Accessory Dwelling Units (ADU) and Junior ADUs (JADU)

What is an accessory dwelling unit?

An Accessory Dwelling Unit (aka, “second unit,” “in-law unit,” or “granny unit”) is an additional dwelling located on the same lot as a single-family or multi-family development, An Accessory Dwelling Unit may be attached to the primary residence, detached from the primary residence, or contained within an existing residence or accessory structure. A Junior Accessory Dwelling Unit (JADU) is a unit that is no more than 500 square feet and contained entirely within the single-family structure

What is the Review Process?

In order to make the review process as efficient as possible, accessory dwelling unit (ADU) and junior accessory dwelling units (JADU) applications will now be submitted to the Building Division as a building permit. Prior to submitting to building, please review the required Application Form and Checklist for ADUs and JADUs with a Planner. The application form and pertinent checklist must be completed and submitted in conjunction with the building permit application. The Planning Division will still do an official required ministerial review during the Building Permit Plan Check timeframe. The Planning review fees are waived for initial review and applied on an hourly (time and material) basis for review of permit revision if necessary. A completed Checklist helps to assure that the project complies with the ADU regulations and minimize the need for plan revisions.

What Regulations Apply to Accessory Dwelling Units?

On January 1, 2020 new state regulations pertaining to Accessory Dwelling Units and junior accessory dwelling units (JADU) (Government Code Section 65852.2, 65852.22 and Health & Safety Code Section 17980.12) became effective. On February 5, 2020, Ordinance 1045 amending Larkspur Municipal Code sections 18.23 Accessory Dwelling Units and 18.24 Junior Accessory Dwelling Units was adopted. The municipal code sections can be reviewed using by clicking ADU or JADU.

Larkspur ADU Restricted Zones

Due to the City’s unique local climatic, geologic and topographic conditions, accessory dwelling units are not permitted in certain hillside residential areas that are determined to have inadequate roadways to provide adequate ingress and egress for emergency access and evacuation in the event of a fire or other emergency. As outlined in LMC 18.23.040, it is the determination of the City, in conjunction with the Central Marin Fire Department, that additional dwelling units in the following mapped areas would present negative impact on traffic flow and public safety: ADU Restricted Zones Map

Larkspur ADU / JADU Checklist

Larkspur Planning Department Staff members have created the Application Form and Checklists for ADUs and JADUs to assist in ensuring a seamless application process. Please review the pertinent Checklist and consult with Planning Staff when you are considering preparing plans for installing and accessory dwelling unit. The application form includes checklists for the four primary types of accessory dwelling units:

• Junior Accessory Dwelling Units – (Checklist A)

• Interior Accessory Dwelling Unit (Checklist B)

• Attached and /Detached Accessory Dwelling Units (Checklist C)

• Multi-Family Accessory Dwelling Units (Checklist D)

Other Resources

Several new tools are now available for homeowners interested in building an accessory dwelling unit (ADU) in Larkspur. ADU Marin is a new partnership between Larkspur and many other local cities and towns, and the County of Marin, to assist property owners that want to generate extra income, create more housing for the local workforce, and/or house family members. The group launched a step-by-step website and workbook along with a webinar series to guide people through the process of building an ADU.

The website covers each step of the process, from thinking about building to permits and construction. It features stories from homeowners who have built an ADU and renters now living and working in Marin, along with more than a dozen floorplans. Plus, there is a calculator to estimate what it might cost and potential rental income. The workbook goes deeper into the process and is full of exercises, checklists, and activities. Whether a homeowner needs to brainstorm ideas, choose a contractor, find a tenant to rent their finished ADU, they will find helpful guidance and resources each step of the way. Creating more housing options, especially affordable units, is a top priority of the cities, towns, and County of Marin. ADUs are an important way to create more housing in Larkspur while maintaining our special community character.