Vista ADU Regulations & Zoning

Vista allows up to 2 detached ADUs for multifamily lots with an existing multi-family building. (Meaning: In order to build 2 ADUs, the property must already have at least a duplex on it, not just a single family dwelling)

Non‐livable space within existing multi‐family structures may be converted into an ADU. Examples of areas that can be converted include storage rooms and garage spaces. The maximum number of ADU allowed in a multi‐family structure is equal to 25% of the number of existing multi‐family units in the structure. Fractional units are rounded down. A minimum of one conversion ADU is allowed.

ADUs are permitted in zones R-1, R-1-B, E-1, A-1, and O-R, as well as any zone that allows single-family residences by right (Vista Development Code, Section 18.31.020 Zones)

The height of a detached ADU can be up to 16′ and may not exceed 1 story, unless building above a garage.

Also, per recent state law change, detached ADUs within half a mile of major transit stops or high-quality transit corridors can use 4′ side & rear setbacks, up to 18 feet tall. An additional 2 feet can be added if the ADU’s roof pitch matches the primary dwelling. This 18’+2′ limit would allow for a two story unit.

Read more about two story ADUs and height limits.

The square footage of any attached ADU may not to exceed 50% of the primary dwelling square footage, or 1,200 sqft, whichever is less, but not less than 800 square feet.

ADUs are encouraged to incorporate the same architectural features, building materials, and color as the primary residence. These features include, but are not limited to, roofing material, roof design, fascia, exterior building finish, color, exterior doors and windows including, but not limited to, ratios of window dimensions and window area to wall area, garage door, and architectural enhancements.

A minimum separation of five feet, measured from eave to eave, shall be maintained between a detached accessory dwelling unit and all other buildings and structures.

Vista typically requires a soils report for all new construction, including ADUs. However, per the city in June 2025, for simple flat lots a soils waiver can be used in order to bypass the requirement.  A soils waiver typically costs $1-2K. Additionally, if the ADU is on a flat pad, a letter from a civil engineer or soil’s engineer is required certifying after inspecting the excavation for the footing that the soils supporting the footing is suitable for the proposed design. If the ADU is built on a hilly area, or if a grading permit is required, a soils report will be required.

Yes, Vista requires site drainage and storm water mitigation for ADUs. Finish grading work to create a bio-swale, drainage basin or other contouring work to handle on-site storm water will cost around $5-10K in most cases. Read more about stormwater mitigation for ADUs.

No areas are subject to Coastal requirements.

SP-TS stands for “Townsite Specific Plan.” A Specific Plan (SP) is like a specialized and local zoning for an area that is likely different than the rest of the City. Within your SP, which has to be approved by Council, whatever the specific plan calls out is allowed, which may vary compared to other properties that are similar located out of the SP.

For example, a property located in SP-TS falls under section “C”. The underlying zoning for a property, located in Section C, is SF-7. This would indicate “Single Family – 7”, which allows for 7 Dwelling Units/Acre. If a property is, say, 6,000 SF or .14 acres (approximately 1/7th of an acre), this would allow for only 1 dwelling unit (e.g. a primary house). Nevertheless, California State ADU laws trump SPs, so you are still permitted to build an ADU and JADU.

No, you cannot stack ADUs on top of each other in Vista. As of October 2025 via email, “Our City Attorney office has determined that stacked ADUs or two-story ADUs are not allowed.” (Junior Planner, Community Development Department, City of Vista)

Yes, you can attach two ADUs to each other in Vista. Per the planning department of Vista in October 2025, “The one-story ADUs can be attached to each other.”

Yes, existing non-livable space may be converted to ADUs (e.g. storage areas and garages). The minimum number of ADU conversions allowed is one, up to a maximum equal to 25% of the number of existing multifamily units. This is in addition to the allowed number of detached ADUs.

If a parking space is required, it may be located within the setbacks and in an existing driveway as tandem parking. Parking spaces don’t need to be replaced when a garage, carport, or covered parking structure is demolished in conjunction with the construction of an ADU or converted to an ADU.