CBC · California Building Code
What seismic-specific requirements apply to concrete design and detailing?
For homeowners: the CBC requires reinforced concrete to meet ACI 318 plus California seismic rules — unreinforced (plain) concrete is tightly restricted in higher seismic zones and only allowed in narrow cases (mostly small detached homes). Footings and walls intended to resist earthquake forces must include the minimum reinforcement and continuity called out in §1905.5 and §1905.6, and some healthcare projects prohibit plain concrete altogether. file
Last reviewed: July 5, 2026
What the code requires — 2-4 sentences
The California Building Code requires that structural concrete comply with ACI 318 plus additional, California‑specific seismic supplements in Section 1905; those supplements add definitions, prohibited plain‑concrete uses, and prescriptive reinforcement and footing requirements for seismic design categories C–F and certain exceptions for one‑ and two‑family dwellings (§ 1905, § 1905.1). The CBC also gives mandatory detail requirements for “detailed plain concrete structural walls” (§ 1905.5) and for the limited permitted uses and reinforcement of structural plain concrete and plain footings (§ 1905.6).
Requirements in detail
Scope and definitions
- Section 1905 establishes that structural concrete must follow ACI 318 as modified by Chapter 19 of the CBC; the chapter adds California definitions such as “cast‑in‑place concrete equivalent diaphragm,” “detailed plain concrete structural wall” and “ordinary plain concrete structural wall” to coordinate terminology used for seismic design. (§ 1905, § 1905.1)
Detailed plain concrete structural walls — when allowed and minimum reinforcement (§ 1905.5 and § 1905.5.1)
- “Detailed plain concrete structural walls” must meet the ordinary plain concrete wall provisions plus the special reinforcement rules in § 1905.5.1; note that OSHPD applies stricter prohibitions in some hospital/healthcare applications (“Plain concrete shall not be permitted.”). (§ 1905.5)
- Minimum reinforcement required by § 1905.5.1:
- Vertical reinforcing: continuous vertical reinforcement not less than 0.20 in² (129 mm²) at each corner, each side of every opening, and at wall ends; the vertical bar beside an opening may substitute for one of the two No.5 bars required by ACI 318 Section 14.6.1. (§ 1905.5.1.1)
- Horizontal reinforcement: not less than 0.20 in² (129 mm²) provided
- continuously at connected roof and floor levels and at the top of walls,
- at the bottom of load‑bearing walls or in the top of doweled foundations, and
- at a maximum spacing of 120 inches (3048 mm). (§ 1905.5.1.2)
Structural plain concrete and plain footings — limits and required reinforcement (§ 1905.6)
- General: Section 1905.6 replaces ACI 318 Section 14.1.4 for plain (unreinforced) structural concrete — and again states “Plain concrete shall not be permitted” where OSHPD prohibits it; otherwise § 1905.6 controls permitted exceptions. (§ 1905.6)
- Seismic Design Categories A and B: Detached one‑ and two‑family dwellings (up to three stories) with stud‑bearing walls are permitted to use plain concrete footings without longitudinal reinforcement. (§ 1905.6.1)
- Seismic Design Categories C, D, E and F: Structural plain concrete is generally not allowed except for limited cases:
- Basement/foundation or other below‑base walls in detached one‑ and two‑family dwellings (≤ 3 stories). For SDC D or E those walls are limited to height ≤ 8 ft (2438 mm), thickness ≥ 7½ in (190 mm), and they may retain not more than 4 ft (1219 mm) of unbalanced fill; such walls must have reinforcement per ACI 318 § 14.6.1. (§ 1905.6.2.1)
- Isolated plain concrete footings for pedestals or columns are permitted provided the footing projection beyond the supported member does not exceed the footing thickness (with an exception for detached one‑ and two‑family dwellings). (§ 1905.6.2.2)
- Plain concrete footings supporting walls are permitted only when they include longitudinal reinforcement as specified: not fewer than two continuous longitudinal bars (no smaller than No.4), total area ≥ 0.002 × gross cross‑sectional area of footing; for footings thicker than 8 in, provide at least one bar at top and one at bottom; continuity at corners/intersections required. (§ 1905.6.2.3)
Decision‑relevant numeric table
| Decision / dimension | Required value or limit | Code reference |
|---|---|---|
| Min vertical reinforcement in detailed plain concrete walls | 0.20 in² (129 mm²) continuous at corners, sides of openings, wall ends | § 1905.5.1.1 |
| Min horizontal reinforcement in detailed plain concrete walls | 0.20 in² (129 mm²); continuous at roof/floor levels and top of walls; bottom of load‑bearing walls; max spacing 120 in (3048 mm) | § 1905.5.1.2 |
| Max spacing for horizontal reinforcement | 120 in (3048 mm) | § 1905.5.1.2 |
| Plain wall allowable thickness (SDC D or E, detached dwellings) | ≥ 7½ in (190 mm) | § 1905.6.2.1 |
| Plain wall allowable height (SDC D or E, detached dwellings) | ≤ 8 ft (2438 mm) | § 1905.6.2.1 |
| Max unbalanced fill retained by the wall (SDC D or E exception) | 4 ft (1219 mm) | § 1905.6.2.1 |
| Footing longitudinal reinforcement — minimum | ≥ two continuous bars, no smaller than No.4; total area ≥ 0.002 × Ag | § 1905.6.2.3 |
| Footing thickness threshold for top & bottom bars | > 8 in (203 mm) → provide at least one bar at top and one at bottom | § 1905.6.2.3 |
| Allow plain footings without longitudinal bars (SDC A/B) | Detached 1–2 family dwellings ≤ 3 stories (stud‑bearing) permitted | § 1905.6.1 |
Exceptions & special cases
- OSHPD (hospital/healthcare) jurisdiction: multiple provisions state “Plain concrete shall not be permitted” for OSHPD‑regulated projects; where OSHPD applies, plain concrete uses allowed elsewhere in the CBC may be prohibited. (§ 1905.5, § 1905.6)
- Detached one‑ and two‑family dwellings have broader allowances: SDC A/B dwellings (≤ 3 stories) may use plain footings without longitudinal reinforcement (§ 1905.6.1), and SDC C dwellings have a limited exception for plain footings (see § 1905.6.2 exceptions). These are specific to the detached one‑ and two‑family occupancy condition. (§ 1905.6.1, § 1905.6.2)
- Where the CBC defers to ACI 318 elsewhere, the designer must apply ACI 318 requirements as modified by Chapter 19; e.g., for foundations resisting earthquake forces § 1905 requires conformance with ACI 318 Section 18.13 unless modified by Chapter 18. (§ 1905.4)
Common mistakes
- Treating ACI 318 alone as sufficient: the CBC explicitly requires ACI 318 plus the Chapter 19 supplements; the California supplements add definitions and prescriptive limits (e.g., plain concrete prohibitions and the specific reinforcement quantities in § 1905.5 and § 1905.6). (§ 1905, § 1905.1)
- Omitting the continuous 0.20 in² horizontal or vertical reinforcement where § 1905.5.1 requires it for detailed plain concrete walls — particularly around openings and at roof/floor levels. (§ 1905.5.1)
- Using unreinforced plain footings or plain walls in SDC C–F without checking the specific exceptions and limits (height, thickness, retained fill, required reinforcement). (§ 1905.6.2)
- Forgetting OSHPD prohibitions: projects under OSHPD jurisdictions must confirm that plain concrete is allowed—CBC language explicitly disallows plain concrete in many OSHPD applications. (§ 1905.5, § 1905.6)
Worked example — two‑bar footing check (numbers applied to the code rules)
Scenario: a plain concrete strip footing supporting a foundation wall in a single detached 2‑story house (Seismic Design Category C). The footing is 24 in wide × 8 in thick (Ag = 24 × 8 = 192 in²). For footings supporting walls in SDC C, § 1905.6.2.3 requires not fewer than two continuous longitudinal bars, not smaller than No.4, and total reinforcement area ≥ 0.002 × Ag.
Compute required reinforcement area:
- Required area = 0.002 × 192 in² = 0.384 in².
- Two No.4 bars provide approximately 0.40 in² total (2 × 0.20 in² per No.4) — which satisfies the 0.384 in² minimum; bars must be continuous and continuity provided at corners/intersections per § 1905.6.2.3. (§ 1905.6.2.3)
Notes: the example arithmetic applies the CBC formula (0.002 × Ag) and the bar‑size limitation from the code; the code requires continuity and top/bottom bar placement if footing thickness exceeds 8 in. (§ 1905.6.2.3)
Related provisions
- Construction documents and what must be shown (concrete strengths, reinforcement sizes and lap lengths, and for SDC D/E/F a slab‑as‑diaphragm statement): § 1901.5.
- Durability requirements and minimum concrete strengths for structural and nonstructural concrete: § 1904.
- Foundations resisting earthquake forces: § 1905.4 (references ACI 318 Section 18.13 as modified). § 1905.4.
- Footings for light‑frame construction (prescriptive thicknesses and when plain footings are allowed): § 1906.1.
- Special inspections and tests for seismic force‑resisting systems: Chapter 17A / § 1705 (special inspection requirements for SDC C–F). § 1705.
Code references
Grounded in the retrieved California Building Code — click a citation to read the verbatim passage:
CBC § 1807.1.6. High relevance — show source text
Interior stud-bearing walls shall be permitted to be supported by isolated footings. The footing width and length shall be twice the width shown in this table, and footings
shall be spaced not more than 6 feet on center.
d. See Section 1905 for additional requirements for concrete footings of structures assigned to Seismic Design Category C, D, E or F.
e. For thickness of foundation walls, see Section 1807.1.6.
f. Footings shall be permitted to support a roof in addition to the stipulated number of floors. Footings supporting roof only shall be as required for supporting one floor.
g. Plain concrete footings for Group R-3 occupancies shall be permitted to be 6 inches thick.|For SI: 1 inch = 25.4 mm, 1 foot = 304.8 mm.
a. Depth of footings shall be in accordance with Section 1809.4.
b. The ground under the floor shall be permitted to be excavated to the elevation of the top of the footing.
c. Interior stud-bearing walls shall be permitted to be supported by isolated footings. The footing width and length shall be twice the width shown in this table, and footings
shall be spaced not more than 6 feet on center.
d. See Section 1905 for additional requirements for concrete footings of structures assigned to Seismic Design Category C, D, E or F.
e. For thickness of foundation walls, see Section 1807.1.6.
f. Footings shall be permitted to support a roof in addition to the stipulated number of floors. Footings supporting roof only shall be as required for supporting one floor.
g. Plain concrete footings for Group R-3 occupancies shall be permitted to be 6 inches thick.|1809.8 Plain concrete footings. [OSHPD 1R, 2 & 5] Not permitted by OSHPD. The edge thickness of plain concrete footings supporting walls of other than light-frame construction shall be not less than 8 inches (203 mm) where placed on soil or rock.
Exception: For plain concrete footings supporting Group R-3 occupancies, the edge thickness is permitted to be 6 inches (152 mm), provided that the footing does not extend beyond a distance greater than the thickness of the footing on either side of the supported wall.
1809.9 Masonry-unit footings. [OSHPD 1R, 2 & 5] Not permitted by OSHPD. The design, materials and construction of masonry-unit footings shall comply with Sections 1809.9.1 and 1809.9.2, and the provisions of Chapter 21.
Exception: Where a specific design is not provided, masonry-unit footings supporting walls of light-frame construction shall be permitted to be designed in accordance with Table 1809.7.
1809.9.1 Dimensions. Masonry-unit footings shall be laid in Type M or S mortar complying with Section 2103.2.1 and the depth shall be not less than twice the projection beyond the wall, pier or column. The width shall be not less than 8 inches (203 mm) wider than the wall supported thereon. 1809.9.2 Offsets. The maximum offset of each course in brick foundation walls stepped up from the footings shall be 1 [1] / 2 inches (38 mm) where laid in single courses, and 3 inches (76 mm) where laid in double courses.
CBC § 18.5 High relevance — show source text
1905 A .3 Intermediate precast structural walls. Intermediate precast structural walls shall comply with Section 18.5 of ACI 318 and this section.
1905 A .3.1 Connections designed to yield. Connections that are designed to yield shall be capable of maintaining 80 percent of their design strength at the deformation induced by the design displacement or shall use Type 2 mechanical splices. [DSA-SS] Connections between wall panels and the foundation shall be designed per Section 1617A.1.15.
1905 A .4 Foundations designed to resist earthquake forces. Foundations resisting earthquake-induced forces or transferring earthquake-induced forces between a structure and the ground shall comply with the requirements of Section 18.13 of ACI 318 and other applicable provisions of ACI 318 unless modified by Chapter 18 A .
1905 A .5 Detailed plain concrete structural walls. Not permitted.
1905 A .6 Structural plain concrete. Not permitted.
1905 A .7 Design requirements for anchors. For the design requirements for anchors, Sections 1905 A .7.1 and 1905 A .7.2 provide exceptions that are permitted to ACI 318.
1905 A .7.1 Anchors in tension. The following exception is permitted to ACI 318 Section 17.10.5.2:
Exception: Anchors designed to resist wall out-of-plane forces with design strengths equal to or greater than the force determined in accordance with ASCE/SEI 7 Equation 12.11-1 and Section 1604A.8.2 of this code shall be deemed to satisfy Section 17.10.5.3(d) of ACI 318.
1905 A .7.2 Anchors in shear. The following exceptions are permitted to ACI 318 Section 17.10.6.2:
Exceptions:
- For the calculation of the in-plane shear strength of anchor bolts attaching wood sill plates of bearing or nonbearing walls of light-frame wood structures to foundations or foundation stemwalls, the in-plane shear strength in accordance with Sections 17.7.2 and 17.7.3 of ACI 318 need not be computed and Section 17.10.6.3 of ACI 318 shall be deemed to be satisfied provided that all of the following are met: 1.1. The allowable in-plane shear strength of the anchor is determined in accordance with ANSI/AWC NDS Table 12E for lateral design values parallel to grain. 1.2. The maximum anchor nominal diameter is [5] / 8 inch (16 mm). 1.3. Anchor bolts are embedded into concrete not less than 7 inches (178 mm). 1.4. Anchor bolts are located not less than 1¾ inches (45 mm) from the edge of the concrete parallel to the length of the wood sill plate. 1.5. Anchor bolts are located not less than 15 anchor diameters from the edge of the concrete perpendicular to the length of the wood sill plate. 1.6. The sill plate is 2-inch (51 mm) or 3-inch (76 mm) nominal thickness.
CBC § 17.2 High relevance — show source text
1904 A .2 Nonstructural concrete. The registered design professional shall assign nonstructural concrete a freeze-thaw exposure class, as defined in ACI 318, based on the anticipated exposure of nonstructural concrete. Nonstructural concrete shall have a minimum specified compressive strength, f´ c, of 2,500 psi (17.2 MPa) for Class F0; 3,000 psi (20.7 MPa) for Class F1; and 3,500 psi (24.1 MPa) for Classes F2 and F3. Nonstructural concrete shall be air entrained in accordance with ACI 318.
SECTION 1905 A —SEISMIC REQUIREMENTS
1905 A .1 General. In addition to the provisions of ACI 318, structural concrete shall comply with the requirements of Section 1905 A .
1905 A .2 ACI 318 Section 2.3. Modify existing definitions and add the following definitions to ACI 318 Section 2.3:
CAST-IN-PLACE CONCRETE EQUIVALENT DIAPHRAGM. A cast-in-place noncomposite topping slab diaphragm, as defined in Section 18.12.5, or a diaphragm constructed with precast concrete components that uses closure strips between precast components with detailing that meets the requirements of ACI 318 for the Seismic Design Category of the structure.
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PRECAST CONCRETE DIAPHRAGM. A diaphragm constructed with precast concrete components, with or without a cast-in-place topping, that includes the use of discrete connectors or joint reinforcement to transmit diaphragm forces.
1905 A .3 Intermediate precast structural walls. Intermediate precast structural walls shall comply with Section 18.5 of ACI 318 and this section.
1905 A .3.1 Connections designed to yield. Connections that are designed to yield shall be capable of maintaining 80 percent of their design strength at the deformation induced by the design displacement or shall use Type 2 mechanical splices. [DSA-SS] Connections between wall panels and the foundation shall be designed per Section 1617A.1.15.
1905 A .4 Foundations designed to resist earthquake forces. Foundations resisting earthquake-induced forces or transferring earthquake-induced forces between a structure and the ground shall comply with the requirements of Section 18.13 of ACI 318 and other applicable provisions of ACI 318 unless modified by Chapter 18 A .
1905 A .5 Detailed plain concrete structural walls. Not permitted.
1905 A .6 Structural plain concrete. Not permitted.
1905 A .7 Design requirements for anchors. For the design requirements for anchors, Sections 1905 A .7.1 and 1905 A .7.2 provide exceptions that are permitted to ACI 318.
1905 A .7.1 Anchors in tension. The following exception is permitted to ACI 318 Section 17.10.5.2:
CBC § 4.09 High relevance — show source text
For anchorage of concrete or masonry walls to roof and floor diaphragms, the out-of-plane strength design force shall not be less than 280 lb/linear ft (4.09 kN/m) of wall. Required anchors in masonry walls of hollow units or cavity walls shall be embedded in a reinforced grouted structural element of the wall. See Sections 1609 for wind design requirements and 1613 A for earthquake design requirements. 1604 A .8.3 Decks. Where supported by attachment to an exterior wall, decks shall be positively anchored to the primary structure and designed for both vertical and lateral loads as applicable. Such attachment shall not be accomplished by the use of toenails or nails subject to withdrawal. Where positive connection to the primary building structure cannot be verified during inspection, decks shall be self-supporting. Connections of decks with cantilevered framing members to exterior walls or other framing members shall be designed for both of the following:
- The reactions resulting from the dead load and live load specified in Table 1607 A .1, or the snow load specified in Section 1608, in accordance with Section 1605 A, acting on all portions of the deck.
- The reactions resulting from the dead load and live load specified in Table 1607 A .1, or the snow load specified in Section 1608 A, in accordance with Section 1605 A, acting on the cantilevered portion of the deck, and no live load or snow load on the remaining portion of the deck. 1604 A .9 Wind and seismic detailing. Lateral force-resisting systems shall meet seismic detailing requirements and limitations prescribed in this code and ASCE 7 Chapters 11, 12, 13, 15, 17 and 18 as applicable, even where wind load effects are greater than seismic load effects.
Exception: References within ASCE 7 to Chapter 14 shall not apply, except as specifically required herein.
1604 A .10 Loads on storm shelters. Loads and load combinations on storm shelters shall be determined in accordance with ICC 500.
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STRUCTURAL DESIGN
SECTION 1605 A —LOAD COMBINATIONS
1605 A .1 General. Buildings and other structures and portions thereof shall be designed to resist the strength load combinations specified in ASCE 7, Section 2.3, the allowable stress design load combinations specified in ASCE 7, Section 2.4, or the alternative allowable stress design load combinations of Section 1605 A .2. Exceptions:
CBC § 1.2 High relevance — show source text
Calculations_ shall be submitted to OSHPD for review and approval. 11. For in-plane collectors transferring axial loads into the sideplate connection, coordination between sideplate and the regis- tered design professional in responsible charge will be required to confirm the collector connection is sufficient to transfer the load into the moment frame system. This requirement shall be satisfied by designing the sideplate connections in the first bay of a multi-bay sideplate moment frame or an end bay to have a minimum connection capacity, including combined shear (V u + V g ) and moment (M pr ) demands, of at least 1.2 times the M pr at the plastic hinge location when the axial load, as determined by ASCE 7, Section 12.10.2.1 without Ω o , exceeds 0.1 F y A g of the sideplate beam. 12. A complete frame analysis for gravity and design wind loading using LRFD load combinations in Section 1605.1 shall be performed including Demand/Capacity Ratios. Frame beam member nominal moment strengths (M n ) used for gravity and design wind loading for the bolted sideplate connection using Class A or Class B faying surfaces shall be taken as 0.80F y Z for frame beams up to 300 plf and 0.60F y Z for frame beams greater than 300 plf. 13. For moment frame beams with maximum beam shear greater than 90 percent of the vertical bolt shear capacity, a second- ary check is to be provided to confirm the vertical bolt shear capacities are sufficient.
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14. Bolted sideplate connections used on heavy-shallow frame beams for beams greater than 200 plf and shallower than 24 inches (610 mm) in depth shall be considered as an alternative system. 15. Skewed beams shall utilize the link-beam fabrication method with CJP welded splices for skew angles. The skew angle shall be less than 15 degrees. 16. For two-sided bolted sideplate connections sharing the same side plates at the same height and depth across the column, the vertical offset in the beams shall not exceed 10 inches (254 mm).
2202.4.4 Modifications to AISC 358 Chapter 12. The Simpson Strong-Tie (SST) Strong Frame bolted moment connection shall be permitted, provided: 1. Only T-stub yield links are permitted. End plate yield links are not permitted. 2. The biaxial dual-strong axis and column minor axis configurations of the moment connection shall be considered as an alternative system. 3. Beam flange width-to-thickness ratio shall satisfy AISC 341 Table D1.1b. 4. Yield-Link stem-to-beam flange connection bolts shall not slip under wind design demand loads. Yield-Link stem-to-beam flange connection shall be designed to prevent slip using AISC 360 Equation J3-4, where the slip resistance, μ , is taken to be 0.3.
5. Double shear plate connection is permitted to increase connection axial capacity for collector loads. A partial joint penetra- tion (PJP) groove weld for second shear plate is permissible due to space restrictions.
CBC § 3107F.2.5.4.1 High relevance — show source text
ε_c
_MRSTS = Maximum Reinforcing Steel Tension Strain,ε_s
_MPSTS = Maximum Prestressing Steel Tension Strain,ε_p|3107F.2.5.4.1 Method A. For Method A, the yield curvature, φ y is the curvature at the intersection of the secant stiffness, EI c , through first yield and the nominal strength, ( ε c = 0.004).
Equation 7-10
φ y = ------EIM yc
FIGURE 31F-7-4 — METHOD A - MOMENT CURVATURE ANALYSIS
3107F.2.5.4.2 Method B. For Method B, the elastic portion of the idealized moment-curvature curve is the same as in Method A (see Section 3107F.2.5.4.1). However, the idealized plastic moment capacity, M p , and the yield curvature, φ y , is obtained by balancing the areas between the actual and the idealized moment-curvature curves beyond the first yield point (see Figure 31F- 7-5). Method B applies to moment-curvature curves that do not experience reduction in section moment capacity.
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MARINE OIL TERMINALS
FIGURE 31F-7-5 — METHOD B – MOMENT CURVATURE ANALYSIS [7.6]
3107F.2.5.5 Ultimate concrete and steel flexural strains. Strain values computed in the nonlinear pushover analysis shall be compared to the following limits.
3107F.2.5.5.1 Unconfined concrete piles: An unconfined concrete pile is defined as a pile having no confinement steel or one in which the spacing of the confinement steel exceeds 12 inches.
Ultimate concrete compressive strain:
Equation 7-11 ε cu = 0.005
3107F.2.5.5.2 Confined concrete piles: Ultimate concrete compressive strain [7.1]:
Equation 7-12 ε cu = 0.004 + (1.4 ρ s f yh ε sm )/f ' cc ≥ 0.005 ε cu ≤ 0.025
where:
ρ s = effective volume ratio of confining steel f yh = yield stress of confining steel ε sm = strain at peak stress of confining reinforcement, 0.15 for grade 40, 0.10 for grade 60
f ' cc = confined strength of concrete approximated by 1.5 f' cc
CBC § 19A-3 High relevance — show source text
1901 A .3 Anchoring to concrete. Anchoring to concrete shall be in accordance with ACI 318 as supplemented in Section 1905 A, and applies to cast-in (headed bolts, headed studs and hooked J- or L-bolts), post-installed expansion (torque-controlled and displacement-controlled), undercut, screw, and adhesive anchors.
1901 A .4 Composite structural steel and concrete structures. Systems of structural steel acting compositely with reinforced concrete shall be designed in accordance with Section 2206 A of this code.
1901 A .5 Construction documents. The construction documents for structural concrete construction shall include:
- The specified compressive strength of concrete at the stated ages or stages of construction for which each concrete element is designed.
- The specified strength or grade of reinforcement.
- The size and location of structural elements, reinforcement and anchors.
- Provision for dimensional changes resulting from creep, shrinkage and temperature.
- The magnitude and location of prestressing forces.
- Anchorage length of reinforcement and location and length of lap splices.
- Type and location of mechanical and welded splices of reinforcement.
- Details and location of contraction or isolation joints.
- Minimum concrete compressive strength at time of posttensioning.
- Stressing sequence for posttensioning tendons.
- For structures assigned to Seismic Design Category D, E or F, a statement if slab on grade is designed as a structural diaphragm. 12. Openings larger than 12 inches (305 mm) in any dimension shall be detailed on the structural drawings.
1901 A .6 Special inspections and tests. S pecial inspections and tests of concrete elements of buildings and structures and concreting operations shall be as required by Chapter 17A and Section 1910A.
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1901 A .7 Tolerances for structural concrete. Where not indicated in construction documents, structural tolerances for concrete structural elements shall be in accordance with this section.
1901 A .7.1 Cast-in-place concrete tolerances. Structural tolerances for cast-in-place concrete structural elements shall be in accordance with ACI 117.
Exceptions:
- Group R-3 detached one- or two-family dwellings are not required to comply with this section.
- Shotcrete is not required to comply with this section. [DSA-SS] Tolerances for shotcrete construction shall be defined by the construction documents.
1901 A .7.2 Precast concrete tolerances. Structural tolerances for precast concrete structural elements shall be in accordance with ACI ITG-7.
Exception: Group R-3 detached one- or two-family dwellings are not required to comply with this section.
SECTION 1902 A —COORDINATION OF TERMINOLOGY
1902 A .1 General. Coordination of terminology used in ACI 318 and ASCE 7 shall be in accordance with Section 1902 A .1.1.
CBC § 1904.2 High relevance — show source text
1904.2 Nonstructural concrete. The registered design professional shall assign nonstructural concrete a freeze-thaw exposure class, as defined in ACI 318, based on the anticipated exposure of nonstructural concrete. Nonstructural concrete shall have a minimum specified compressive strength, f´ c, of 2,500 psi (17.2 MPa) for Class F0; 3,000 psi (20.7 MPa) for Class F1; and 3,500 psi (24.1 MPa) for Classes F2 and F3. Nonstructural concrete shall be air entrained in accordance with ACI 318.
SECTION 1905—SEISMIC REQUIREMENTS
1905.1 General. In addition to the provisions of ACI 318, structural concrete shall comply with the requirements of Section 1905.
1905.2 ACI 318 Section 2.3. Modify existing definitions and add the following definitions to ACI 318 Section 2.3:
CAST-IN-PLACE CONCRETE EQUIVALENT DIAPHRAGM. A cast-in-place noncomposite topping slab diaphragm, as defined in Section 18.12.5, or a diaphragm constructed with precast concrete components that uses closure strips between precast components with detailing that meets the requirements of ACI 318 for the Seismic Design Category of the structure.
DETAILED PLAIN CONCRETE STRUCTURAL WALL. A wall complying with the requirements of Chapter 14, and Section 1905.5 of the California Building Code .
ORDINARY PLAIN CONCRETE STRUCTURAL WALL. A wall complying with the requirements of Chapter 14, excluding 14.6.2.
ORDINARY PRECAST STRUCTURAL WALL. A precast wall complying with the requirements of Chapters 1 through 13, 15, 16 and 19 through 26.
ORDINARY REINFORCED CONCRETE STRUCTURAL WALL. A cast-in-place wall complying with the requirements of Chapters 1 through 13, 15, 16 and 19 through 26.
PRECAST CONCRETE DIAPHRAGM. A diaphragm constructed with precast concrete components, with or without a cast-in-place topping, that includes the use of discrete connectors or joint reinforcement to transmit diaphragm forces.
1905.3 Intermediate precast structural walls. Intermediate precast structural walls shall comply with Section 18.5 of ACI 318 and this section.
1905.3.1 Connections designed to yield. Connections that are designed to yield shall be capable of maintaining 80 percent of their design strength at the deformation induced by the design displacement or shall use Type 2 mechanical splices.
1905.4 Foundations designed to resist earthquake forces. Foundations resisting earthquake-induced forces or transferring earthquake-induced forces between a structure and the ground shall comply with the requirements of Section 18.13 of ACI 318 and other applicable provisions of ACI 318 unless modified by Chapter 18.
1905.5 Detailed plain concrete structural walls. Detailed plain concrete structural walls are walls conforming to the requirements of ordinary plain concrete structural walls and Section 1905.5.1. [OSHPD 1R, 2 & 5] Plain concrete shall not be permitted.
CBC § 1.3. High relevance — show source text
The maximum anchor nominal diameter is [5] / 8 inch (16 mm). 1.3. Anchor bolts are embedded into concrete not less than 7 inches (178 mm). 1.4. Anchor bolts are located not less than 1¾ inches (45 mm) from the edge of the concrete parallel to the length of the wood sill plate. 1.5. Anchor bolts are located not less than 15 anchor diameters from the edge of the concrete perpendicular to the length of the wood sill plate. 1.6. The sill plate is 2-inch (51 mm) or 3-inch (76 mm) nominal thickness. 2. For the calculation of the in-plane shear strength of anchor bolts attaching cold-formed steel track of bearing or nonbearing walls of light-frame construction to foundations or foundation stemwalls, the in-plane shear strength in accordance with Sections 17.7.2 and 17.7.3 of ACI 318 need not be computed and 17.10.6.3 shall be deemed to be satisfied provided that all of the following are met:
Allowable in-plane shear strength of exempt anchors, parallel to the edge of concrete, shall be permitted to be determined in accordance with AISI S100 Section J3.3.1.
2.1. The maximum anchor nominal diameter is [5] / 8 inch (16 mm). 2.2. Anchors are embedded into concrete a minimum of 7 inches (178 mm).
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2.3. Anchors are located a minimum of 1 [3] / 4 inches (45 mm) from the edge of the concrete parallel to the length of the track.
2.4. Anchors are located a minimum of 15 anchor diameters from the edge of the concrete perpendicular to the length of the track. 2.5. The track is 33 to 68 mil (0.84 mm to 1.73 mm) designation thickness. 3. In light-frame construction bearing or nonbearing walls, shear strength of concrete anchors less than or equal to 1 inch (25 mm) in diameter attaching sill plate or track to foundation or foundation stemwalls need not satisfy Sections 17.10.6.3(a) through (c) when the design strength of the anchors is determined in accordance with Section 17.7.2.1(c) of ACI 318.
SECTION 1906—FOOTINGS FOR LIGHT-FRAME CONSTRUCTION
[OSHPD 1R, 2 & 5] Plain concrete footings not permitted by OSHPD.
1906.1 Plain concrete footings. For Group R-3 occupancies and buildings of other occupancies less than two stories above grade plane of light-frame construction, the required thickness of plain concrete footings is permitted to be 6 inches (152 mm), provided that the footing does not extend more than 4 inches (102 mm) on either side of the supported wall.
SECTION 1907—SLABS-ON-GROUND
1907.1 Structural slabs-on-ground. Structural concrete slabs-on-ground shall comply with all applicable provisions of this chapter. Slabs-on-ground shall be considered structural concrete where required by ACI 318 or where designed to transmit either of the following:
- Vertical loads or lateral forces from other parts of the structure to the soil.
- Vertical loads or lateral forces from other parts of the structure to foundations.
CBC § 1903A.4 High relevance — show source text
1903A.4 Steel fiber reinforcement – Not permitted.
1903A.5 Welding of reinforcing bars - Modify ACI 318 Section 26.6.4.2(b) by adding the following:
Subject to prior approval of the enforcing agency, longitudinal holding wires, conforming to ASTM A1064 of maximum wire size W5, that are machine resistance welded to stirrup/tie cage (or spiral assemblies) consisting of low alloy steel reinforcing conforming to ASTM A706 are permitted when performed under continuous competent control in a fabrication shop. Tack welding of primary reinforcing bars together or to stirrups/ties is not permitted. Holding wire weld locations shall not occur on any longitudinal or primary reinforcing nor on any portion of a reinforcing bar that is or will be bent in accordance with ACI 318 Section 25.3 for the extents specified in AWS D1.4 Section 4.2.6.
[DSA-SS] Exception: Mat reinforcing for slabs or isolated footings shall be permitted to have holding wires located no more than six bar diameters from the free end of reinforcing. Such free ends shall not be associated with any welded splices, couplers or other free- end modifications involving reinforcement development.
Quality control tests shall be performed on shop-welded specimens by the fabricator. Reinforcing steel specimens containing the holding wire shall be tested for yield and tensile strength at the frequency required by Section 1910A.2. Test reports shall be available on request to the approved agency, design professional and enforcement agency.
SECTION 1904 A —DURABILITY REQUIREMENTS
1904 A .1 Structural concrete. Structural concrete shall conform to the durability requirements of ACI 318.
1904 A .2 Nonstructural concrete. The registered design professional shall assign nonstructural concrete a freeze-thaw exposure class, as defined in ACI 318, based on the anticipated exposure of nonstructural concrete. Nonstructural concrete shall have a minimum specified compressive strength, f´ c, of 2,500 psi (17.2 MPa) for Class F0; 3,000 psi (20.7 MPa) for Class F1; and 3,500 psi (24.1 MPa) for Classes F2 and F3. Nonstructural concrete shall be air entrained in accordance with ACI 318.
SECTION 1905 A —SEISMIC REQUIREMENTS
1905 A .1 General. In addition to the provisions of ACI 318, structural concrete shall comply with the requirements of Section 1905 A .
1905 A .2 ACI 318 Section 2.3. Modify existing definitions and add the following definitions to ACI 318 Section 2.3:
CAST-IN-PLACE CONCRETE EQUIVALENT DIAPHRAGM. A cast-in-place noncomposite topping slab diaphragm, as defined in Section 18.12.5, or a diaphragm constructed with precast concrete components that uses closure strips between precast components with detailing that meets the requirements of ACI 318 for the Seismic Design Category of the structure.
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CBC § 1705A.2.1 High relevance — show source text
Additionally, the applicable portions in Table 1705A.2.1 of the California Building Code shall apply.
1705 A .13.1.2 Structural steel elements. Special inspections of structural steel elements in the seismic force-resisting systems of buildings and structures assigned to Seismic Design Category D, E or F other than those covered in Section 1705 A .13.1.1, including struts, collectors, chords and foundation elements, shall be performed in accordance with the quality assurance requirements of AISC 341 and this code .
[DSA-SS, DSA-SS/CC] Quality assurance application is not permitted for the following AISC 341, Chapter J Sections: 1. J6 (Inspection Tasks). 2. J7 (Welding Inspection and Nondestructive Testing). 3. J10 (Inspection of Composite Structures). 4. J11 (Inspection of H-Piles).
Additionally, the applicable portions in Table 1705A.2.1 of the California Building Code shall apply.
1705 A .13.2 Structural wood. For the seismic force-resisting systems of structures assigned to Seismic Design Category D, E or F:
- Continuous special inspection shall be required during field gluing operations of elements of the seismic force-resisting system.
- Periodic special inspection shall be required for nailing, bolting, anchoring and other fastening of elements of the seismic force-resisting system, including wood shear walls, wood diaphragms, drag struts, braces, shear panels and hold-downs.
1705 A .13.3 Cold-formed steel light-frame construction. For the seismic force-resisting systems of structures assigned to Seismic Design Category D, E or F, periodic special inspection shall be required for both:
- Welding operations of elements of the seismic force-resisting system.
- Screw attachment, bolting, anchoring and other fastening of elements of the seismic force-resisting system, including shear walls, braces, diaphragms, collectors (drag struts) and hold-downs.
[DSA-SS, DSA-SS/CC] Requirements specified in Section 1705A.2.9 shall also apply.
1705 A .13.4 Special inspection for special seismic certification . For structures assigned to Seismic Design Category D, E or F, the special inspector shall examine equipment and components requiring special seismic certification in accordance with Section 1705A.14.3 or ASCE 7 , Section 13.2.3 and verify that the label, anchorage and mounting conform to the certificate of compliance.
1705 A .13.5 Architectural components. Periodic special inspection is required for the erection and fastening of exterior cladding, interior and exterior nonbearing walls, ceilings and interior and exterior veneer in structures assigned to Seismic Design Category D, E or F.
[OSHPD 1] E x ception: Periodic special inspection is not required where continuous inspection of the work is performed in accor- dance with Section 7-145 of the CAC .
1705 A .13.5.1 Access floors. Periodic special inspection is required for the anchorage of access floors in structures assigned to Seismic Design Category D, E or F.
CBC § 3.4. High relevance — show source text
_ 4. Site data report in accordance with the CBC 1980 shall establish that seismically induced differential settlement does not exceed 1 ″ in 40 ′ .
5. Adjacent buildings shall satisfy the SPC building separation requirements in accordance with the California Administrative Code, Chapter 6 Section 3.4. 6. The addition of new structural elements or strengthening of existing structural elements for retrofit of nonconforming build- ings to SPC-4D shall comply with the following: a) The seismic demand (forces or displacements) shall be in accordance with the CBC 1980; b) Capacity, detailing and connections for new structural elements shall satisfy the requirements in the CBC 2025 for new construction; and c) The strengthening of existing structural elements shall use capacities determined in accordance with the CBC 2025 for new construction consistent with the detailing and connections used in the strengthened member. 7. All construction, quality assurance and quality control shall be in accordance with the new construction provisions of CBC 2025.
8. Elements not part of the Seismic Force-Resisting System (SFRS), including those identified in the California Administrative Code Chapter 6, Article 10, shall be evaluated using seismic forces and the requirements of the CBC 1980. 9. Any column or wall that forms part of two or more intersecting SFRS and is subjected to axial load due to seismic forces acting along either principal plan axis equaling or exceeding 20 percent of the axial design strength of the column or wall shall be evaluated for the most critical load effect due to application of seismic force in any direction. The most critical load effect may be deemed to be satisfied if members and their foundations are evaluated for 100 percent of the forces for one direction plus 30 percent of the forces for the perpendicular direction, whereby the combination produces the maximum effect. Exceptions: The following buildings (with structural irregularities or unusual configuration/system) shall not be eligible for the SPC-4D upgrade using the prescriptive provisions in this section: 1. Buildings with prohibited irregularities in accordance with California Building Code 2022 Section 1617A.1.10.
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PRESCRIPTIVE COMPLIANCE METHOD
2. Buildings taller than 5 stories or 65' height above the base having horizontal or vertical irregularities in accordance with ASCE 7-10 Tables 12.3-1 Items #1a, 1b and 3 or 12.3-2 Items #1a, 1b, 5a and 5b.
3. Buildings with unusual configuration or structural system, as determined by the building official.
501A.3.2 Prescriptive compliance provisions for SPC-4D using the new building design requirements of this code. Structures satisfying the requirements of the California Building Code for new general acute care hospital buildings design shall be deemed to satisfy the SPC-4D requirements of Table 2.5.3, Chapter 6 of the California Administrative Code.
CBC § 1810.3.10.4.1 High relevance — show source text
1810.3.10.4.1 Seismic requirements. [OSHPD 1R, 2 & 5] For structures assigned to Seismic Design Category D, E or F, a perma- nent steel casing having a minimum thickness of [3] / 8 inch shall be provided from the top of the micropile down to a minimum of 120 percent of the point of zero curvature. Capacity of micropiles shall be determined in accordance with Section 1810.3.3 by at least two project specific pre-production tests for each soil profile, size and depth of micropile. At least two percent of all produc- tion piles shall be proof tested to design strength determined by using load combinations in ASCE 7, Section 2.3.6.
Steel casing length in soil shall be considered as unbonded and shall not be considered as contributing to friction. Casing shall provide confinement at least equivalent to hoop reinforcing required by ACI 318 Section 18.13.5.
Reinforcement shall have Class 1 corrosion protection in accordance with PTI Recommendations for Prestressed Rock and Soil Anchors. Steel casing design shall include at least [1] / 16 -inch corrosion allowance.
Micropiles shall not be considered as carrying any horizontal loads.
1810.3.11 Pile caps. Pile caps shall conform with ACI 318 and this section. Pile caps shall be of reinforced concrete, and shall include all elements to which vertical deep foundation elements are connected, including grade beams and mats. The soil immediately below the pile cap shall not be considered as carrying any vertical load, with the exception of a combined pile raft. [OSHPD 1R, 2 & 5] A combined pile raft foundation shall be an alternative system. The tops of vertical deep foundation elements shall be embedded not less than 3 inches (76 mm) into pile caps and the caps shall extend not less than 4 inches (102 mm) beyond the edges of the elements. The tops of elements shall be cut or chipped back to sound material before capping.
1810.3.11.1 Seismic Design Categories C through F. For structures assigned to Seismic Design Category C, D, E or F, concrete deep foundation elements shall be connected to the pile cap in accordance with ACI 318.
For resistance to uplift forces, anchorage of steel pipes, tubes or H-piles to the pile cap shall be made by means other than concrete bond to the bare steel section. Concrete-filled steel pipes or tubes shall have reinforcement of not less than 0.01 times the cross-sectional area of the concrete fill developed into the cap and extending into the fill a length equal to two times the required cap embedment, but not less than the development length in tension of the reinforcement.
1810.3.11.2 Seismic Design Categories D through F. For structures assigned to Seismic Design Category D, E or F, deep foundation element resistance to uplift forces or rotational restraint shall be provided by anchorage into the pile cap, designed considering the combined effect of axial forces due to uplift and bending moments due to fixity to the pile cap. Anchorage shall develop not less than 25 percent of the strength of the element in tension. Anchorage into the pile cap shall comply with the following:
- In the case of uplift, the anchorage shall be capable of developing the least of the following: 1.1. The nominal tensile strength of the longitudinal reinforcement in a concrete element. 1.2.
CBC § 0.20 High relevance — show source text
- Horizontal reinforcement of not less than 0.20 square inch (129 mm [2] ) in cross-sectional area shall be provided: 2.1. Continuously at structurally connected roof and floor levels and at the top of walls. 2.2. At the bottom of load-bearing walls or in the top of foundations where doweled to the wall. 2.3. At a maximum spacing of 120 inches (3048 mm).
Reinforcement at the top and bottom of openings, where used in determining the maximum spacing specified in Item 2.3, shall be continuous in the wall.
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1905.6 Structural plain concrete. Structural plain concrete elements shall comply with this section in lieu of Section 14.1.4 of ACI 318. [OSHPD 1R, 2 & 5] Plain concrete shall not be permitted.
1905.6.1 Seismic Design Categories A and B. In structures assigned to Seismic Design Category A or B, detached one- and twofamily dwellings three stories or less in height constructed with stud-bearing walls are permitted to have plain concrete footings without longitudinal reinforcement.
1905.6.2 Seismic Design Categories C, D, E and F. Structures assigned to Seismic Design Category C, D, E or F shall not have elements of structural plain concrete, except as follows:
Structural plain concrete basement, foundation or other walls below the base as defined in ASCE/SEI 7 are permitted in detached one- and two-family dwellings three stories or less in height constructed with stud-bearing walls. In dwellings assigned to Seismic Design Category D or E, the height of the wall shall not exceed 8 feet (2438 mm), the thickness shall be not less than 7 [1] / 2 inches (190 mm), and the wall shall retain not more than 4 feet (1219 mm) of unbalanced fill. Walls shall have reinforcement in accordance with Section 14.6.1 of ACI 318.
Isolated footings of plain concrete supporting pedestals or columns are permitted, provided that the projection of the footing beyond the face of the supported member does not exceed the footing thickness. Exception: In detached one- and two-family dwellings three stories or less in height, the projection of the footing beyond the face of the supported member is permitted to exceed the footing thickness.
Plain concrete footings supporting walls are permitted, provided that the footings have not fewer than two continuous longitudinal reinforcing bars. Bars shall not be smaller than No. 4 and shall have a total area of not less than 0.002 times the gross cross-sectional area of the footing. For footings that exceed 8 inches (203 mm) in thickness, not fewer than one bar shall be provided at the top and bottom of the footing. Continuity of reinforcement shall be provided at corners and intersections.
Exceptions:
- Where assigned to Seismic Design Category C, detached one- and two-family dwellings three stories or less in height constructed with stud-bearing walls are permitted to have plain concrete footings without longitudinal reinforcement.
CBC § 1901.1.2 High relevance — show source text
1901.1.2 Amendments in this chapter. [DSA-SS/CC, OSHPD] DSA-SS/CC and OSHPD adopts this chapter as amended.
1901.1.3 Identification of amendments. [DSA-SS/CC, OSHPD] 1. Division of the State Architect - Structural Safety/Community Colleges amendments appear in this chapter preceded by the appropriate acronym, as follows:
[DSA-SS/CC] – For applications listed in Section 1.9.2.2. 2. [OSHPD 1R, 2 & 5] Office of Statewide Hospital Planning and Development (OSHPD) amendments appear in this chapter preceded by the appropriate acronym, as follows:
[OSHPD 1R ] – For applications listed in Section 1.10.1.
[OSHPD 2] – For applications listed in Section 1.10.2.
[OSHPD 5] – For applications listed in Section 1.10.5.
1901.1.4 Reference to other chapters. [DSA-SS/CC] Where reference within this chapter is made to sections in Chapters 17 and 18, the provisions in Chapters 17A and 18A respectively shall apply instead.
1901.1.5 Additional amendments. [DSA-SS/CC] See Section 1909 for additional requirements.
1901.2 Plain and reinforced concrete. Structural concrete shall be designed and constructed in accordance with the requirements of this chapter and ACI 318 as supplemented in Section 1905 of this code.
1901.2.1 Structural concrete with GFRP reinforcement. Cast-in-place structural concrete internally reinforced with glass fiber reinforced polymer (GFRP) reinforcement conforming to ASTM D7957 and designed in accordance with ACI CODE 440.11 shall be permitted where fire-resistance ratings are not required and only for structures assigned to Seismic Design Category A.
1901.3 Anchoring to concrete. Anchoring to concrete shall be in accordance with ACI 318 as supplemented in Section 1905, and applies to cast-in (headed bolts, headed studs and hooked J- or L-bolts), post-installed expansion (torque-controlled and displacement-controlled), undercut, screw, and adhesive anchors.
1901.3.1 Power actuated fasteners. [OSHPD 1R, 2 & 5] Power actuated fasteners qualified in accordance with ICC-ES AC 70 shall be deemed to satisfy the requirements of ASCE 7, Section 13.4.5.
Power actuated fasteners shall be permitted in seismic shear for components exempt from construction documents review by ASCE 7, Section 13.1.4 and for interior non-bearing non-shear wall partitions only. Power actuated fastener shall not be used to anchor seismic bracing, exterior cladding or curtain wall systems.
Exception: Power actuated fasteners in steel to steel connections prequalified for seismic application by cyclic tests in accordance with ICC-ES AC 70 shall be permitted for seismic design.
CBC § 1901.2 High relevance — show source text
1901.2 Plain and reinforced concrete. Structural concrete shall be designed and constructed in accordance with the requirements of this chapter and ACI 318 as supplemented in Section 1905 of this code.
1901.2.1 Structural concrete with GFRP reinforcement. Cast-in-place structural concrete internally reinforced with glass fiber reinforced polymer (GFRP) reinforcement conforming to ASTM D7957 and designed in accordance with ACI CODE 440.11 shall be permitted where fire-resistance ratings are not required and only for structures assigned to Seismic Design Category A.
1901.3 Anchoring to concrete. Anchoring to concrete shall be in accordance with ACI 318 as supplemented in Section 1905, and applies to cast-in (headed bolts, headed studs and hooked J- or L-bolts), post-installed expansion (torque-controlled and displacement-controlled), undercut, screw, and adhesive anchors.
1901.3.1 Power actuated fasteners. [OSHPD 1R, 2 & 5] Power actuated fasteners qualified in accordance with ICC-ES AC 70 shall be deemed to satisfy the requirements of ASCE 7, Section 13.4.5.
Power actuated fasteners shall be permitted in seismic shear for components exempt from construction documents review by ASCE 7, Section 13.1.4 and for interior non-bearing non-shear wall partitions only. Power actuated fastener shall not be used to anchor seismic bracing, exterior cladding or curtain wall systems.
Exception: Power actuated fasteners in steel to steel connections prequalified for seismic application by cyclic tests in accordance with ICC-ES AC 70 shall be permitted for seismic design.
1901.3.2 Mechanical anchors and specialty inserts. [OSHPD 1R, 2 & 5] Mechanical anchors qualified in accordance with ICC-ES AC 193 shall be deemed to satisfy the requirements of this section. Specialty inserts, including cast-in-place specialty inserts, tested in accordance with ICC-ES AC 232 or AC 446 shall be deemed to satisfy the requirements of this section.
Note: The removal and resetting of post-installed mechanical anchors are prohibited by ACI 318 Section 17.1.3.
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1901.3.3 Post-installed adhesive anchors. [OSHPD 1R, 2 & 5] Post-installed reinforcing bars, adhesive anchors, and torque- controlled adhesive anchors qualified in accordance with ICC-ES AC 308 shall be deemed to satisfy the requirements of this section.
1901.3.4 Proof tests for post-installed anchors in concrete. [OSHPD 1R, 2 & 5] When post-installed anchors are used in lieu of cast- in place bolts, the proof test loads, frequency and acceptance criteria shall be in accordance with this section.
Exceptions. Proof tests are not required for the following:
1. Undercut anchors that allow visual confirmation of full set.
CBC § 1903.5 High relevance — show source text
1903.5 Welding of reinforcing bars - [OSHPD 1R, 2 & 5] Modify ACI 318 Section 26.6.4.1(b) by adding the following:
Subject to prior approval of the enforcing agency, longitudinal holding wires conforming to ASTM A1064, of maximum wire size W5, that are machine resistance welded to stirrup/tie cage (or spiral assemblies) consisting of low alloy steel reinforcing conforming to ASTM A706 are permitted when performed under continuous competent control in a fabrication shop. Tack welding of primary rein- forcing bars together or to stirrups/ties is not permitted. Holding wire weld locations shall not occur on any longitudinal or primary reinforcing nor on any portion of a reinforcing bar that is or will be bent in accordance with ACI 318 Section 25.3 for the extents speci- fied in AWS D1.4 Section 4.2.6.
Quality control tests shall be performed on shop welded specimens by the fabricator. Reinforcing steel specimens containing the holding wire shall be tested for yield and tensile strength at the frequency required by Section 1910.2. Test reports shall be available on request to the approved agency, design professional and enforcement agency.
SECTION 1904—DURABILITY REQUIREMENTS
1904.1 Structural concrete. Structural concrete shall conform to the durability requirements of ACI 318.
Exception: For Group R-2 and R-3 occupancies not more than three stories above grade plane, the specified compressive strength, f´ c, for concrete in basement walls, foundation walls, exterior walls and other vertical surfaces exposed to the weather shall be not less than 3,000 psi (20.7 MPa).
1904.2 Nonstructural concrete. The registered design professional shall assign nonstructural concrete a freeze-thaw exposure class, as defined in ACI 318, based on the anticipated exposure of nonstructural concrete. Nonstructural concrete shall have a minimum specified compressive strength, f´ c, of 2,500 psi (17.2 MPa) for Class F0; 3,000 psi (20.7 MPa) for Class F1; and 3,500 psi (24.1 MPa) for Classes F2 and F3. Nonstructural concrete shall be air entrained in accordance with ACI 318.
SECTION 1905—SEISMIC REQUIREMENTS
1905.1 General. In addition to the provisions of ACI 318, structural concrete shall comply with the requirements of Section 1905.
1905.2 ACI 318 Section 2.3. Modify existing definitions and add the following definitions to ACI 318 Section 2.3:
CAST-IN-PLACE CONCRETE EQUIVALENT DIAPHRAGM. A cast-in-place noncomposite topping slab diaphragm, as defined in Section 18.12.5, or a diaphragm constructed with precast concrete components that uses closure strips between precast components with detailing that meets the requirements of ACI 318 for the Seismic Design Category of the structure.
DETAILED PLAIN CONCRETE STRUCTURAL WALL. A wall complying with the requirements of Chapter 14, and Section 1905.5 of the California Building Code .
ORDINARY PLAIN CONCRETE STRUCTURAL WALL. A wall complying with the requirements of Chapter 14, excluding 14.6.2.
CBC § 18-22 High relevance — show source text
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SOILS AND FOUNDATIONS
1810.3.2.6 Allowable stresses. The allowable stresses for materials used in deep foundation elements shall not exceed those specified in Table 1810.3.2.6.
TABLE 1810.3.2.6—ALLOWABLE STRESSES FOR MATERIALS USED IN DEEP FOUNDATION ELEMENTS Col2 MATERIAL TYPE AND CONDITION MAXIMUM ALLOWABLE STRESSa 1. Concrete or grout in compressionb
Cast-in-place with a permanent casing in accordance with Section 1810.3.2.7
or Section 1810.3.5.3.4
Cast-in-place in other permanent casing or rock
Cast-in-place without a permanent casing
Precast nonprestressed
Precast prestressed0.4_f ′c_
0.33_f ′c_
0.3_f ′c_
0.33_f ′c_
0.33_f ′c_ - 0.27_fpc_2. Nonprestressed reinforcement in compression 0.4_fy_ ≤ 30,000 psi 3. Steel in compression
Cores within concrete-filled pipes or tubes
Pipes, tubes or H-piles, where justified in accordance with Section 1810.3.2.8
Pipes or tubes for micropiles
Other pipes, tubes or H-piles
Helical piles0.5_Fy_ ≤ 32,000 psi
0.5_Fy ≤ 32,000 psi
0.4_Fy ≤ 32,000 psi
0.35_Fy_ ≤ 24,000 psi
0.6_Fy_ ≤ 0.5_Fu_4. Nonprestressed reinforcement in tension
Within micropiles
Other conditions
For load combinations that do not include wind or seismic loads
For load combinations that include wind or seismic loads0.6_fy_
0.5_fy_ ≤ 30,000 psi
0.5_fy_ ≤ 40,000 psi5. Steel in tension
Pipes, tubes or H-piles, where justified in accordance with Section 1810.3.2.8
Other pipes, tubes or H-piles
Helical piles0.5_Fy_ ≤ 32,000 psi
0.35_Fy_ ≤ 24,000 psi
0.6_Fy_ ≤ 0.5_Fu_6. Timber In accordance with the ANSI/AWC NDS a.f ′c is the specified compressive strength of the concrete or grout;fpc is the compressive stress on the gross concrete section due to effective prestress forces only;fy is the spec-
ified yield strength of reinforcement;Fy is the specified minimum yield stress of steel;Fu is the specified minimum tensile stress of structural steel.
b. The stresses specified apply to the gross cross-sectional area of the concrete for precast prestressed piles and to the net cross-sectional area for all other piles.
Frequently asked questions
When does § 1905 apply instead of plain ACI 318 provisions?
Section 1905 supplements and modifies ACI 318 for California seismic requirements — where Chapter 19 provides a specific requirement or exception, the CBC (Chapter 19) controls; see § 1905 and § 1905.1.
Are plain (unreinforced) concrete walls allowed in high seismic areas?
Generally no. § 1905.6 restricts structural plain concrete in Seismic Design Categories C–F except for narrow, explicit exceptions for detached one‑ and two‑family dwellings and limited footing cases; OSHPD may prohibit plain concrete entirely for certain facilities. (§ 1905.6, § 1905.5) file
How much reinforcement must I show at openings in a detailed plain concrete wall?
Vertical reinforcement of at least 0.20 in² (129 mm²) must be provided continuously at each side of each opening; horizontal reinforcement rules also apply and spacing cannot exceed 120 in. (§ 1905.5.1)
Can a small detached house in SDC B use plain concrete footings with no longitudinal bars?
Yes — § 1905.6.1 explicitly permits plain concrete footings without longitudinal reinforcement for detached one‑ and two‑family dwellings up to three stories in SDC A or B.
If my footing is 10 in thick, must I provide top and bottom bars?
Yes — for footings exceeding 8 in thickness § 1905.6.2.3 requires at least one bar at the top and one at the bottom in addition to the minimum two continuous longitudinal bars.
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- Roofing & Roof Assemblies
- Structural Design
- Special Inspections & Tests
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