Everything You Need to Know About Pre-Approved ADU Plans in California

Want to Build an ADU Without the Headaches? Here’s a Smarter Way

Starting an ADU project in California often feels like entering a maze. Between complex building codes, long permit waits, and expensive architectural fees, many homeowners stall before the first shovel hits the ground. The most common frustration? Permits. Homeowners are eager to build, but city requirements and endless revisions slow everything down.

offer a proven solution to this challenge. These plans are already reviewed by local cities for compliance, so homeowners can skip months of design uncertainty and move directly into the permitting phase. Whether the goal is to house family or earn rental income, pre-approved plans provide a faster, more affordable path to an approved ADU.

What Are Pre-Approved ADU Plans?

Pre-approved ADU plans are fully designed units that have already been evaluated and accepted by a local jurisdiction. These designs meet both state and local building requirements—making the permit process smoother and significantly faster.

Unlike custom ADUs, where each design must go through a full review, pre-approved plans have already passed structural and code inspections. This gives homeowners peace of mind and allows them to focus on getting started, not getting stuck in red tape.

Many California cities, including San Jose, Los Angeles, and San Diego, now offer libraries of these pre-approved designs. Options range from compact studios to spacious two-bedroom layouts, with many cities offering free downloads online.

Why Cities Are Pushing Pre-Approved Plans

With California’s housing shortage growing each year, local governments are actively encouraging ADU construction. Pre-approved plans are part of this effort—they help streamline the ADU permit process and reduce city staff workload.

By offering a simplified pathway, cities benefit from:

• Faster housing development

• Reduced plan-check bottlenecks

• More legal and code-compliant ADUs

• Less strain on housing infrastructure

A recent study by the Terner Center at UC Berkeley revealed that permit-ready and pre-approved ADU options significantly increase construction speed while maintaining safety and quality.

Key Benefits of Pre-Approved ADU Plans

1. Faster Permitting

With much of the plan-check process already completed, cities can often issue building permits in a fraction of the usual time. In some areas, permits can be granted in less than 30 days.

2. Lower Design and Engineering Costs

Typical ADU design and engineering fees range between $5,000 and $15,000. Pre-approved plans are either low-cost or completely free, cutting thousands off the project budget.

3. Fewer Delays

Plans are compliant from the start, meaning there’s less chance of redline corrections, back-and-forth with city reviewers, or surprise setbacks during the permitting process.

4. Peace of Mind

These plans are vetted by professionals and approved by the city, giving homeowners a higher level of confidence in code compliance, structural integrity, and design feasibility.

What’s Included in a Pre-Approved Plan?

Pre-approved plan sets are typically comprehensive and ready for direct submission to the city, with elements such as:

• Floor plans and elevations

• Structural calculations

• Title 24 energy reports

• Electrical and plumbing schematics

• Exterior materials list

• Site placement guidance

Some plans even come with modular layout options and suggested finish packages, giving homeowners some flexibility while still maintaining fast approval benefits.

Step-by-Step Guide to Using a Pre-Approved ADU Plan

Step 1: Check If Your City Offers Pre-Approved Plans

Not all cities participate, so start by visiting your local planning or building department’s website. Look for terms like “permit-ready ADU” or “pre-approved ADU program.”

Step 2: Choose a Plan That Matches Your Lot

Consider lot size, orientation, and access to utilities. Some cities provide adaptability guides to help determine which plans suit which lot types.

Step 3: Prepare a Site Plan

Although the ADU layout is pre-approved, the city still needs to see how it fits on the property. A site plan shows placement, distances to property lines, driveways, and existing structures.

Step 4: Submit for ADU Permit

Submit the full packet to your city’s building department. Since the building plans are pre-approved, the city will only review the site-specific elements before issuing the permit.

Step 5: Start Building

Once the permit is issued, the construction phase can begin. Using a contractor familiar with local ADU requirements will ensure the process stays smooth and compliant.

Notable Cities Offering Pre-Approved ADU Programs

Several California cities lead the way in supporting ADU construction with permit-ready designs:

• San Jose – A library of downloadable plans, including single-story and garage-conversion options.

• Los Angeles – The Standard Plan Program features over 20 designs from multiple architecture firms.

• San Diego – Provides flexible pre-approved plan sets tailored to local design preferences.

• Fremont – Offers free access to vetted plans with detailed instructions.

• Oakland – Features studio and one-bedroom layouts that can be modified slightly for site-specific needs.

Each program has unique plan options and submission guidelines, so reviewing city-specific details is essential before moving forward.

Considerations Before Choosing a Pre-Approved Plan

Lot Compatibility

Not all properties will suit pre-approved plans. Narrow lots, sloped terrain, or irregular shapes may require design adjustments or a custom layout.

Customization Limits

These plans are intended to reduce permitting friction, so cities often restrict major changes to maintain approval status. If extensive changes are required, a custom ADU plan may be a better fit.

Utility Access

Make sure the site has proper access to water, sewer, electricity, and gas. Sometimes utility upgrades are required, which can impact timelines and budgets.

Design Preferences

While most plans are modern and efficient, some homeowners may prefer more tailored architectural features, which aren’t typically available in permit-ready designs.

Real Example: Pre-Approved Plan Success

In San Jose, a homeowner selected a 500 sq. ft. pre-approved one-bedroom layout. After submitting a basic site plan and utility diagram, the city issued a permit in just three weeks. The design saved over $7,000 in architectural and engineering fees, and the entire project—from planning to move-in—was completed in under five months.

Final Thoughts: Build Smarter with Pre-Approved Plans

Pre-approved ADU plans offer one of the smartest, most efficient ways to build additional housing in California. For homeowners looking to fast-track their project without compromising on quality or compliance, this approach delivers real value. By removing common roadblocks like permit delays and design fees, these plans provide a clear, city-backed path to success.

If there are any questions about whether pre-approved ADU plans are a good fit for your lot or how to begin the process, please leave a comment below. The team will respond as soon as possible to help guide the next steps.