Can I Build an ADU in Coronado?

Yes — by right

ADUs and JADUs are allowed by right in all residential and mixed-use zones; ministerial approval, no hearing.

State law controls: at least 1 ADU + 1 JADU (plus § 66323 combinations)

Coronado's ordinance text limits a single-family lot to 'one JADU OR one ADU' (CMC § 86.56.105.B.5). HCD found this significantly more restrictive than State ADU Law, which requires ministerial approval of the full range of § 66323 ADU + JADU combinations. The state allowance governs until the ordinance is corrected.

Conversion ADUs (≥1, up to 25% of units) + up to 8 detached

Conversions of non-livable space (at least 1, or up to 25% of existing units) plus up to 8 detached ADUs on a lot with existing multifamily — never exceeding the number of existing units. JADUs are single-family only.

Allowed

Up to 500 sq ft, within the walls of an existing single-family home (single-family lots only).

1,000 sq ft

Coronado's ordinance caps an attached/detached ADU at 850 sq ft (studio/1-bedroom) or 1,000 sq ft (2+ bedrooms). HCD's 2025-12-10 letter found this cap INVALID for three of the four § 66323 unit types (single-family conversion, multifamily conversion, and ADUs detached from a multifamily dwelling), which may not be size-capped. The 800 sq ft by-right floor is always protected; treat 850/1,000 as the local target for a standard new detached ADU only, not an enforceable ceiling on all units.

850 sq ft (studio/1-bedroom) or 1,000 sq ft (2+ bedrooms) per CMC § 86.56.105.B.7 — but state minimums (≥850 sq ft, ≥1,000 for 2+ bedrooms) and the § 66323 no-size-cap rule prevail

800 sq ft

An 800 sq ft ADU must be allowed regardless of FAR/lot-coverage caps; a city also cannot cap an attached ADU below 850 sq ft (1,000 for 2+ bedrooms).

500 sq ft

16 ft

16 ft baseline; cities must allow 18 ft within ½ mi of a major transit stop or where the primary dwelling is two-story, and 20 ft on a lot with a multistory multifamily building.

4 ft

A city cannot require more than 4 ft side or rear setback; conversions of existing structures are exempt.

4 ft

No front setback may block the mandatory 800 sq ft / 16-ft / 4-ft-setback ADU; otherwise per base zone

None required

No statewide separation requirement between the ADU and the primary dwelling.

Up to 1 space

At most 1 space per ADU (or per bedroom, whichever is less) — and waived in the common cases below.

Yes — no parking required near transit & for conversions

No parking may be required within ½ mi walking distance of transit, in a historic district, for an ADU within an existing structure, within one block of car-share, or in certain permit-parking areas.

Not required

When a garage/carport is demolished or converted to build an ADU, replacement parking cannot be required.

Ministerial (by right)

ADU/JADU permits are ministerial. Note: the ordinance previously layered conformance with all underlying-zone development standards (FAR, lot coverage) and a pre/post-construction land-survey requirement; HCD found these exceed the city's authority under Gov. Code § 66314, so they cannot be imposed on a qualifying ADU.

60 days

The agency must act within 60 days of a complete application — and the ADU is deemed approved if it does not.

Only for a JADU

No owner-occupancy requirement for ADUs (the prior sunset was removed). A JADU may require owner-occupancy, principally where it shares sanitation with the main house.

Waived under 750 sq ft

An ADU of 750 sq ft or less pays no impact fees (the 750 sq ft threshold itself is exempt under § 66311.5); larger ADUs pay fees proportional to the primary dwelling. JADUs (≤ 500 sq ft) are exempt.

Building permit

Only a ministerial building permit — no conditional use permit or discretionary design review for a qualifying ADU.