San Diego County (unincorporated) ADU Regulations Accessory Dwelling Unit Regulations

Update: San Diego County recently passed a fee waiver that will save homeowners an average of 14K on permitting fees

San Diego County Passes Granny Flat Fee Waiver

San Diego County just took major steps to promote the building of accessory dwelling units, commonly called granny flats. They passed a fee waiver saving homeowners an average of $14,000 on permit costs.  This waiver will only be in effect till 2023 so act quickly to take advantage of this. 

This fee waiver may mean it’s much more feasible for you to build!

Affordable housing advocates hope this will spur ADU development in San Diego County where rental prices have soared and vacancy rates hover at just 3.3%.

California passed Senate Bill 1069 in January of 2017 stating that any single-family home could build a second rentable unit. In major cities across California, accessory dwelling unit permit applications spiked in a reaction to the passage of the bill.

San Diego County, until recently, was still charging Development Impact Fees of close to $14,000. (San Diego passed a major fee waiver in July of 2018 and has since seen a large uptick in permit applications.)

So if you’ve been on the fence about starting a project, now is a fantastic time!

Lot size

There is no minimum or maximum lot size requirement to build an accessory dwelling unit.

Min/Max Building Sizes

Detached ADU: For a detached ADU, the total floor space area of the ADU should not be more than 1,200 square feet, regardless of the size of the primary residence.

Height Restrictions

ADU’s are limited to 24 feet in height.


Detached ADU’s are required to have one parking space per bedroom or unit. Off street parking is allowed to be tandem or within the residence’s setbacks given that it is safe to access. If the ADU’s construction involves a conversion, replacement off street parking must be provided.

Parking not required if the ADU is:

  • Located within ½ mile of public transit
  • Located within an architecturally and historically significant historic district
  • Part of an existing primary residence or an existing accessory structure
  • In an area where on-street parking permits are required, but not offered to the occupant of the ADU
  • Is located within one block of a car share area, attached ADU’s built within the existing residence do not require additional parking.  This part can get tricky, so we recommend booking a free appointment with a San Diego ADU expert to find out what your lot needs.


A setback is the minimum distance a structure must be away from the street, buildings, or other features.

Two-story ADU’s are required to have a setback of five feet from the side and rear lot lines.

Attached ADU’s must follow the setback regulations of the main residence.


California passed Senate Bill 1069 in an effort to increase the supply of housing to the state. For this reason, any accessory dwelling unit may be used for a long-term rental. No short term rentals (less than 30 days) are allowed.

How to Evaluate ROI

Building an accessory dwelling unit, especially if you intend to keep the property for a few years, represents an enormously beneficial opportunity to maximize your property.

By constructing an accessory dwelling unit you are adding additional square footage to the property. So if you can build a unit for $275 a square foot, but the average value of homes in your neighborhood are worth $400 a square foot you are gaining instant equity through the project. Plus, you also now have the added benefit of a flexible space that can be rented or used for family.

Additional notes

  • Fire sprinklers are not required in ADUs, if they not required in the main residence.
  • The building of a passageway is not required.

Ready to dive in?   Start with a free preliminary phone call.  888-987-6638

Updated 12/20/2018


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