For many California homeowners, an accessory dwelling unit feels like a straightforward project. You already own the land, you have a clear use case, and you have seen ADUs built in your neighborhood. Then you step into permitting and realize it is a process with real structure. Permitting is not meant to block ADUs, but it is designed to confirm that the new home is safe, code compliant, and compatible with the site. Understanding the steps before you start helps you avoid delays and keeps your expectations aligned with how cities actually review projects.

California’s statewide ADU laws have improved access, but they did not create one single permitting pathway. Each city and county still administers its own workflow, checklists, and review culture. That is why permitting looks different in San Jose than it does in Santa Cruz, San Francisco, Sacramento, Santa Rosa County areas, San Luis Obispo County, Santa Barbara, Los Angeles County, Orange County, and San Diego. The core steps are similar, but timelines, documentation expectations, and required coordination can vary.

This guide explains the permitting process in a practical way, from early feasibility and design to plan check, permits, and final inspection. It also includes a strong San Jose focus, including neighborhood realities and nearby cities such as Campbell, Palo Alto, Redwood City, and other Bay Area communities where homeowners often compare experiences.

Step One: Confirm Feasibility Before You Design

Permitting starts long before you submit plans. The strongest ADU projects begin with feasibility. This means confirming your jurisdiction, your zoning designation, and any overlay conditions that could affect review. A property within a city boundary follows different standards than one in an unincorporated county area. This distinction matters in places like Santa Cruz County, Santa Rosa County areas, and Los Angeles County, where two properties close to each other can have different permitting pathways.

Feasibility also includes understanding your site conditions. Setbacks, easements, slopes, existing structures, and utility locations shape what is possible. Homeowners who choose a floor plan before mapping these constraints often face redesign during plan check. A basic site sketch with property lines, existing buildings, and a proposed ADU placement is one of the best early tools you can use.

San Jose: Why the Site Plan Should Lead

In San Jose, the process tends to be most efficient when the site plan is clear early. Lots in Willow Glen, Cambrian, the Rose Garden area, Evergreen, Berryessa, and Almaden Valley can differ significantly in access, lot geometry, and utility routing. A plan that works in one neighborhood may need adjustments in another. Starting with a site plan helps ensure your design fits the buildable envelope before you invest in detailed architecture.

Step Two: Decide on ADU Type and Project Scope

Permitting requirements vary depending on what you are building. A detached ADU, an attached ADU, and a conversion ADU each come with different structural and documentation considerations. Detached ADUs often require full site planning, new foundation work, and clear utility routing. Attached ADUs may involve additions, structural tie-ins, and careful fire separation. Conversion ADUs can be faster in some cases, but they still require compliance upgrades for light, ventilation, insulation, and egress.

Choosing the right ADU type is part of a smart permitting strategy. When zoning limits buildable area or lot coverage, conversions and compact designs may reduce friction. When privacy is the top priority, a detached plan with defined outdoor space may be worth the additional planning. Aligning ADU type with site reality reduces correction cycles later.

Step Three: Prepare the Core Permit Documents

Most jurisdictions require a complete plan set that shows the project clearly and consistently. While the exact checklist varies, permit submittals usually include a site plan, floor plans, elevations, sections, structural details, and Title 24 energy compliance documentation. Many projects also require grading or drainage information, especially on sloped sites or where stormwater management is sensitive.

For ADUs, the site plan is often the anchor document. It should show property lines, setbacks, easements, existing structures, the proposed ADU location, and key distances. Many plan check delays come from unclear site plans. If reviewers cannot confirm compliance quickly, they will ask for clarification and issue corrections.

Utilities and Service Capacity

Utilities are a common source of permitting complexity. Cities may require information about sewer connection approach, water service sizing, electrical panel capacity, and drainage routing. In older neighborhoods across San Jose, Santa Cruz, San Francisco, and Sacramento, upgrades can be more common. Planning for utility needs early helps keep scope and budget realistic.

In Southern California jurisdictions, including Los Angeles County, Orange County, and San Diego, utility coordination can also be influenced by site access and service provider requirements. This is another reason why early site analysis matters.

Step Four: Submit Plans and Enter Plan Check

Plan check is the formal review process where the city or county evaluates your project for zoning and building code compliance. Some jurisdictions offer digital submittal portals and streamlined ADU pathways. Others have more manual review cycles. Regardless of the platform, the goal is the same. Reviewers confirm that setbacks, height, lot coverage, structural safety, energy compliance, and life safety requirements are met.

Plan check timelines vary widely. Workload, staffing, and submittal quality influence how quickly you move. In high-volume jurisdictions like San Jose and Los Angeles, clear documentation can reduce back-and-forth and help your plans move through the queue more efficiently.

Common Correction Cycle Triggers

Most correction cycles are caused by missing information or inconsistencies. Examples include unclear property lines, missing setback dimensions, conflicting floor area calculations, incomplete structural notes, or unclear utility approaches. Another common trigger is a plan that meets code but does not show how it meets code. Reviewers need the drawing to prove compliance.

It also helps to keep design choices aligned with zoning reality. For example, if privacy is a concern, window placement should reflect that in elevations. If the site is tight, access and staging notes may help reviewers understand feasibility. Good plans anticipate questions.

Step Five: Respond to Comments and Revise Plans

Most projects receive plan check comments, even when well prepared. The goal is to respond efficiently and keep revisions coordinated. When changes are made to one drawing, they must be reflected across the entire set. This is where many delays occur. A change to an elevation may affect height calculations. A change to a layout may affect Title 24 forms. A change to placement may affect setbacks and utility runs.

Homeowners in San Jose and nearby cities like Campbell, Santa Clara, Cupertino, Milpitas, Sunnyvale, Mountain View, Palo Alto, Menlo Park, Los Altos, and Redwood City often notice that different departments have different priorities. Planning, building, and public works may each have their own comments. Coordinating responses across departments keeps the project moving.

Step Six: Permit Issuance and Pre-Construction Planning

Once plans are approved, the jurisdiction issues building permits and you can begin construction planning. Permit issuance often includes fees, school fees in some cases, and documentation such as approved plan stamps. At this stage, homeowners should also plan inspections and construction sequencing. The way the project is built affects inspection efficiency and overall timeline.

Factory-built and modular ADUs can support predictable sequencing because much of the construction is coordinated earlier. This can reduce site disruption and help timelines stay consistent, especially in areas with tight access. While permitting requirements still apply, clear assemblies and defined dimensions often support cleaner documentation and coordination.

Step Seven: Inspections and Final Approval

During construction, inspectors verify that the work matches approved plans and complies with code. Typical inspections may include foundation, framing, plumbing, electrical, insulation, and final inspection. If corrections are required during inspection, they must be resolved before proceeding. This is why choosing experienced professionals and maintaining consistent documentation matters.

Final approval occurs when all required inspections pass and the jurisdiction signs off on the completed unit. At that point, the ADU is ready for occupancy. A well managed process keeps the final approval phase smooth and avoids last minute surprises.

Regional Differences Across California

While the steps above describe a typical permitting path, regional differences are real. Santa Cruz projects may involve additional attention to site conditions, drainage, and coastal considerations depending on location. San Francisco projects often require careful planning for light, privacy, and dense lot conditions, and some scopes can trigger additional review layers.

Sacramento can offer more generous lots in many areas, but older infrastructure can influence utility planning. Santa Rosa County areas and wildfire-prone regions may involve additional considerations related to defensible space and fire-resilient details. Santa Barbara and San Luis Obispo County projects may intersect with design expectations and overlay conditions depending on neighborhood context.

In Los Angeles County, Orange County, and San Diego, high ADU volume makes plan quality important. Each correction cycle can extend timelines, so clarity and completeness at submittal often matter more than homeowners realize.

How to Make Permitting Feel Less Stressful

The easiest way to reduce permitting stress is to treat it like a structured project rather than an uncertain hurdle. Start with feasibility, map setbacks and easements, and confirm jurisdiction before design. Build a plan set that tells a consistent story. Coordinate utilities early. Respond to comments quickly and keep changes consistent across drawings. When the process is organized, it becomes more predictable.

For homeowners in San Jose, a practical approach is to start with the site plan, confirm access and utility routing, and choose an ADU type that fits the lot without forcing awkward compromises. In nearby cities like Campbell, Palo Alto, and Redwood City, privacy and documentation clarity often carry extra weight. In Santa Cruz, site conditions and long-term durability tend to be central. Across all regions, the fundamentals remain the same.

Closing Guidance

Understanding the ADU permitting process in California helps homeowners make better decisions from the first sketch through final inspection. State law has expanded access to ADUs, but local permitting workflows still shape timelines and documentation requirements. When you approach permitting with a clear site plan, coordinated drawings, and realistic utility planning, you reduce delays and protect budget clarity.

Whether your project is in San Jose, Santa Cruz, San Francisco, Sacramento, Santa Rosa County areas, San Luis Obispo County, Santa Barbara, Los Angeles County, Orange County, or San Diego, a permitting-informed design approach supports better outcomes. The result is not only approval, but an ADU that feels like a real home and holds its value for years to come.

What Homeowners Should Expect in San Jose

San Jose homeowners often benefit from clear city resources, but the process still depends on site specifics and plan quality. Neighborhoods like Willow Glen, Cambrian, the Rose Garden area, Evergreen, Berryessa, and Almaden Valley each have different lot patterns and privacy conditions. Access is also a major variable. If a side yard is tight, it can influence construction method, utility routing, and inspection sequencing.

Homeowners also compare experiences across nearby cities. Campbell, Santa Clara, Cupertino, Milpitas, Sunnyvale, Mountain View, Palo Alto, Menlo Park, Los Altos, and Redwood City may have different plan check expectations and different correction cycles. These differences do not mean the project is harder. They simply mean you should rely on the correct jurisdiction’s checklist and confirm assumptions early.

The Role of Pre-Checks and Early Coordination

Some jurisdictions offer pre-check services or early consultation options. Even when formal pre-checks are not available, homeowners can reduce risk by verifying key assumptions before submittal. This includes confirming setback application, identifying easements, and clarifying whether any overlays apply. Early coordination also includes verifying how address assignment works and whether a separate meter is planned or required.

In coastal and hillside regions, early technical input can be valuable. For example, a drainage plan or geotechnical awareness can prevent late surprises. In dense neighborhoods, early privacy planning improves design and can reduce neighbor concerns later.

How Factory-Built and Modular ADUs Fit the Process

Factory-built and modular ADUs can support more predictable documentation and scheduling. Because the unit is coordinated early, the plan set often has clear dimensions and assemblies. This can help confirm zoning compliance and reduce revisions. It can also shorten site disruption, which is valuable in tight neighborhoods or when homeowners are living on-site during construction.

Permitting still requires full compliance with local review standards, but a coordinated approach often reduces uncertainty. In regions like San Jose, Santa Cruz, and Los Angeles County, predictability can be a real advantage for homeowners who want clearer timelines and fewer surprises.

Common Timeline Drivers

Permitting timelines are influenced by factors that homeowners can control and factors they cannot. Workload and staffing are outside your control. Plan clarity, completeness, and early coordination are within your control. The most common timeline drivers include how quickly corrections are addressed, whether utility upgrades are needed, and whether the site has overlays or technical constraints.

Homeowners who plan for these drivers early usually experience smoother progress. Instead of reacting to each comment, the project moves with fewer rounds of revisions and fewer stalled steps.