ADU builders and rules in Coronado

Coronado ADU rules

Coronado's ADU rules are in Coronado Municipal Code § 86.56.105, last rewritten by Ordinance 2024-02 in April 2024. The city's ADU page recognizes detached ADUs, attached ADUs and conversions of existing space such as a bedroom, attached garage or accessory structure, plus junior ADUs of up to 500 sq ft inside the house. The table below reflects the code as published through Ordinance 2026-05 (June 16, 2026).

Two Coronado rules catch people out. First, if you build a new house and an ADU together, the code makes the whole project meet the zone's floor area ratio limits. Second, the code says any ADU must conform to the zone's height, setback, lot coverage and floor area rules except where it spells out an exception. The state housing department has challenged both (see the next section). For the state baseline, read our guide to California ADU laws; for a unit inside the house, see the junior ADU guide.

The height rule matters more here than in most cities. HCD's review notes that Coronado's ferry terminal meets the state definition of a major transit stop, so lots within a half-mile walk of it may qualify for the 18-foot limit.

Is Coronado's ADU ordinance up to date?

No, according to the state. On December 10, 2025, HCD sent Coronado 31 written findings that its 2024 ordinance fails to comply with state ADU law, and gave the city until January 9, 2026 to respond. Among the findings:

• Rental term. The six-month minimum must drop to the state's 30-day limit for ADUs and JADUs.
• Floor area ratio. A detached ADU built with a new house can't be held to the zone's floor area ratio.
• Size caps. The 850/1,000 sq ft limits can't apply to conversions of existing space or to ADUs on multifamily lots.
• Design. “Same architectural style” and equal-quality materials are subjective and must go.
• Surveys. Requiring pre- and post-construction land surveys for same-footprint conversions exceeds the city's authority.
• Covenants and owner occupancy. A recorded covenant can't be required for an ADU, and JADU owner occupancy may only apply when the JADU shares a bathroom.
• Separate sale. The city must allow a qualifying ADU to be sold separately under state rules.
• Multifamily lots. The city must allow up to eight detached ADUs on a lot with existing apartments, not two.

The city's code itself says that where it conflicts with state law, state law controls.

Coronado's coastal zone and ADU parking

The city's ADU code states that Coronado is located entirely within the Coastal Zone, with a Local Coastal Program certified in 1983. The city uses that, and the more than 2 million visitors a year it cites, to justify parking rules that are tighter than state law:

• Up to one parking space per ADU. None for a JADU, and none for an ADU deed-restricted to low, very low or extremely low income households.
• If an ADU replaces a garage or required parking, you must provide replacement spaces. They can be uncovered, tandem, or in side and rear setbacks.

HCD didn't call these parking rules illegal outright. It said they may be justified under the Coastal Act but that the city must cite the specific Coastal Act provisions and should consider less restrictive options. If you plan a garage conversion ADU, budget for replacement parking somewhere else on the lot.

Do you need a Coastal Development Permit? Often not. Under Coronado's coastal permit rules, uses allowed without a discretionary approval are exempt from the city's coastal permit outside the areas under Coastal Commission appeal or direct jurisdiction. Where a coastal permit is needed, the code says no building permit issues until the coastal permit does; HCD told the city the two reviews must run concurrently for ADUs. Ask Planning early whether your lot is in an appealable area.

Carriage house ADUs

Coronado has a building type you won't find in most cities: the carriage house, a two-story detached building with an enclosed garage below and up to 400 sq ft of living space above. Adding a kitchen and bathroom turns it into a carriage house ADU. Under § 86.56.110, a carriage house is allowed on single-family lots with both street and alley access, needs 25 ft of open space from the main house, caps the first floor at 600 sq ft, and allows no balconies or roof decks.

The city's housing plan counted 129 carriage houses in Coronado and aims to see 103 of them converted to housing by 2029. The code lets a carriage house become an ADU only if it keeps meeting the carriage house standards, but HCD told the city that a converted carriage house must be permitted as an ADU, not held to those stricter rules.

Coronado ADU fees

The code requires most new ADUs to have their own utility connection, though a submeter may be allowed. Water comes from California American Water's Coronado district, so ask Cal Am about meter costs separately. Under the state's ADU handbook, school districts can't charge fees on an ADU of 500 sq ft or less, and under state law no impact fees apply to an ADU of 750 sq ft or less. For the build itself, see what an ADU costs in San Diego or try the ADU cost calculator.

Getting a Coronado ADU permit

Coronado doesn't take ADU applications online. The ADU application (Handout 721) is filed with the Community Development Department at 1825 Strand Way, and incomplete or faxed applications aren't accepted. For the building permit, visit City Hall Monday through Friday, 8:00 a.m. to 4:30 p.m.; building questions go to 619-522-7331, and Planning & Zoning is at 619-522-7328. The city's planning page also lists a pre-application meeting form.

The code says the Community Development Director decides a complete ADU application ministerially within 60 days, matching the state's 60-day limit. If you file the ADU with a new house, the city can hold the ADU until it acts on the house.

Pre-approved plans aren't available yet as far as we could find. The housing plan committed the city to pre-approved ADU plans by July 1, 2025, but we found none posted on the city's ADU page. Our pre-approved ADU plans guide covers regional options. For scale, the same plan reports Coronado permitted 74 ADUs from 2017 through 2022, including 20 in 2021 and 18 in 2022.

Before you sign, read how to hire an ADU contractor, check a contractor's license, and compare verified ADU builders in San Diego County. If you plan to rent, our ADU rental income guide covers the numbers.

Common questions