Solano County

Benicia ADU rules

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

Last checked October 26, 2026.

City or county ADU page

Benicia 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.

Which rules apply
Benicia's ADU rules are in Municipal Code Section 17.90.020 (Ordinance 25-12). A size cap on ADUs inside the home and two siting rules are left out of this summary because they may conflict with state law; state rules apply to those items.
Source: Benicia Municipal Code Sec. 17.90.020 Accessory dwelling units and junior accessory dwelling units (eCode360; Ord. 25-12), Sec. 17.90.020, accessed 2026-10-25.

Where ADUs are allowed
ADUs: in districts that allow single-family or multifamily homes, on a lot with an existing or proposed home. Junior ADUs: in districts that allow single-family homes, with an existing or proposed single-family home.
Source: Benicia Municipal Code Sec. 17.90.020 Accessory dwelling units and junior accessory dwelling units (eCode360; Ord. 25-12), Sec. 17.90.020(B), accessed 2026-10-25.

Review and timing
An ADU or junior ADU that meets the standards is handled through the building permit, with no other permit or hearing. The City says within 15 working days whether an application is complete and acts within 60 days of a complete application. ADUs that deviate from the standards go through design review or a variance.
Source: Benicia Municipal Code Sec. 17.90.020 Accessory dwelling units and junior accessory dwelling units (eCode360; Ord. 25-12), Sec. 17.90.020(C)(1)-(2), accessed 2026-10-25.

State-protected units
Allowed with only limited standards: one ADU and one junior ADU inside a single-family home or accessory structure (up to 150 sq ft added for entry); one new detached ADU up to 800 sq ft, 16 ft tall (18 ft near major transit, plus 2 ft to match the roof pitch), with 4 ft side and rear setbacks; ADUs in non-livable multifamily space (at least one, up to 25% of units); and up to eight detached ADUs with an existing multifamily building (not more than the existing units) or two with a proposed one.
Source: Benicia Municipal Code Sec. 17.90.020 Accessory dwelling units and junior accessory dwelling units (eCode360; Ord. 25-12), Sec. 17.90.020(G), accessed 2026-10-25.

Number of units
Not more than one ADU per lot except for the state-protected units, and not more than one junior ADU per lot.
Source: Benicia Municipal Code Sec. 17.90.020 Accessory dwelling units and junior accessory dwelling units (eCode360; Ord. 25-12), Sec. 17.90.020(D)(1), (E), accessed 2026-10-25.

Junior ADUs
Separate entrance, a kitchen with at least 3 linear ft of counter and 3 linear ft of cabinets, and an interior door to the home if the bathroom is shared. The owner must live on site only if the bathroom is shared (not for a government agency, land trust or housing organization). A deed restriction is recorded, and rentals must be at least 30 days.
Source: Benicia Municipal Code Sec. 17.90.020 Accessory dwelling units and junior accessory dwelling units (eCode360; Ord. 25-12), Sec. 17.90.020(D), accessed 2026-10-25.

Size limits (other ADUs)
Attached: 50% of the existing home or 850 sq ft (one bedroom or less) / 1,000 sq ft (more than one bedroom), whichever is greater. Detached: 1,200 sq ft. Junior ADU: 500 sq ft. Floor area, floor area ratio, open space and front yard rules may not prevent an 800 sq ft ADU with 4 ft side and rear setbacks.
Source: Benicia Municipal Code Sec. 17.90.020 Accessory dwelling units and junior accessory dwelling units (eCode360; Ord. 25-12), Sec. 17.90.020(I)(1)-(3), accessed 2026-10-25.

Setbacks and separation
4 ft side and rear setbacks; front setback same as the main home for attached ADUs. At least 5 ft between a detached ADU and the main building. Converted or same-footprint replacement structures do not need to meet setbacks.
Source: Benicia Municipal Code Sec. 17.90.020 Accessory dwelling units and junior accessory dwelling units (eCode360; Ord. 25-12), Sec. 17.90.020(I)(4)-(6), accessed 2026-10-25.

Height (other ADUs)
Attached: same as the main home. Detached, outside the H overlay: 16 to 24 ft depending on roof pitch and distance from the side or rear line (Table 17.90-4). In H overlay districts, see Table 17.90-3.
Source: Benicia Municipal Code Sec. 17.90.020 Accessory dwelling units and junior accessory dwelling units (eCode360; Ord. 25-12), Sec. 17.90.020(I)(7), accessed 2026-10-25.

Design standards (other ADUs)
Objective standards for second-story decks, outdoor stairs, dormers, gables and roof pitch (4:12 or more unless the home is flatter), with added material and window standards in H overlay districts.
Source: Benicia Municipal Code Sec. 17.90.020 Accessory dwelling units and junior accessory dwelling units (eCode360; Ord. 25-12), Sec. 17.90.020(J), accessed 2026-10-25.

Parking
No added parking for an ADU or junior ADU, and no replacement parking when a garage or parking area is converted or removed for an ADU.
Source: Benicia Municipal Code Sec. 17.90.020 Accessory dwelling units and junior accessory dwelling units (eCode360; Ord. 25-12), Sec. 17.90.020(K), accessed 2026-10-25.

Sale and rentals
An ADU may be rented but not sold separately unless Gov. Code 66341 is met, and not leased for less than 30 days.
Source: Benicia Municipal Code Sec. 17.90.020 Accessory dwelling units and junior accessory dwelling units (eCode360; Ord. 25-12), Sec. 17.90.020(H)(1), accessed 2026-10-25.

Where to ask
Benicia Community Development Department. The City's ADU page has its ADU information.
Source: City of Benicia, ADU page, accessed 2026-10-25.

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 Benicia?

State law sets a baseline for ADUs in Benicia, 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 the City of Benicia Community Development Department, or run a free address summary.

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