Vallejo Zoning and ADU Guide for Homeowners

Last updated November 13, 2026. Reviewed by the Cash Home Buyers CA team.

Vallejo’s own ADU guide says a detached accessory dwelling unit can be up to 1,200 square feet, and that an ADU of 800 square feet or less can go straight to a building permit without a separate zoning review. This guide summarizes the city’s ADU rules for homeowners, including size, height, setbacks, parking, fees, review timelines, and how Vallejo treats older unpermitted units, then explains what it all means if you plan to sell.

Vallejo ADU rules at a glance

Governing code	Vallejo Municipal Code Chapter 16.303 (the city has an ADU Ordinance Update project to align it with state law)
Planning Division	(707) 648-4326, planning@cityofvallejo.net, 555 Santa Clara Street
Building Division	(707) 648-4522, building.division@cityofvallejo.net
Detached ADU size	Up to 1,200 square feet
Attached or conversion ADU size	50 percent of the primary home’s living area or 1,200 square feet, whichever is less
JADU size	Up to 500 square feet, inside the existing home or attached garage
Height	Detached 16 feet; attached 25 feet
Setbacks	Front 15 feet; side, street side and rear 4 feet
Review time	Ministerial approval; complete building permit applications reviewed within 60 days

Types of units Vallejo allows

The city’s ADU Mini-Guide describes an ADU as a self-contained home legally part of the same property. ADUs and junior ADUs (JADUs) must have their own entryway and be at least 150 square feet. Both must be rented for 30 days or more, so short-term rentals are not allowed.

An ADU can be attached or detached, new construction or converted from an existing building, and must have its own bathroom and a full kitchen.

A JADU is a conversion of no more than 500 square feet inside an existing home, including an attached garage, and needs at least a sink, a counter and smaller appliances. RVs, tiny homes on wheels, yurts and storage structures do not count as ADUs.

How many units you can build

On a single-family lot the city’s summary sheet, citing Government Code section 66323, allows a total of three units: one ADU converted from space in the home or an accessory structure, one JADU inside the home, and one newly constructed detached ADU.

A residential dwelling must already exist on the lot, or be built together with the ADU.

On lots with multifamily buildings, the sheet allows up to two detached ADUs with a proposed multifamily building or up to eight with an existing one (not more than the number of existing units), plus interior conversions of at least one unit or up to 25 percent of existing units.

Development standards

• Size: detached up to 1,200 square feet; attached or interior up to the lesser of 50 percent of the main home’s living area or 1,200 square feet.
• Height: 16 feet detached and 25 feet attached, with exceptions available under Government Code section 66321(b)(4). Multifamily detached ADUs are 16 feet one-story and 18 feet multi-story.
• Setbacks: 15 feet front and 4 feet side, street side and rear. No setback is required for a unit created within existing living area or an accessory structure, or one that replaces a structure in the same footprint, height and volume.
• State exemption ADU: local standards cannot prohibit an ADU of up to 800 square feet, 16 feet tall, with 4-foot side and rear setbacks, and an 800-square-foot ADU may sit in the front setback if no other location works.
• Parking: one off-street space per ADU, with exceptions such as being within half a mile walking distance of public transit, being part of the existing home or an existing accessory structure, or a car share vehicle within one block. Replacing garage parking is not required when a garage or carport is converted or demolished.
• Fire sprinklers: only required for the ADU if the main residence requires them. Shared walls need a one-hour fire rating in non-sprinklered buildings and half-hour in sprinklered ones.
• Solar: new detached ADUs generally must include solar, except those under 500 square feet or where the system would produce less than 1.8 kilowatts.

Rules for owners and renters

Short-term rentals under 30 days are prohibited. An ADU cannot be sold separately from the main home in Vallejo, and a JADU cannot either.

Owner occupancy is not required for an ADU, but if there is a JADU the owner must live in either the JADU or the main home, and a deed restriction must be recorded with the Solano County Clerk-Recorder. Homeowners associations cannot prohibit ADUs or unreasonably restrict them.

The city also notes that building an ADU increases property taxes, because the county assessor appraises new construction at fair market value under Proposition 13; see our Prop 13 reassessment guide and the Solano County property tax guide.

Steps, timeline and fees

Learn the rules and design

Gather your parcel number, lot size, zoning and any flood, seismic or fire zones, then meet with planning staff. The city strongly recommends hiring an architect or designer and a licensed contractor, and notes garage conversions need moisture barriers and other design elements.

Apply for permits

If the ADU is over 800 square feet, you must first obtain Planning Division zoning compliance review before applying for a building permit. At 800 square feet or less you may submit the building permit application directly through eTRAKiT or in person.

Plans route to Building, Planning, Public Works, Water and Fire Prevention and the Vallejo Flood and Wastewater District. The city lists an initial review of 4 to 6 weeks and 2 to 4 weeks for resubmittals, and says complete applications are reviewed within 60 days.

A soils report is generally required for new construction, and a new address is requested through Public Works.

Budget for fees

The mini-guide gives a rough planning range of $250 to $350 per square foot including design and permits, and a fee table for fiscal year 2025 to 2026. Building permit fees, for example, start at $253.09 for lower valuations, with plan review, mechanical, electrical and plumbing fees calculated as percentages of the building permit fee.

Development impact fees are not charged for ADUs under 750 square feet, and the school district fee does not apply under 500 square feet. Sewer capacity charges vary by size. The CalHFA program offers grants of up to $40,000 to eligible lower and moderate income owners for pre-development costs, in limited application windows.

Inspect and move in

Inspections are scheduled through eTRAKiT or the city’s automated line at (707) 648-4384. After the final inspection, your signed inspection card serves as the certificate of occupancy. If you build a new house and an ADU together, the ADU does not get a certificate of occupancy until the house is complete.

Unpermitted ADUs in Vallejo

The city says that if you built an ADU without permits you may want to legalize it.

It states that contacting Planning staff will not trigger fines or enforcement, that owners can request a delay of citations for unpermitted ADUs, as long as there are no safety issues, until 2030, and that an unpermitted ADU built before 2020 can be legalized even if it violates building standards or ADU rules, unless it is deemed substandard or poses a health and safety hazard.

This matters at sale time, and our Vallejo code enforcement guide explains how violations are handled.

Selling a Vallejo home with an ADU or unpermitted unit

A legal ADU can help a property show well, but you cannot sell it separately, and rented units bring tenant rules into the sale; see our tenant-occupied sale guide. An unpermitted unit has to be disclosed under the rules in our statewide unpermitted work guide.

Owners generally choose among legalizing the unit before listing, disclosing it and selling on the open market, or selling as-is to a cash buyer. A short list to start with:

• Confirm with the Building Division which units on the property have permits.
• Note when each unit was built, since the pre-2020 legalization path depends on it.
• Check for tenants, leases and the rent charged, as 30-day minimum rental rules apply.
• Ask Planning what it would take to legalize the unit and what it would cost.
• Compare that route with a sale that takes the property as-is.

How to sell a house in Vallejo

1. List every structure and unit on the lot and what is permitted.
2. Gather permits, leases and city notices.
3. Request a no-obligation cash offer for the property as it stands.
4. Choose your closing date.
5. Close without legalizing, repairs or showings.

Learn more on our Vallejo cash offer process page.

Frequently asked questions

How big can an ADU be in Vallejo?

Detached ADUs can be up to 1,200 square feet. Attached or converted ADUs can be up to 50 percent of the main home’s living area or 1,200 square feet, whichever is less. JADUs are capped at 500 square feet.

How many ADUs can I build on a single-family lot in Vallejo?

The city’s summary sheet allows up to three: one converted ADU, one JADU and one new detached ADU.

Do I need to live on the property if I have an ADU?

Not for an ADU. If the property has a JADU, the owner must live in either the JADU or the main home.

Can I rent my Vallejo ADU on Airbnb?

No. The city requires ADUs and JADUs to be rented for more than 30 days, so short-term rentals are prohibited.

Can I sell my ADU separately from the house?

No. Vallejo does not allow an ADU or JADU to be sold separately from the main home.

Can I legalize an ADU built without permits?

The city says an unpermitted ADU built before 2020 can be legalized unless it is substandard or a health and safety hazard, and owners can request a citation delay until 2030 if there are no safety issues.

Can I sell my Vallejo house if the ADU is unpermitted?

Yes. You can disclose it and sell as-is, including to a cash buyer.

More guides

• We Buy Houses in Vallejo
• We Buy Houses in Solano County
• Solano County Property Tax Guide
• Vallejo Building Permits Guide
• Vallejo Code Enforcement Guide
• All California Guides

Sources

• City of Vallejo: ADU Mini-Guide and Summary Sheet
• City of Vallejo: ADU Ordinance Update

This guide is general information from public sources, not legal advice. Confirm current rules with the city.