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 are submitted to the Building Division as a building permit. See the Permit Process Page for Small Project and Large Project processing. Prior to submitting, please review the required Application Forms 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?

The City follows State ADU law. See the updated ADU Handbook. Local ADU regulations are found in Chapter 18.23 (ADUs) and Chapter 18.24 (Junior ADUs).

Larkspur ADU Restricted Zones

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. See LMC 18.23.040.

ADU Restricted Zones Map

Other Resources - ADU Marin

See ADU Marin for information on 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 for Larkspur.