National City's Building Division issues the permit for any ADU, remodel, addition or new house in the city, and an ADU application can go in by email. Its ADU rules date from November 2021 and still cite the old state sections, but they say state law prevails where the two conflict, and on October 19, 2026 the Planning Commission started a full rewrite, expected in early 2027. Until then the statute governs: up to eight detached units on a lot with apartments, 18 feet near transit, and a junior ADU owner on site only with a shared bathroom. The City is more generous than the state on attached units and height over a garage, the 2025 fire map puts no part of the city in a hazard zone, and ADU permits made up most of its new housing in 2025.
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BHI Builders takes on ADUs, remodels, additions and custom homes in National City, where ADUs made up most of the new homes the City permitted in 2025 and a rewrite of the ADU code began in October 2026. Every rule here comes from National City's code, staff reports and handbook, and the state statutes above them.
Who issues permits here, and how does plan check run?
National City's Building Division issues building permits. Its ADU page asks for the application from the Building forms page with a card authorization, sent by email or left at the counter Monday to Thursday; the handbook says the Engineering Division sees the plans first and may require its own permit for grading, drainage, the right of way or a new sewer connection, before Planning, Engineering and Fire review them. Plan check fees are a share of the building permit fee and are paid at submittal, and an application left idle for six months lapses unless extended.
The code decides an ADU ministerially within 60 days of a complete application; the statute adds a completeness answer within 15 business days and deems the application approved if the City does not act. The handbook expects review to take several weeks, the City posts no ADU plan check time, and inspections are booked online a day ahead, Monday to Thursday only.
For the projects homeowners bring most often:
- An ADU or junior ADU: the building permit by email or at the counter, Sweetwater Authority's own application for water, the fire department's 150-foot hose measurement from the curb, and impact fees only on a unit above 750 square feet.
- Kitchen or bath work that shifts pipes, wires or walls: a building permit, its plan check a share of the permit fee, with the same email submittal and inspections.
- An addition or a second story: the zone's height and the City's infill design rules, the specific plan's rules where one applies, and Sweetwater Union High's fee on new floor area.
- A new house: full plans, Engineering's permit, the flood overlay's elevation certificate near the channels, the coastal program on the west side, and the City's impact fees by the square foot.
Where do National City's ADU rules differ from state law?
National City's ADU and junior ADU rules are Municipal Code 18.30.380 and 18.30.390, first adopted by Ordinance 2021-2490 on November 2, 2021, after a 3 to 2 vote that removed parking and restored the 1,200 square foot size, and carried into the rewritten Land Use Code by Ordinance 2024-2529 on April 2, 2024 without change in substance. Both sections still cite the state's old ADU sections, and both say that where they conflict with state law, state law prevails.
The City knows the text is behind. On October 19, 2026 the Planning Commission voted unanimously to start a full rewrite; the staff report calls the sections obsolete, says staff already follow the newer laws, and expects a draft in early 2027 that also takes in two state laws signed on September 29, 2026 and due to take effect January 1, 2027: AB 956, two detached new units on a single-family lot, and SB 1117, impact fees on a larger ADU counted only on the area above 750 square feet. The table states today's law.
| Rule | In the City of National City |
|---|---|
| Where | The single-family, multifamily, mixed-use and specific plan zones listed in the use table; inside a specific plan, the plan's own rules take precedence. |
| Units on a single-family lot | One ADU and one junior ADU under the code; state law's combination of a converted unit, a new detached unit and a junior ADU governs, and from January 1, 2027 AB 956 allows two new detached units. |
| Apartment lots | Converted space for one unit up to a quarter of the homes; detached units, two under the code and up to eight under state law on a lot with existing apartments, never more than its homes; the state's count governs. |
| Size | At least 150 square feet; a detached unit up to 1,200; an attached unit up to half the house or 1,200, whichever is greater, which is more than the state requires; no limit inside an existing footprint; an 850 or 1,000 square foot unit allowed in any case. The handbook's FAQ says "whichever is less"; the code governs. |
| Height | The house's height or 16 feet, whichever is greater, and 25 feet over a garage or on a lot under 5,000 square feet; 16 feet for a detached unit on an apartment lot. State law goes further: 18 feet near major transit, plus 2 if the roof pitch matches the house, the same 18 beside a multistory apartment building, and 25 feet attached; it governs. |
| Setbacks and design | A 15-foot front setback, 4 feet at the sides and rear, none for a conversion, one 24-inch box tree and the infill design standards. On the units state law makes every city approve, none of those extras may apply, and a front setback may never block an 800 square foot unit. |
| Parking | None, and garage spaces converted to an ADU are not replaced. |
| Sprinklers | Only if the house is required to have them. |
| Junior ADU | 150 to 500 square feet within a house, plus 150 for its entrance, with an efficiency kitchen; the code and its covenant want the owner on site in every case, but since January 1, 2026 state law asks it only with a shared bathroom, and governs. |
| Covenant | The code records an agreement on every ADU before the permit, against separate sale and rentals under 31 days; state law provides a recorded restriction only for junior ADUs, so raise it at intake. |
| Rentals | No rental of the ADU, or of the house on an ADU lot, for less than 31 days; an ADU or junior ADU applied for since January 1, 2020 can never be licensed as a short-term rental. |
| Selling a unit on its own | Not allowed under the code, apart from the qualified nonprofit sale state law keeps open; National City has adopted no condominium option. |
| Fees | The code exempts an ADU "with less than" 750 square feet; state law exempts 750 or less and governs. Above that, the City's 2026 impact fee report already charges only the area over 750, the method SB 1117 makes law in 2027. |
Where the City's other documents read differently, and what governs:
- The handbook of March 2024 gives both 30 and 31 days for rentals and both "greater" and "less" for the attached size; it says the code prevails, and the code says 31 days and the greater.
- The handbook asks for the 2022 code cycle on cover sheets; the City adopted the 2025 codes in November 2025, so ask Building which applies at submittal.
- The building information guide of 2023 asks for four paper sets; the ADU page's email submittal is the later instruction.
Can you build from a pre-approved ADU plan here?
No. The City's ADU page, handbook and building pages offer no pre-approved plan set, and no page invites outside designers to submit plans for pre-approval, which state law has asked of every city since January 2025. The handbook points to a free online tool for property information and sketches instead. A plan drawn for the lot goes through the regular review.
The coastal zone, flood overlays and the specific plans
CAL FIRE's 2025 table of jurisdictions records no fire hazard severity zone of any class in National City, and its 2025 map shows only non-wildland inside the city, so no hazard zone construction rules apply. The fire department's one ADU check is reach: a hose laid from the curb must get to the farthest point of the unit within 150 feet.
On the west side, land marked as coastal zone must also meet the City's Local Coastal Program, whose implementation plan still points to the Land Use Code before 2024; staff told the Commission in 2026 that the older code's uses and standards apply there and that the City is now rewriting the implementation plan. Which ADU text applies in the coastal zone is a question to settle at intake; where a coastal permit is needed, state law gives the City 60 days and no hearing. In the flood overlays a floodplain permit comes before the building permit, and a new home's lowest floor sits at least a foot above the base flood elevation. Inside the Westside and Downtown specific plans, the plan's own zoning governs.
Under Civil Code 4751, an HOA's rules cannot prohibit an ADU or junior ADU or limit it unreasonably.
What does National City charge for an ADU?
The City adopted a new citywide impact fee schedule on January 20, 2026, in force from April 20, charged by the square foot for administration, police, fire, library, parks and multi-modal transportation and replacing fees set in 2005; on an ADU only the area over 750 square feet is charged. City staff and SANDAG treat ADUs as exempt from the regional transportation fee, though the City's code names only guest dwellings. Building fees follow the fiscal 2027 user fee schedule.
- Sewer. The City's sewer capacity fee per equivalent dwelling unit stays at its old level after a proposed increase was continued in April 2025, and the City's consultant notes that capacity fees are not charged on ADUs under state law; monthly service bills an ADU at the multifamily rate beside the house's single-family rate.
- Water. Sweetwater Authority needs its own application for an added ADU, about six weeks to review and eight to build a service, and charges a capacity fee in proportion to the unit's plumbing fixtures unless an exemption applies; state law governs any charge.
- School fees. Sweetwater Union High charges a rate per square foot on additions and conversions, raised in June 2026; National School District's rate was not found. A unit under 500 square feet adds no assessable space.
How many ADUs National City permits
National City went from no ADU permits in 2018 to 49 in 2023, and 49 again in 2025.
- 02018
- 52019
- 22020
- 92021
- 282022
- 492023
- 322024
- 492025
National City's ADU building permits as reported to HCD each year (Table A2, ADU category), units permitted rather than finished, junior ADUs inside the count. The City's 2025 report agrees: 49 ADUs permitted, 49 of the 51 housing units it permitted that year, and 39 finished. A May 2025 Council report counted 10, 23 and 22 ADUs finished in 2022 to 2024 against 108 permits issued.
Recent changes in National City
What has changed in the City's permit rules since 2024, newest first.
National City already charges impact fees only on an ADU's area above 750 square feet, so SB 1117 makes its practice state law; AB 956's two new detached units apply from this date too, ahead of the City's rewrite, due in draft early that year. The guide to both laws.
The Planning Commission voted unanimously to start rewriting the ADU and junior ADU sections, with a draft expected in early 2027.
AB 956 and SB 1117 were signed into law, two detached new ADUs on a single-family lot and impact fees only above 750 square feet, both taking effect January 1, 2027.
The regional transportation fee rose for new homes; City staff treat ADUs as exempt.
The City's new impact fee schedule took effect, adopted January 20, 2026, charging ADUs only on the area above 750 square feet.
The City's 2025 progress report counted 49 ADU permits among 51 housing permits.
The City adopted the 2025 California building codes.
The short-term rental ordinance was adopted, barring ADUs and junior ADUs applied for since 2020 from short-term licenses.
The sewer service charges through fiscal 2030 were adopted, billing an ADU at the multifamily rate.
Ordinance 2024-2529 rewrote the Land Use Code and carried the ADU sections over.
How BHI approaches a National City project
What we look at first on a National City lot.
In National City we begin with which rules apply to the lot: state law where the 2021 code lags, a specific plan's zoning where one covers it, and the coastal program on the west side. The fire department's 150-foot hose reach from the curb matters on a deep lot. Book a call to work through yours.
What an ADU might rent for in National City
Rents for ADUs alone are not published anywhere, so the table shows HUD's FY2027 Small Area Fair Market Rent for National City's ZIP code, the number the ROI calculator opens with: per bedroom count, the rent four in ten recent movers paid less than, utilities in.
| ZIP | Studio | 1 bed | 2 bed | 3 bed |
|---|---|---|---|---|
| 91950 | $1,720 | $1,840 | $2,220 | $2,940 |
HUD's FY2027 rents for ZIP 91950 by bedroom count, the ROI calculator's starting figures. Run your own lot through the ROI calculator over 30 years.
Next steps
Read your lot against the code, the state law ahead of it and the coastal line, price the unit, then go on to the pages that fit.