ADU rules in Hayward

Detached ADUs are a permitted (P) use in every residential district (RNP, RL, RM, RH) and a permitted or secondary use in the commercial (RO, CO, CN-R, CN, CG, CB), central-city, sustainable mixed-use, airport-terminal, agricultural, Mission Boulevard and Downtown districts wherever the primary use is residential (Table 10-1.202, Table 10-1.802, 10-24.2.3.010, 10-28.2.3.010). Since Ord. 24-01 (adopted 1-23-2024) Hayward has no local ADU standards: HMC 10-1.2741 references state ADU law 'as amended from time to time', so a detached unit is allowed on any lot with a proposed or existing single-family or multifamily dwelling (Gov. Code 66314(d)(2)-(3)), and the 2017 limits (ADUs only in listed zones where one single-family home was the primary structure, one ADU per parcel, no new attached or detached units in Planned Development districts) are gone. The April 2026 checklist applies 4-ft side and rear setbacks, the zoning district's front setback and 5 ft from other structures (HMC 10-1.204(n)), and Gov. Code 66323(a)(2) separately guarantees a detached new-construction unit of up to 800 sq ft with 4-ft setbacks. On multifamily lots staff allow up to eight detached ADUs, never more than the number of existing units, or two with a proposed multifamily building (66323(a)(4)); in the Downtown Code zones detached ADUs must take the Carriage Building form (10-28.3.3.030(D)(3)).

ADUs attached to the home as additions, or created inside the existing or proposed home, an attached garage or an existing accessory structure, are allowed wherever detached units are, under the state standards HMC 10-1.2741 incorporates (Gov. Code 66314(d)(3)). Conversions of existing permitted space have no size or height limit and need no setbacks, with up to 150 sq ft of expansion for ingress and egress on the state-exempt path (Gov. Code 66323(a)(1)); the city requires a separate exterior entrance and, under the Building Code's fire-separation rules, no interior door between an ADU and the main house. A JADU of up to 500 sq ft may also be carved out of a single-family home or its attached garage (never a detached structure), one per lot. On multifamily lots staff allow conversions of non-livable space (storage rooms, garages, carports) up to 25 percent of the existing units, at least one, while JADUs are not permitted there.

Hayward applies the state caps: a new detached ADU may have up to 1,200 sq ft of interior livable space and a new attached ADU up to 50 percent of the primary dwelling's floor area, while conversions of existing permitted structures have no size limit (SFR ADU checklist item 5; Gov. Code 66314(d)(4)-(5)). The 50 percent cap cannot block an ADU of at least 800 sq ft of interior livable space with 4-ft side and rear setbacks, because Gov. Code 66321(b)(3) voids percentage, lot coverage, floor area ratio, open space and front setback limits that would; HCD's March 2026 handbook reads the 850 sq ft (1,000 sq ft with more than one bedroom) floors of 66321(b)(2) into percentage caps as well. Detached units may be 16 ft tall, or 18 ft within one-half mile of a major transit stop or high-quality transit corridor or on a lot with a multistory multifamily building (state law adds 2 ft near transit for a roof pitch matching the main house), attached units may reach the zoning district's height for the main building (30 ft and two stories for a detached home in the residential districts, HMC 10-1.203), and conversions have no height limit. JADUs are capped at 500 sq ft including any 150 sq ft ingress addition, and on multifamily lots detached ADUs are capped at 1,200 sq ft, with units over 800 sq ft meeting the zone's open space standard.

No owner occupancy is required for an ADU, at application or afterward: Ord. 24-01 repealed the 2017 rule (former HMC 10-1.2744(i)) that the owner live in the main house or the ADU, together with the ADU deed restriction of former 10-1.2747(b), and Gov. Code 66315 bars owner-occupant requirements for ADUs in any case. For JADUs the city's July 2026 checklist follows Gov. Code 66333(b) as amended by AB 1154: the owner must live in either the main home or the JADU only when the two share sanitation facilities, with a deed restriction recorded at the Alameda County Clerk-Recorder before the building permit issues, and a JADU with its own bathroom carries no occupancy requirement. The city's October 2023 process handout and January 2021 FAQ still describe a universal JADU owner-occupancy rule that no longer applies.

Hayward's code no longer requires parking for an ADU: Ord. 24-01 repealed the 2017 parking section (former HMC 10-1.2746, one space per new ADU with transit, historic-district and car-share exemptions and garage-replacement parking) and struck the ADU row from the residential parking table in HMC 10-2.310, and neither the April 2026 ADU checklists nor the city ADU page lists a parking item. Under state law no replacement parking may be required when a garage, carport or parking space is converted or demolished for an ADU (Gov. Code 66314(d)(11)), JADUs never need parking (66334(a)), and any ADU parking a city could impose is capped at one space per unit or bedroom and barred within one-half mile walking distance of public transit (bus stops count), for units inside the home or an accessory structure, and in the other 66322(a) cases. The only remaining hook is the unlisted-use clause of HMC 10-2.300 (the Planning Director assigns the most similar use's ratio), which the city's checklists do not invoke; the Fire Department's ADU checklist asks about off-street parking only as a fire-access question on narrow streets.

ADUs and JADUs are approved ministerially on a building permit filed through the city's e-Permit Portal ('Residential - Accessory Dwelling Unit (ADU)', or the pre-approved-plans variant for sets bought from the Hayward ADU Plans Gallery), with staff checking the ADU or JADU eligibility checklist; an application that answers yes or N/A to every item 'is eligible for ministerial ADU review by staff'. The separate Zoning Conformance Permit of former HMC 10-1.2747 was repealed by Ord. 24-01, and Gov. Code 66317 requires a completeness decision within 15 business days and approval or denial within 60 days without discretionary review or a hearing. ADUs are a permitted (P) use in every district that allows them, so no use permit or hearing applies.

An ADU may be rented long term, but the city's April 2026 ADU checklists and July 2026 JADU checklist require the owner to acknowledge that the unit 'shall not be utilized as commercial short-term rentals (i.e. rentals less than 30 days)'. Gov. Code 66315 lets a city require rental terms of 30 days or longer for ordinary ADUs, while state law itself requires terms longer than 30 days for units approved on the state-exempt path (66323(e)) and for JADUs (66333(g)). The codified 30-day rule of the 2017 ordinance (former HMC 10-1.2744(i)(1)) was repealed by Ord. 24-01, so the bar now rests on the checklists and on the zoning code's closed use list: dwelling units are defined for 'permanent living and sleeping purposes', lodging uses such as hotels and bed and breakfasts are not listed for the residential districts, and unlisted uses are prohibited there (HMC 10-1.202, 10-1.3510); Hayward has no short-term rental permit program, and stays of 30 days or less owe transient occupancy tax of up to 14 percent (HMC 8-4.10, 8-4.20). ADUs cannot be sold separately from the main home (no Gov. Code 66342 condominium opt-in; only the 66341 nonprofit route), and ADU tenancies fall under the city's just-cause eviction rules (HMC 12-1.13), though an ADU on an owner-occupied lot is exempt from the 5 percent rent-increase threshold (12-1.04(e)(3), 12-1.05).