Accessory Dwelling Unit (ADU) Frequently Asked Questions

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Am I  Allowed to Build An ADU on My Lot? 

Your property must be located in the following zones in order to allow for an ADU (the ADU can be attached, detached, or repurposed) to be built on the lot: R-1-B, R-1, E-1, A-1 and O-R zones. An ADU is also permitted if located within a repurposed existing space on any lot in a zone that allows single-family residences by right.  But please note that ADUs are not allowed in the Specific Plan No. 24, Shadowridge Specific Plan, and Vista Business Park Specific Plan, even if you repurpose existing space in a zone that allows single-family residences within these specific plan areas. Check with the Planning Division regarding the zoning for your lot first, before considering an ADU on your property.

How Large Can the ADU Be? 

  • Attached ADU
    Maximum size of 50% of the primary residence or 1,200 square feet, whichever is less.
  • Detached ADU
    Maximum size of 1,200 square feet, which does not include square footage for a garage or non-habitable accessory structure proposed in conjunction with the ADU.

Do I Need Any Extra Parking For the ADU? What If I Convert  My Existing Garage into An ADU? 

You don’t need to provide one (1) parking space for the ADU if:

  • The ADU is located within one-half mile of public transit.
  • The ADU is located within one block of a car share vehicle.
  • The ADU is located within an architecturally and historically significant historic district.
  • The ADU is part of the proposed or existing primary residence or part of an accessory structure. So if the ADU is created through a garage conversion, the ADU will not require a new parking space; however, you will need to replace the off-street parking spaces required for the single-family primary residence, that is two (2) required parking spaces plus two (2) guest parking spaces) on the same lot as the ADU, in any configuration (these can be covered, uncovered, or tandem spaces). 

Am I Required To Provide Fire Sprinklers For the ADU?

Please check with the Vista Fire Department if fire sprinklers will apply or not based on the Fire Code. 

What Development Impact Fees Apply For an ADU?
Do I Need a Grading Permit? 

Fire, Parks, Traffic, School and Public Facilities are all required Development Impact Fees (DIF). Approximately a total of $14,700 in DIF per ADU subject to annual adjustments of the City’s Fee Schedule adopted by the City Council. Keep in mind that a grading permit may be required, so please check with Land Development Engineering staff for more information on that.

Am I Eligible For a Waiver of Development Impact Fees?

  • Your are eligible if your ADU qualifies as an affordable unit per the U.S. Department of Housing and Urban Development (HUD), meaning that it must be occupied by a household whose income is at or below 80% of the area median income for San Diego, adjusted for family size. Please contact the City Housing Division for information on whether your ADU may qualify as an affordable unit. Specific restrictions will apply.
  • You are eligible if the ADU is occupied by a family member or caregiver providing regular care to an owner of the primary residence in need of that care. Please contact the City Housing Division for more information on whether your ADU can qualify under this caregiver category.  Specific restrictions will apply.
  • Keep in mind that plan check and inspections fees would still apply in the development of any ADU, regardless of whether or not the DIF were waived. It is important to note the DIF waiver will discontinue after five years from August 13, 2019 or after the first 100 ADU's that qualify for the waiver are permitted by the City, which ever comes first.


Community Development
Planning Division
P: 760.639.6100