Compton Zoning and ADU Guide for Homeowners and Sellers

Last updated November 13, 2026. Reviewed by the Cash Home Buyers CA team. Information comes from the City of Compton ADU pages; sources are listed at the end.

Compton publishes an ADU page and FAQ that spell out how many units a lot can have and how large they can be. Check current requirements with the city before you build, legalize or sell a unit.

Compton ADU rules at a glance

How many ADUs can I build in Compton?

On a lot with a single-family home, one ADU and/or one JADU. On multifamily property, up to two detached ADUs, or converted ADUs in portions of existing buildings that are not livable space, up to 25% of the existing units.

How big can a Compton ADU be?

The city’s FAQ says a new detached ADU cannot exceed 1,200 sq ft for two or more bedrooms. A new attached ADU is limited to 1,200 sq ft or 50% of the primary home’s floor area, whichever is less, and up to 800 sq ft if the main home is under 1,600 sq ft.

How an ADU or garage conversion affects selling a house in Compton

A permitted ADU can be a selling point. An unpermitted one is a problem lenders and inspectors notice. In California, sellers generally must disclose known unpermitted work. On a traditional listing you can try to permit the unit, remove it, price it in, or offer a credit.

How to sell a Compton house with an unpermitted ADU

1. Check the city’s records for what is permitted at the address.
2. Gather what you have: plans, receipts, inspection cards.
3. Compare options: legalize, remove, or sell as-is.
4. Disclose honestly. A cash offer does not change disclosure duties but removes repair steps.

We buy Compton houses as they are. See selling as-is in Compton, our Compton building permits guide and code enforcement guide.

Questions about a unit on your property? Call (424) 435-2326 or request a cash offer. There is no cost and no obligation.

Compton’s ADU FAQ: the city’s own answers

The city’s Community Development pages include an ADU FAQ. It says there is no minimum lot size requirement, because state law does not impose one. A second floor of an existing home can be converted to an ADU, as long as a separate exterior entrance is provided.

On a lot with a single-family home, only one ADU and/or one JADU may be built.

On multifamily properties, up to two detached ADUs are allowed, or one or more converted ADUs within portions of existing multifamily structures that are not livable space, up to 25% of the existing units on the lot.

Size limits

The FAQ says the maximum size of an ADU with two or more bedrooms is 1,200 square feet, and a new detached ADU over 1,200 square feet is not allowed. A new attached ADU may be 1,200 square feet or 50% of the primary dwelling’s floor area, whichever is less.

If the primary residence is under 1,600 square feet, the attached ADU may have up to 800 square feet. For questions, the city directs people to the Building Department at (310) 605-5509.

Starting an ADU or legalizing one

1. Confirm the lot and house type with the city, since the unit limits differ for single-family and multifamily properties.
2. Gather plans and the city’s ADU documents and forms.
3. Apply through Building and Safety, which issues permits and inspections.
4. Finish with a final inspection so the unit is recorded as legal.

State law sets the floor

State ADU law limits what a city can require, and it requires cities to act on complete applications within set time limits. If you think a local rule conflicts with state law, ask the city to explain which standard it applied. The California Department of Housing and Community Development publishes a handbook that summarizes the rules.

Selling a Compton house with an unpermitted unit

Many older garages and rear rooms were converted without permits.

California Civil Code section 1102.1 keeps your disclosure duty in place in an as-is sale, and section 1102.3 gives a buyer three days after in-person delivery or five days after mailing or agreed electronic delivery to cancel if a required disclosure arrives after an offer.

Choices are to legalize, remove the unit, price the house to match or sell to a cash buyer who accepts it as it stands. See our Compton building permits guide for the records check.

How the multifamily rules differ

On a single-family lot Compton allows one ADU and/or one JADU. On a multifamily lot the city says up to two detached ADUs are allowed, or converted ADUs in non-livable portions of existing buildings, up to 25% of the existing units on the lot.

If you own a duplex or small apartment building, the unit count on your lot determines how many conversions fit. Ask the Building Department at (310) 605-5509 how the count applies to your parcel.

Second-floor conversions and entrances

The city says a second-floor conversion is allowed with a separate exterior entrance. When you buy or sell a house where an upstairs room was turned into a unit, the exterior entrance is a visible clue to how it was set up. A unit with no separate entrance may not meet the standard, which a buyer’s inspector may notice.

Checking whether a unit fits the size limits

• Two or more bedrooms: up to 1,200 square feet.
• New attached ADU: 1,200 square feet or 50% of the main home’s floor area, whichever is less.
• Main home under 1,600 square feet: an attached ADU may reach 800 square feet.

If your unit is outside those numbers, it may need legalizing or a closer look. See our Compton building permits guide and California as-is guide.

Compton zoning and ADU FAQ

How many ADUs can I build on a Compton single-family lot?

One ADU and/or one JADU, according to the city’s FAQ.

What is the largest ADU allowed in Compton?

The city says a unit with two or more bedrooms is capped at 1,200 sq ft, and a new attached ADU is limited to 1,200 sq ft or 50% of the primary home’s floor area, whichever is less.

Can I sell a Compton house with an unpermitted ADU?

Yes. It must be disclosed, but a cash buyer can purchase the property as it is.

Is there a minimum lot size for a Compton ADU?

No. The city’s ADU FAQ says there is no minimum lot size requirement because state law does not impose one.

How big can a Compton ADU be?

The city says an ADU with two or more bedrooms is limited to 1,200 square feet, and a new attached ADU is the lesser of 1,200 square feet or 50% of the primary home’s floor area.

How many ADUs can I build on a Compton single-family lot?

The city says only one ADU and/or one JADU on a property developed or proposed to be developed with a single-family home.

How many ADUs are allowed on a Compton multifamily lot?

The city says up to two detached ADUs, or converted ADUs in non-livable portions of existing buildings up to 25% of the existing units.

Is there a minimum lot size for a Compton ADU?

No. The city says state law does not impose one.

Sources

• City of Compton: ADU FAQ
• City of Compton: Accessory Dwelling Units

This guide is general information, not legal advice. Zoning rules change; confirm with the City of Compton.