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Chapter 4 — FOUNDATIONS

Section R402 — MATERIALS

2025 California Residential Code (Title 24, Part 2.5) · 2025 edition · updated 2026-07-29 · California

Italicized text is a California amendment to the model code, as printed in the official publication.

R402.1 Wood foundations.

Wood foundation systems shall be designed and installed in accordance with the provisions of this code.

R402.1.1 Fasteners. Fasteners used below grade to attach plywood to the exterior side of exterior basement or crawl-space wall studs, or fasteners used in knee wall construction, shall be of Type 304 or 316 stainless steel. Fasteners used above grade to attach plywood and all lumber-to-lumber fasteners except those used in knee wall construction shall be of Type 304 or 316 stainless steel, silicon bronze, copper, hot-dipped galvanized (zinc coated) steel nails, or hot-tumbled galvanized (zinc coated) steel nails. Electro-galvanized steel nails and galvanized (zinc coated) steel staples shall not be permitted.

R402.1.2 Wood treatment. Lumber and plywood shall be pressure-preservative treated and dried after treatment in accordance with AWPA U1 (Commodity Specification A, Special Requirement 4.2), and shall bear the label of an accredited agency. Where lumber or plywood is cut or drilled after treatment, the treated surface shall be field treated with copper naphthenate, the concentration of which shall contain not less than 2-percent copper metal, by repeated brushing, dipping or soaking until the wood cannot absorb more preservative.

R402.2 Concrete.

Concrete shall have a minimum specified compressive strength of f′ c , as shown in Table R402.2. Concrete

R402.2 Concrete. Concrete shall have a minimum specified compressive strength of f′ c, as shown in Table R402.2. Concrete subject to moderate or severe weathering as indicated in Table R301.2 shall be air entrained as specified in Table R402.2. The maximum weight of fly ash, other pozzolans, silica fume, slag or blended cements that is included in concrete mixtures for garage floor slabs and for exterior porches, carport slabs and steps that will be exposed to deicing chemicals shall not exceed the percentages of the total weight of cementitious materials specified in Section 19.3.3.4 of ACI 318. Materials used to produce concrete and testing thereof shall comply with the applicable standards listed in Chapters 19 and 20 of ACI 318 or ACI 332.

crete mixtures for garage floor slabs and for exterior porches, carport slabs and steps that will be exposed to deicing chemicals shall not exceed the percentages of the total weight of cementitious materials specified in Section 19.3.3.4 of ACI 318. Materials used to produce concrete and testing thereof shall comply with the applicable standards listed in Chapters 19 and 20 of ACI 318 or ACI 332.

TABLE R402.2—MINIMUM SPECIFIED COMPRESSIVE STRENGTH OF CONCRETE

** TYPE OR LOCATION OF CONCRETE CONSTRUCTION** ** MINIMUM SPECIFIED COMPRESSIVE STRENGTHa (****f′c)** ** MINIMUM SPECIFIED COMPRESSIVE STRENGTHa (****f′c)** ** MINIMUM SPECIFIED COMPRESSIVE STRENGTHa (****f′c)**
** TYPE OR LOCATION OF CONCRETE CONSTRUCTION** ** Weathering Potentialb** ** Weathering Potentialb** ** Weathering Potentialb**
** TYPE OR LOCATION OF CONCRETE CONSTRUCTION** ** Negligible** ** Moderate** ** Severe**
Basement walls, foundations and other concrete not exposed to the weather 2,500 2,500 2,500c
Basement slabs and interior slabs on grade, except garage floor slabs 2,500 2,500 2,500c
Basement walls, foundation walls, exterior walls and other vertical concrete work
exposed to the weather		 2,500 3,000d 3,000d
Porches, carport slabs and steps exposed to the weather, and garage floor slabs 2,500 3,000d, e, f 3,500d, e, f
For SI: 1 pound per square inch = 6.895 kPa.
a. Strength at 28 days psi.
b. See Table R301.2 for weathering potential.
c. Concrete in these locations that is subject to freezing and thawing during construction shall be air-entrained concrete in accordance with Note d.
d. Concrete shall be air-entrained. Total air content (percent by volume of concrete) shall be not less than 5 percent or more than 7 percent.
e. See Section R402.2 for maximum cementitious materials content.
f. For garage floors with a steel-troweled finish, reduction of the total air content (percent by volume of concrete) to not less than 3 percent is permitted if the specified
compressive strength of the concrete is increased to not less than 4,000 psi.

R402.2.1 Materials for concrete. Materials for concrete shall comply with the requirements of Section R608.5.1.

R402.3 Precast concrete.

Precast concrete foundations shall be designed in accordance with Section R404.5 and shall be installed in accordance with the provisions of this code and the manufacturer’s instructions.

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

FOUNDATIONS

R402.3.1 Precast concrete foundation materials. Materials used to produce precast concrete foundations shall meet the following requirements:

  1. All concrete used in the manufacture of precast concrete foundations shall have a minimum compressive strength of 5,000 psi (34 470 kPa) at 28 days. Concrete exposed to a freezing and thawing environment shall be air entrained with a minimum total air content of 5 percent.

  2. Structural reinforcing steel shall meet the requirements of ASTM A615, A706M or A996M. The minimum yield strength of reinforcing steel shall be 40,000 psi (Grade 40) (276 MPa). Steel reinforcement for precast concrete foundation walls shall have a minimum concrete cover of [3] / 4 inch (19.1 mm).

  3. Panel-to-panel connections shall be made with Grade II steel fasteners.

  4. The use of nonstructural fibers shall conform to ASTM C1116.

  5. Grout used for bedding precast foundations placed on concrete footings shall meet ASTM C1107.

R402.4 Masonry.

Masonry systems shall be designed and installed in accordance with this chapter and shall have a minimum specified compressive strength of 1,500 psi (10.3 MPa).

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▸ Contents — 2025 California Residential Code (Title 24, Part 2.5)
2025 California Residential Code (Title 24, Part 2.5)
  1. Chapter 1 — ADMINISTRATION
  2. Chapter 2 — DEFINITIONS
  3. Chapter 3 — BUILDING PLANNING
  4. ▸ Chapter 4 — FOUNDATIONS
    Overview
    1. Section R401 — GENERAL
    2. Section R402 — MATERIALS
    3. Section R403 — FOOTINGS
    4. Section R404 — FOUNDATION AND RETAINING WALLS
    5. Section R405 — FOUNDATION DRAINAGE
    6. Section R406 — FOUNDATION WATERPROOFING AND DAMPPROOFING
    7. Section R407 — COLUMNS
    8. Section R408 — UNDER-FLOOR SPACE
  5. Chapter 5 — FLOORS
  6. Chapter 6 — WALL CONSTRUCTION
  7. Chapter 7 — WALL COVERING
  8. Chapter 8 — ROOF-CEILING CONSTRUCTION
  9. Chapter 9 — ROOF ASSEMBLIES
  10. Chapter 10 — CHIMNEYS AND FIREPLACES
  11. Chapter 44 — REFERENCED STANDARDS
  12. Appendix AA — BOARD OF APPEALS
  13. Appendix AB — PERMIT FEES
  14. Appendix AC — RESERVED
  15. Appendix BA — RESERVED
  16. Appendix BB — TINY HOUSES
  17. Appendix BC — RESERVED
  18. Appendix BD — RESERVED
  19. Appendix BE — RADON CONTROL METHODS
  20. Appendix BF — PATIO COVERS
  21. Appendix BG — SOUND TRANSMISSION
  22. Appendix BH — AUTOMATIC VEHICULAR GATES
  23. Appendix BI — LIGHT STRAW-CLAY CONSTRUCTION
  24. Appendix BJ — STRAWBALE CONSTRUCTION
  25. Appendix BK — COB CONSTRUCTION (MONOLITHIC ADOBE)
  26. Appendix BL — HEMP-LIME (HEMPCRETE) CONSTRUCTION
  27. Appendix BM — 3D-PRINTED BUILDING CONSTRUCTION
  28. Appendix BN — EXTENDED PLATE WALL CONSTRUCTION
  29. Appendix BO — EXISTING BUILDINGS AND STRUCTURES
  30. Appendix CA — RESERVED
  31. Appendix CB — RESERVED
  32. Appendix CC — RESERVED
  33. Appendix CD — RESERVED
  34. Appendix CE — RESERVED
  35. Appendix CF — RESERVED
  36. Appendix CG — NONSEWERED SANITATION SYSTEMS
  37. Appendix CH — PRIVATE SEWAGE DISPOSAL
  38. Appendix CI — SWIMMING POOL SAFETY ACT
  39. Appendix CJ — EMERGENCY HOUSING
  40. Appendix CK — AREAS PROTECTED BY THE FACILITIES OF THE CENTRAL…

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