What Are the Major Changes in the 2025 California Building Code Volume 2?

Volume 2 of the 2025 California Building Code brings sweeping structural, materials, and construction-phase updates across Chapters 16–35 and Appendices I–Q.

The most significant themes include:

1. Major Structural Design Updates (Chapter 16)

• Updated wind, snow, and tornado design criteria
• Revised risk categories (especially for I-2, I-3, and PV systems)
• Reworked seismic design categories and rainfall load calculations
• Reorganization of live load tables and load combinations

2. Strengthening of Special Inspections (Chapter 17)

• Stainless steel added as a structural material
• New inspection requirements for pre-engineered metal buildings
• Deferred submittal items must now be explicitly listed in the SI statement

3. New Foundation & Retaining Wall Safety Provisions (Chapter 18)

• New guardrail rules for site retaining walls
• New grade beam design section
• Expanded deep foundation requirements

4. Structural Material Updates (Chapters 19–26)

• Concrete seismic requirements reorganized
• New stainless steel and cold-formed steel provisions
• New hillside construction requirements in wood chapter
• Updated water-resistive barrier and gypsum panel system rules
• New foam-plastic insulation and climate-controlled structure rules

5. Large Expansion in Steel Standards (Chapter 22)

• Industrial platforms
• Boltless steel shelving
• Metal building systems
• New AISC and ANSI references

6. New Elevator Safety Provisions (Chapter 30)

• Revised hoistway door protection
• New smoke curtain options
• New provisions for private residence elevators

7. Special Construction Overhaul (Chapter 31)

• Temporary structure rules expanded
• New structural requirements and serviceability criteria
• New controlled-occupancy procedures for tsunami & reduced-load cases

8. New Site Safety Requirements During Construction (Chapter 33)

• Owners now must prepare and maintain a Site Safety Plan before permits are issued

9. New Sleeping Lofts Appendix (Appendix P)

A major new appendix covering:

• Ceiling heights
• Maximum loft area
• Exit systems
• Alternating tread devices, ships ladders, standard ladders
• Guard and smoke alarm requirements

What are the key changes in Chapter 16 Structural Design of CBC 2025

High-Impact Summary

Chapter 16 receives some of the largest structural updates in CBC 2025, including:

1. Expanded Snow, Wind & Tornado Design Criteria

• Updated loading tables
• New tornado provisions (ASCE 7-22)
• Ground snow load tables now include risk categories

2. Revised Risk Categories for Buildings

• Revisions to Risk Categories III & IV
• New risk category rules for PV installations
• Expanded criteria for designated emergency systems

3. Major Live Load Table Reorganization

• Garage loads, railing loads, helipad loads, and hotel/multifamily loads reorganized
• New loads for public restrooms, assembly roofs, and truss point loads

4. Seismic Design Category Overhaul

• New SDC tables and graphics
• Removal of legacy Ss/S1/MCE figures
• Coordination with ASCE 7-22

5. New Rain Load Formula

• dh, dp, ds redefined
• Alternate procedure removed
• Risk category designations added
  
  

6. New Rules for Temporary Structures

• Explicit reference to CBC 3103.6 subsections for seismic/wind/flood loads

7. New Conveyance System Requirements

• Elevators, escalators, etc. now explicitly required to meet ASCE 7 wind + ASCE 24 flood + ASME A17.1 seismic criteria

This chapter substantially affects all structural engineers and architects working on new construction.

Full Detailed Table of All Changes  -  Chapter 16

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Expert Commentary  -  Chapter 16

1. This chapter is one of the biggest structural updates in years

Structural engineers cannot rely on 2022 numbers - snow, wind, tornado, seismic, and rain load calculations all changed.

2. Risk Category revisions are huge

Hospitals (I-2), jails (I-3), PV installations, and buildings with emergency systems now fall into expanded risk-category triggers.

3. Live load table reorganizations matter in daily design

Especially for:

• Multifamily
• Hotels
• Parking structures
• Roof decks
• Assembly spaces

4. Seismic Design Categories fully rewritten

The shift to ASCE 7-22 means:

• New SDC mapping
• Old Ss/S1 figures removed
• New figure 1613.2(1) adopted

5. Temporary structures quietly became stricter

CBC now explicitly requires using 3103.6 structural criteria.

6. Conveyance systems (elevators) now have integrated wind+flood+seismic design mandates

Previously, many designers treated these loads separately - now it’s centralized and coordinated.

What are the key changes in Chapter 17 Structural Tests & Special Inspections of CBC 2025

High-Impact Summary

Chapter 17 introduces meaningful changes that clarify special inspection scope, modernize materials coverage, and expand oversight of prefabricated metal building systems.

The most notable updates include:

1. Structural stainless steel is now explicitly recognized

Multiple sections add stainless steel as a structural material requiring inspection and qualification standards.

2. Metal building systems get explicit special inspection criteria

A major update clarifies how pre-engineered metal buildings (PEMBs) must be inspected, certified, and verified.

3. Deferred submittals must be fully identified in the Special Inspection statement

This closes a loophole where omitted items caused confusion and enforcement issues.

4. Concrete and welding tables revised

New references to AWS and ACI standards.

5. New rules for proprietary systems & industrialized construction

Codified inspection pathways for nontraditional structural systems.

Full Detailed Table of All Changes  -  Chapter 17

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Expert Commentary  -  Chapter 17

1. Stainless steel is now a first-class structural citizen

This matches reality: stainless is increasingly used for exposed conditions, corrosive environments, and architectural structures. Its addition means:

• New welding certifications
• New inspection checklists
• New QA/QC procedures

2. Metal building systems (MBS / PEMBs) finally have clear requirements

For decades, PEMBs created ambiguity between:

• Who designed what
• Who inspected what
• Who certified components

CBC 2025 clarifies this with a dedicated section and definition.

3. Proprietary systems pathways matter for modern construction

Industrialized construction, prefabricated components, and proprietary seismic systems now have inspection routes.

4. More clarity for soils & foundations

Compaction and fill placement clarifications reduce inspection conflicts.

What are the key changes in Chapter 18 Soils & Foundations of CBC 2025

High-Impact Summary

Chapter 18 adds new geotechnical triggers, clarifies requirements for:

• Retaining walls and guardrails
• Grade beams
• Shallow and deep foundations
• Compaction & placement of structural fill
• Excavation safety during seismic events

While not as sweeping as Chapter 16, these updates materially affect site design, structural engineering, and civil coordination.

Full Detailed Table of All Changes  -  Chapter 18

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Expert Commentary  -  Chapter 18

1. Retaining walls now explicitly require guardrails where applicable

This resolves repeated plan check disputes: any retaining wall that creates a >30" fall hazard now triggers guard requirements (§1015).

2. Grade beams finally get a formal section

Instead of relying on scattered commentary, CBC creates:

• Clear load path rules
• Minimum reinforcement criteria
• Bearing/settlement expectations

3. Significant updates to deep foundation criteria

This affects:

• Pile design
• Caisson design
• Micropile criteria
• Seismic reinforcement for foundations

4. Excavation + seismic effects now explicitly tied together

CBC now requires evaluating seismic effects when excavating near existing structures.

This ensures safer urban construction and reduces collapse / soil movement risks.

What are the key changes in Chapter 19 Concrete of CBC 2025

High-Impact Summary

CBC 2025 Chapter 19 modernizes concrete provisions by:

1. Updating references to the latest ACI standards
2. Changing classification of slabs-on-ground
3. Updating and reorganizing seismic modifications to ACI 318
4. Adding coordination for glass fiber-reinforced polymer (GFRP) reinforcement

No radical changes, but many important technical updates for engineers.

Full Detailed Table of All Changes  -  Chapter 19

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Expert Commentary  -  Chapter 19

A quiet but important modernization

Concrete designers must be aware that:

• Slabs-on-ground being nonstructural shifts liability away from structural engineers unless specifically designed.
• Seismic modifications cleanup reduces confusion on what is or isn’t subject to ACI 318 Chapter 18.
• GFRP reinforcement is increasingly used in corrosive conditions; clearer references mean easier adoption.

What are the key changes in Chapter 20 Aluminum of CBC 2025

High-Impact Summary

CBC 2025 Chapter 20 has no changes. The aluminum structural provisions are unchanged from 2022.

This chapter remains stable because aluminum structural elements are:

• Not widely used in primary structural systems
• Governed heavily by AA ADM and manufacturer specs
• Typically utilized in curtainwall systems (governed under Ch. 24)

What are the key changes in Chapter 21 Masonry of CBC 2025

High-Impact Summary

CBC 2025 Chapter 21 has no changes, similar to Chapter 20.

Masonry codes continue to rely on:

• TMS 402/602 for structural masonry
• Minimal CA amendments

This stability reduces risk of mismatches for structural engineers.

What are the key changes in Chapter 22 Steel of CBC 2025

High-Impact Summary

CBC 2025 Chapter 22 contains some of the most significant structural material updates in the entire Volume 2.
Key themes:

1. Stainless Steel Becomes a Fully Recognized Structural Material

• New section 2204
• References AISC 370 + AISC 313
• Requires stainless steel QA, design rules, and inspections

2. Cold-Formed Steel Seismic Requirements Updated

Aligns with AISI S100/S220, including:

• Collectors
• Shear walls
• Anchors
• Panel shear distribution

3. Major Overhaul for Metal Building Systems

• New references
• New design requirements
• Stronger QA & submittal alignment
• Coordinates with new Chapter 17 inspection rules

4. New Industrial Steel Platform Requirements

Per ANSI MH32.1-2021:

• Uniform loads
• Concentrated loads
• Lateral loads
• Stair & guard coordination

5. Revisions to Nonstructural Steel Element Testing

• Stainless steel
• Mechanical/chemical properties
• Bolts, welds, anchors

This chapter materially affects structural engineers in commercial, industrial, and pre-engineered building sectors.

Full Detailed Table of All Changes  -  Chapter 22

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Expert Commentary  -  Chapter 22

1. Stainless steel becoming fully codified is huge

Prior CBC editions treated stainless steel like an accessory material.
CBC 2025 gives it:

• Full design rules (AISC 370)
• Full structural identification rules
• Welding requirements
• Special inspections

This reflects stainless steel’s growth in:

• Hospitals
• Coastal sites
• High-end architectural structures
• Corrosive industrial environments

2. Cold-formed steel seismic provisions are now far more aligned with ASCE 7-22

This is especially important for:

• Shear wall distribution
• Collector design
• Anchorage
• Light-frame multi-family

3. Metal building systems (MBS / PEMBs) now have strong accountability

This chapter + Chapter 17 together form a complete compliance workflow:

• Design → Fabrication → Special inspection → Installation
• No more ambiguity about manufacturer responsibilities

4. Industrial work platforms are finally recognized

Industrial mezzanines used to be governed by a messy mix of standards.
CBC 2025 makes them straightforward and enforceable.

What are the key changes in Chapter 23 Wood of CBC 2025

High-Impact Summary

Chapter 23 incorporates several meaningful updates related to:

1. Fire-Retardant-Treated (FRT) Wood

• Expanded scope for classification
• Clearer requirements on labeling & performance

2. Load Duration & Fire Design Coordination

• New load duration rules added
• Seismic/horizontal load criteria clarified

3. Hillside Residential Construction

• Significant clarifications for hillside anchorage, lateral loads, and framing systems

4. Wood Connector Requirements

• Major clarifications on where cold-formed steel or light-gauge connectors can be used
• Connection-specific restrictions adjusted

5. Notching, Drilling, and Cuts

• New explicit limits for sawn lumber and glu-lam members

6. New requirements for uplift hardware and tables

• Heavy uplift connectors updated
• Tables aligned with new testing standards

These additions modernize wood construction design and address common field issues.

Full Detailed Table of All Changes  -  Chapter 23

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Expert Commentary  -  Chapter 23

1. Hillside construction changes are a big deal for California

The new requirements reflect post-wildfire, post-landslide risk realities.

2. Notching & drilling clarifications reduce RFIs

Field inspectors have long had inconsistent interpretations  -  CBC 2025 resolves many of these.

3. Uplift resistance requirements better match modern hardware

Heavy uplift events (wind, seismic) are better accounted for.

4. CNC wood member section acknowledges real industry trends

Prefabricated, mass timber, and modular systems are growing  -  CBC now gives them a compliance pathway.

What are the key changes in Chapter 24 Glass & Glazing of CBC 2025

High-Impact Summary

Chapter 24 does not dramatically change glazing rules, but includes targeted updates:

1. Skylight Screening Section Reformatted

• No substantive change, but readability improved

2. Hazardous Locations Updated through Exceptions

• Exception 14 revised
• Exception 15 removed
• Aligns CBC with current safety glazing criteria

3. Handrail & Guard Glass Stress Limit Correction

• “2lbf” typo corrected to 200 lbf as intended
• Safety correction aligned with testing standards

These are precision updates but extremely important for façade consultants and architects.

Full Detailed Table of All Changes  -  Chapter 24

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The load correction (2 lbf → 200 lbf) is the most important update  -  the incorrect number could have resulted in catastrophic misdesign if taken literally.

What are the key changes in Chapter 25 Gypsum Panel Products & Plaster of CBC 2025

High-Impact Summary

Chapter 25 updates are meaningful for both architectural and envelope design teams:

1. Terminology Modernization

• “Gypsum board” replaced with “gypsum panel products”
• Aligns CBC with ASTM definitions

2. Water-Resistive Barriers (WRBs)

• WRB installation text rewritten
• Additional drainage requirements for dry climates (>20” rainfall exception clarified)

3. Coordination with Chapter 14 WRB/Vapor Sections

These changes unify the vertical envelope requirements across multiple chapters.

Full Detailed Table of All Changes  -  Chapter 25

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Expert Commentary  -  Chapter 25

1. WRB updates reflect increasing building science sophistication

Drainage plane clarity is critical in mixed/dry climates and avoids mold claims.

2. Terminology unification simplifies cross-referencing

The shift to “gypsum panel products” was long overdue.

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What are the key changes in Chapter 26 Plastic of CBC 2025

High-Impact Summary

Chapter 26 introduces two key updates:

1. New Insulation Sheathing Section

• Defines requirements for rigid plastic foam sheathing
• Coordinates with Chapter 14 (Exterior Walls)
• Addresses fire & moisture concerns

2. New Rules for Foam Insulation in Small Nonsprinklered Group U Structures

• Clarifies when foam plastic insulation is allowed
• Adds provisions for thermal barriers, ignition barriers, and coverings

Full Detailed Table of All Changes  -  Chapter 26

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Expert Commentary  -  Chapter 26

1. CI (Continuous Insulation) growth forced these updates

Rigid insulation is now standard in high-performance walls; code finally provides clear compliance pathways.

2. Small-U occupancy foam rules simplify residential design

Historically unclear, this section ensures safer garage/shed insulation practices.

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What are the key changes in Chapter 30 Elevators & Conveying Systems

High-Impact Summary

CBC 2025 includes several meaningful clarifications and expansions in Chapter 30:

1. Elevator Emergency Communication Modernized

• Text reformatted
• Operational requirements remain the same but clearer

2. Conveyance Systems Must Meet Updated Structural Load Criteria

Explicitly ties:

• Wind design → ASCE 7
• Flood design → ASCE 24
• Seismic design → ASCE 7 + ASME A17.1/CSA B44

3. Expanded Hoistway Door Protection Requirements

Especially in:

• State-owned buildings
• Institutional buildings
• Buildings with rated corridor walls adjacent to elevator doors

4. New Allowance: Smoke Curtain Assemblies

A major addition for hoistway door protection.

5. Private Residence Elevators Added

• Entirely new section
• Defines requirements for one- and two-family elevators
  
  

Full Detailed Table of All Changes  -  Chapter 30

Expert Commentary  -  Chapter 30

1. Hoistway door protection is now significantly expanded

Especially important for:

• State facilities
• Buildings with rated corridors
• Healthcare, detention, and public buildings

2. Smoke-protective curtains becoming mainstream

This aligns CBC with recent NFPA/ICC trends and supports design flexibility in constrained spaces.

3. Private residence elevator rules fill a longstanding gap

Previously, designers relied heavily on ASME/IRC  -  now CBC provides explicit California guidance.

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What are the key changes in Chapter 31 Special Construction

Chapter 31 in the 2025 CBC has major new content, especially around temporary structures and public-occupancy installations. This is the single largest change chapter in Volume 2.

High-Impact Summary

1. Temporary Structures Overhauled

CBC 2025 introduces new structure, organization, and requirements for tents, membrane structures, public-occupancy temporary buildings, and special event structures.

2. Temporary Structures May Now Stay in Place Longer

• Public-occupancy structures may stay up to 180 days or more, but not over 1 year, under strict conditions.

3. New Structural Requirements for Temporary Structures

CBC adds:

• Wind load requirements
• Flood load provisions
• Ice load provisions
• Tsunami-related occupancy procedures

4. New “Controlled Occupancy Procedures” Section

For public-occupancy temporary structures designed with reduced loads, or used in tsunami zones.

5. New Bleacher Requirements

• Bleachers not part of a building must comply with ICC 300

6. Shipping Containers Rules Expanded

• Stacked container structures must follow new §3114.8.4
• Seismic system revised for stacked units

Full Detailed Table of All Changes  -  Chapter 31

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Expert Commentary  -  Chapter 31

1. Temporary structures are treated more like permanent buildings

Given wildfire winds, extreme weather, and large event usage, this change is overdue.

2. Controlled Occupancy Procedures = a new category of risk management

This will heavily impact:

• Stadiums
• Festivals
• Seasonal events
• Tsunami-prone coastal installations

3. Shipping container structures (popular in CA) now have clear seismic design rules

This impacts:

• Modular pop-ups
• Job-site offices
• Temporary housing
• Retail/restaurant containers

This resolves a major regulatory grey area.

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What are the key changes in Chapter 32 Encroachments Into The Public Way

CBC 2025 Chapter 32 has no changes.

Designers can rely on existing public-way encroachment rules.

What are the key changes in Chapter 33 Safeguards During Construction

High-Impact Summary

Only one major change  -  but it is significant:

1. Owners Must Prepare a Site Safety Plan

Before a building permit is issued, the owner must submit and maintain a comprehensive Site Safety Plan covering:

• Fire protection
• Emergency access
• Hazard mitigation
• Material storage
• Onsite operations

This brings California closer to NYC DOB-style safety planning.

Full Detailed Table  -  Chapter 33

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Expert Commentary  -  Chapter 33

This will affect:

• Large contractors
• Developers
• Design-build teams
• Construction managers

It essentially formalizes what responsible builders already do, but enforcement will be tighter.

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What are the key changes in Chapter 35  Referenced Standards

Summary

CBC 2025 updates numerous referenced standards across structural, mechanical, geotechnical, and fire safety domains.

Updating referenced standards ensures the CBC stays aligned with:

• ASCE 7-22
• ACI 318-19
• AISC 370 / 360
• AISI S100 / S220 / S400
• AWS D1.1 / D1.6
• Many others

These referenced standards contain hundreds of pages of technical content  -  but the CBC now formally recognizes the newest versions.

What are the key changes in Appendix I  -  Patio Covers

Appendix I is unchanged in the 2025 CBC.

Appendix I remains stable because patio cover standards are mature and typically controlled by prescriptive structural requirements and local zoning overlays rather than major code cycles.

What are the key changes in Appendix J  -  Grading

Appendix J is unchanged in CBC 2025.

This appendix already works harmoniously with Chapter 33, local grading ordinances, and CEQA requirements  -  so changes tend to occur only when geotechnical engineering standards change significantly.

What are the key changes in Appendix K  -  Flood-Resistant Construction (Central Valley Flood Protection For R3 & R3.1)

Appendix K is unchanged.

Appendix K is tied directly to Central Valley flood regulations and DWR (Department of Water Resources) mandates  -  which did not introduce changes requiring CBC updates this cycle.

What are the key changes in Appendix Q  -  Emergency Housing

Appendix Q has no changes in the 2025 CBC.

Emergency housing continues to follow state policy direction, which remained stable during this building code cycle.

What are the key changes in Appendix P  -  Sleeping Lofts

Appendix P brings a complete and entirely new regulatory framework for sleeping lofts - a rapidly growing design feature in compact residential units, ADUs, and micro-apartments.

High-Impact Summary

Appendix P defines minimum safety, dimensional, access, egress, guard, and fire protection requirements for sleeping lofts in Group R occupancies.

This appendix matters because:

• Sleeping lofts were previously governed only by “equivalency” interpretations.
• Many jurisdictions struggled with ADUs, micro-units, and alternative residential designs.
• The lack of clear access/egress rules created inconsistent enforcement.

CBC 2025 now brings full clarity.

Full Detailed Table of All Changes  -  Appendix P

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What are the key changes in Appendix P  -  Expanded Interpretation & Expert Commentary

1. Why Appendix P matters for architects & ADU designers

Small-unit housing is exploding in California  -  ADUs, tiny homes, micro-units, and efficiency studios. Loft sleeping areas are a cornerstone feature in these unit types.

Before Appendix P, designers had to negotiate with plan reviewers case-by-case, often resorting to:

• mezzanine rules
• alternate means & methods
• discretionary judgment
• inconsistent clearances

This appendix eliminates ambiguity.

2. Ceiling height requirement (3 ft over 50% of the area)

This is intentionally low compared to full habitable spaces, but:

• It matches IRC Tiny House provisions
• It maintains safety by requiring enough clearance for sitting, turning, and movement
• It maintains guard, alarm, and egress expectations

3. Access system flexibility is crucial

By allowing:

• Ladders
• Alternating tread devices (ATDs)
• Ships ladders
• Conventional stairs

Appendix P supports creative ADU/micro-unit layouts.

4. Emergency egress rules are strict  -  and necessary

Lofts cannot be blind, enclosed platforms.
CBC requires:

• Direct access to a room with an EERO, OR
• Their own dedicated opening

This balances flexibility with fire safety.

5. Loft area limits (70 sq ft max)

This cap ensures lofts remain secondary spaces and are not used to circumvent full habitable room requirements.

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References

1. ‍2022 California Building Code, Title 24, Part 2 (Volumes 1 & 2) with July 2024 Supplement updated

2. 2025 California Building Code Volumes 1 and 2, Title 24, Part 2

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