Ch. 19A Concrete — 2025 California Building Code

User notes:

About this chapter: Chapter 19A provides minimum accepted practices for the design and construction of buildings and structural components using concrete, both plain and reinforced. Chapter 19A is applicable to structures regulated by the Division of the State Architect- Structural Safety—including public elementary and secondary schools, community colleges, and state-owned or state-leased essential services buildings (applications listed in Sections 1.9.2.1 [DSA-SS] and 1.9.2.2 [DSA-SS/CC])—and by the Department of Health Care Access and Information/Office of Statewide Hospital Planning and Development—including hospitals and correctional treatment centers (applications listed in Sections 1.10.1 [OSHPD 1] and 1.10.4 [OSHPD 4]).

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. (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

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

CONCRETE

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, OR COMBINED MOMENT AND AXIAL FORCE

NET TENSILE STRAIN εt	CLASSIFICATION	φ	φ	φ	φ
NET TENSILE STRAIN εt	CLASSIFICATION	Type of transverse reinforcement	Type of transverse reinforcement	Type of transverse reinforcement	Type of transverse reinforcement
NET TENSILE STRAIN εt	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 = 0.1Agfc′_ 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.

1909A.1.12 ACI 318, Section 24.2.1. Add Section 24.2.1.1 to ACI 318 as follows:

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:

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.

19A-8 2025 CALIFORNIA BUILDING CODE

CONCRETE

Exceptions & meaning →