Taking your design through the permitting process may seem overwhelming, but with thorough preparation and an understanding of what to expect, it can be straight-forward. Permitting starts with an application package and ends with a building permit, which signals your ability to start construction.
Timeline
Most ADU projects take 12-18 months to complete, but some extend to 24 months or more. The permitting phase typically lasts 1-6 months.
Key Resources for Permitting
RELEVANT WEBINARS
We also offer webinars about permitting in specific locations – check out all our webinars here.
FAQs
Here are a few of the most frequently asked questions about permitting.
-
If you are on a septic system, it is important to ensure with your local agency that you have septic capacity to add an ADU or Junior ADU with your desired number of bedrooms before you move forward on plans for your project. Upgrading a septic system can be costly or challenging, and it is good to assess realistic needs upfront. Learn a ton more about septic systems from our detailed blog post on the topic right here. You can do so by reaching out to your local agency:
For Sonoma County please contact Permit Sonoma Well & Septic at PermitSonoma-Well-Septic@sonoma-county.org or at (707) 565-2849.
For Napa County please contact the Napa County Environmental Health Division at Environmental@countyofnapa.org or at (707) 253-4417.
If you don't currently have septic capacity for your ADU project and do not want to upgrade the system, ask your local planning department about the possibility of a "bedroom swap," which allows you to make construction changes to an existing bedroom in the primary residence to convert it to non-bedroom space (e.g., an office) and then use the newly freed up septic capacity for your ADU. Again, whether or not this is a possibility for you depends on your local jurisdiction.
If your property gets water from a well, you may be required to show that you have enough water flow and pressure to support an ADU as well as the main house. This testing typically occurs only during the dry season (July-October). The agencies listed above can help explain the testing requirements needed to prove you have enough water.
-
Title 24 regulates minimum energy efficiency for new construction in California. For example, these standards dictate how much insulation is required and the types of light fixtures that can be used. All new ADUs will need to demonstrate compliance with Title 24, which usually requires hiring a consultant and typically costs less than $500. Typically, your designer or architect will manage the relationship with the Title 24 Consultant.
For a detailed blog post on Title 24 read here. In some cases, like newly constructed detached ADUs, you might need to add solar panels to meet the rules. For a list of Title 24 consultants, check out our Vendor Registry.
-
Newly constructed ADUs are subject to the Energy Code requirement to provide solar panels if the unit(s) is a newly constructed, non-manufactured, *detached ADU.* Per the California Energy Commission (CEC), the panels can be installed on the ADU or on the primary dwelling unit. ADUs that are constructed within existing space, or as an addition to existing homes, including detached additions where an existing detached building is converted from non-residential to residential space, are not subject to the Energy Code requirement to provide solar panels.
Please refer to the CEC on this matter. For more information, see the CEC’s website www.energy.ca.gov.
You may email your questions to: title24@energy.ca.gov, or contact the Energy Standards Hotline at 800-772-3300. CEC memos can also be found on HCD’s website.
For important information for homeowners thinking of going solar, reference the California Public Utilities Commission (CPUC)'s California Solar Consumer Protection Guide.
If you're curious about solar rebates, as of May 2023 our research indicates that PG&E currently offers no rebates or incentives for residential solar installation. MCE Clean Energy (which operates in Napa County but not Sonoma County) offers a solar storage credit program which offers a monthly credit of up to $20 for systems that have a battery system installed and programmed according to their guidelines.
There is a 30% solar investment tax credit – also known as the ITC or Residential Clean Energy Credit.
This federal tax credit is worth 30% of the cost of installing solar and battery storage systems. The ITC will remain at 30% until 2032 and beginning on January 1, 2023 applies to battery storage that isn’t hooked up to solar.
-
In most cases, state law no longer allows cities and counties to comment on pre-existing zoning issues unrelated to the ADU. For example, you should not receive comments about correcting the main house or a fence unrelated to the ADU, unless there is an obvious public safety issue.
-
Because the SB-9 law is relatively new, cities are still in progress on determining exactly how they will apply it. To that end, below is some background information on SB-9 to review, and from here we advise you to speak directly with the city to get more information specific to your property and how the city is applying SB-9 as of now. Some information can be found at this Maxable blog post. You can also look at the California Department of Housing and Community Development SB-9 Fact Sheet. Finally, the Casita Coalition webinar on SB-9 is available to watch.
-
Each local jurisdiction has a different Code Enforcement process and protocol with regard to unpermitted ADUs. Many jurisdictions are focused on a collaborative approach to help homeowners bring their ADU up to code. A new state law as of January 2020 indicated that local jurisdictions should provide homeowners up to 5 years to bring a unit up to code *if the local jurisdiction does not determine that there is a health or safety issue* with the unpermitted unit. As of now, in our experience most jurisdictions determine that there is a health or safety issue, so we have not yet seen this delay in enforcement applied. For more detailed information, we recommend watching this on-demand webinar from the Casita Coalition on unpermitted ADUs.
Steps in the Process
BEFORE YOU BEGIN It’s helpful to meet with local Planning staff before submitting your application. While not required, meeting with staff and your design team before you submit your application might save time later in the process.
If you haven’t yet gotten one of our Feasibility Consults, it’s not too late!
Prepare Your Application Package
Once the initial design and engineering is complete, it is time to apply for a permit. You can learn more about the Permitting process in our ADU Workbook or via our webinar How to Create an ADU Permit Application. Each jurisdiction has its own set of requirements, but in general you'll need:
A site plan showing the property boundaries, along with existing structures and the proposed ADU.
Floor plan of the ADU.
Elevations, or side-on views of the proposed ADU.
Drawings showing the construction details of the proposed ADU.
Any engineering calculations and diagrams. These could include a soils report, civil engineering reports, structural plans, truss calculations or additional reports required by your jurisdiction.
Energy analysis (Title 24) and CalGreen checklist
A completed application and a payment for any relevant fees. If the ADU is under 750 square feet, impact fees will be waived, except school fees unless the ADU is less than 500 square feet.
Most fees, such as plan review and building inspection fees are paid at the time of service, such as when you submit the permit.
School District Fees are calculated based on the district and the size of the ADU.
Napa Valley Unified School District fees are $4.08 per square foot and must be paid before application for a building permit.
NapaSan typically charges approximately $1,000 per 100 sf of new living space as a usage fee.
KEY RESOURCES
Napa & Sonoma ADU Workbook
Your go-to guide to developing an ADU, from first thoughts through move-in.
Submit Your Application
Each jurisdiction handles application submission differently, so double-check all details with your local staff. Some places require applications to be submitted online while others require paper copies of various sizes of paper. In most cases you’ll submit all materials at once, but a few jurisdictions require planning or zoning approval before submitting building permit materials.
If you haven't settled on a General Contractor when the plans are submitted, it is time to begin looking while the jurisdiction is reviewing your plans.
Revise Your Application
Once the application has been submitted, and the fees paid your project will be reviewed by various government departments for comment. Typically, this includes but is not limited to Planning, Building, Engineering, and the Fire Department. They may have comments on the details of your plans and request changes to match current regulations.
The jurisdiction will either approve or deny your building permit within 60 days of submitting for a permit if your submittal package is complete.
Your Build Team (Designer, Engineers, etc.) will respond to those comments either with further explanation or changes to the design and then your plans can be resubmitted.
In most cases, state law no longer allows cities and counties to comment on pre-existing zoning issues unrelated to the ADU. For example, you should not receive comments about correcting the main house or a fence unrelated to the ADU, unless there is an obvious public safety issue.
State law also says that most ADUs must be approved as a "ministerial action." This means there are no hearings, and no public feedback.
Receive Permits
Once your application is approved by all involved parties, all applicable fees are paid (see below) and your Building Permit is issued, you can move onto construction!
Permit & Application Fees
A variety of fees are required for ADUs, such as application fees, impact fees, and others, and the total amount depends on your property. Individual fees typically range from a few hundred dollars to over $30,000. Some fees are based on the details of the project while others are fixed. Surprisingly, your local jurisdiction does not control many of the most expensive fees, like school and water fees, which are assessed by other agencies and dependent on the size or location of your ADU.
KEY RESOURCE: Our ADU Calculator can help you estimate the fees for your project.
Here are some of the more commonly required fees:
Entitlement fees are levied by cities to cover the administrative costs of applications. These typically range from hundreds to thousands of dollars and are not levied in all cities.
Building permit fees cover the costs of inspections before, during, and after construction. These fees can vary and are often a few thousand dollars. Check with your city for the latest information on fees.
Development impact fees help pay for new infrastructure in your neighborhood and the surrounding area, such as new roads or parks. ADUs under 750 square feet are exempt from these fees.
Water and sewer fees support the cost of providing water and sewer service to the community. Recent changes to state law have significantly reduced the water fees for ADUs: existing buildings do not require water fees, while new buildings can only be charged fees in proportion to the size of the unit.
