CBC · California Building Code

What CBC modifications or coordination with ACI 318/ACI provisions exist (including Chapter 19A)?

For California projects, ACI 318 is the starting point for concrete design but the CBC (Chapter 19/19A and § 1909A) changes certain numeric limits, testing and sampling rules, shotcrete requirements, and seismic definitions — always check § 1903, § 1905, and § 1909A and apply those CBC modifications rather than ACI 318 verbatim.

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Last reviewed: July 5, 2026

What the code requires

The California Building Code (CBC) adopts ACI 318 as the baseline for concrete design and construction but explicitly modifies and supplements ACI 318 through Chapter 19 and Chapter 19A. Key coordination points are: material and test specifications (§ 1903), seismic-specific definitions and supplements (§ 1905), and a set of direct modifications to ACI 318 collected in the “Modifications to ACI 318” section (§ 1909A). These CBC provisions mandate which ACI provisions apply as written, which are changed, and where additional California requirements (for example for shotcrete, sampling, f'c limits, and reinforcement minima) must be used instead of or in addition to ACI 318 .

Requirements in detail

Scope & how to read CBC vs. ACI 318

  • ACI 318 is the referenced standard for concrete; where CBC has a specific modification or addition, the CBC text controls (order of precedence) — see § 1.1.7.1–1.1.7.3 (CBC administration) and the Chapter 19A introductory statements that ACI 318 text is modified as indicated in § 1909A. Use § 1903 for material/test coordination, § 1905 for seismic coordination, and § 1909A for concrete-specific ACI modifications .

Decision-relevant table (common numeric limits and mandatory minima)

Decision item Required value / rule Code Reference
Minimum specified compressive strength for many applications (general) See Table 19.2.1.1; general minimum 3000 psi; special cases higher (see table) § 1909A.1.10 and Table 19.2.1.1
Shotcrete minimum f'c 4000 psi for shotcrete (listed in modified Table 19.2.1.1) § 1909A.1.10 / Table 19.2.1.1
Sampling frequency for concrete strength cylinders Not less than once per day, or once per 50 cy, or once per 2,000 ft² of surface for slabs/walls (additional at mix change/start) § 1909A.1.16 (modifies ACI 318 § 26.12.2.1(a))
Minimum reinforcement for foundation walls (wood-frame/light-steel buildings) Equivalent of one No.5 at top and bottom; intermediate horizontal if >3 ft height at ≤ 2 ft spacing; minimum vertical No.3 @ 24 in. § 1909A.1.6 / ACI 318 add § 11.9
Diaphragm reinforcement around openings At least two No.5 bars for two-layer diaphragms; one No.5 for single-layer diaphragms around openings >12 in. § 1909A.1.7 (adds ACI 318 § 12.7.3.4)
Collector/boundary element topping thickness over precast Minimum 3 in. or 6·db (largest bar diameter) § 1909A.1.9 (adds ACI 318 § 18.12.6.2)
Welding / holding-wire splice controls Holding wire welding allowed only with enforcing-agency approval and QC testing; tack welding primary bars prohibited § 1903.5 (modifies ACI 318 § 26.6.4.x)

(Where the table cites a modified ACI provision, use the CBC modification text in § 1909A or the Chapter 19A section indicated.)

Key CBC modifications called out in § 1909A (high-level)

  • CBC explicitly states that “The text of ACI 318 shall be modified as indicated in Sections 1909A.1.1 through 1909A.1.16” (this is the authority that makes the listed edits binding) — § 1909A.1 .
  • Examples of specific edits included in § 1909A (selection):
    • Prestressed-member end restraints: add requirement to analyze stresses and induced loads per PCI Design Handbook (ACI 318 § 4.12.2.2 modified) — § 1909A.1.1 .
    • Limits on use of certain crack-control provisions for seismic-resisting members (limits on ACI 318 § 9.6.1.3) — § 1909A.1.3 .
    • Added minimum anchorage/tying requirements for precast walls, continuous ties at roof line, development of horizontal wall steel, etc. (ACI 318 § 11.x modifications and additions) — § 1909A.1.4–1.5 .
    • Diaphragm opening reinforcement and collector/boundary element minimum thickness as noted above — §§ 1909A.1.7, 1909A.1.9 .
    • Modified strength sampling frequency and shotcrete-specific sampling and form requirements — § 1909A.1.16 and § 1909A.1.15 .

Seismic coordination (what § 1905 changes or clarifies)

  • § 1905 requires that structural concrete must meet ACI 318 plus the seismic supplements in § 1905; it adds and/or redefines terms used in ACI 318 for seismic design (for example “cast-in-place concrete equivalent diaphragm,” “detailed plain concrete structural wall,” and “ordinary plain concrete structural wall”) so that ACI terminology and ASCE 7/CBC seismic rules are aligned in California designs .
  • Where CBC introduces seismic design definitions or exceptions, those override or refine ACI 318 definitions for use in California projects (see § 1905.2 and Chapter 19A introductory material) .

Exceptions & special cases

  • OSHPD / DSA special jurisdictions: several of the Chapter 19/19A modifications carry brackets such as [OSHPD 1R, 2 & 5] or [DSA-SS/CC] indicating alternate or not-permitted provisions for those agencies (e.g., steel fiber reinforcement and certain ICF systems are restricted or not permitted by OSHPD) — see § 1903 and related bracketed notes .
  • Group R exceptions for durability/tolerances: § 1904 contains a durability exception that reduces f'c requirements for certain low-rise Group R occupancies; also shotcrete tolerance exceptions are noted in tolerances language — see § 1904 and § 1901.7.1 .
  • Precast or prestressed special requirements: CBC adds references to PCI Design Handbook for certain prestressed end conditions and connection analyses — these are mandatory where cited in § 1909A.1.1–.1.2 .

Common mistakes

  • Applying ACI 318 verbatim without checking Chapter 19/19A: designers sometimes miss CBC modifications (for example diaphragm opening reinforcement, shotcrete f'c, foundation-wall minimum bars). Always confirm ACI 318 sections against § 1909A modifications and the Chapter 19A tables .
  • Ignoring sampling frequency and test documentation changes: CBC raises or specifies sampling and QC requirements (daily/50 cy/2,000 ft²) that are stricter than some project practices — see § 1909A.1.16 .
  • Failing to account for jurisdictional exceptions: OSHPD/DSA restrictions (e.g., on steel fiber reinforcement or ICF) are not optional; check § 1903 and bracketed notes before selecting materials or methods .
  • Using higher f'c where CBC limits it (e.g., lightweight concrete in special moment frames): CBC limits certain f'c uses unless experimental evidence is provided — see the modified 19.2.1.1 items in § 1909A.1.10 .

Worked example — special structural wall with lightweight concrete

Scenario: You are designing a special structural wall (Seismic Design Category D) using lightweight normal-strength concrete and Grade 60 reinforcement. You plan to specify f'c = 6000 psi for higher stiffness.

CBC guidance:

  • The CBC modification to ACI 318 Section 19.2.1.1 states that f'c for lightweight concrete in special moment frames and special structural walls shall not exceed 5000 psi unless experimental evidence demonstrates equivalent strength and toughness to normalweight concrete (see item (d) in the modified text) — § 1909A.1.10 .

Application:

  • Because your wall is a special structural wall, the intended f'c = 6000 psi for lightweight concrete exceeds the § 1909A limit of 5000 psi. To proceed you have two options:
    1. Change the mix to normalweight concrete (6000 psi is permitted per Table 19.2.1.1 if other limits are met) or
    2. Provide experimental evidence demonstrating that the lightweight mix at 6000 psi provides equivalent strength/toughness to comparable normalweight members and include that documentation with the submittal — otherwise the CBC limit controls and you must limit specified f'c to 5000 psi for lightweight concrete in this application .

Related provisions

  • § 1903 — Specifications for tests and materials (materials/test standards, GFRC, ICF notes) .
  • § 1904 — Durability requirements for structural and nonstructural concrete (exemptions for limited Group R) .
  • § 1905 — Seismic requirements and added/modified seismic definitions for use with ACI 318 in California .
  • § 1909A (and subparts 1909A.1.1–.1.16) — Specific modifications to ACI 318 (the register of edits you must apply in California) .
  • § 1910A — Concrete, reinforcement and anchor testing (sampling, cementitious material certification, reinforcing bar tests) .
  • Chapter 17A / § 1705A — Special inspection and testing requirements referenced for concrete and shotcrete operations .

Code references

Grounded in the retrieved California Building Code — click a citation to read the verbatim passage:

  • CBC § 1705A.3.9.2 High relevance — show source text

    SECTION 1908 A —SHOTCRETE

    1908 A .1 General. Shotcrete shall be in accordance with the requirements of ACI 318 and the provisions of ACI 506R. 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 accordance 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.

    Shotcrete construction shall be in accordance with the requirements of ACI 506.2.

    SECTION 1909A—MODIFICATIONS TO ACI 318

    1909A.1 General. The text of ACI 318 shall be modified as indicated in Sections 1909A.1.1 through 1909A.1.16.

    1909A.1.1 ACI 318, Section 4.12.2.2. Modify ACI 318, Section 4.12.2.2 by adding the following:

    Where prestressed concrete elements are restrained from movement, an analysis of the stresses in the prestressed elements and loads in the adjoining structural system induced by the above-described effects shall be made in accordance with PCI Design Handbook.

    1909A.1.2 ACI 318, Section 4.12.2.3. Modify ACI 318, Section 4.12.2.3 by adding the following:

    For prestressed concrete members with recessed or dapped ends, an analysis of the connections shall be made in accordance with procedures given in PCI Design Handbook.

    1909A.1.3 ACI 318, Section 9.6.1.3. Modify ACI 318, Section 9.6.1.3 by adding the following:

    This section shall not be used for members that resist seismic loads, except for either of the following conditions: 1. Foundation members for one-story wood-frame or one-story light steel buildings. 2. Foundation members designed for seismic load combinations including the overstrength factor. [OSHPD 1 & 4] The A s provided shall not be less than that required by 1.2 times the cracking load based upon f r defined in Section 19.2.3.

    1909A.1.4 ACI 318, Section 11.2.4.1. Replace ACI 318, Section 11.2.4.1 as follows:

    11.2.4.1 – Walls shall be anchored to intersecting elements such as floors or roofs; or to columns, pilasters, buttresses, of intersect- ing walls and footings with reinforcement at least equivalent to No. 4 bars at 12 inches (305 mm) on center for each layer of reinforcement.

    1909A.1.5 ACI 318, Section 11.7. Add Section 11.7.6 to ACI 318.1 as follows:

  • CBC § 19A-3 High relevance — show source text

    1901A General. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .19A-3

    1902A Coordination of Terminology . . . . . . . . . . . . . . . . . . . .19A-4

    1903A Specifications for Tests and Materials . . . . . . . . . . . .19A-4

    1904A Durability Requirements . . . . . . . . . . . . . . . . . . . . . . . .19A-4

    1905A Seismic Requirements . . . . . . . . . . . . . . . . . . . . . . . . . .19A-4

    1906A Reserved . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .19A-5

    1907A Slabs-on-Ground . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .19A-5

    1908A Shotcrete . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .19A-6

    1909A Modifications to ACI 318. . . . . . . . . . . . . . . . . . . . . . . . .19A-6

    1910A Concrete, Reinforcement and Anchor Testing . . . . .19A-9

    1911A Existing Concrete Structures. . . . . . . . . . . . . . . . . . . 19A-10

    CHAPTER 20 ALUMINUM . . . . . . . . . . . . . . . . . . . . . . . . . . 20-1

    2001 General. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 20-3

    2002 Materials . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 20-3

    2003 Testing and Inspection. . . . . . . . . . . . . . . . . . . . . . . . . . .20-3

    CHAPTER 21 MASONRY . . . . . . . . . . . . . . . . . . . . . . . . . . . 21-1

    2101 General. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 21-3

    2102 Notations. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 21-4

    2103 Masonry Construction Materials . . . . . . . . . . . . . . . . 21-4

  • CBC § 1909A.1.3 High relevance — show source text

    For prestressed concrete members with recessed or dapped ends, an analysis of the connections shall be made in accordance with procedures given in PCI Design Handbook.

    1909A.1.3 ACI 318, Section 9.6.1.3. Modify ACI 318, Section 9.6.1.3 by adding the following:

    This section shall not be used for members that resist seismic loads, except for either of the following conditions: 1. Foundation members for one-story wood-frame or one-story light steel buildings. 2. Foundation members designed for seismic load combinations including the overstrength factor. [OSHPD 1 & 4] The A s provided shall not be less than that required by 1.2 times the cracking load based upon f r defined in Section 19.2.3.

    1909A.1.4 ACI 318, Section 11.2.4.1. Replace ACI 318, Section 11.2.4.1 as follows:

    11.2.4.1 – Walls shall be anchored to intersecting elements such as floors or roofs; or to columns, pilasters, buttresses, of intersect- ing walls and footings with reinforcement at least equivalent to No. 4 bars at 12 inches (305 mm) on center for each layer of reinforcement.

    1909A.1.5 ACI 318, Section 11.7. Add Section 11.7.6 to ACI 318.1 as follows:

    11.7.6 – Reinforcement. Perimeters of precast walls shall be reinforced continuously with a minimum of one No. 5 bar extending the full height and width of the wall panel. Where wall panels do not connect to columns or other wall panels to develop at least 75 percent of the horizontal wall steel as noted below, vertical perimeter bars shall be retained by hooked wall bars.

    A continuous tie or bond beam shall be provided at the roof line either as a part of the roof structure or part of the wall panels as described in the next paragraph below. This tie may be designed as the edge member of the roof diaphragm but, in any case, shall not be less than equivalent to two No. 6 bars continuous. A continuous tie equivalent to two No. 5 bars minimum shall also be provided either in the footing or with an enlarged section of the floor slab.

    Wall panels of shear wall buildings shall be connected to columns or to each other in such a manner as to develop at least 75 percent of the horizontal wall steel. No more than half of this continuous horizontal reinforcing shall be concentrated in bond or tie beams at the top and bottom of the walls and at points of intermediate lateral support. If possible, cast-in-place joints with rein- forcing bars extending from the panels into the joint a sufficient distance to meet the splice requirements of Section 25.5.2, for Class A shall be used. The reinforcing bars or welded tie details shall not be spaced over eight times the wall thickness vertically

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    nor fewer than four used in the wall panel height. Where wall panels are designed for their respective overturning forces, the panel connections need not comply with the requirements of this paragraph.

  • CBC § 1909A.1.15 High relevance — show source text

    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) condition before shotcrete is deposited.

    1909A.1.15 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.

    1909A.1.16 ACI 318, Section 26.12.2.1(a). Replace ACI 318 Section 26.12.2.1(a) by the following:

    26.12.2.1(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 (345 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 7-day compressive strength tests shall be taken for each class of concrete at the begin- ning of the concrete work or whenever the mix or aggregate is changed.

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    SECTION 1910A—CONCRETE, REINFORCEMENT AND ANCHOR TESTING

    1910A.1 Cementitious material. The concrete supplier shall furnish to the enforcement agency certification that the cement proposed for use on the project has been manufactured and tested in compliance with the requirements of ASTM C150 for portland cement and ASTM C595 or ASTM C1157 for blended hydraulic cement, whichever is applicable. When a mineral admixture or ground granulated blast-furnace slag is proposed for use, the concrete supplier shall furnish to the enforcement agency certification that they have been manufactured and tested in compliance with ASTM C618 or ASTM C989, whichever is applicable. The concrete producer shall provide copies of the cementitious material supplier's Certificate of Compliance that represents the materials used by date of shipment for concrete. Cementitious materials without Certification of Compliance shall not be used.

    1910A.2 Tests of reinforcing bars. Samples shall be taken from bundles as delivered from the mill, with the bundles identified as to heat number and the accompanying mill certificate. One tensile test and one bend test shall be made from a sample from each 10 tons (9080 kg) or fraction thereof of each size of reinforcing steel.

  • CBC § 25.4 High relevance — show source text

    Installation of all adhesive anchors in horizontal and upwardly inclined positions shall be performed by an ACI/CRSI Certified Adhesive Anchor Installer, except where the factored_
    design tension on the anchors is less than 100 pounds and those anchors are clearly noted on the approved construction documents or where the anchors are shear dowels across
    cold joints in slabs on grade where the slab is not part of the lateral force-resisting system.|For SI: 1 inch = 25.4 mm.
    a. Where applicable, see Section 1705_A_.13.
    b. Specific requirements for special inspection shall be included in the research report for the anchor issued by an approved source in accordance with 26.13 in ACI 318, or other
    qualification procedures. Where specific requirements are not provided, special inspection requirements shall be specified by the registered design professional and shall be
    approved by the building official prior to the commencement of the work.
    c. Installation of all adhesive anchors in horizontal and upwardly inclined positions shall be performed by an ACI/CRSI Certified Adhesive Anchor Installer, except where the factored
    design tension on the anchors is less than 100 pounds and those anchors are clearly noted on the approved construction documents or where the anchors are shear dowels across
    cold joints in slabs on grade where the slab is not part of the lateral force-resisting system.|

    1705 A .3.1 Welding of reinforcing bars. Special inspections of welding and qualifications of special inspectors for reinforcing bars shall be in accordance with Section 1705A.2.7, the requirements of AWS D1.4 for special inspection and of AWS D1.4 for special inspector qualification.

    1705 A .3.2 Material tests. In the absence of sufficient data or documentation providing evidence of conformance to quality standards for materials in Chapters 19, 20 and 26 of ACI 318, as modified by Chapter 19A, the building official shall require testing of materials in accordance with the appropriate standards and criteria for the material in Chapters 19, 20 and 26 of ACI 318 as modi- fied by Chapter 19A. Cementitious materials shall be in accordance with 1910A.1 ([DSA-SS/CC] 1909.2.3). Tests of reinforcing bars shall be in accordance with Section 1910A.2 ( [DSA-SS/CC] 1909.2.4).

    1705A.3.3 Batch plant inspection. Except as provided under this section, the quality and quantity of materials used in transit-mixed concrete and in batched aggregates shall be continuously inspected by an approved agency at the location where materials are measured.

    [DSA-SS, DSA-SS/CC] The minimum requirements for a qualified batch plant inspector shall be possession of either: 1. Both of the following: a. A valid certification from ACI as a Concrete Field or Lab Testing Technician.

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    b. Approved agency documented training records of batch plant inspection and California Administrative Code requirements. 2. A valid California Civil Engineering license.

    _**1705A.3.3.1 Waiver of continuous batch plant inspection.

  • CBC § 11.6 Medium relevance — show source text

    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) 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 Section 11.6 and 11.7.

    1909A.1.7 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 either direction 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.

    1909A.1.8 ACI 318, Section 18.10.6.5. Modify ACI 318, Section 18.10.6.5 by adding the following:

    (c) Where boundary members are not required by 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 in accordance with Section 18.10.6.4 (a), (b) and (c).

    1909A.1.9 ACI 318, Section 18.12.6. Add Section 18.12.6.2 to ACI 318 as follows:

    18.12.6.2 – 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.

    1909A.1.10 ACI 318, Section 19.2.1.1 and Table 19.2.1.1. Modify ACI 318, Section 19.2.1.1 and Table 19.2.1.1 as follows: 19.2.1.1 The value of f´ c shall be in be in accordance with (a) through (e): (a) Limits for f´ c in Table 19.2.1.1. Limits apply to both normalweight and lightweight concrete. (b) Durability requirements in Table 19.3.2.1. (c) Structural strength requirements.

  • CBC § 25.5.2 Medium relevance — show source text

    A continuous tie or bond beam shall be provided at the roof line either as a part of the roof structure or part of the wall panels as described in the next paragraph below. This tie may be designed as the edge member of the roof diaphragm but, in any case, shall not be less than equivalent to two No. 6 bars continuous. A continuous tie equivalent to two No. 5 bars minimum shall also be provided either in the footing or with an enlarged section of the floor slab.

    Wall panels of shear wall buildings shall be connected to columns or to each other in such a manner as to develop at least 75 percent of the horizontal wall steel. No more than half of this continuous horizontal reinforcing shall be concentrated in bond or tie beams at the top and bottom of the walls and at points of intermediate lateral support. If possible, cast-in-place joints with rein- forcing bars extending from the panels into the joint a sufficient distance to meet the splice requirements of Section 25.5.2, for Class A shall be used. The reinforcing bars or welded tie details shall not be spaced over eight times the wall thickness vertically

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    nor fewer than four used in the wall panel height. Where wall panels are designed for their respective overturning forces, the panel connections need not comply with the requirements of this paragraph.

    Exception: Nonbearing, nonshear panels such as nonstructural architectural cladding panels or column covers are not required to meet the provisions of this section.

    1909A.1.6 ACI 318, Section 11.9. Modify ACI 318 by adding Section 11.9 as follows:

    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) 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 Section 11.6 and 11.7.

    1909A.1.7 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 either direction 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.

    1909A.1.8 ACI 318, Section 18.10.6.5. Modify ACI 318, Section 18.10.6.5 by adding the following:

  • CBC § 18.10.6.2 Medium relevance — show source text

    (c) Where boundary members are not required by 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 in accordance with Section 18.10.6.4 (a), (b) and (c).

    1909A.1.9 ACI 318, Section 18.12.6. Add Section 18.12.6.2 to ACI 318 as follows:

    18.12.6.2 – 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.

    1909A.1.10 ACI 318, Section 19.2.1.1 and Table 19.2.1.1. Modify ACI 318, Section 19.2.1.1 and Table 19.2.1.1 as follows: 19.2.1.1 The value of f´ c shall be in be in accordance with (a) through (e): (a) Limits for f´ c in Table 19.2.1.1. Limits apply to both normalweight and lightweight concrete. (b) Durability requirements in Table 19.3.2.1. (c) Structural strength requirements. (d) f´ c for lightweight concrete in special moment frames and special structural walls, and their foundations, shall not exceed 5000 psi, unless demonstrated by experimental evidence that members made with lightweight concrete provide strength and toughness equal to or exceeding those of comparable members made with normalweight concrete of the same strength. (e) Reinforced normal weight concrete with specified compressive strength higher than 8,000 psi (55 MPa) shall be consid- ered as an alternative system.

    TABLE 19.2.1.1—LIMITS FOR f ′
    c    		 Col2
    APPLICATION MINIMUMf c′, psi
    General 3000
    Special moment frames
    Special structural walls with Grade 60 or 80 reinforcement    		 3000
    Special structural walls with Grade 100 reinforcement 5000
    Precast-nonprestressed driven piles
    Drilled shafts    		 4000
    Precast-prestressed driven piles 5000
    Shotcrete 4000

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    1909A.1.11 ACI 318, Table 21.2.2.[DSA-SS] Replace Table 21.2.2 as follows :

    |TABLE 21.2.2—STRENGTH REDUCTION FACTOR φ FOR MOMENT, AXIAL FORCE,

  • CBC § 19-5 Medium relevance — show source text

    1903 Specifications for Tests and Materials . . . . . . . . . . . 19-5

    1904 Durability Requirements . . . . . . . . . . . . . . . . . . . . . . . 19-6

    1905 Seismic Requirements . . . . . . . . . . . . . . . . . . . . . . . . . 19-6

    1906 Footings for Light-Frame Construction . . . . . . . . . . 19-8

    1907 Slabs-on-Ground . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19-8

    1908 Shotcrete. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19-8

    1909 Additional Requirements for Community Colleges

    [DSA-SS/CC]. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .19-8

    1910 Additional Requirements for Skilled Nursing Facilities, Intermediate Care Facilities, Acute Psychiatric and Non-GAC Buildings

    [OSHPD 1R, 2 & 5]. . . . . . . . . . . . . . . . . . . . . . . . . . . . .19-12

    1911 Existing Concrete Structures [OSHPD 1R, 2 & 5]. . . . . . .19-13

    CHAPTER 19A CONCRETE . . . . . . . . . . . . . . . . . . . . . . . . . . 19A-1

    1901A General. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .19A-3

    1902A Coordination of Terminology . . . . . . . . . . . . . . . . . . . .19A-4

    1903A Specifications for Tests and Materials . . . . . . . . . . . .19A-4

    1904A Durability Requirements . . . . . . . . . . . . . . . . . . . . . . . .19A-4

    1905A Seismic Requirements . . . . . . . . . . . . . . . . . . . . . . . . . .19A-4

    1906A Reserved . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .19A-5

    1907A Slabs-on-Ground . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .19A-5

    1908A Shotcrete . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .19A-6

    1909A Modifications to ACI 318. . . . . . . . . . . . . . . . . . . . . . . . .19A-6

  • CBC § 2.1.1 Medium relevance — show source text

    24.2.1.1 – Span to depth ratio. Prestressed beam and slab span to depth ratios for continuous prestressed concrete members shall not exceed the following, except when calculations of deflections and vibration effects prove that greater values may be used without adverse effects:

    Beams...............................30

    One-way slabs..................40

    Two-way floor slabs.........40

    Two-way roof slabs..........44

    These ratios should be decreased for special conditions such as heavy loads and simple spans.

    Maximum deflection criteria shall be in accordance with ACI 318 Section 24.2.2.

    1909A.1.13 ACI 318, Section 25.2.10. Replace ACI 318 Section 25.2.10 by the following:

    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.

    1909A.1.14 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 acceptable 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) condition before shotcrete is deposited.

    1909A.1.15 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.

    1909A.1.16 ACI 318, Section 26.12.2.1(a). Replace ACI 318 Section 26.12.2.1(a) by the following:

  • CBC § 19A-5 Medium relevance — show source text

    2025 CALIFORNIA BUILDING CODE 19A-5

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

    CONCRETE

    1907 A .2 Nonstructural slabs-on-ground. Nonstructural slabs-on-ground shall be required to comply with Sections 1904 A .2, 1907 A .3 and 1907 A .4. Portions of the nonstructural slabs-on-ground used to resist uplift forces or overturning shall be designed in accordance with accepted engineering practice throughout the entire portion designated as dead load to resist uplift forces or overturning. 1907 A .3 Thickness. The thickness of concrete floor slabs supported directly on the ground shall be not less than 3 [1] / 2 inches (89 mm).

    1907 A .4 Vapor retarder. A 6-mil (0.006 inch; 0.15 mm) polyethylene vapor retarder with joints lapped not less than 6 inches (152 mm) shall be placed between the base course or subgrade and the concrete floor slab, or other approved equivalent methods or materials shall be used to retard vapor transmission through the floor slab.

    Exception: A vapor retarder is not required:

    1. For detached structures accessory to occupancies in Group R-3, such as garages, utility buildings or other unheated facilities.

    2. For unheated storage rooms having an area of less than 70 square feet (6.5 m [2] ) and carports attached to occupancies in Group R-3.

    3. For buildings of other occupancies where migration of moisture through the slab from below will not be detrimental to the intended occupancy of the building.

    4. For driveways, walks, patios and other flatwork that will not be enclosed at a later date.

    5. Where approved based on local site conditions.

    SECTION 1908 A —SHOTCRETE

    1908 A .1 General. Shotcrete shall be in accordance with the requirements of ACI 318 and the provisions of ACI 506R. 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 accordance 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.

    Shotcrete construction shall be in accordance with the requirements of ACI 506.2.

    SECTION 1909A—MODIFICATIONS TO ACI 318

    1909A.1 General. The text of ACI 318 shall be modified as indicated in Sections 1909A.1.1 through 1909A.1.16.

    1909A.1.1 ACI 318, Section 4.12.2.2. Modify ACI 318, Section 4.12.2.2 by adding the following:

  • CBC § 1810.2.2 Medium relevance — show source text

    Where deep foundation elements of the same type are being spliced, splices shall develop not less than 50 percent of the bending strength of the weaker section. Where deep foundation elements of different materials or different types are being spliced, splices shall develop the full compressive strength and not less than 50 percent of the tension and bending strength of the weaker section. Where structural steel cores are to be spliced, the ends shall be milled or ground to provide full contact and shall be full-depth welded.

    Exception: For buildings assigned to Seismic Design Category A or B, splices need not comply with the 50-percent tension and bending strength requirements where justified by supporting data.

    Splices occurring in the upper 10 feet (3048 mm) of the embedded portion of an element shall be designed to resist at allowable stresses the moment and shear that would result from an assumed eccentricity of the axial load of 3 inches (76 mm), or the element shall be braced in accordance with Section 1810.2.2 to other deep foundation elements that do not have splices in the upper 10 feet (3048 mm) of embedment.

    1810.3.6.1 Seismic Design Categories C through F. For structures assigned to Seismic Design Category C, D, E or F splices of deep foundation elements shall develop the lesser of the following:

    1. The nominal strength of the deep foundation element.
    2. The axial and shear forces and moments from the seismic load effects including overstrength factor in accordance with Section 2.3.6 or 2.4.5 of ASCE 7.

    1810.3.7 Top of element detailing at cutoffs. Where a minimum length for reinforcement or the extent of closely spaced confinement reinforcement is specified at the top of a deep foundation element, provisions shall be made so that those specified lengths or extents are maintained after cutoff.

    1810.3.8 Precast concrete piles. Precast concrete piles shall be designed and detailed in accordance with ACI 318.

    Exceptions:

    1. For precast prestressed piles in Seismic Design Category C, the minimum volumetric ratio of spirals or circular hoops required by Section 18.13.5.10.4 of ACI 318 shall not apply in cases where the design includes full consideration of load combinations specified in ASCE 7, Section 2.3.6 or Section 2.4.5 and the applicable overstrength factor, Ω 0 . In such cases, minimum transverse reinforcement index shall be as specified in Section 13.4.5.6 of ACI 318. [OSHPD 1R, 2 & 5] not permitted by OSHPD.
    2. For precast prestressed piles in Seismic Design Categories D through F and in Site Class A, B, BC, C, CD, D or DE sites, the minimum volumetric ratio of spirals or circular hoops required by Section 18.13.5.10.5(c) of ACI 318 shall not apply in cases where the design includes full consideration of load combinations specified in ASCE 7, Section 2.3.6 or Section 2.4.5 and the applicable overstrength factor, Ω 0 . In such cases, minimum transverse reinforcement shall be as specified in Section 13.4.5.6 of ACI 318. [OSHPD 1R, 2 & 5] not permitted by OSHPD.

Frequently asked questions

Do I need to read both ACI 318 and Chapter 19/19A when designing concrete in California?

Yes. Use ACI 318 as the baseline but apply the CBC’s Chapter 19 and Chapter 19A modifications where they alter or supplement ACI 318; § 1909A lists the specific modifications to follow .

Where is shotcrete governed — ACI 318 or CBC?

Shotcrete is governed by ACI 318 together with CBC shotcrete provisions in Chapter 19A (including preconstruction mockup/testing and f'c limits); see § 1908A and the related modifications in § 1909A .

Can I specify steel-fiber reinforcement in California?

Chapter 19/19A indicates restrictions and jurisdictional exceptions (for example some OSHPD/DSA jurisdictions prohibit steel fiber reinforcement); check § 1903 and your enforcing agency’s rules before using steel fibers .

What concrete sampling frequency must I plan for?

CBC requires at least one strength sample per day, or per 50 cubic yards, or per 2,000 ft² of slabs/walls, with additional samples at mix changes — this is a modification to ACI 318 sampling rules in § 1909A.1.16 .

If ACI 318 and CBC conflict, which controls?

The CBC (its text and the specific modifications in Chapter 19A/§ 1909A) controls. The CBC explicitly modifies ACI 318 where noted, and the CBC’s administration section establishes precedence rules .

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Where are requirements for reinforcement specification, cover and splice details referenced?

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