ADU rules in Alameda

Detached ADUs are allowed on any lot in a district where residential use is permitted or conditionally permitted and that has a proposed or existing primary dwelling; R-1 through R-6, C-1 and C-2 list ADUs and JADUs as permitted uses, the C-C and North Park Street districts allow them as regulated by 30-5.18, and Alameda Point allows them where a primary dwelling exists. The codified text counts one ADU (attached or detached) plus one JADU on a single-family lot and two detached ADUs on a multifamily lot, but state law adds a detached new-construction unit of up to 800 sq ft with 4 ft side and rear setbacks to a conversion ADU and a JADU (Gov. Code 66323(a)(1)-(2)) and allows up to eight detached units, never more than the existing unit count, beside an existing multifamily building (66323(a)(4)). Detached units need 4 ft side and rear setbacks (none for conversions or same-footprint rebuilds of existing structures, and none for a unit 16 ft or lower with 1-hour construction that sits at least 75 ft from the front line beside neighbors' rear yards), 6 ft of separation from other buildings and 60 percent aggregate lot coverage, which may never block an 800 sq ft unit. The ordinance on the 10-6-2026 consent calendar writes the state counts into a new 'State-Mandated ADUs' subsection, adds a 20 ft front setback for local-track ADUs (adjustable under 30-5.6 on lots under 100 ft deep and never applied to block a 66323 unit) and leaves building separation to the Building Code.

An ADU may be attached to or created within a proposed or existing primary dwelling, including attached garages and storage areas, with independent exterior access and a lockable fire-rated door if an interior connection is kept; it follows the main house's height, coverage, yard and setback rules within 60 percent aggregate lot coverage. Conversions inside a house or a legal accessory structure (plus up to 150 sq ft for ingress and egress in an accessory structure) are state-exempt units under Gov. Code 66323(a)(1), and on multifamily lots any number of ADUs may be created within portions of existing buildings (the pending ordinance's state-mandated track names non-livable space such as storage rooms, attics and garages), more than the state floor of 25 percent of the units. JADUs of up to 500 sq ft sit entirely inside a single-family dwelling with an efficiency kitchen and a separate entrance, with their own bathroom or a shared one; the codified text also allows a 150 sq ft addition for a JADU, which the pending ordinance drops. The pending ordinance defines an attached ADU as new construction that structurally abuts the main house (above or below it included) and caps it at 50 percent of the existing home's floor area (see maxSize).

The codified 30-5.18.c.2 caps every ADU at 1,200 sq ft while guaranteeing an 800 sq ft, 16 ft unit with 4 ft side and rear setbacks, and it has no percentage cap on attached units; the city measures 'floor area' from the exterior faces of the building, counting stairways and spaces more than 50 percent enclosed (AMC 30-2, applied on the city ADU page), whereas the 850 and 1,000 sq ft floors in Gov. Code 66321(b)(2) are interior livable space. Conversions inside existing space under 66323(a)(1) are not subject to local size caps (66323(b)), and JADUs top out at 500 sq ft. Detached ADUs may be 18 ft tall, or 20 ft where the roof pitch matches the main house (above the 16 and 18 ft state floors in 66321(b)(4)), with a flood-zone allowance to clear base flood elevation; attached units follow the main house's height limit. The ordinance on the 10-6-2026 consent calendar keeps 1,200 sq ft for local-track ADUs but measures every ADU and JADU in interior livable space (new 30-5.18.n), limits an attached ADU to 50 percent of the existing home's floor area (the 66314(d)(4) rule, subject to the 850/1,000 sq ft floors through its state-law-prevails clause), sets the state-mandated detached unit at 800 sq ft, and lets the ADU roof pitch merely approximate the main roof for the extra 2 ft.

Neither the codified text nor the pending ordinance requires the owner to live on a lot with an ADU, and Gov. Code 66315 bars any owner-occupant condition. The codified JADU deed restriction (30-5.18.c.6(h)(2)) still makes the applicant an owner-occupant of either the main house or the JADU, and the city ADU page and January 2023 packet repeat that universal rule, but since 1-1-2026 Gov. Code 66333(b) (AB 1154) limits JADU owner occupancy to JADUs that share sanitation with the main home. The pending ordinance deletes the owner-occupancy clause from the JADU declaration (the staff report says the deed restrictions were revised 'to match State law') and defers to the Government Code on any conflict (new 30-5.18.o), so a JADU that shares a bathroom still carries the state owner-occupancy rule while one with its own bathroom does not. Owners still record the City Attorney-approved JADU declaration (no separate sale, rentals longer than 30 days, size limits) before the building permit issues.

AMC 30-7.3(a), adopted with the 2021 parking rewrite (Ord. 3309 N.S.), requires no off-street vehicle parking for any use except accessible spaces, and Table A of the same section sets one space per ADU as the most a property may provide. AMC 30-5.18.d waives replacement of a garage, carport or covered space demolished or converted for an ADU, and JADUs need no parking (30-5.18.c.6(f)); a leftover driveway and curb cut may stay only if the driveway is at least 18 ft deep behind the property line, otherwise it must be abandoned and the curb restored under AMC 22-18.3. The pending ordinance restates the rule as 'No off-street parking is required for any accessory dwelling unit' (new 30-5.18.g) and keeps the driveway rule.

ADU applications that meet 30-5.18 are reviewed ministerially within 60 days of a complete application, without discretionary review or a public hearing, through a building permit with a Planning Division zoning check (30-5.18.f.1; Gov. Code 66317). Discretion survives only around the ADU: design review for non-ADU work filed with it, such as raising a building or adding upper decks (the 2026 staff report notes the ADU itself is not subject to design review, and the pending ordinance exempts upper decks of 50 sq ft or less that meet 10 ft rear and 5 ft side setbacks), discretionary review of a new primary dwelling on a vacant lot, and the historic Certificate of Approval required to demolish a pre-1942 garage or accessory building under AMC 13-21. The codified text waives notice and discretionary review for such a demolition only outside historic districts, and the pending ordinance waives historic review only for state-mandated ADUs, so a local-track ADU that replaces a pre-1942 structure still faces that step, a possible conflict with Gov. Code 66317(a) and (c).

AMC 30-5.18.e requires any ADU rental to be for a period longer than 30 days and bars separate sale except under the qualified-nonprofit route (legacy 65852.26, now Gov. Code 66341); the JADU declaration carries the same term. Gov. Code 66315 lets a city require terms of 30 days or longer for ordinary ADUs, so Alameda's 31-day floor is one day stricter for them, while 66323(e) and 66333(g) themselves require terms longer than 30 days for state-exempt units and JADUs. Alameda has no short-term rental chapter today (hosts and platforms owe transient occupancy tax under AMC 3-61); a new Section 30-19 that would bar every unit built under an ADU or JADU permit from STR use unless it is the host's primary residence was introduced on 9-15-2026, but its final passage was withdrawn from the 10-6-2026 agenda. The pending ADU ordinance adds Section 30-5.19, opting into Gov. Code 66342 so a home and its ADU can be split into condominiums ministerially through a subdivision map (HOA, CC&Rs, lienholder consent, a safety inspection and a 60-day tenant right of first refusal), and qualifies the 30-day rule with 'unless otherwise authorized by this Code'. Rented ADUs fall under the Rent Control, Limitations on Evictions and Relocation Payments ordinance: a permitted ADU counts within the Single Dwelling Unit (AMC 6-58.15), and units exempt under state law (Costa-Hawkins) are spared only the rent-control portions (6-58.22.C, Ord. 3398 N.S.), so eviction limits, relocation payments and program fees still apply.