Solano County

Vallejo ADU rules

Research summary of local ADU rules on file for Vallejo in Solano County. Not a determination for a specific lot.

Last checked October 23, 2026.

City or county ADU page

Vallejo rules on file

Local rules recorded in this project for this jurisdiction. Where a city figure on file is stricter than the state baseline on file, both are shown.

Detached ADU size
Detached ADUs up to 1,200 sq ft. ADUs and junior ADUs must be at least 150 sq ft and have their own entry. Local standards may not prevent an 800 sq ft ADU, 16 feet tall, with 4-foot side and rear setbacks (statewide exemption ADU).
Source: City of Vallejo ADU Mini-Guide and ADU Summary Sheet (March 2026), Summary Sheet: Size; Statewide Exemption ADU; Mini-Guide: What is an ADU?, accessed 2026-10-23.

Height
Detached: 16 feet (one story) or 18 feet on multistory multifamily lots. Attached: 25 feet. Height exceptions may be granted where Government Code 66321(b)(4) is met.
Source: City of Vallejo ADU Mini-Guide and ADU Summary Sheet (March 2026), Summary Sheet: Height, accessed 2026-10-23.

Side and rear setbacks
4 feet side, street side and rear. None for an ADU or junior ADU in existing space or rebuilt in the same footprint, height and volume as an existing structure.
Source: City of Vallejo ADU Mini-Guide and ADU Summary Sheet (March 2026), Summary Sheet: Setbacks, accessed 2026-10-23.

Parking
One off-street space per ADU, except within a half mile walk of public transit, in a historic district, for ADUs in existing space, where on-street permits are not offered, within a block of car share, or when applied for with a new home or multifamily building. Garage, carport or covered parking removed for an ADU need not be replaced. Junior ADUs need no parking.
Source: City of Vallejo ADU Mini-Guide and ADU Summary Sheet (March 2026), Summary Sheet: Parking; JADU; Common Questions 4, accessed 2026-10-23.

How many units (single-family lot)
Up to three: one ADU in converted space of the home or an accessory structure, one junior ADU, and one newly built detached ADU.
Source: City of Vallejo ADU Mini-Guide and ADU Summary Sheet (March 2026), Summary Sheet: Number of ADUs, accessed 2026-10-23.

Multifamily lots
Up to two detached ADUs with a proposed multifamily building, or up to eight with an existing one (not more than existing units). Conversion ADUs: at least one, up to 25% of existing units. Detached multifamily ADUs: up to 1,200 sq ft.
Source: City of Vallejo ADU Mini-Guide and ADU Summary Sheet (March 2026), Summary Sheet: ADUs on Lots with a Multi-Family Dwelling, accessed 2026-10-23.

Junior ADUs
Up to 500 sq ft inside an existing single-family home (an attached garage can be converted, a detached one cannot). Needs an independent exterior entrance and a kitchen or efficiency kitchen; if it has no bathroom of its own, it also needs an interior entry to the home.
Source: City of Vallejo ADU Mini-Guide and ADU Summary Sheet (March 2026), Summary Sheet: JADU; Mini-Guide: Garage Conversions, accessed 2026-10-23.

Which application to file
ADUs over 800 sq ft first need zoning compliance review by the Planning Division, then a building permit. ADUs of 800 sq ft or less go straight to the Building Division. Both can be filed on eTRAKiT or in person at City Hall.
Source: City of Vallejo ADU Mini-Guide and ADU Summary Sheet (March 2026), Mini-Guide Step 4: Review Process, accessed 2026-10-23.

Plan check
A complete application is routed to Building, Planning, Public Works, Water, Fire Prevention and the Vallejo Flood and Wastewater District. Expect about 4 to 6 weeks for the first review and 2 to 4 weeks for resubmittals. The City must act within 60 days of a complete application.
Source: City of Vallejo ADU Mini-Guide and ADU Summary Sheet (March 2026), Mini-Guide Step 4; Common Questions 11, accessed 2026-10-23.

Impact fees
No development impact fees for ADUs under 750 sq ft; larger ADUs pay in proportion to a primary home. The Vallejo City Unified School District fee does not apply under 500 sq ft. Many fees are set by outside agencies and updated yearly.
Source: City of Vallejo ADU Mini-Guide and ADU Summary Sheet (March 2026), Mini-Guide: ADU Project Fees; Common Questions 7, accessed 2026-10-23.

Meters and rentals
ADUs can have separate utility meters. ADUs and junior ADUs must be rented for more than 30 days.
Source: City of Vallejo ADU Mini-Guide and ADU Summary Sheet (March 2026), Common Questions 2, 3, 5, accessed 2026-10-23.

Building with a new home
A new house and an ADU may be built together, but the ADU's Certificate of Occupancy waits until the house is done.
Source: City of Vallejo ADU Mini-Guide and ADU Summary Sheet (March 2026), Common Questions 8, accessed 2026-10-23.

Who to contact
Planning: (707) 648-4326, planning@cityofvallejo.net. Building: (707) 648-4522. Addressing: Public Works (707) 648-4433. Water: (707) 648-4307. Wastewater: Vallejo Flood & Wastewater District (707) 644-8949.
Source: City of Vallejo ADU Mini-Guide and ADU Summary Sheet (March 2026), Mini-Guide: Contact Information, accessed 2026-10-23.

California state rules on file

The statewide baseline recorded from state law and the HCD ADU Handbook.

Detached size cap described in state law
1,200 sq ft. Recorded in this rules file from Government Code section 66314.
Source: California Government Code section 66314, 66314, accessed 2026-10-16.

Side and rear setback cap for a new ADU
4 ft. Recorded in this rules file from Government Code section 66314, which describes a cap on side and rear setbacks for a new ADU.
Source: California Government Code section 66314, 66314, accessed 2026-10-16.

Setback for a conversion of an existing structure
No additional setback, as recorded in this rules file from Government Code section 66314 for a conversion of an existing structure.
Source: California Government Code section 66314, 66314, accessed 2026-10-16.

Minimum lot size
A city may not impose a minimum lot size for an ADU, as recorded in this rules file from Government Code section 66314.
Source: California Government Code section 66314, 66314, accessed 2026-10-16.

Minimum unit the handbook says cities must allow
At least an 800 sq ft ADU with 4 ft side and rear setbacks. The HCD ADU Handbook (updated March 2026) describes this under section 66321(b)(3).
Source: HCD ADU Handbook, 66321(b)(3); handbook updated March 2026, accessed 2026-10-16.

Detached height described in the handbook
16 ft, or 18 ft or 20 ft in some cases. The HCD ADU Handbook (updated March 2026) describes this under section 66321(b)(4).
Source: HCD ADU Handbook, 66321(b)(4); handbook updated March 2026, accessed 2026-10-16.

Permit decision deadline
60 days. Recorded in this rules file from Government Code section 66317(a)(3): the permitting agency must decide on (approve or deny) a completed ADU application within 60 days when an existing single-family or multifamily dwelling is on the lot. Section 66317(a)(1) says the application is considered ministerially, without discretionary review or a hearing.
Source: California Government Code section 66317, 66317(a)(1), (a)(3), accessed 2026-10-17.

Owner-occupancy requirement
None. Recorded in this rules file from Government Code section 66315: a local agency may not impose an owner-occupancy requirement on an ADU. It may require that the property be used for rentals of terms 30 days or longer. The HCD ADU Handbook (updated March 2026) describes the same rule.
Source: California Government Code section 66315, 66315; HCD ADU Handbook updated March 2026, accessed 2026-10-17.

Parking near public transit
No parking standards within one-half mile walking distance of public transit. Recorded in this rules file from Government Code section 66322(a)(1). Section 66322(a) lists several other cases where parking standards may not be imposed.
Source: California Government Code section 66322, 66322(a), accessed 2026-10-17.

Ministerial categories
The HCD ADU Handbook (updated March 2026) states that Government Code section 66323 sets four ministerial categories. This rules file does not restate those four categories.
Source: HCD ADU Handbook, 66323; handbook updated March 2026, accessed 2026-10-16.

Fire Hazard Severity Zones
If your lot is in a Fire Hazard Severity Zone, the CAL FIRE Office of the State Fire Marshal says in Information Bulletin 25-004 (issued March 3, 2025): “Fire Hazard Severity Zones (FHSZs) should not restrict the development of Accessory Dwelling Units (ADUs). However, additional building standards may be necessary, including but not limited to California Fire Code Chapter 49 and California Building Code Chapter 7A.” State ADU law does not itself bar an ADU there. A city or county may still apply its building code, including wildfire-resistant construction (Gov. Code 66314(d)(8)); require side and rear setbacks “sufficient for fire and safety” for a unit converted under 66323(a)(1); and decline parking in setbacks on specific fire and life safety findings (66314(d)(10)(B)). It may also consider public safety when it designates where ADUs may be permitted (66314(a)). Sprinklers can't be required in an ADU or JADU if the primary residence doesn't need them (66314(d)(12), 66323(d)). Some cities and counties still apply their own fire-zone limits. Where this summary has one, it is listed with the local rules. This summary does not look up your lot. Check the CAL FIRE Fire Hazard Severity Zone map viewer linked from the State Fire Marshal's Fire Hazard Severity Zones page: https://experience.arcgis.com/experience/5065c998b4b0462f9ec3c6c226c610a9
Source: CAL FIRE Office of the State Fire Marshal Information Bulletin 25-004, page 4, issued March 3, 2025; Gov. Code 66314, 66323, accessed 2026-10-20.

State baseline on the directory → · State ADU rules on the homepage →

Can I build an ADU in Vallejo?

State law sets a baseline for ADUs in Vallejo, and the local standards on file are listed on this page. Whether a specific lot can add an ADU depends on zoning, utilities, and other site facts this page does not measure. Confirm with City of Vallejo Planning and Building Services Department, or run a free address summary.

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