How Will 2026 ADU Laws Change Timelines and Requirements?

Major ADU Law Changes Coming in 2026

California's ADU landscape is constantly evolving, and 2026 brings some of the most significant changes since the landmark ADU reforms of 2019-2020. If you are planning to build an Accessory Dwelling Unit in California, understanding these changes is essential for planning your project timeline, budget, and design strategy.

In this comprehensive guide, we will cover every major ADU law change taking effect in 2026, explain how each change affects homeowners in Los Angeles and across California, and provide practical advice on how to take advantage of new opportunities while navigating new requirements. We will also look ahead to additional changes that may come in 2027 and beyond.

Whether you are in the early planning stages or already have plans drawn, this guide will help you understand the regulatory environment and make informed decisions about your ADU project.

Key ADU Law Changes in 2026

1. Streamlined Permit Processing Requirements

One of the most impactful changes for 2026 is the strengthening of permit processing timelines. While the 60-day processing requirement has been in place since 2020, enforcement has been inconsistent, with many cities routinely exceeding this deadline. New legislation adds teeth to the 60-day requirement by establishing penalties for cities that consistently fail to meet the deadline, requiring cities to report permit processing times to HCD quarterly, allowing homeowners to seek damages for unreasonable delays, and mandating that cities deem applications complete within 15 business days of submittal or provide a specific, code-based list of missing items.

This is significant because one of the biggest sources of delay has been the "completeness" determination. Some cities have used the completeness review as a way to slow down the process by repeatedly finding new items that were "missing" from the application. The new requirement forces cities to provide a comprehensive list of missing items upfront, preventing the drip-feed approach that some jurisdictions have used.

Processing Step	Previous Requirement	2026 Requirement
Completeness determination	No specific timeline	15 business days
Plan check review	60 days from complete application	60 days, with penalties for delays
Correction response review	No specific timeline	30 days from resubmittal
Permit issuance after approval	No specific timeline	5 business days

For homeowners, this means that well-prepared ADU applications should receive faster processing. Learn how to prepare plans that pass plan check on the first try to take full advantage of these shortened timelines.

2. Expanded Height Allowances

Building on the height increases introduced by SB 897 in 2023, the 2026 updates further clarify and expand ADU height allowances. Detached ADUs can now be up to 18 feet in all zones (previously limited to properties near transit in some cases). Two-story ADUs are explicitly permitted up to 18 feet without requiring proximity to transit. ADUs on multifamily lots can be up to 18 feet if the existing buildings are taller. Cities cannot impose height limits lower than these state standards.

The expanded height allowances are particularly impactful for homeowners with smaller lots who need to build up rather than out. A two-story ADU on a smaller footprint can provide the same living space as a single-story ADU while leaving more yard space available.

3. New Design Standard Restrictions

California continues to tighten the restrictions on what design standards cities can impose on ADU projects. The 2026 changes further clarify the distinction between "objective" standards (allowed) and "subjective" standards (prohibited). Cities can no longer require specific architectural styles such as "Craftsman" or "Spanish Colonial," minimum lot landscaping percentages that exceed state standards, decorative elements like shutters, trim profiles, or specific window grille patterns, or materials matching requirements that significantly increase construction costs.

Cities can still impose objective dimensional standards (like maximum roof pitch angles), minimum quality material standards (like requiring durable cladding materials), and color palette requirements if based on objective criteria. For more information on how local rules interact with state law, see our detailed guide.

4. Impact Fee Reforms

The 2026 law changes include further restrictions on impact fees for ADUs. The blanket exemption for ADUs under 750 square feet remains in place. For ADUs over 750 square feet, the proportionality calculation has been further refined to ensure fees are truly proportional. New reporting requirements mandate that cities and special districts (including school districts) publicly report all fees charged for ADU projects. Cities that charge excessive or disproportionate fees may face enforcement action from HCD.

These reforms are particularly important for homeowners building larger ADUs (over 750 square feet) who have been subject to significant impact fees in some jurisdictions. Learn more about specific fee impacts in our guide on school impact fees for ADUs.

5. ADU Separate Ownership (AB 1033 Implementation)

One of the most groundbreaking changes taking shape in 2026 is the continued implementation of AB 1033, which allows ADUs to be sold separately from the primary dwelling unit. This effectively creates a new form of homeownership where an ADU can be individually owned, similar to a condominium unit.

Key provisions include cities opting in to allow ADU separate ownership (not all cities have opted in), the ADU must comply with all building codes and be on a lot with proper access, a condominium map (or equivalent) must be recorded, the ADU becomes independently financeable and transferable, and the primary dwelling owner and ADU owner share common elements (like the lot).

AB 1033 Feature	Details	Impact on Homeowners
Separate sale	ADU sold independently	New investment opportunity
Independent financing	ADU gets own mortgage	More buyers can qualify
City opt-in required	Not available everywhere	Check local adoption
Condo map required	Additional process and cost	$5,000 - $20,000 for mapping

6. Updated Building Code Requirements (2025 CBC Cycle)

The 2025 California Building Code (which takes effect in the 2025-2026 code cycle) includes updates that affect ADU construction. Key changes include updated energy efficiency requirements under Title 24 (including electric-ready requirements), revised seismic design provisions, updated fire safety requirements for certain areas, new accessibility provisions, and updated plumbing and mechanical code requirements.

For homeowners, these building code updates primarily affect construction costs and design specifications. Your architect and engineer should be designing to the current code, and your builder should be constructing to the code in effect at the time your permit is issued.

How 2026 Changes Affect Your Project Timeline

The combined effect of 2026 law changes should generally reduce ADU project timelines. Here is how the typical timeline is expected to change:

Project Phase	2025 Average	2026 Expected
Pre-design and research	2-4 weeks	1-3 weeks
Design and plan preparation	6-12 weeks	6-10 weeks
Permit processing	8-20 weeks	6-12 weeks
Construction	4-8 months	4-8 months
Total project	9-18 months	7-14 months

The biggest improvements are in the permitting phase, where stronger processing timelines and clearer rules should reduce delays. Construction timelines are not expected to change significantly, as they are driven by labor availability, material supply, and weather conditions rather than regulations.

How to Prepare for 2026 ADU Law Changes

Whether you are starting a new ADU project or already in the middle of one, here are practical steps to prepare for and benefit from the 2026 law changes:

For Projects Not Yet Started

• Start planning now: Research your property's ADU potential, obtain a survey, and consult with a designer
• Check your city's updated ADU ordinance: Cities are required to update their ordinances to reflect new state law. Check whether your city has adopted the latest changes
• Consider a two-story design: With expanded height allowances, a two-story ADU may give you more design flexibility and living space
• Budget for current costs: While some fees may decrease, construction costs continue to rise. Budget based on current market rates and adjust for any fee savings. See our complete cost guide
• Explore separate ownership: If you plan to sell your ADU independently, check whether your city has opted in to AB 1033 provisions

For Projects Already in Progress

• Review your city's processing timeline: If your permit has been pending beyond the statutory deadline, the new enforcement provisions may help you get a decision faster
• Challenge excessive fees: If you have been charged impact fees that seem disproportionate, the new reporting and enforcement requirements may support a challenge
• Check for design standard changes: If your city required design modifications that you believe are subjective, the clarified 2026 standards may support your case

Looking Ahead: ADU Legislation Beyond 2026

The trend in California ADU legislation is clearly toward further simplification and support for ADU construction. Based on current legislative activity and advocacy efforts, we can expect continued movement toward statewide pre-approved plan libraries, further reduction or elimination of impact fees, expansion of AB 1033 separate ownership to more cities, potential increases in maximum ADU size (currently 1,200 sq ft in most cases), streamlined inspection processes, and additional protections for ADU builders against unreasonable local restrictions.

California's housing crisis continues to drive legislative action, and ADUs remain one of the most politically supported solutions. Homeowners who invest in ADU construction now are well-positioned to benefit from both current and future policy improvements.

Frequently Asked Questions

Do the 2026 law changes apply to ADU projects already in the permitting process?

Generally, new laws apply to projects that have not yet received a permit as of the effective date. If your ADU application is pending when the new laws take effect, you may benefit from the new provisions (such as faster processing requirements). However, if your plans were submitted under the previous code cycle, building code requirements typically apply based on the code in effect when the permit application was submitted. Check with your building department for guidance on how the transition affects your specific project.

Will the 2026 changes make ADUs cheaper to build?

The law changes themselves may reduce some permit fees and impact fees, potentially saving $1,000 to $5,000 depending on your project and jurisdiction. However, construction costs (materials, labor, equipment) are driven by market forces and continue to trend upward. The biggest financial benefit of the 2026 changes is likely the reduction in permitting delays, which saves money through reduced professional fees, avoided cost escalation, and earlier rental income.

Can I take advantage of AB 1033 separate ownership in any California city?

No. AB 1033 requires cities to opt in to the separate ownership program. As of early 2026, a growing number of cities have opted in, but many have not. Check with your city's planning department to determine whether separate ADU ownership is available in your jurisdiction. If your city has not opted in, you can advocate for adoption by contacting your city council members.

Will the new height allowances change neighborhood character?

This is a common concern. The expanded height allowances (up to 18 feet for two-story ADUs) are designed to provide design flexibility while maintaining reasonable scale. An 18-foot-tall ADU is roughly the height of a typical single-story home with a pitched roof. Most two-story ADUs at 18 feet are actually shorter than many existing two-story primary dwellings in California neighborhoods. Cities retain the ability to impose objective design standards to ensure ADUs are compatible with the surrounding area.

How do the 2026 changes affect the over-the-counter approval process?

The 2026 changes encourage more cities to offer expedited or OTC approval processes by strengthening processing timeline requirements. Cities that consistently fail to meet the 60-day processing requirement may find it advantageous to implement OTC programs for qualifying ADU projects as a way to manage their workload and meet statutory deadlines. We expect more cities to offer some form of expedited review in response to the strengthened timeline requirements.

What should I do if my city has not updated its ADU ordinance to reflect the 2026 changes?

State law applies regardless of whether a city has updated its local ordinance. If your city's ordinance conflicts with the 2026 state law provisions, state law controls. You can request that your building department apply the current state law, file a complaint with HCD if they refuse, and advocate for your city to update its ordinance. The California HCD regularly reviews local ADU ordinances for compliance and has the authority to compel updates.

Frequently Asked Questions About 2026 ADU Law Changes

Will the 2026 ADU law changes affect projects already in the permitting process?

Generally, ADU projects that have already received permit approval will be governed by the rules in effect at the time of approval. If your application is still under review when new laws take effect, you may be able to choose whether to proceed under the existing rules or opt into the new provisions if they are more favorable. Contact your local building department for specific guidance on how pending applications will be handled during the transition period. For current approval processes, review our guide on over-the-counter vs. plan check ADU approval.

Are there new size limits or height allowances expected in 2026?

Several proposed bills would increase the maximum allowable height for detached ADUs from the current limits to as much as 25 feet in some zones, particularly near transit corridors. Size limits for ADUs are also being reviewed, with discussions around increasing the maximum from 1,200 square feet to 1,500 square feet in certain situations. These changes aim to provide homeowners with more flexibility in ADU design while addressing California's ongoing housing shortage. Stay informed by checking HCD's website for the latest legislative updates.

How will the 2026 changes impact ADU construction costs and fees?

Several legislative proposals aim to further reduce the fees and costs associated with ADU construction. Expected changes include expanded impact fee exemptions for ADUs up to 850 square feet (up from 750), streamlined utility connection requirements that could reduce hookup costs, and incentives for cities that process ADU permits within 30 days. These fee reductions could save California homeowners several thousand dollars on their ADU projects. For a detailed breakdown of current costs, see our article on school impact fees for ADUs in California.