Accessory dwelling units are now allowed across most of California, but homeowners quickly discover that zoning rules are far from uniform. While state law has created strong protections for ADU development, cities and counties still control how those laws are applied locally. These city-by-city differences can dramatically affect what homeowners are able to build, how long approvals take, and how much design flexibility is available.

Many homeowners assume that if ADUs are legal statewide, the rules must be largely the same everywhere. In practice, zoning differences between cities can be significant. Setbacks, height limits, lot coverage, design review requirements, overlay zones, and approval processes all vary. Two properties with similar lot sizes and zoning designations can face very different constraints depending on location.

Understanding these differences early is one of the most important steps in successful ADU planning. City-specific zoning knowledge helps homeowners avoid redesigns, delays, and unexpected costs, while also allowing them to take full advantage of what is permitted in their area.

How State ADU Law Interacts With Local Zoning

California’s ADU laws were designed to address the housing shortage by making it easier for homeowners to add housing on existing residential properties. State law requires most cities and counties to allow at least one ADU on qualifying residential lots. It also limits how restrictive local zoning can be in areas such as setbacks, parking requirements, minimum unit size, and owner occupancy rules.

However, state law does not eliminate local zoning authority entirely. Cities still control many aspects of how ADUs fit into their communities. Local governments can regulate architectural design, maximum size above state minimums, height allowances beyond baseline limits, lot coverage, and how ADUs relate visually and spatially to surrounding homes.

This balance creates a situation where ADUs are broadly allowed, but implemented differently depending on city priorities, geography, and development patterns. Homeowners who understand this relationship between state law and local zoning are far better positioned to plan realistic projects.

Why Zoning Differences Exist Between Cities

Zoning differences reflect the diversity of California itself. Coastal cities face environmental and visual constraints that inland cities do not. Dense urban areas prioritize infill housing, while suburban communities often emphasize neighborhood compatibility. Fire-prone regions must consider access, defensible space, and safety infrastructure.

Local zoning rules are shaped by factors such as lot sizes, street widths, infrastructure capacity, political priorities, and historical development patterns. These influences affect how aggressively a city promotes ADUs and how much discretion is built into the approval process.

Zoning differences are not necessarily intended to block ADUs. In most cases, they are meant to manage how new housing integrates into existing neighborhoods.

ADU Zoning in San Jose and Silicon Valley Cities

Silicon Valley cities are among the most active ADU markets in California. San Jose, Campbell, Palo Alto, Redwood City, Cupertino, Mountain View, Sunnyvale, and surrounding communities generally allow ADUs on most residential properties. However, zoning details vary widely.

San Jose is often considered one of the more permissive jurisdictions. It allows relatively large ADUs, supports detached units, and has clear pathways for both new construction and conversions. Setbacks are often manageable, and parking requirements are minimal in many situations.

Smaller Silicon Valley cities may apply stricter design standards. Height limits can be lower. Roof forms, exterior materials, and window placement may be reviewed closely to ensure compatibility with existing homes. Some cities require additional design review for ADUs located near property lines or within historic districts.

ADU Zoning in Santa Cruz and Coastal Communities

Coastal communities such as Santa Cruz and unincorporated Santa Cruz County present unique zoning challenges. While ADUs are allowed under state law, properties within coastal zones are subject to additional layers of review.

Coastal zoning often focuses on visual impact, height sensitivity, site disturbance, and environmental protection. Even when an ADU complies with basic zoning standards, it may still require coastal development permits or additional review steps.

These requirements do not prohibit ADUs, but they can extend timelines and influence design choices. Height limits may be stricter. Placement may need to preserve views or minimize grading. Exterior materials may be reviewed more carefully.

ADU Zoning in Los Angeles and Southern California

Los Angeles and many Southern California cities have become leaders in ADU production. Zoning in these regions is often structured to encourage ADU development as a response to housing demand.

Los Angeles generally allows both attached and detached ADUs with flexible size allowances and limited parking requirements, especially near transit. Garage conversions are common and often face fewer zoning hurdles than new construction.

Zoning complexity increases in hillside areas, high fire hazard zones, and neighborhoods with special overlays. In these areas, access requirements, slope limitations, and safety considerations can influence ADU placement and design.

ADU Zoning in San Francisco and Dense Urban Areas

San Francisco presents a different zoning environment due to its density and lot constraints. ADUs are often internal or created through garage conversions rather than detached backyard units.

Zoning review in dense urban areas often focuses on height, shadow impacts, privacy between neighboring buildings, and compatibility with existing structures. While ADUs are permitted, approvals may require more detailed documentation.

ADU Zoning in Sacramento and Northern California

Sacramento and surrounding regions often provide more straightforward zoning pathways for ADUs. Larger lot sizes and fewer overlays can make placement and design simpler than in coastal or dense urban areas.

While design review still applies, zoning constraints are often less complex, resulting in faster approvals and fewer revisions.

Building ADUs With Local Zoning Clarity

City-specific zoning knowledge is one of the most valuable tools a homeowner can have when planning an ADU. Understanding how state law and local rules interact allows homeowners to design projects that comply with regulations while maximizing long-term value.

Clear zoning understanding leads to smoother approvals, more efficient design, and better outcomes for both homeowners and communities.