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4-3
R402 Materials . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4-5
R403 Footings. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4-6
R404 Foundation and Retaining Walls . . . . . . . . . . . . . . . . 4-24
R405 Foundation Drainage . . . . . . . . . . . . . . . . . . . . . . . . . . 4-42
R406 Foundation Waterproofing and Dampproofing . . . 4-43
R407 Columns. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4-44
R408 Under-Floor Space . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4-44
CHAPTER 5 FLOORS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5-3
R501 General . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5-3
R502 Wood Floor Framing . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5-3
R503 Floor Sheathing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5-12
R504 Pressure Preservative-Treated Wood
CRC § 4.1 High relevance — show source text
Drainage tiles or perforated pipe shall be placed on not less than 2 inches (51 mm) of washed gravel or crushed rock not less than one sieve size larger than the tile joint opening or perforation and covered with not less than 6 inches (152 mm) of the same material.
Exception: A drainage system is not required where the foundation is installed on well-drained ground or sand-gravel mixture soils according to the Unified Soil Classification System, Group I soils, as detailed in Table R401.4.1(2).
R405.1.1 Precast concrete foundation. Precast concrete walls that retain earth and enclose habitable or useable space located below-grade that rest on crushed stone footings shall have a perforated drainage pipe installed below the base of the wall on either the interior or exterior side of the wall, not less than 1 foot (305 mm) beyond the edge of the wall. If the exterior drainage pipe is used, an approved filter membrane material shall cover the pipe. The drainage system shall discharge into an approved sewer system or to daylight.
R405.2 Wood foundations. Wood foundations enclosing habitable or usable spaces located below grade shall be adequately drained in accordance with Sections R405.2.1 through R405.2.3.
R405.2.1 Base. A porous layer of gravel, crushed stone or coarse sand shall be placed to a minimum thickness of 4 inches (102 mm) under the basement floor. Provision shall be made for automatic draining of this layer and the gravel or crushed stone wall footings.
R405.2.2 Vapor retarder. A 6-mil-thick (0.15 mm) polyethylene vapor retarder shall be applied over the porous layer with the basement floor constructed over the polyethylene.
R405.2.3 Drainage system. In other than Group I soils, a sump shall be provided to drain the porous layer and footings. The sump shall be not less than 24 inches (610 mm) in diameter or 20 inches square (0.0129 m [2] ), shall extend not less than 24 inches (610
4-42 2025 CALIFORNIA RESIDENTIAL CODE
on Jul 18, 2025 11:14 AM (CDT) THEREUNDER.
FOUNDATIONS
mm) below the bottom of the basement floor and shall be capable of positive gravity or mechanical drainage to remove any accumulated water. The drainage system shall discharge into an approved sewer system or to daylight.
SECTION R406 —FOUNDATION WATERPROOFING AND DAMPPROOFING
R406.1 Concrete and masonry foundation dampproofing. Except where required by Section R406.2 to be waterproofed, foundation walls that retain earth and enclose interior spaces and floors below grade shall be dampproofed from the finished grade to the
higher of the top of the footing or 6 inches (152 mm) below the top of the basement floor. Masonry walls shall have not less than [3] / 8inch (9.5 mm) Portland cement parging applied to the exterior of the wall. The parging shall be dampproofed in accordance with one of the following:
- Bituminous coating.
- Three pounds per square yard (1.63 kg/m [2] ) of acrylic modified cement.
- One-eighth-inch (3.2 mm) coat of surface-bonding cement complying with ASTM C887.
- Any material permitted for waterproofing in Section R406.2.
- Other approved methods or materials.
California Residential Code High relevance — show source text
Chapter 1 Scope and Administration.
Chapter 1 establishes the limits of applicability of the code and describes how the code is to be applied and enforced. The provisions of Chapter 1 establish the authority and duties of the code official appointed by the authority having jurisdiction and also establish the rights and privileges of the design professional, contractor and property owner.
Chapter 2 Definitions.
Chapter 2 is the repository of the definitions of terms used in the body of the code. The user of the code should be familiar with and consult this chapter because the definitions are essential to the correct interpretation of the code and because the user may not be aware that a term is defined.
Chapter 3 Building Planning.
Chapter 3 provides guidelines for a minimum level of structural integrity, life safety, fire safety and livability for inhabitants of dwelling units regulated by this code. Chapter 3 is a compilation of the code requirements specific to the building planning sector of the design and construction process. This chapter sets forth code requirements dealing with light, ventilation, sanitation, minimum room size, ceiling height and environmental comfort. Chapter 3 establishes life-safety provisions including limitations on glazing used in hazardous areas, specifications on stairways, use of guards at elevated surfaces, window and fall protection, and rules for means of egress. Snow, wind and seismic design live and dead loads and flood-resistant construction, as well as solar energy systems are addressed in this chapter.
Chapter 4 Foundations.
Chapter 4 provides the requirements for the design and construction of foundation systems for buildings regulated by this code. Provisions for seismic load, flood load and frost protection are contained in this chapter. A foundation system consists of two interdependent components: the foundation structure itself and the supporting soil.
The prescriptive provisions of this chapter provide requirements for constructing footings and walls for foundations of wood, masonry, concrete and precast concrete. In addition to a foundation’s ability to support the required design loads, this chapter addresses several other factors that can affect foundation performance. These include controlling surface water and subsurface drainage, requiring soil tests where conditions warrant and evaluating proximity to slopes and minimum depth requirements. The chapter also provides requirements to minimize adverse effects of moisture, decay and pests in basements and crawl spaces.
Chapter 5 Floors.
Chapter 5 provides the requirements for the design and construction of floor systems that will be capable of supporting minimum required design loads. This chapter covers four different types: wood floor framing, wood floors on the ground, cold-formed steel floor framing and concrete slabs on the ground. Allowable span tables are provided that greatly simplify the determination of joist, girder and sheathing sizes for raised floor systems of wood framing and cold-formed steel framing. This chapter also contains prescriptive requirements for wood-framed exterior decks and their attachment to the main building.
Chapter 6 Wall Construction.
Chapter 6 contains provisions that regulate the design and construction of walls. The wall construction covered in Chapter 6 consists of five different types: wood framed, cold-formed steel framed, masonry, concrete and structural insulated panel (SIP). The primary concern of this chapter is the structural integrity of wall construction and transfer of all imposed loads to the supporting structure. This chapter provides the requirements for the design and construction of wall systems that are capable of supporting the minimum design vertical loads (dead, live and snow loads) and lateral loads (wind or seismic loads). This chapter contains the prescriptive requirements for wall bracing and/or shear walls to resist t
CRC § 2025 High relevance — show source text
The prescriptive provisions of this chapter provide requirements for constructing footings and walls for foundations of wood, masonry, concrete and precast concrete. In addition to a foundation’s ability to support the required design loads, this chapter addresses several other factors that can affect foundation performance. These include controlling surface water and subsurface drainage, requiring soil tests where conditions warrant and evaluating proximity to slopes and minimum depth requirements. The chapter also provides requirements to minimize adverse effects of moisture, decay and pests in basements and crawl spaces.
Chapter 5 Floors.
Chapter 5 provides the requirements for the design and construction of floor systems that will be capable of supporting minimum required design loads. This chapter covers four different types: wood floor framing, wood floors on the ground, cold-formed steel floor framing and concrete slabs on the ground. Allowable span tables are provided that greatly simplify the determination of joist, girder and sheathing sizes for raised floor systems of wood framing and cold-formed steel framing. This chapter also contains prescriptive requirements for wood-framed exterior decks and their attachment to the main building.
Chapter 6 Wall Construction.
Chapter 6 contains provisions that regulate the design and construction of walls. The wall construction covered in Chapter 6 consists of five different types: wood framed, cold-formed steel framed, masonry, concrete and structural insulated panel (SIP). The primary concern of this chapter is the structural integrity of wall construction and transfer of all imposed loads to the supporting structure. This chapter provides the requirements for the design and construction of wall systems that are capable of supporting the minimum design vertical loads (dead, live and snow loads) and lateral loads (wind or seismic loads). This chapter contains the prescriptive requirements for wall bracing and/or shear walls to resist the imposed lateral loads due to wind and seismic activity.
Chapter 6 also regulates exterior windows and doors installed in walls. This chapter contains criteria for the performance of exterior windows and doors and includes provisions for testing and labeling, garage doors, windborne debris protection and anchorage details.
Chapter 7 Wall Covering.
Chapter 7 contains provisions for the design and construction of interior and exterior wall coverings. This chapter establishes the various types of materials, materials standards and methods of application permitted for use as interior coverings, including interior plaster, gypsum board, ceramic tile, wood veneer paneling, hardboard paneling, wood shakes and wood shingles. Chapter 7 also contains requirements for the use of vapor retarders for moisture control in walls.
2025 CALIFORNIA RESIDENTIAL CODE xv
on Jul 18, 2025 11:14 AM (CDT) THEREUNDER.
Exterior wall coverings provide the weather-resistant exterior envelope that protects the building’s interior from the elements. Chapter 7 provides the requirements for wind resistance and water-resistive barrier for exterior wall coverings. This chapter prescribes the exterior wall coverings as well as the water-resistive barrier required beneath the exterior materials. Exterior wall coverings regulated by this section include aluminum, stone and masonry veneer, wood, hardboard, particleboard, wood structural panel siding, wood shakes and shingles, exterior plaster, steel, vinyl, fiber cement and exterior insulation finish systems.
Chapter 8 Roof-Ceiling Construction.
CRC § 5.2 High relevance — show source text
R404.5.2 Precast concrete foundation design drawings. Precast concrete foundation wall design drawings shall be submitted to the building official and approved prior to installation. Drawings shall include, at a minimum, the following information:
Design loading as applicable.
Footing design and material.
Concentrated loads and their points of application.
Soil bearing capacity.
Maximum allowable total uniform load.
Seismic design category.
Basic wind speed.
R404.5.3 Identification. Precast concrete foundation wall panels shall be identified by a certificate of inspection label issued by an approved third-party inspection agency.
SECTION R405 —FOUNDATION DRAINAGE
R405.1 Concrete or masonry foundations. Drains shall be provided around concrete or masonry foundations that retain earth and enclose habitable or usable spaces located below grade. Drainage tiles, gravel or crushed stone drains, perforated pipe or other approved systems or materials shall be installed at or below the top of the footing or below the bottom of the slab and shall discharge by gravity or mechanical means into an approved drainage system. Gravel or crushed stone drains shall extend not less than 1 foot (305 mm) beyond the outside edge of the footing and 6 inches (152 mm) above the top of the footing and be covered with an approved filter membrane material. The top of open joints of drain tiles shall be protected with strips of building paper. Except where otherwise recommended by the drain manufacturer, perforated drains shall be surrounded with an approved filter membrane or the filter membrane shall cover the washed gravel or crushed rock covering the drain. Drainage tiles or perforated pipe shall be placed on not less than 2 inches (51 mm) of washed gravel or crushed rock not less than one sieve size larger than the tile joint opening or perforation and covered with not less than 6 inches (152 mm) of the same material.
Exception: A drainage system is not required where the foundation is installed on well-drained ground or sand-gravel mixture soils according to the Unified Soil Classification System, Group I soils, as detailed in Table R401.4.1(2).
R405.1.1 Precast concrete foundation. Precast concrete walls that retain earth and enclose habitable or useable space located below-grade that rest on crushed stone footings shall have a perforated drainage pipe installed below the base of the wall on either the interior or exterior side of the wall, not less than 1 foot (305 mm) beyond the edge of the wall. If the exterior drainage pipe is used, an approved filter membrane material shall cover the pipe. The drainage system shall discharge into an approved sewer system or to daylight.
R405.2 Wood foundations. Wood foundations enclosing habitable or usable spaces located below grade shall be adequately drained in accordance with Sections R405.2.1 through R405.2.3.
R405.2.1 Base. A porous layer of gravel, crushed stone or coarse sand shall be placed to a minimum thickness of 4 inches (102 mm) under the basement floor. Provision shall be made for automatic draining of this layer and the gravel or crushed stone wall footings.
R405.2.2 Vapor retarder. A 6-mil-thick (0.15 mm) polyethylene vapor retarder shall be applied over the porous layer with the basement floor constructed over the polyethylene.
CRC § 3-73 High relevance — show source text
R326 Sanitation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-73
R327 Toilet, Bath and Shower Spaces. . . . . . . . . . . . . . . . . 3-73
R328 Aging-in-Place Design and Fall Prevention . . . . . . . . 3-73
R329 Solar Energy Systems . . . . . . . . . . . . . . . . . . . . . . . . . . 3-74
R330 Energy Storage Systems . . . . . . . . . . . . . . . . . . . . . . . 3-76
R331 Stationary Engine Generators. . . . . . . . . . . . . . . . . . . 3-79
R332 Stationary Fuel Cell Power Systems . . . . . . . . . . . . . 3-79
R333 Reserved . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-79
R334 Construction Waste Reduction, Disposal and Recycling . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-79
R335 Special Provisions for Licensed 24-Hour Care Facilities in a Group R-3.1 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-79
R336 Large Family Day-Care Homes . . . . . . . . . . . . . . . . . . . 3-82
R337 Materials and Construction Methods for Exterior
Wildfire Exposure . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-83
R338 Electric Vehicle . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-83
2025 CALIFORNIA RESIDENTIAL CODE xxi
on Jul 18, 2025 11:14 AM (CDT) THEREUNDER.
CONTENTS
R339 Reserved . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-84
R340 Pollutant Control . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-84
CHAPTER 4 FOUNDATIONS . . . . . . . . . . . . . . . . . . . . . . . . . 4-3
R401 General . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4-3
R402 Materials . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4-5
CRC § 2.4 High relevance — show source text
Framing members that are both load-bearing and stabilization members shall meet the requirements of Section R602 and this section. Nonstructural stabilization members shall be not more than 32 inches (813 mm) on center. 2. Horizontal stabilization shall be installed at not more than 24 inches (610 mm) on center and in accordance with Figure BI103.2.4(1), BI103.2.4(2) or BI103.2.4(3). Horizontal stabilization shall be of any of the following with the stated minimum dimensions: [3] / 4 -inch (19.1 mm) bamboo, [1] / 2 -inch (12.7 mm) fiberglass rod, 1-inch (25 mm) wood dowel or nominal 1-inch by 2-inch (25 mm by 51 mm) wood.
FIGURE BI103.2.4(1)—LIGHT STRAW-CLAY WALL WITH LARSEN TRUSSES
DOUBLE TOP PLATE
VERTICAL SOLID BLOCKING
FLAT SOLID BLOCKING
LADDER (LARSEN) TRUSSES MADE WITH 2x4s AND GUSSETS PER SECTION BI103.2.4, ITEM 1
GUSSETS: [3] / 8 ″ x 3 ″ PLYWOOD OR 1x4 FASTENERS: 4–4d NAILS OR 4–1¾ ″ STAPLES
WOOD OR METAL STRAP BRACING (LIB) PER TABLE 602.10.4 WHERE APPLICABLE PER SECTION R602.10
LIGHT STRAW-CLAY INFILL
HORIZONTAL STABILIZATION OF LIGHT STRAW-CLAY PER SECTION BI103.4, ITEM 2
ANCHORAGE PER SECTION R403.1.6
2X SILL PLATE
CONCRETE OR MASONRY FOUNDATION PER SECTION R401
FRAMING FASTENERS PER TABLE R602.3(1)
For SI: 1 inch = 25.4 mm.
APPENDIX BI-4 2025 CALIFORNIA RESIDENTIAL CODE
on Jul 18, 2025 11:14 AM (CDT) THEREUNDER.
APPENDIX BI — LIGHT STRAW-CLAY CONSTRUCTION
FIGURE BI103.2.4(2)—LIGHT STRAW-CLAY WALL, SINGLE STUD WIDTH
DOUBLE TOP PLATE
FLAT SOLID BLOCKING
WOOD METAL STRAP BRACING (LIB) PER TABLE R602.10.4 WHERE APPLICABLE PER SECTION R602.10
2X STUDS PER SECTION BI103.2.4, ITEM 1
1x1 CLEAT CENTERED ON EACH STUD FACE BETWEEN HORIZONTAL STABILIZATION
HORIZONTAL STABILIZATION OF LIGHT STRAW-CLAY PER SECTION BI103.2.4, ITEM 2
LIGHT STRAY-CLAY INFILL
ANCHORAGE PER SECTION R403.1.6
2X SILL PLATE
CONCRETE OR MASONRY FOUNDATION PER SECTION R401
FRAMING FASTENERS PER TABLE R602.3(1)
FIGURE BI103.2.4(3)—LIGHT STRAW-CLAY WALL WITH BLIND STUDS
DOUBLE TOP PLATES
2X LET-IN PLATE
WOOD METAL BRACING (LIB) PER TABLE R602.10.4 WHERE APPLICABLE PER SECTION R602.10
2x6 MINIMUM STUDS PER SECTION BI103.2.4, ITEM 1
LIGHT STRAW-CLAY INFILL
CRC § 2025 High relevance — show source text
It is important to understand that the IRC contains coverage for what is conventional and common in residential construction practice. While the IRC will provide all of the needed coverage for most residential construction, it might not address construction practices and systems that are atypical or rarely encountered in the industry. Therefore, the IRC contains several references to other codes either as an alternative to the provisions of the IRC or where the IRC lacks coverage for a particular type of structure, design, system, appliance or method of construction. In other words, the IRC is meant to be all inclusive for typical residential construction and it relies on other codes only where alternatives are desired or where the code lacks coverage for the uncommon aspect of residential construction. Of course, the IRC constantly evolves to address new technologies and construction practices that were once uncommon, but are now common.
The IRC is unique in that much of it, including Chapters 3 through 9 and Chapters 34 through 43, is presented in an ordered format that is consistent with the normal progression of construction, starting with the design phase and continuing through the final trimout phase. This is consistent with the “cookbook” philosophy of the IRC.
2025 CALIFORNIA RESIDENTIAL CODE xiii
on Jul 18, 2025 11:14 AM (CDT) THEREUNDER.
xiv 2025 CALIFORNIA RESIDENTIAL CODE
on Jul 18, 2025 11:14 AM (CDT) THEREUNDER.
Arrangement and Format of the 2025 CRC
The CRC is divided into nine main parts, specifically: Part I—Administrative, Part II—Definitions, Part III—Building Planning and Construction, Part IV—Energy Conservation, Part V—Mechanical, Part VI—Fuel Gas, Part VII—Plumbing, Part VIII—Electrical and Part IX—Referenced Standards. Parts IV through VIII of IRC are not adopted in California and replaced with references to appropriate parts of Title 24. The following provides a brief description of the content of each chapter and appendix of the CRC:
Chapter 1 Scope and Administration.
Chapter 1 establishes the limits of applicability of the code and describes how the code is to be applied and enforced. The provisions of Chapter 1 establish the authority and duties of the code official appointed by the authority having jurisdiction and also establish the rights and privileges of the design professional, contractor and property owner.
Chapter 2 Definitions.
Chapter 2 is the repository of the definitions of terms used in the body of the code. The user of the code should be familiar with and consult this chapter because the definitions are essential to the correct interpretation of the code and because the user may not be aware that a term is defined.
Chapter 3 Building Planning.
Chapter 3 provides guidelines for a minimum level of structural integrity, life safety, fire safety and livability for inhabitants of dwelling units regulated by this code. Chapter 3 is a compilation of the code requirements specific to the building planning sector of the design and construction process. This chapter sets forth code requirements dealing with light, ventilation, sanitation, minimum room size, ceiling height and environmental comfort. Chapter 3 establishes life-safety provisions including limitations on glazing used in hazardous areas, specifications on stairways, use of guards at elevated surfaces, window and fall protection, and rules for means of egress. Snow, wind and seismic design live and dead loads and flood-resistant construction, as well as solar energy systems are addressed in this chapter.
Chapter 4 Foundations.
CRC § 8.2 High relevance — show source text
1808 A .8.2 Concrete cover. The concrete cover provided for prestressed and nonprestressed reinforcement in foundations shall be not less than the largest applicable value specified in Table 1808 A .8.2. Longitudinal bars spaced less than 1 [1] / 2 inches (38 mm) clear distance apart shall be considered to be bundled bars for which the concrete cover provided shall be not less than that required by Section 20.5.1.3.5 of ACI 318. Concrete cover shall be measured from the concrete surface to the outermost surface of the steel to which the cover requirement applies. Where concrete is placed in a temporary or permanent casing or a mandrel, the inside face of the casing or mandrel shall be considered to be the concrete surface.
TABLE 1808A.8.2—MINIMUM CONCRETE COVER Col2 FOUNDATION ELEMENT OR CONDITION MINIMUM COVER 1. Shallow foundations In accordance with Section 20.5 of ACI 318 2. Precast nonprestressed deep foundation elements
Exposed to seawater
Not manufactured under plant conditions
Manufactured under plant control conditions3 inches
2 inches
In accordance with Section 20.5.1.3.3 of ACI 3183. Precast prestressed deep foundation elements
Exposed to seawater
Other2.5 inches
In accordance with Section 20.5.1.3.3 of ACI 3184. Cast-in-place deep foundation elements not enclosed by a steel pipe, tube or permanent
casing2.5 inches 5. Cast-in-place deep foundation elements enclosed by a steel pipe, tube or permanent casing 1 inch 6. Structural steel core within a steel pipe, tube or permanent casing 2 inches 7. Cast-in-place drilled shafts enclosed by a stable rock socket 1.5 inches For SI:1 inch = 25.4 mm. For SI:1 inch = 25.4 mm. 1808 A .8.3 Placement of concrete. Concrete shall be placed in such a manner as to ensure the exclusion of any foreign matter and to secure a full-size foundation. Concrete shall not be placed through water unless a tremie or other method approved by the building official is used. Where placed under or in the presence of water, the concrete shall be deposited by approved means to ensure minimum segregation of the mix and negligible turbulence of the water. Where depositing concrete from the top of a deep foundation element, the concrete shall be chuted directly into smooth-sided pipes or tubes or placed in a rapid and continuous operation through a funnel hopper centered at the top of the element.
2025 CALIFORNIA BUILDING CODE 18A-13
on Jul 18, 2025 11:14 AM (CDT) THEREUNDER.
SOILS AND FOUNDATIONS
1808 A .8.4 Protection of concrete. Concrete foundations shall be protected from freezing during depositing and for a period of not less than 5 days thereafter. Water shall not be allowed to flow through the deposited concrete.
Frequently asked questions
What exactly does “foundation spaces” mean in Chapter 4?
Foundation spaces are the enclosed below‑grade or under‑floor areas the foundation walls or slabs create — typically basements, crawl spaces/under‑floor spaces, and slab-on-grade areas; Chapter 4 provides requirements for their drainage, moisture control and structural support (see § R401.1 and § R408).
Are perimeter drains always required?
Perimeter drains are required around concrete or masonry foundations that retain earth and enclose habitable/usable below‑grade space, except where the foundation sits on well‑drained Group I soils as shown in Table R401.4.1(2) (see § R405.1 and its exception).
Can I use a wood foundation for a two‑story house?
The prescriptive provisions allow wood foundations only for buildings not more than two floors and a roof and with other spacing limits; seismic category limits also apply (see the Exception in § R401.1). For other situations, engineered design may be required.
How deep must frost‑protected footings be?
Frost‑protected shallow foundation (FPSF) minimum footing depth and insulation requirements are shown in § R403.3 and Table R403.3(1); FPSF use is limited to heated buildings maintained at a monthly mean temperature not less than 64°F (18°C). Consult the table/figure for exact D and R‑values.
Where do I find the prescriptive footing sizes?
Prescriptive footing widths and thicknesses for light‑frame construction are in Table R403.1(1) under § R403; use those unless an engineered footing per § R403/ACI is required.
More in California Residential Code
Ask about the CRC
Get cited, plain-English answers on the California Residential Code for your project — any code section, any scenario.
Start Free Trial