Accessory dwelling units are widely promoted as one of the most accessible housing solutions in California, yet many homeowners are surprised by how long permitting can take. In most cases, delays are not caused by one single issue. They result from a series of small misalignments between zoning rules, site conditions, documentation quality, and local review processes.

Understanding what typically slows an ADU permit down allows homeowners to plan more intelligently and avoid unnecessary frustration. While California law has made ADUs easier to approve, local jurisdictions still require clear proof that each project meets zoning and building code requirements. When information is missing, unclear, or inconsistent, permits stall.

This article explains the most common reasons ADU permits are delayed and how homeowners can prevent those delays. The guidance applies across California, including Santa Cruz, San Jose, San Francisco, Sacramento, Santa Rosa County areas, San Luis Obispo County, Santa Barbara, Los Angeles County, Orange County, and San Diego. There is also a strong focus on San Jose and nearby cities such as Campbell, Palo Alto, and Redwood City, where homeowners often compare timelines and expect similar outcomes.

Starting Design Before Confirming Feasibility

One of the most common causes of delay happens before plans are even submitted. Homeowners often fall in love with a layout or floor plan before confirming whether it fits their lot. Setbacks, easements, lot coverage limits, and access conditions can significantly reduce the buildable area.

When a design does not align with the site, the permitting process becomes a cycle of redesign. Each revision adds time. This issue shows up frequently in compact neighborhoods across San Jose, Santa Cruz, and San Francisco, where lot geometry and existing development leave little margin for error.

How to Prevent This Delay

Start with a feasibility review. Confirm zoning, map setbacks, identify easements, and understand utility locations before design begins. A simple site plan that shows what can actually be built saves weeks or months later.

Unclear or Incomplete Site Plans

The site plan is the most important document in an ADU permit set. Many delays happen because the site plan does not clearly demonstrate compliance. Missing dimensions, unclear property lines, or omitted easements force reviewers to issue correction notices.

In high-volume jurisdictions like San Jose and Los Angeles County, reviewers rely heavily on the site plan to quickly verify zoning compliance. If they cannot confirm setbacks, placement, or distances at a glance, the project is likely to be paused.

How to Prevent This Delay

Ensure the site plan clearly shows property lines, setbacks, easements, existing structures, proposed ADU placement, and all relevant dimensions. Label everything clearly and keep it consistent across the plan set.

Easements Discovered Late

Easements are one of the most frequent and disruptive surprises in ADU permitting. Utility easements along side or rear property lines can restrict where foundations can be placed or require additional approvals.

In San Jose, Campbell, Palo Alto, and Redwood City, easements are a common reason projects are sent back for redesign after submittal. Even when building over an easement is allowed, it often requires extra documentation.

How to Prevent This Delay

Review the title report and survey early. Confirm easement locations before finalizing the footprint. If an easement is present, design around it from the beginning.

Inconsistent Drawings and Calculations

Permits are delayed when different sheets in the plan set tell different stories. Floor area calculations that do not match the floor plan, elevations that conflict with height limits, or structural details that do not align with architectural drawings all trigger correction cycles.

This issue is especially common when changes are made late in the process and not coordinated across all documents. Each inconsistency requires clarification and resubmittal.

How to Prevent This Delay

Coordinate revisions carefully. Any change to layout, size, or height should be updated everywhere in the plan set, including Title 24 and structural documents.

Utility Capacity Questions

Utility capacity is a major driver of permit delays. Sewer connection requirements, water meter sizing, electrical panel capacity, and drainage planning often raise questions during plan check.

In older neighborhoods across San Jose, Santa Cruz, San Francisco, and Sacramento, infrastructure may not easily support an additional dwelling unit without upgrades. In Southern California markets like Los Angeles County, Orange County, and San Diego, coordination with service providers can add time.

How to Prevent This Delay

Evaluate utilities early. Identify whether upgrades are likely and include clear notes and diagrams in the permit set that explain the approach.

Overlay Zones and Special Districts

Overlay zones add another layer of review that homeowners sometimes overlook. Coastal zones, hillside overlays, flood zones, historic districts, and specific plan areas can introduce additional requirements.

Santa Cruz and Santa Barbara projects may involve coastal considerations. San Francisco projects may require extra documentation in historic areas. Hillside neighborhoods in San Diego and parts of Los Angeles County can trigger grading and drainage review.

How to Prevent This Delay

Confirm overlays during feasibility. If an overlay applies, plan for the additional documentation and timeline rather than discovering it during plan check.

Plan Check Corrections Handled Slowly

Even well-prepared projects usually receive plan check comments. Delays occur when responses take weeks or when revisions introduce new inconsistencies.

In busy jurisdictions like San Jose, Sacramento, and Los Angeles County, slow response cycles can significantly extend total approval time.

How to Prevent This Delay

Respond promptly and comprehensively to all comments. Address every item clearly and ensure revisions are consistent across the entire plan set.

San Jose Focus: Why Neighborhoods Matter

San Jose is not a single permitting environment. Neighborhoods like Willow Glen, Cambrian, the Rose Garden area, Evergreen, Berryessa, Almaden Valley, and North San Jose all have different lot patterns, access conditions, and utility layouts.

Nearby cities such as Campbell, Santa Clara, Cupertino, Milpitas, Sunnyvale, Mountain View, Palo Alto, Menlo Park, Los Altos, and Redwood City also apply ADU rules differently. Comparing timelines across these cities often leads to unrealistic expectations.

How Factory-Built and Modular ADUs Can Reduce Risk

Factory-built and modular ADUs often reduce permitting delays because designs are coordinated early. Dimensions, assemblies, and systems are clearly defined, which helps reviewers confirm compliance faster.

This approach does not eliminate permitting requirements, but it can reduce revision cycles and support more predictable timelines in high-demand markets.

Planning Ahead Without Losing Momentum

Permitting delays feel worse when homeowners are not prepared for them. When permitting is treated as a planned phase rather than an obstacle, the experience becomes more manageable.

Use the permit review period to finalize selections, plan construction logistics, and prepare for inspections. This keeps the project moving even when approvals are in progress.

Closing Guidance

Most ADU permit delays are preventable. They come from incomplete feasibility work, unclear documentation, unaddressed utilities, or slow response cycles. By starting with a site-informed design, preparing clear plans, and coordinating revisions carefully, homeowners can significantly reduce approval time.

Whether you are building in Santa Cruz, San Jose, San Francisco, Sacramento, Santa Rosa County areas, San Luis Obispo County, Santa Barbara, Los Angeles County, Orange County, or San Diego, the strategy is the same. Plan early, document clearly, and treat permitting as a structured process. The result is a smoother path to approval and an ADU that feels intentional and built to last.

Regional Patterns Across California

Permitting delays often follow regional patterns. San Jose and Los Angeles County experience high application volume. San Francisco deals with tight sites and dense neighborhoods. Santa Cruz and Santa Barbara may involve coastal or hillside constraints. Sacramento and Santa Rosa County areas often face infrastructure-related questions.

Two Timelines Homeowners Should Track

There is the city timeline and the homeowner timeline. Homeowners cannot control review queues, but they can control design clarity, response speed, and coordination. Focusing on the second timeline shortens the overall process.

A Practical Prevention Checklist

Confirm zoning and overlays, map setbacks and easements, evaluate utilities, prepare a clear site plan, coordinate all drawings, and respond quickly to plan check comments. These steps do not guarantee instant approval, but they remove the most common sources of delay.

The Real Goal

The goal is not just speed. It is predictability. When homeowners understand what delays permits and how to prevent them, the process becomes manageable. That clarity leads to better design decisions and stronger long-term value.