Brea, CA Zoning and ADU Guide for Homeowners

Last updated November 13, 2026. Reviewed by the Cash Home Buyers CA team.

Brea regulates accessory dwelling units (ADUs) and junior ADUs in Chapter 20.52 of its zoning code, which follows the statewide framework while setting local size, height and setback standards. This guide summarizes the standards in Brea’s ADU chapter, how applications are reviewed and what owners should check before selling a house with an extra unit or a converted garage. Zoning codes are amended often, so confirm the current text with the Planning Division.

Brea ADU rules at a glance

Where the rules are	Brea City Code Chapter 20.52, Accessory Dwelling Units
Review process	Ministerial review through the building permit plan check process, with no hearing
Review time	Approve or deny within 60 days of a completed application on a lot with an existing home
Attached ADU size	150 sq ft minimum; no more than 50% of the primary home or 1,200 sq ft, whichever is less
Detached ADU size	150 sq ft minimum; 1,200 sq ft maximum
JADU size	150 to 500 sq ft
Detached height and setbacks	16 feet maximum; 4-foot side and rear setbacks
Rentals	Rentals must be for 30 consecutive days or more

Where Brea’s ADU rules live

Chapter 20.52 of the Brea City Code states that the city recognizes the importance of livable housing and notes that the State Legislature has declared ADUs and junior ADUs a valuable form of housing.

The chapter then sets the local development standards, which sit alongside the Two Unit Developments (SB 9) and ADU information the city publishes for homeowners.

The city also runs a pre-approved ADU plans program, in which a completed building permit application with the required plans is still submitted to the Building Division.

Size and height standards

Under the chapter, an attached ADU must be at least 150 square feet and no larger than 50 percent of the existing primary dwelling or 1,200 square feet, whichever is less. A detached ADU has a 150 square foot minimum and a 1,200 square foot maximum.

A junior ADU is 150 to 500 square feet, and up to 150 square feet may be added to the existing home to provide ingress and egress.

When an ADU is created by converting existing space, there is no maximum size, and the conversion may expand by up to 150 square feet only to provide access.

At a minimum the chapter allows 850 square feet for an ADU with one bedroom and 1,000 square feet for one with more than one bedroom. Non-livable space such as attached garages, porches, patios and balconies is not counted when calculating unit size.

A detached ADU is limited to 16 feet in height, with additional height allowed as provided in Government Code section 66321(b)(4). An attached ADU is limited to 25 feet or the underlying zone standard, whichever is lower.

Setbacks and placement

A detached ADU needs 4-foot side and rear setbacks, and the front setback follows the underlying zone. The detached unit must be located no closer than the front-most building wall of the primary dwelling. A junior ADU and an attached ADU follow the standards of the underlying zone.

No additional setback is required when an ADU is created by converting existing space in the same location and to the same dimensions. The front setback can be reduced when applying the zone standard would prevent an 800 square foot unit.

Owner occupancy, rentals and fire sprinklers

If a property has a junior ADU with shared sanitation facilities, the legal owner must live in one of the dwellings on the property while the junior ADU exists.

Owner occupancy is not required if the junior ADU has separate sanitation facilities, or if the owner is a governmental agency, land trust or housing organization. Any ADU or junior ADU used as a rental must be rented for no less than 30 consecutive days.

The chapter says fire sprinklers are not required in an ADU or junior ADU if they are not required for the primary residence, and building a new ADU does not trigger sprinklers in an existing multifamily building. Construction still has to meet the city’s building and fire codes.

Application review

ADU applications are reviewed ministerially through the city’s building permit plan check process, without discretionary review or a hearing. On a lot with an existing single-family or multifamily home, the city must approve or deny a completed application within 60 days, subject to tolling if the applicant requests a delay.

If an ADU is proposed with a new home, the city may wait to act until it acts on the new home. All applications must come with the required application fee. Parking is governed by Section 20.08.040.D of the city code, so confirm what applies to your lot.

Garage conversions, unpermitted units and selling

A permitted ADU is a selling point, but it generally cannot be sold separately from the house. An unpermitted garage conversion or backyard unit can complicate appraisal and financing.

Start by asking the Building and Safety Division what is on file for your address, then decide whether to legalize the unit or sell as-is. Legalizing can require plans, egress, electrical and plumbing upgrades and fees. Selling as-is to a cash buyer avoids that work.

State ADU law and Brea

California’s ADU statute, Government Code section 66314 and following, sets a floor that every city must follow, and local ordinances fill in the details.

The state requires ministerial review within 60 days of a complete application, bars a city from requiring more than a limited set of standards, and generally allows an ADU or conversion inside existing space without added setbacks.

The California Department of Housing and Community Development (HCD) publishes a handbook and keeps a list of the state requirements. Because state law changes often, treat the city’s current ordinance and handout as the final word on size, height, parking and fees for your lot.

ADUs, garage conversions and selling a Brea house

Many older homes have a converted garage or a backyard unit built without permits. Buyers and lenders ask about them, and California sellers generally disclose known unpermitted work. Our guide to selling as-is with unpermitted work explains the rules, and our Prop 13 guide explains how new construction can affect property tax. Before you list:

• Check city records for permits on any ADU, conversion or addition.
• Ask Planning whether the structure could qualify under current rules.
• Estimate plans, fees and corrections needed to legalize it.
• Compare that with selling as-is and letting a cash buyer take on the legalization.

Questions to ask Planning before you design

• Does my lot and zone allow an ADU, a junior ADU, or both?
• Is a pre-approved or pre-reviewed ADU plan available?
• What are the current impact, utility and school fees for the size I am considering?
• Can my existing garage or accessory structure be converted without changing its footprint?
• Are there fire, slope, easement or utility constraints on my lot?

Junior ADUs and garage conversions in more detail

State law treats a junior ADU as a unit of up to 500 square feet created inside the walls of an existing or proposed single-family home, with an efficiency kitchen and a recorded restriction that keeps it from being sold apart from the house.

A garage conversion is a different path: the unit replaces the garage, and state law generally does not require the city to demand replacement parking. Both are common sources of unpermitted space in older Brea neighborhoods, which is why buyers’ agents and appraisers ask for the permit record.

If a conversion was done without a permit, the usual fix is to submit as-built drawings, pay the fees and pass inspection, which can take months and cost real money.

Fees, utilities and property tax

State law limits the impact fees a city can charge on smaller ADUs and on conversions of existing space, and it limits when a separate utility connection can be required.

Larger new units can still carry impact fees, school fees and water or sewer connection charges, so ask for an itemized estimate before you commit to plans. New construction is generally reassessed for property tax under Prop 13, which means an ADU can raise the bill for the whole property. Our Prop 13 guide explains how reassessment works.

Why ADUs matter for resale

A permitted ADU can add rental income and appeal for some buyers, but an unpermitted one can complicate financing and appraisal. Lenders typically want permitted living area, and an appraiser may not count unpermitted space.

Because an ADU generally cannot be sold separately from the main home, its value comes through the sale of the whole property.

If you inherited a house with an old backyard unit, or bought one with a converted garage, check what the city has on file before you decide how to sell. Our probate home sale guide covers inherited property.

How to sell a house in Brea

1. Ask the city for the permit record on any ADU or conversion.
2. Collect plans, inspection records and any city notices.
3. Request a no-obligation cash offer for the house as it stands.
4. Choose your closing date.
5. Close with no repairs, legalization or showings required.

See also our Brea page, the Brea as-is sale page, the Brea inherited house page and the Orange County hub.

Frequently asked questions

Does Brea allow ADUs?

Yes. Chapter 20.52 of the Brea City Code sets standards for ADUs and junior ADUs, and applications are reviewed ministerially.

How big can an ADU be in Brea?

A detached ADU can be up to 1,200 square feet and an attached ADU up to 50 percent of the main home or 1,200 square feet, whichever is less. A junior ADU is 150 to 500 square feet.

How tall can a detached ADU be in Brea?

The chapter sets 16 feet for a detached ADU, with additional height allowed as provided in state law.

How long does the city have to review an ADU?

On a lot with an existing home, the city must approve or deny a completed application within 60 days.

Can I rent my ADU in Brea?

Yes, but ADU and junior ADU rentals must be for at least 30 consecutive days.

Can I sell a Brea house with an unpermitted ADU?

Yes. You can disclose it and sell as-is, including to a cash buyer. Our statewide guide explains the disclosure rules.

More guides

• We Buy Houses in Brea
• We Buy Houses in Orange County
• Orange County Property Tax Guide
• Brea Building Permits Guide
• Brea Code Enforcement Guide
• Sell Your Brea House As-Is
• Brea Cash Offer Process
• Sell My Brea House Fast
• All California Guides

Sources

• Brea City Code Chapter 20.52: Accessory Dwelling Units
• City of Brea: Two Unit Developments (SB 9) and ADUs/JADUs
• City of Brea: Pre-Approved ADU Plans Program
• City of Brea: ADU Plan Check Submittal Worksheet
• California HCD: Accessory Dwelling Units

This guide is general information from public sources, not legal advice. Confirm current rules, fees and hours with the city.