What architects, developers, and owners need to know as the new 2025 California Building Standards Code takes effect

California’s next major building code cycle is almost here, and with it comes meaningful changes that will affect how structural engineers design buildings across the state. Beginning January 1, 2026, all new permit applications must comply with the 2025 California Building Standards Code (Title 24)—an update that brings new structural design requirements, expanded mass-timber allowances, revised height and area limits, and stricter provisions for adaptive reuse and exterior elevated elements.

For architects, developers, contractors, and owners, understanding these changes early can protect project budgets, avoid design-phase surprises, and ensure smooth permit reviews. Below, we break down the major structural-related updates and what they mean for projects moving forward.

A New Code Cycle Goes Into Effect January 1, 2026

Every three years, California adopts an updated version of its statewide building standards, including the California Building Code (CBC), California Existing Building Code (CEBC), and CALGreen. While these are labeled as “2025,” jurisdictions begin enforcing them January 1, 2026.

For design teams, this means:

• Any project submitted prior to Jan 1, 2026 can remain under the 2022 cycle.
• Any project submitted on or after Jan 1, 2026 must meet the new 2025 standards.
• Schematic and feasibility studies happening now should start referencing 2025 requirements to avoid last-minute redesigns.

At ISE Structural Engineers, we are already transitioning our calculations, templates, and detailing standards to the new code cycle so clients experience a seamless shift.

1. Updated Structural Loads: ASCE 7-22 Becomes the New Basis of Design

One of the most significant changes for structural engineers is the statewide adoption of ASCE 7-22, replacing ASCE 7-16 as the governing standard for seismic, wind, and other environmental loads.

What ASCE 7-22 Means for California Projects

• Revised seismic hazard maps and characteristics
  MCER values and site coefficients shift in several regions, altering base shear and lateral-system demands.
• New wind design maps and procedures
  Changes to wind speed maps and importance factors may increase or decrease wind pressures depending on project location.
• New tornado load provisions
  While limited in geographic impact, certain essential facilities must now consider a new hazard.
• Adjustment to load combinations and live-load reductions
  Several familiar reduction pathways have changed or been removed, requiring updates to standard calculations.

For owners and developers, small shifts in design loads can have outsized effects on steel tonnage, shear-wall requirements, and foundation sizing. Early coordination helps keep budgets grounded in the most current code realities.

2. Revisions to Building Height & Area Limits

The 2025 CBC includes several important updates that affect how large—and how tall—certain building types can be.

Key Height & Area Changes:

• New caps on allowable area increases
  The commonly applied “Sa = 4” multiplier is eliminated. Under the 2025 CBC, Sa is now capped at:
  2 for Groups A, E, H, I, L, and R
  3 for most remaining occupancy types
  
  This can significantly reduce feasible floor plates on larger mixed-use, residential, and assembly projects.
  
  
• Group I-2 restrictions grow more stringent
  Type IIIB and VB construction are no longer permitted for any height for I-2 occupancies, reducing options for hospitals and care facilities relying on light-framed systems.
  
  
• Updated rules for occupiable roofs
  Clarifications and new exceptions affect how rooftop amenities are classified, which in turn impacts structural loads, fire ratings, and access requirements.
  

How this impacts design teams

Developers may find that building configurations that worked under the 2022 cycle may no longer pencil the same way. At ISE, we often start with an early code-feasibility study to validate massing concepts before projects advance into design development.

3. Expanded Mass Timber Flexibility

Mass timber continues to evolve—and the 2025 CBC introduces new opportunities for exposed wood and taller hybrid systems.

Notable Updates

• Type IV-B mass timber buildings now allow far more exposed wood
  The previous 20% limit on exposed mass timber ceilings in units and fire areas increases to 100% under certain conditions.
• Greater allowances for unprotected undersides of floors
  This gives architects more freedom for expressive timber structures without compromising compliance.
• Clarified rules in Type IV-HT
  Only combustible surfaces require fire protection, reducing unnecessary treatments to non-combustible components.

For project teams

The shift supports the growing demand for low-carbon construction and warm, natural aesthetics—while still requiring rigor in fire-resistance detailing, connection protection, and interface design. ISE’s mass-timber team is already implementing updated detailing strategies for 2026 projects.

4. Major Updates for Existing Buildings & Adaptive Reuse

California’s 2025 Existing Building Code brings clearer guidance—and more flexibility—for renovations, retrofits, and change-of-use projects.

Why this matters now more than ever

With the rise of adaptive reuse in urban areas, owners need predictable pathways for turning:

• offices into housing,
• retail into mixed-use, or
• older stock into safe, modern buildings.

The revised CEBC strengthens the Prescriptive, Work Area, and Performance compliance paths, providing:

• More clearly defined structural triggers
• Better guidance for partial retrofits
• Improved alignment with the International Existing Building Code

For owners, this means adaptive reuse often becomes more achievable and cost-effective, but also requires experienced engineering judgment to select the correct compliance pathway.

5. Wildland–Urban Interface (WUI) Changes Affect Structural Detailing

In a major reorganization, California has relocated its wildfire-resistant building requirements into a new California Wildland–Urban Interface Code (Part 7).

Implications for structural engineers:

While primarily focused on fire performance, WUI provisions affect:

• balcony and deck materials and connections
• exterior wall assemblies and fastening patterns
• roof systems, overhangs, and soffit design
• ember-resistant detailing that must integrate with structural load paths

Projects within WUI zones should expect more coordination between structural, architectural, and materials teams starting with early schematic design.

6. CALGreen Pushes Toward Low-Carbon Structural Solutions

The 2025 CALGreen code, effective with the 2026 enforcement date, expands requirements for:

• electric-ready infrastructure
• construction waste diversion
• optional embodied-carbon reduction measures
• coordination with PV and EV infrastructure that influences roof loading and conduit routing

Expect a continued rise in structural systems that support lower embodied carbon, such as mass timber, hybrid steel-timber systems, optimized concrete mixes, and efficient framing layouts.

ISE has been integrating carbon-conscious framing strategies into design packages for years; the 2025 cycle makes this even more central to project delivery.

7. Exterior Elevated Elements (EEE) Inspection Requirements Intensify in 2026

Separate from Title 24 but highly relevant to structural engineering is the statewide requirement for periodic inspection of balconies, exterior walkways, and other elevated elements under SB 721 (apartments) and SB 326 (condominiums).

A recent update—AB 2579—extends certain deadlines to January 1, 2026, meaning many owners will require structural assessments in the coming year.

What this means for the market

• Demand for licensed structural engineers to inspect EEEs is increasing
• Many HOAs and property managers are moving toward multi-year maintenance plans
• Failures in aging wood-framed decks have heightened public scrutiny and liability concerns

ISE regularly performs these inspections, prepares repair documents, and advises owners on long-term durability strategies.

8. More Consistency in Residential Requirements: AB 130 Limits Local Amendments

Starting October 1, 2025, and lasting until June 1, 2031, local jurisdictions will have limited authority to impose more stringent residential building standards.

This creates:

• greater statewide uniformity in seismic and structural requirements
• fewer local “one-off” rules, unless a jurisdiction demonstrates special safety needs

For design teams, this reduces uncertainty when working across different California cities—an improvement in predictability for developers and cost estimators.

What Should Project Teams Do Now?

As California transitions to its 2026 enforcement date, project teams should begin preparing today. ISE recommends:

1. Start code analysis early

Even feasibility studies should reference 2025 code rules to avoid redesigns later.

2. Update standard details and calculation templates

Rain loads, wind pressures, seismic forces, and live-load reductions all shift under ASCE 7-22.

3. Reevaluate large building massing concepts

New area caps and height limits may change project viability.

4. Coordinate exposed timber, fire protection, and WUI requirements early

Many structural decisions tie directly to fire ratings and finish choices.

5. Prepare for increased demand in existing-building and balcony inspections

Owners will need support complying with SB 721, SB 326, and CEBC pathway requirements.

How ISE Can Help

At ISE Structural Engineers, we stay ahead of regulatory changes so our clients don’t have to. Our team is already integrating the 2026 code cycle into our workflows, including:

• Updated seismic and wind analysis based on ASCE 7-22
• Mass timber modeling and fire-resistance detailing aligned with new allowances
• Early feasibility and code-compliance studies for architects and developers
• Adaptive reuse evaluations using the updated CEBC
• Balcony and EEE inspection programs for multi-family owners
• WUI and CALGreen coordination for projects in wildfire-risk zones

If you have a project beginning design in late 2024 or 2025, now is the ideal time to understand how the 2026 rules may affect its structure, cost, and schedule.

Planning a Project Under the 2026 Code Cycle? Let’s Talk.

Whether you’re designing a new development, planning an adaptive reuse, or preparing for balcony inspections, ISE can help you navigate the evolving building code landscape with clarity and confidence.

Contact us today to discuss upcoming projects or request a code-impact assessment tailored to your site and building type.