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Chapter 19 — CONCRETE

2025 California Building Code (Title 24, Part 2) · 2025 edition · updated 2026-07-29 · California

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

User notes:

About this chapter: Chapter 19 provides minimum accepted practices for the design and construction of buildings and structural components using concrete—both plain and reinforced. Chapter 19 relies primarily on the reference to American Concrete Institute (ACI) 318, Building Code Requirements for Structural Concrete. Structural concrete must be designed and constructed to comply with this code and all listed standards. There are also specific provisions addressing slabs-on-ground and shotcrete.

This chapter was extensively reorganized for the 2024 edition. For complete information, see the relocations table in the Preface information of this code.

ICC code development note: Code change proposals to this chapter will be considered by the IBC—Structural Code Development Committee during the

2025 (Group B) Code Development Cycle.

11.9 - Foundation walls.

Horizontal reinforcing of concrete foundation walls for wood-frame or light-steel buildings shall consist of the equivalent of not less than one No. 5 bar located at the top and bottom of the wall. Where such walls exceed 3 feet (914 mm)

19-10 2025 CALIFORNIA BUILDING CODE

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

CONCRETE

in height, intermediate horizontal reinforcing shall be provided at spacing not to exceed 2 feet (610 mm) on center. Minimum verti- cal reinforcing shall consist of No. 3 bars at 24 inches (610 mm) on center.

Where concrete foundation walls or curbs extend above the floor line and support wood-frame or light-steel exterior, bearing or shear walls, they shall be doweled to the foundation wall below with a minimum of No. 3 bars at 24 inches (610 mm) on center. Where the height of the wall above the floor line exceeds 18 inches (457 mm), the wall above and below the floor line shall meet the requirements of ACI 318 Section 11.6 and 11.7.

1909.3.2 ACI 318, Section 12.7.3. Add Section 12.7.3.4 to ACI 318 as follows:

12.7.3.4 – At least two No. 5 bars in diaphragms having two layers of reinforcement in both directions and one No. 5 bar in diaphragms having a single layer of reinforcement in both directions shall be provided around openings larger than 12 inches in any dimension in addition to the minimum reinforcement required by Section 12.6.

1909.3.3 ACI 318, Chapter 14. Plain concrete is not permitted.

1909.3.4 ACI 318, Section 18.10.6.5. Modify ACI 318, Section 18.10.6.5 by adding the following:

Where boundary members are not required by ACI 318 Section 18.10.6.2 or 18.10.6.3, minimum reinforcement parallel to the edges of all structural walls and the boundaries of all openings shall consist of twice the cross-sectional area of the minimum shear reinforce- ment required per lineal foot of wall. Horizontal extent of boundary element shall be per ACI 318 Section 18.10.6.4 (a), (b) and (c).

1909.3.5 ACI 318, Section 18.12.6. Add Section 18.12.6.2 to ACI 318 as follows:

Collector and boundary elements in topping slabs placed over precast floor and roof elements shall not be less than 3 inches (76 mm) or 6 d b thick, where d b is the diameter of the largest reinforcement in the topping slab.

1909.3.6 ACI 318, Table 21.2.2. Replace Table 21.2.2 as follows:

TABLE 21.2.2 STRENGTH REDUCTION FACTOR φ FOR MOMENT, AXIAL FORCE, OR COMBINED MOMENT AND AXIAL FORCE

NET TENSILE STRAINεt CLASSIFICATION φ φ φ φ
NET TENSILE STRAINεt CLASSIFICATION Type of transverse reinforcement Type of transverse reinforcement Type of transverse reinforcement Type of transverse reinforcement
NET TENSILE STRAINεt CLASSIFICATION Spirals conforming to 25.7.3 Spirals conforming to 25.7.3 Other Other
εt ≤ εty Compression-controlled 0.75 (a) 0.65 (b)
εty < εt < (εty + 0.003) Transition1,2 0.75
0.15
ε_t_
ε_ty_
–
ε_t_
ε_ty_
–
----------------
+
*		 (c) 0.65
0.25
ε_t_
ε_ty_
–
ε_t_
ε_ty_
–
----------------
+
*		 (d)
εt ≥ (εty + 0.003) Tension-controlled_3_ 0.9 (e) 0.9 (f)
1. For sections classified as transition, it shall be permitted to useφ corresponding to compression-controlled sections.
2. ε_t_
* is the greater of net tensile strain calculated for Pn = 0.1Agf c′_ and (ε_ty + 0.003).
3. For sections with factored axial compression force Pu ≥ 0.1Agfc′, φ shall be calculated using equation (c) or (d) for sections classified as transition, as applicable.

1909.3.7 ACI 318, Section 25.2.10. Modify ACI 318 Section 25.2.10 as follows:

25.2.10 - For ties and hoops in columns to be placed with shotcrete, minimum clear spacing shall be 3 in. Shotcrete shall not be applied to spirally tied columns.

1909.3.8 ACI 318, Section 26.5.2. Modify ACI 318 Section 26.5.2.1 by replacing Items (l), (m) and (n) and adding item (q) as follows:

(l) Shotcrete surfaces intended to receive subsequent shotcrete placement following an interruption of 30 minutes or more shall be roughened to a full amplitude of approximately [1] / 4 in. before the shotcrete has reached final set. The film of laitance which forms on the surface of the shotcrete shall be removed within approximately 2 hours after application by brushing with a stiff broom. If this film is not removed within 2 hours, it shall be removed by thorough wire brushing or a mechanical method accept- able to the enforcement agency.

(m) Before placing additional material onto hardened shotcrete, laitance shall be removed, joints shall be cleaned and the surface shall be dampened. Construction joints over 8 hours old shall be thoroughly cleaned with air and water prior to receiving shotcrete.

(n) In-place fresh concrete that exhibits sags, sloughs, segregation, honeycombing, sand pockets, or other obvious defects shall be removed and replaced. Shotcrete above sags and sloughs shall be removed and replaced while still plastic.

(q) Surface preparation: Concrete or masonry to receive shotcrete shall have the entire surface thoroughly cleaned and rough- ened by a mechanical method acceptable to the enforcement agency, and just prior to receiving shotcrete, shall be thoroughly cleaned of all debris, dirt and dust. Concrete and masonry shall be brought to a saturated surface-dry (SSD) before shotcrete is deposited.

1909.3.9 ACI 318, Section 26.11.1.2. Modify ACI 318, Section 26.11.1.2 by adding Item (e) as follows:

(e) Forms for shotcrete shall be substantial and rigid. Forms shall be built and placed so as to permit the escape of air and rebound. Adequate ground wires, which are to be used as screeds, shall be placed to establish the thickness, surface planes and form of the shotcrete work. All surfaces shall be rodded to these wires.

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

CONCRETE

1909.3.10 ACI 318, Section 26.12.2.1. Modify ACI 318, Section 26.12.2.1 by replacing Item (a) as follows:

(a) Samples for strength tests of each class of concrete placed each day shall be taken not less than once a day, or not less than once for each 50 cubic yards (38.2 m [3] ) of concrete, or not less than once for each 2,000 square feet (186 m [2] ) of surface area for slabs or walls. Additional samples for seven-day compressive strength tests shall be taken for each class of concrete at the beginning of the concrete work or whenever the mix or aggregate is changed.

1909.4 Shotcrete.

Shotcrete shall also conform to the provisions of ACI 506.2 and ACI 506R. The specified compressive strength of shot- crete shall not be less than 4,000 psi (27.6 MPa). Preconstruction tests of one or more shotcrete mockup panels prepared in accordance with Section 1705A.3.9.2 are required. In addition to testing requirements in ACI 318, special inspection and testing shall be in accor- dance with Section 1705A.3.9. The evaluation of the shotcrete mockup panel to qualify bar clearance dimensions in accordance with ACI 318 Section 25.2.7 or contact lap splices in accordance with ACI 318 Section 25.5.1.7 shall be in accordance with the requirements of ACI 506.4R with a core quality category of Very Good given in ACI 506.6T. Tolerances for shotcrete construction shall be defined by the construction documents.

1909.5 Existing concrete structures.

The structural use of existing concrete with a core strength less than 1,500 psi (10.3MPa) is not permitted in rehabilitation work.

For existing concrete structures, sufficient cores shall be taken at representative locations throughout the structure, as designated by the architect or structural engineer, so that knowledge will be had of the in-place strength of the concrete. At least three cores shall be taken from each building for each 4,000 square feet (372 m [2] ) of floor area, or fraction thereof. Cores shall be at least 4 inches (102 mm) in diameter. Cores as small as 2.75 inches (70 mm) in diameter may be allowed by the enforcement agency when reinforcement is closely spaced and the coarse aggregate does not exceed [3] / 4 inch (19 mm).

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▸ Contents — 2025 California Building Code (Title 24, Part 2)
2025 California Building Code (Title 24, Part 2)
  1. Chapter 1 — ADMINISTRATION
  2. Chapter 2 — DEFINITIONS
  3. Chapter 3 — OCCUPANCY CLASSIFICATION AND USE
  4. Chapter 4 — SPECIAL DETAILED REQUIREMENTS BASED ON OCCUPANCY A…
  5. Chapter 5 — GENERAL BUILDING HEIGHTS AND AREAS
  6. Chapter 6 — TYPES OF CONSTRUCTION
  7. Chapter 7 — FIRE AND SMOKE PROTECTION FEATURES
  8. Chapter 7A — MATERIALS AND CONSTRUCTION METHODS FOR EXTERIOR W…
  9. Chapter 8 — INTERIOR FINISHES
  10. Chapter 9 — FIRE PROTECTION AND LIFE SAFETY SYSTEMS
  11. Chapter 10 — MEANS OF EGRESS
  12. Chapter 11 — RESERVED
  13. Chapter 11A — HOUSING ACCESSIBILITY
  14. Chapter 11B — ACCESSIBILITY TO PUBLIC BUILDINGS, PUBLIC ACCOMM…
  15. Chapter 12 — INTERIOR ENVIRONMENT
  16. Chapter 13 — ENERGY EFFICIENCY
  17. Chapter 14 — EXTERIOR WALLS
  18. Chapter 15 — ROOF ASSEMBLIES AND ROOFTOP STRUCTURES
  19. Chapter 16 — STRUCTURAL DESIGN
  20. Chapter 16A — STRUCTURAL DESIGN
  21. Chapter 17 — SPECIAL INSPECTIONS AND TESTS
  22. Chapter 17A — SPECIAL INSPECTIONS AND TESTS
  23. Chapter 18 — SOILS AND FOUNDATIONS
  24. Chapter 18A — SOILS AND FOUNDATIONS
  25. ▸ Chapter 19 — CONCRETE
    Overview
    1. Section 1901 — GENERAL
    2. Section 1902 — COORDINATION OF TERMINOLOGY
    3. Section 1903 — SPECIFICATIONS FOR TESTS AND MATERIALS
    4. Section 1904 — DURABILITY REQUIREMENTS
    5. Section 1905 — SEISMIC REQUIREMENTS
    6. Section 1906 — FOOTINGS FOR LIGHT-FRAME CONSTRUCTION
    7. Section 1907 — SLABS-ON-GROUND
    8. Section 1908 — SHOTCRETE
    9. Section 1909 — ADDITIONAL REQUIREMENTS FOR COMMUNITY COLLEGES …
    10. Section 1910 — ADDITIONAL REQUIREMENTS FOR SKILLED NURSING FAC…
    11. Section 1911 — EXISTING CONCRETE STRUCTURES [OSHPD 1R, 2 & 5]
  26. Chapter 19A — CONCRETE
  27. Chapter 20 — ALUMINUM
  28. Chapter 21 — MASONRY
  29. Chapter 21A — MASONRY
  30. Chapter 22 — STEEL
  31. Chapter 22A — STEEL
  32. Chapter 23 — WOOD
  33. Chapter 24 — GLASS AND GLAZING
  34. Chapter 25 — GYPSUM PANEL PRODUCTS AND PLASTER
  35. Chapter 26 — PLASTIC
  36. Chapter 27 — ELECTRICAL
  37. Chapter 28 — MECHANICAL SYSTEMS
  38. Chapter 29 — PLUMBING SYSTEMS
  39. Chapter 30 — ELEVATORS AND CONVEYING SYSTEMS
  40. Chapter 31 — SPECIAL CONSTRUCTION
  41. Chapter 31A — SYSTEMS FOR WINDOW CLEANING OR EXTERIOR BUILDING…
  42. Chapter 31B — PUBLIC POOLS
  43. Chapter 31C — RADIATION
  44. Chapter 31D — FOOD ESTABLISHMENTS
  45. Chapter 31F — MARINE OIL TERMINALS
  46. Chapter 32 — ENCROACHMENTS INTO THE PUBLIC RIGHT-OF-WAY
  47. Chapter 33 — SAFEGUARDS DURING CONSTRUCTION
  48. Chapter 34 — RESERVED
  49. Chapter 35 — REFERENCED STANDARDS
  50. Appendix A — EMPLOYEE QUALIFICATIONS
  51. Appendix B — BOARD OF APPEALS
  52. Appendix C — GROUP U—AGRICULTURAL BUILDINGS
  53. Appendix D — FIRE DISTRICTS
  54. Appendix E — RESERVED
  55. Appendix F — RODENTPROOFING
  56. Appendix G — FLOOD-RESISTANT CONSTRUCTION
  57. Appendix H — SIGNS
  58. Appendix I — PATIO COVERS
  59. Appendix J — GRADING
  60. Appendix K — GROUP R-3 AND GROUP R-3.1 OCCUPANCIES PROTECTED B…
  61. Appendix L — EARTHQUAKE RECORDING INSTRUMENTATION
  62. Appendix M — TSUNAMI-GENERATED FLOOD HAZARDS
  63. Appendix N — REPLICABLE BUILDINGS
  64. Appendix O — PERFORMANCE-BASED APPLICATION
  65. Appendix P — SLEEPING LOFTS
  66. Appendix Q — EMERGENCY HOUSING

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