Vallejo ADU Rules (Solano County): Size, Setbacks, Parking & Permits

ADU Regulations in Vallejo, California

Updated September 29, 2026

Vallejo replaced its entire ADU chapter in 2026. Ordinance No. 1890 N.C.(2d) was adopted on 8 September 2026 and takes effect on 8 October 2026, turning a six-section chapter into a new fifteen-section Chapter 16.303. The figures below are correct under both the outgoing and the incoming chapter, with two exceptions: the minimum unit size rises from 150 to 190 sq ft, and JADU owner occupancy narrows to shared-sanitation cases only.

Below is a summary of the key zoning rules applicable to Accessory Dwelling Units in Vallejo as of 2026. Regulations are governed by California Government Code sections 66310 to 66342 (the ADU statutes, renumbered by SB 477 in 2024) layered on the Vallejo Municipal Code Chapter 16.303, which was rewritten by Ordinance No. 1890 N.C.(2d) and takes effect on 8 October 2026.

Additional Local Requirements for Vallejo

• Up to 3 units on a single-family lot: 1 JADU, plus one attached or conversion ADU, plus one detached ADU
• On a lot with an existing multifamily building: up to 8 detached ADUs, capped at the number of existing units; ADUs created inside existing non-livable space can be at least 1 and up to 25% of the existing units
• Detached ADU height: 16 ft, rising to 18 ft (plus a 2 ft roof-pitch allowance) within 1/2 mile of a major transit stop; attached ADUs may reach 25 ft
• No replacement parking is required when a garage or carport is demolished or converted for an ADU
• Impact fees apply only to new ADUs of 750 sq ft or more, and must be charged proportionally to the main home's fees; conversions and JADUs pay no new utility connection fees
• New detached ADUs need solar panels under the California Energy Code (exempt below 500 sq ft or 1.8 kW)
• Fire sprinklers cannot be required in an ADU unless the main home already requires them
• Rentals must run 30 consecutive days or longer; the ADU cannot be sold separately, and the deed restriction is recorded with the Solano County Assessor/Recorder
• Approval is ministerial — no public hearing — and the city must decide within 60 days of a complete application or the permit is deemed approved
• An ADU built before 1 January 2020 without permits can be legalised, with enforcement on health and safety issues delayed to 1 January 2030

Vallejo's ADU ordinance changed in 2026 — what that means for you

Vallejo repealed and replaced Chapter 16.303 in its entirety. Ordinance No. 1890 N.C.(2d) was introduced on 4 August 2026, adopted on 8 September 2026, and became effective on 8 October 2026 after the standard 30-day period. Until that date the old six-section chapter still governs.

There is a second layer to the story. On 8 October 2025 the state Department of Housing and Community Development wrote to Vallejo noting that the most recent ADU ordinance on file dated from 2018 and may not comply with state ADU law. Under Government Code section 66316, an ADU ordinance that fails to meet state law is null and void — and state standards apply instead. Ordinance 1890 is the city's compliance response.

The practical rule for a homeowner: if a local standard blocks your project, ask whether it is stricter than state law allows. Where the two conflict, state law wins (VMC section 16.303.15).

How many ADUs can I build on a Vallejo lot?

• Single-family lot: three units in total — one JADU, one attached or conversion ADU, and one detached ADU.
• Lot with an existing multifamily building: up to 8 detached ADUs, capped at the number of existing units; conversion ADUs inside existing non-livable space are allowed at a minimum of one and up to 25% of the existing units.
• Lot with a proposed multifamily building: up to 2 detached ADUs.
• ADUs and JADUs do not count toward the site's allowable residential density.

On top of these local limits, California requires every city to approve certain ADU types ministerially, including one ADU plus one JADU on a single-family lot and a detached new-construction ADU of up to 800 sq ft with 4 ft side and rear setbacks. Those by-right units cannot be refused for parking, or because the site has non-conforming conditions.

Vallejo ADU size, height and setback limits

Parking: Vallejo does require a space, with a long list of exceptions

Most summaries of Vallejo's rules state that no parking is required. That is wrong. The city requires one off-street space per ADU, and tandem spaces count. A space cannot be required, however, in any of these cases:

• the ADU is 500 sq ft or less;
• it sits within 1/2 mile walking distance of public transit;
• it is in a historic district;
• it is located entirely within the main dwelling or an accessory structure;
• the street is permit-parking only and the city does not offer a permit to the ADU occupant;
• a car-share vehicle is available within one block.

Two further points save money. No replacement parking is required when you demolish or convert a garage or carport for the ADU, and the by-right units listed in Government Code section 66323 cannot be conditioned on parking at all.

Owner occupancy, renting and selling a Vallejo ADU

• An ADU does not require owner occupancy. State law bars the requirement for ADUs.
• A JADU does under the current chapter; from 8 October 2026 the requirement applies only when the JADU shares sanitation facilities with the main home.
• Rentals must be 30 days or longer. Short-term and vacation rentals of an ADU are not allowed in Vallejo.
• The unit cannot be sold separately from the main house, and the deed restriction that records these limits is filed with the Solano County Assessor/Recorder — that is the county's only role inside the city, since Solano County's own zoning chapter governs unincorporated land only.

Permits, fees and the 60-day rule

• Ministerial approval, no hearing. The city must approve or deny a complete application within 60 days; if it does nothing, the permit is deemed approved.
• The 800 sq ft by-right ADU. Vallejo must allow at least an 800 sq ft ADU with 4 ft side and rear setbacks, and site rules such as lot coverage, floor-area ratio, open space and front setbacks cannot be used to preclude it.
• Impact fees only above 750 sq ft, and only in proportion to what the main home would pay. Conversions and JADUs are not charged new utility connection or capacity fees.
• Design standards apply narrowly: objective design rules for newly built attached or detached ADUs over 800 sq ft must be met; they do not apply to by-right state units.
• Fire sprinklers and passageways cannot be imposed beyond what the main residence already requires.
• Unpermitted ADUs: a unit built before 1 January 2020 can be legalised, and enforcement is delayed to 1 January 2030 where there is no health or safety issue.

Because the ordinance changed in October 2026, confirm the fee schedule and front setback for your specific zoning district with Vallejo Planning before you draw anything. The figures above come from the ordinance text, the city's own ADU summary sheet and California statute — all linked below.

Frequently Asked Questions About ADUs in Vallejo

Are ADUs allowed in Vallejo?

Yes. Vallejo allows ADUs and JADUs on residential lots that have a proposed or existing dwelling, and approval is ministerial with no public hearing. Chapter 16.303 was rewritten by Ordinance No. 1890 N.C.(2d), effective 8 October 2026.

How big can an ADU be in Vallejo?

A detached ADU can be up to 1,200 sq ft. An attached ADU is capped at the lesser of 50% of the main home's floor area or 1,200 sq ft. Garage and interior conversions have no size limit. The minimum unit size becomes 190 sq ft on 8 October 2026, up from 150 sq ft.

What are the setback and parking requirements for an ADU in Vallejo?

New units need 4 ft side and 4 ft rear setbacks; conversions and JADUs need none. One off-street parking space per ADU is required unless an exemption applies — an ADU of 500 sq ft or less, within 1/2 mile of transit, in a historic district, inside the main or accessory structure, on a permit-only street where no permit is offered to the ADU occupant, or within one block of a car-share vehicle. No replacement parking is needed for a garage conversion.

How many ADUs can I build in Vallejo?

On a single-family lot, three units in total: one JADU plus one attached or conversion ADU plus one detached ADU. A lot with an existing multifamily building can take up to 8 detached ADUs, capped at the number of existing units, and interior conversion ADUs can be at least one and up to 25% of the existing units.

Do I have to live in the property to rent out a Vallejo ADU?

No for an ADU — California law bars an owner-occupancy requirement for ADUs and Vallejo dropped it. A JADU does require owner occupancy today, and from 8 October 2026 it does so only where the JADU shares sanitation facilities with the main home. Rentals must be for 30 consecutive days or longer.

Can I convert my garage into an ADU in Vallejo?

Yes. A legally built garage, barn or studio can be converted, and Vallejo treats a converted garage as a conversion ADU: no setback requirement, no minimum or maximum floor area, and no replacement parking. Demolishing a detached garage can be permitted at the same time as the ADU.

How long does a Vallejo ADU permit take?

Vallejo must approve or deny a complete ADU application within 60 days, and the review is ministerial with no public hearing. If the city misses the deadline, the permit is deemed approved under state law.

Do Vallejo's rules or California's rules apply?

Both, and state law wins where they conflict. California's ADU statutes (Government Code sections 66310 to 66342) set the floor: they limit what a city can require on size, setbacks, parking, owner occupancy and fees. Vallejo's chapter 16.303 adds local standards, but section 66316 makes a non-compliant ordinance null and void — which is why the state sent Vallejo a technical assistance letter in October 2025.

Sources

• Vallejo Ordinance No. 1890 N.C.(2d) — full ordinance text (PDF)
• City of Vallejo — ADU Ordinance Update project page
• Vallejo Municipal Code Chapter 16.303 — Accessory dwelling units (Municode)
• City of Vallejo — ADU Mini-Guide and Summary Sheet (PDF)
• California Government Code 66314 — development standards
• California Government Code 66321 — size and height floors
• California Government Code 66323 — by-right ministerial approvals
• HCD — technical assistance letter to Vallejo (8 October 2025, PDF)
• HCD — ADU Handbook and ordinance review
• Solano County — ADU information (unincorporated areas)