ADU Rules in Corona (2026): What You Can Build

An accessory dwelling unit (ADU) is a self-contained second home — kitchen, bathroom and its own entrance — on the same lot as a house. Corona permits ADUs under California state law (Government Code 66310–66342) and its own ordinance, Corona Municipal Code Chapter 17.85, rewritten in March 2025. Green Design and Build is a licensed general contractor (CSLB #1110975) serving homeowners across Los Angeles County, Orange County, Ventura County, western Riverside County and western San Bernardino County, including Corona. The headline number: a detached ADU in Corona can be up to 1,200 square feet, and no city standard may block a unit of at least 800 square feet and 16 feet in height with 4-foot side and rear setbacks.

Who we are

Green Design and Build is led by Dekel Sofer. We have completed hundreds of projects and hold a 4.7-star rating across 146 Yelp reviews. We are a full-service residential general contractor and design-build remodeler, not an ADU specialist: we build ADUs, garage conversions and JADUs alongside kitchens, bathrooms, additions and whole-home renovations, and we run the Corona permit from eTrakit submittal to final inspection.

ADU rules in Corona at a glance

Rule	Corona (CMC 17.85, Ordinance 3410) and the state floor
Detached ADU, maximum size	1,200 sq ft
Attached ADU, maximum size	50% of the house under the city ordinance; state law requires at least 850 sq ft, or 1,000 sq ft with more than one bedroom
Junior ADU (JADU)	Up to 500 sq ft inside the walls of the house, with an efficiency kitchen and separate entrance
Height	No separate city figure; state floors apply: 16 ft detached; 18 ft within a half-mile walk of a major transit stop (plus 2 ft to match the house’s roof pitch); attached ADU 25 ft or the zone limit, whichever is lower
Setbacks	4 ft side and rear for new construction, including lot lines on a street; none for conversions of existing living area or an existing accessory building
Parking	One space per unit or bedroom, whichever is less, allowed on the driveway; none for conversions, units within a half-mile walk of public transit, or historic districts; parking removed for an ADU is not replaced
Owner-occupancy	Not required for an ADU; for a JADU, Corona’s ordinance requires it, and since 1 January 2026 state law requires it only where the JADU shares a bathroom
Units on a single-family lot	Up to two ADUs under the city ordinance; state law requires at least one ADU plus one JADU
Short-term rental	Prohibited; rentals longer than 30 days for both units
Impact fees	None at 750 sq ft or less; proportional to the house above that
Review	Ministerial, through building plan check, within 60 days of a complete application
Where to apply	Building Division, 400 South Vicentia Avenue, Suite 120, Corona, CA 92880 (Monday–Thursday 7 AM–6 PM), online through eTrakit at etrakit.coronaca.gov

This page is part of our ADU rules by city series; the rules below were checked against the city ordinance and state law in September 2026.

Size, height and setbacks

Corona’s ordinance follows the state framework almost word for word: a detached ADU up to 1,200 square feet, an attached ADU up to half the floor area of the house. State law sets the floor, so the 50 percent rule cannot shrink an attached unit below 850 square feet, or 1,000 square feet with two or more bedrooms — on a 1,400 square foot ranch north of the 91, a two-bedroom attached ADU can still be 1,000 square feet.

The most useful sentence in the ordinance says no development standard shall apply to prohibit an ADU of at least 16 feet in height and 800 square feet. Lot coverage and open-space rules in the underlying zone can trim a 1,200 square foot unit; they cannot stop an 800 square foot unit with 4-foot side and rear setbacks. The city does require the ADU to match the house in style, roof pitch, color and exterior materials. Our ADU rules calculator shows the state floor for your lot.

Two local twists matter more than the numbers. Much of South Corona and Sierra del Oro, against the Cleveland National Forest, sits in Very High Fire Hazard Severity Zones, which the city’s online map confirms by address; an ADU there is built to Chapter 7A with an ignition-resistant exterior, Class A roof and ember-resistant vents. And South Corona, Eagle Glen, Dos Lagos and most communities built since the 1980s have HOA architectural committees. Under Civil Code 4751 an HOA cannot prohibit or unreasonably restrict an ADU, but it can review design and materials, so we submit the HOA package before the city set.

Garage conversions and JADUs in Corona

A garage conversion is the lowest-cost way to add a unit in Corona because no setback applies to existing living area or an existing accessory building, and the 1960s–80s tracts north and west of the 91 have attached two-car garages on slab that convert directly. State law lets the footprint grow by up to 150 square feet where needed for entry and exit, and the parking the garage provided does not have to be replaced. Fire sprinklers follow the main house: if the house is not sprinklered, the city cannot require them in the ADU or JADU.

A junior ADU is up to 500 square feet carved out of the existing house, with an efficiency kitchen, its own exterior entrance and, optionally, a shared bathroom, under a recorded deed restriction barring a separate sale and requiring rentals longer than 30 days. Corona’s ordinance requires the owner to live in the house or the JADU; state law, since January 2026, requires that only when the JADU shares a bathroom with the house. A JADU needs no parking, and the house can carry a JADU and a full ADU at the same time.

Pre-approved plans, fees and utilities

Corona has set up a pre-approved ADU plan program under AB 1332, but as of this writing the Building Division has posted no plans, so unlike the Los Angeles Standard Plan Program there is no off-the-shelf set in Corona; every ADU goes through full plan check with its own drawings. If your lot is in Temescal Valley, the unincorporated area south of the city, Riverside County Building and Safety (4080 Lemon Street, Riverside) has jurisdiction and its Permit Ready ADU program offers four single-story plans of 499 to 909 square feet. Our Riverside County page shows where our coverage ends.

The fee items are plan check fees (paid at submittal under CMC 17.85.070), building permit fees, development impact fees, school fees and utility connection charges. State law exempts an ADU of 750 square feet or less from impact fees and charges them proportionally above that; school fees apply only above 500 square feet. A conversion or JADU cannot be required to take a separate utility connection or pay a connection fee (Government Code 66324); a new detached unit can, at a fee proportionate to its size. Electricity is Southern California Edison; water and sewer are the City of Corona’s own utility. The city publishes its fee tables as PDFs; we price the actual amounts for your lot in the estimate.

The permit process in Corona, step by step

1. Check the lot. Confirm the zone, run the address through the city’s fire hazard severity zone map, and pull the CC&Rs if there is an HOA.
2. HOA architectural approval where an association applies, so the city set matches what the HOA approved.
3. Design and engineering. Site plan, floor plan, elevations, structural calculations, Title 24 for Climate Zone 10, a soils report where expansive clay calls for one, and the Chapter 7A sheet on fire-zone lots.
4. Submit through eTrakit to the Building Division at 400 South Vicentia Avenue; plan check fees are paid at submittal.
5. Plan check. The city must approve or deny within 60 days of a complete application; its stated goal is approval by the third round.
6. Permit issuance, with impact fees (over 750 square feet), school fees (over 500 square feet) and utility charges paid.
7. Construction and inspections — foundation, framing, rough trades, insulation, drywall and lath — scheduled online, Monday to Thursday.
8. Final inspection and certificate of occupancy, address assignment, and SCE and Corona Utilities energize the connections.

End to end, a Corona ADU runs six months to a year: design and HOA review, the 60-day plan check window plus corrections, then construction.

What an ADU costs in Corona

Using the budgeting ranges we publish across the site: a garage conversion runs $100,000–$200,000; a detached 500 square foot ADU $180,000–$260,000; a 700–800 square foot unit $225,000–$350,000; a 1,000 square foot unit $300,000–$450,000 or more. Plan on $300–$450 per square foot all-in, and $500 or more on difficult lots.

Corona adds drivers of its own. Expansive clay soils, common across the flat tracts and the older Grand Boulevard lots, often push the foundation toward a post-tensioned or deepened slab with a geotechnical report behind it; fire-zone lots add the Chapter 7A exterior package; HOA review adds time and sometimes upgraded materials; and summer heat above 100°F makes a cool roof and low-E glass the best money spent on any Corona unit. Our guides on how much it costs to build an ADU and why ADU quotes vary so much walk through real projects line by line.

Frequently asked questions

How big can an ADU be in Corona?

A detached ADU in Corona can be up to 1,200 square feet under Corona Municipal Code 17.85, and an attached ADU up to 50 percent of the house but never less than the state floor of 850 square feet (1,000 square feet with more than one bedroom). A junior ADU is capped at 500 square feet inside the house. Whatever the zoning says about lot coverage, Corona cannot block a unit of at least 800 square feet with 4-foot side and rear setbacks.

Do I need parking for an ADU in Corona?

Corona can require one parking space for a new ADU (one per unit or per bedroom, whichever is less), and it can be on the existing driveway. No space is required for a conversion, a JADU, an ADU within a half-mile walk of public transit or one in a historic district, and parking lost to a garage conversion does not have to be replaced.

Can my Corona HOA stop me from building an ADU?

No. Under California Civil Code 4751, CC&Rs that prohibit or unreasonably restrict an ADU or JADU are void, so an HOA in South Corona, Eagle Glen or Dos Lagos cannot say no to the unit itself. It can review the design for compatibility, which is why we get architectural approval before the Corona city submittal.

How long does a Corona ADU permit take?

Corona must approve or deny a complete ADU application within 60 days, and its Building Division’s stated goal is approval by the third plan-check round. Counting design, HOA review, corrections and construction, a Corona ADU typically takes six months to a year from first meeting to certificate of occupancy.

Do I have to live on the property to rent out an ADU in Corona?

Not for an ADU: state law bars Corona from imposing an owner-occupancy requirement, and both the house and the ADU can be rented for terms longer than 30 days. For a junior ADU, Corona’s ordinance requires the owner to live on site, and state law since January 2026 requires that only where the JADU shares a bathroom with the house.

Does Corona have pre-approved ADU plans?

Corona has created a pre-approved plan program under AB 1332 but, as of this writing, has not posted any plans on its Building Division site, so every Corona ADU is designed and plan-checked individually. Riverside County’s Permit Ready ADU program, with four plans from 499 to 909 square feet, applies only to unincorporated areas such as Temescal Valley.

Find out what your Corona lot can hold

Send us the address and we will check the zone, the fire hazard map and the HOA, then come out for a free site visit and give you a written, itemized estimate for the ADU that fits. We design to Corona's ordinance and submit through eTrakit so plan check goes in clean.