In short
- 185 ADU permits on record, nearly all since 2021.
- 49 in 2025, up 58% from 2024.
- Typical permit time: 340 days from application to permit (median of 22 permits with both dates recorded).
About this data
- Source: California HCD Housing Element Annual Progress Reports. The state data does not say whether an ADU is detached, attached, a garage conversion or a JADU, so most records show as 'unknown'. Permit valuations are not published in this source. Timelines use the application date the city reported to the state, matched to the permit where possible; some cities report their planning application date, so timelines can include planning review. Each project is counted once, in its building-permit year (or completion year when no permit date was reported).
- National City's state reports include no ADUs for 2018.
- National City reported the building-permit date as the application date for most of its ADUs in 2019, 2020 and 2023, so approval times for those years can't be measured from the state reports and are left out.
Permits by year
Permits by year and type (table)
| Year | All ADU permits | Garage conversions | Detached |
|---|---|---|---|
| 2019 | 5 | — | — |
| 2020 | 2 | — | — |
| 2021 | 10 | — | — |
| 2022 | 28 | — | — |
| 2023 | 60 | — | — |
| 2024 | 31 | — | — |
| 2025 | 49 | — | — |
“—” means the source for that year does not report ADU type.
Read more: ADU types explained
ADU rules in National City
State law check: HCD sent a technical-assistance letter (December 5, 2025) noting the city's ordinance on file, from 2021, may be outdated; no formal findings.
| Rule | National City's code | State law guarantees |
|---|---|---|
| Maximum size | Detached: 1,200 sq ft. Attached: 50% of the house or 1,200 sq ft, whichever is greater. No cap inside an existing building. At least 150 sq ft. Junior ADU 150 to 500 sq ft. | At least 850 sq ft (1,000 sq ft with 2+ bedrooms) must be allowed; an 800 sq ft detached ADU always is. Conversions of existing space have no size cap. Junior ADU: up to 500 sq ft. |
| Height | Single-family lots: the house's height or 16 ft, whichever is greater; 25 ft over a garage or on lots under 5,000 sq ft. Detached ADUs on apartment lots: 16 ft. | Detached: at least 16 ft (18 ft within ½ mile of transit, plus 2 ft for a matching roof). Attached: 25 ft or the zone's limit, whichever is lower. |
| Setbacks | 15 ft front; 4 ft side, street side and rear; none for conversions. | No more than 4 ft side and rear; none for conversions of existing space. |
| Parking | None, and no replacement when a garage becomes an ADU or junior ADU. | At most 1 space; none within ½ mile of transit and in several other cases. No replacement parking when a garage is converted. |
| Owner living on site | None for ADUs. Junior ADU: the owner lives in the house or the junior ADU. | None for ADUs. A junior ADU that shares a bathroom with the house requires the owner to live in one of them. |
| How many on a single-family lot | One ADU and one junior ADU on a single-family lot. Apartment lots: two detached ADUs, plus conversions of up to 25% of the units. | One ADU converted from existing space, one junior ADU and one new detached ADU (up to 800 sq ft). From January 1, 2027: two new detached ADUs (a city then needn't allow a junior ADU on that lot). |
| Short-term rentals | 31 days or more, for the ADU and the house (in a recorded agreement). | No guarantee: cities may require rentals of more than 30 days, and junior ADUs can't be short-term rentals. |
- The code was last amended April 2, 2024 (Ordinance 2024-2529).
- Every ADU needs a recorded agreement with the city (no separate sale, no rentals under 31 days); HCD's 2025 guidance says deed restrictions can't be required on ADUs.
- A 24-inch box tree is required in the front yard or parkway, and ADUs follow the city's single-family infill design standards.
- No impact fees for ADUs under 750 sq ft; the city publishes an ADU handbook.
Where local rules conflict with state law, state law controls. Sources: National City Municipal Code 18.30.380 · National City Municipal Code 18.30.390 · HCD letter (December 5, 2025); HCD's list of review letters; California ADU rules. Verified Oct 5, 2026. Rules change and every lot is different: confirm with the city before you design.
How long permits take
| Type | Median days, application to permit | Middle half | Permits |
|---|---|---|---|
| Unclassified | 340 | 286 – 430 | 22 |
Middle half: the range covering the middle 50% of permits (a quarter were lower, a quarter higher).
Read more: How long ADUs take to build
From permit to completion
Of the 87 ADU permits National City reported issuing from 2020 through 2023, 42 (48%) have a completion reported to the state. For those, the median time from permit to completion was 14 months.
The state reports don't record expired or cancelled permits, and a completion the city hasn't reported looks the same as an unfinished project, so the share is a floor. Years with incomplete reports are left out.
What neighbors declared as cost
Cost data (declared permit valuations) is not published for this area in these sources.
Read more: How to choose an ADU builder
An ADU builder serving National City? Feature your business on this page.
Questions about ADUs in National City
How many ADUs have been permitted in National City?
Public records show 185 ADU permits in National City through 2025, nearly all since 2021. 49 in 2025, up 58% from 2024. These counts come from the city's reports to the state, which place a project in its completion year when no permit date was reported.
How long does an ADU permit take in National City?
Among the 22 ADU permits in National City with both dates recorded, half were issued within 340 days of the application; the middle half took 286 to 430 days. That includes plan-check corrections and resubmittals, not just the review itself.
Can I build an ADU on my property in National City?
California law allows ADUs on most lots with a house, including in National City, but what you can build depends on your lot, local rules and utilities. This site shows permits, not eligibility. See California ADU rules.
Where do I apply for an ADU permit in National City?
Apply with National City's Building Division, by emailing the application packet or dropping it off at City Hall. Official ADU page.
How current is this?
- State annual progress reports: through 2025 (published once a year)
How our data works · Download the data · Free to reuse with credit to SoCal ADU Tracker (socaladutracker.com), under CC BY 4.0.