The Complete Marin County ADU Requirements Guide
If you’re considering building an accessory dwelling unit (ADU) in Marin County, it helps to know the regulations and requirements. Fortunately, Marin County has made it easy to build ADUs in most residentially-zoned areas.
An ADU is a self-contained housing unit with living, cooking, and sanitation spaces added to a residential property. It can be attached to the main residence or detached, like a backyard home. However you use your ADU, it’s a great way to maximize your lot’s value.
Read on to learn everything you need to know about the regulations for building an ADU in Marin County and how to make the building process even easier with Samara.
Marin County ADU regulations at a glance
Since 2016, the state of California has passed a series of laws that make it easier to build ADUs. Marin County has kept up with these statewide changes, with the only major exception being restrictions in environmentally sensitive areas.
In accordance with state law, your Marin County ADU application should be reviewed within 60 days. The full permitting process usually takes about three to four months.
Size and lot requirements
The minimum size for a Marin County ADU is 220 square feet of floor area. Size and height restrictions depend on the type of ADU being built:
- Detached ADUs can reach 850 square feet for studio and one-bedroom units. Two-bedroom ADUs are normally capped at 1,000 square feet, but can reach 1,200 square feet if compliant with floor area ratio requirements. No matter the number of bedrooms, detached ADUs can’t be taller than 18 feet.
- Attached ADUs are limited to 50 percent of the primary dwelling’s floor area or 1,200 square feet, whichever is smaller. The height limit is 25 feet and set by underlying zoning requirements.
- Junior ADUs (JADUs) are capped at 500 square feet.
Additionally, all Marin County ADUs must have setbacks of at least four feet from the rear and side yard property lines.
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Parking requirements
Studio and one-bedroom ADUs in Marin County require one parking space. No parking is required for JADUs. If you live within a half-mile of a public transit stop or within a historic district, you may not be required to follow the parking requirement.
Zoning eligibility
In Marin County, ADUs are permitted on any lot zoned for residential use (whether single- or multi-family) with an existing primary residence or one under development. Additional restrictions apply in areas with sensitive habitats and high fire severity. ADUs created in the coastal zone require a Coastal Development Permit.
Number of ADUs allowed
Single-family properties in Marin County can have one ADU greater than 800 square feet and one JADU, or two ADUs smaller than 800 square feet.
Lots with existing multi-family properties can have up to eight detached ADUs. However, the overall number of detached ADUs can’t exceed the number of multifamily units. Non-residential spaces, such as storage areas and offices, can be converted into ADUs as long as the total number of conversions is not greater than 25 percent of the existing of units.
Meet the KurodasStreamline your ADU in Marin County
If you’re looking to build an ADU, Samara makes it easy. We handle everything from permits to installation and even offer our own financing. Call us at 650-420-2607 to schedule a 15-minute consultation and discover how simple adding a Backyard ADU can be.
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