California Building Code (CBC) 2022: what's new for residential structural design

What CBC 2022 is and how local ordinances work

The California Building Code is part of Title 24 of California's regulations. It is based on the International Building Code, typically released one year after each IBC edition with California-specific amendments layered on top. The 2022 edition, based on IBC 2021, came into effect on January 1, 2023. For most California jurisdictions, CBC 2022 is now the enforceable standard for new permit submittals.

Local jurisdictions can adopt ordinances that are more conservative than the state code, and some already have. The California Building Standards Commission maintains a searchable list of these ordinances, organized by city and county. A white row means no local amendments; a listed ordinance number means specific provisions apply. Laurent demonstrated this by looking up Pleasanton, California, which adopted Ordinance 2041. That ordinance amends Section 1905.1.7 of the CBC, removing exceptions for plain concrete in basement walls and effectively requiring reinforcement where the base code might otherwise allow plain concrete. Laurent noted that the commission responds quickly to email requests when an ordinance is difficult to locate.

General changes that affect all structural projects

One of the broader changes in the CBC 2022 cycle is that ASCE 7 now handles all load calculations and load combinations. The previous arrangement, where IBC and ASCE 7 load combinations existed in parallel with slight discrepancies, has been resolved in favor of ASCE 7 exclusively. Designers who have not already been working entirely within ASCE 7 load combinations should confirm their templates are updated.

For components and cladding wind design, CBC 2022 now requires drawings to show the location and dimensions of each wind pressure zone, not just zone 3 as was previously required. On irregular plan forms the zone boundaries can shift, and showing all zones ensures that a separate cladding designer or contractor works from the same pressure assumptions.

Structural observation requirements have also been expanded. A professional engineer must now perform on-site structural observation for any building in Risk Category 3 or 4, and for any seismic design category building with more than two stories above grade. What a structural observation must specifically cover is now codified, filling in detail that was previously absent.

Seismic design under CBC 2022

CBC 2022 retains ASCE 7-16 as its seismic reference, which is a California-specific amendment to the IBC 2021 framework. Two supplements to ASCE 7-16 are also referenced. The supplements clarify when site-specific analysis is required.

For site class D, if SS exceeds 1.2, which describes much of California, the one-second design acceleration is increased by 50 percent. For site class E, if SS exceeds 2.2 or S1 exceeds 1.0, the short-period acceleration is used as a conservative proxy. Both supplements reduce the ambiguity around when a site-specific analysis is required. For typical residential structures, the practical effect on design loads is modest, but engineers working near site class boundaries should reconfirm their parameters under the updated criteria. Laurent also highlighted that Calcs.com released its seismic load calculator incorporating these two supplements.

Foundation and deep element updates

A specific addition in CBC 2022 requires that exits without a facing door be frost-protected. The concern is frost heave at the slab in front of an exit blocking the door during an emergency. For most of California this is rarely relevant, but it does apply to projects in mountain locations. Laurent noted that the typical fix is extending foundation insulation under the door opening radius.

For deep foundations, precast pile design is now explicitly tied to ACI 318. In high seismic zones, which encompasses most of California, additional requirements apply and include specific reference to ACI 341 for seismic design of steel piles. Engineers designing helical piles, precast piles, or other driven elements for California projects should confirm their design references align with the updated provisions.

Shear wall changes under SDPWS 2021

CBC 2022 adopts the 2021 Special Design Provisions for Wind and Seismic, replacing the 2015 edition. For wood panel shear walls designed using LRFD, there is approximately an 11 percent reduction in tabulated unit shear values. For gypsum board or plaster used as shear panels in ASD designs, the reduction can reach 30 percent. Both reductions follow from a unification of how safety factors are applied across the standard.

Weak story provisions are now more restrictive in high seismic design categories under SDPWS 2021 than under ASCE 7 alone. Engineers who have relied only on the ASCE 7 weak story criteria will need to cross-check against the SDPWS requirements for projects with mixed stiffness over height. A new addition in this edition is provisions for cross-laminated timber as a shear wall and diaphragm material, which were not present in earlier editions.

Concrete under ACI 318-19: the change with the most immediate impact

The update from ACI 318-14 to ACI 318-19 is where most engineers will see the largest practical difference in day-to-day work. Two changes stand out.

The first is allowable reinforcement strength. ACI 318-19 permits high-strength rebar up to 100 ksi, increased from 80 ksi under ACI 318-14. The practical effect depends on what grades are specified locally, as 60 ksi bars remain common for most residential and small commercial work.

The second and more consequential change is to the concrete shear capacity formula. For members without shear reinforcement, the formula was substantially revised. Laurent demonstrated a spread footing under identical loads and dimensions in both ACI 318-14 and ACI 318-19. The 2014 version showed 100 percent utilization on shear. The 2019 version showed 171 percent utilization. Increasing the footing thickness from 12 inches to 18 inches was required to bring it back into compliance. Wall footings are expected to see similar or larger increases in required depth.

An additional shear size factor reduces the shear capacity of members deeper than 10 inches that do not have transverse reinforcement. A 24-inch thick slab without stirrups sees its shear capacity reduced by a further 25 percent on top of the base formula change. Footings are explicitly excepted from this size factor, but walls and slabs without stirrups are not.