Permitting for Accessory Dwelling Units: What You Need to Know About This Complex Process


erry Brown, Governor of California, signed two bills to promote ADUs in the state. These came into effect on January 1, 2018.

Since then, there’s been a huge rise in the number of accessory dwelling units in the state.

The housing shortage in many areas of the United States and Canada has inspired many people to choose to live in an accessory house.

Unfortunately, you can’t just build it and move in. There is a complex procedure (and a lot of forms) involved. Read on to get an overview of the permitting process for ADUs.

Contact Local Zoning Commission First

Every state and city has different requirements. To comply with local zoning laws, you need to contact your local zoning commission to be sure you get the right info.

The planning and zoning department of your local municipality will tell you exactly what you can and can’t build on your land.

This is a good resource to learn about the various permits you need, too.

Another good resource is Here you will find a list of state and city regulations. But don’t rely on this information alone. Always confirm with your local zoning commission.

Apply for Approval for an Accessory House

First, you need to get approval that your ADU meets the basic zoning requirements. This permit looks at the size, location, and parking of accessory dwelling units.

These are some of the most common requirements for zoning approval.

Site Plan

A site plan indicates the outline and dimensions of your current property. You will also need to indicate the location and dimensions of the proposed ADU.

What you have to put on your site plan depends on where you live. Check with your city to understand what to include.

Design Elements

You might have to submit your ADU’s exterior features for review. This is called a design review process.

The reviewers could be city staff or a city design review group.

The colors you choose, the ADU’s front door placement and your choice of materials will all be under inspection.

Understand that this is not the same thing as a building permit approval. This sub-committee will just approve the design, not the actual construction.

Nearby Property Owners

You might have to submit the contact information for any homeowners that live within a specified distance of your property. The application package should outline where you can get this information.

This is needed so that the city can notify your neighbors that you intend to build an ADU or (in some cases) to let them know that you have been approved.

Apply for a Building Permit

Next, you need to apply for a separate building permit. This permit is so that you can perform construction.

Sometimes, you must apply for the ADU approval before you can even apply for a building permit.

Depending on where you live, you might have to get other permits for electrical work and so on. Ask your local building officials about electrical permits. Find out where to call for inspections in your area.


To apply for a building permit, you’ll need to present specific documentation to the zoning board.

The requirements may be different in your city but this is a general list of what you might need to provide:

  • Building permit application form
  • Four copies of your site plan
  • Completed Net Stable Funding Ratio (NSFR) Intake Packet if your ADU will be detached from your residence
  • Residential system development charge form
  • A set of site and building construction plans

There is a lot of paperwork and a tremendous amount of work for this step. If you are working with a contractor or an designer, you may want to hand this task to them.

If so, you need to write this into your contract.

Permit Review

Once you’ve submitted everything, your permit will be reviewed. How long it takes for your application to be finished can vary.

Once your municipality approves your design (sometimes on the condition of certain changes) that design becomes your final design.

This design is what your contractors will use during construction. Always run any city-imposed changes by your contractors and lenders to check if those changes affect your project or loan.

You might need to modify your bid because of changes. In that case, you’ll need a change order for your construction contract.

Make sure you know how to stop change order charges to keep your project on budget.

Changes To Final Design of an Accessory House

After the city approves your ADU design, you can still make additional changes. If you don’t have to, that makes it easier for you.

If you have to make changes, you will need to ask your city if you need another city review and another round of approval. Keep in mind that an additional review could lead to project delay.

Run your changes by your contractor and designer first to see if those design changes affect other parts of the project.

You will need to check with your lender to verify if your changes need additional loan approval and additional paperwork.

Again, be sure that your construction contract refers to the revised final design and not an earlier version.

Final Word on Accessory Dwelling Units Permits

The process to get permits for accessory dwelling units can be complicated but Acton ADU can help you with this process. We hope this guide has given you the basic information you need so you know how to get started.

At Acton ADU, we specialize in designing, navigating and building accessory dwelling units in California.

Talk to an ADU specialist today to get your project in motion.

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