Petaluma 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 Petaluma Accessory Dwelling Units page; sources are listed at the end.

Petaluma says ADUs and junior ADUs are permitted by right on any residentially zoned lot. The city allows internal conversions, attached additions and detached units. Here are the rules the city states and what they mean if you are selling.

Petaluma ADU rules at a glance

Occupancy and rental rules

For a JADU, the parcel owner must live in the primary dwelling or the JADU as a principal residence. The city says ADUs permitted after September 7, 2017 may only be rented for terms longer than 30 days and cannot be used as short-term vacation rentals. The city’s page does not address parking or list fee amounts, so ask Planning staff.

The process the city lists

1. Design the unit to the development standards in Section 7.030 of the Implementing Zoning Ordinance. A building permit is required, and the Building Division’s ADU Checklist lists what to submit.
2. Get approval for a building permit and an address assignment application before construction begins.
3. The Building Division inspects for code compliance, and a Certificate of Occupancy is the final step.

How an ADU affects selling a house in Petaluma

A permitted ADU can be a selling point, while an unpermitted one is a disclosure and legalization question. See our Petaluma building permits guide and code enforcement guide for the related steps.

How to sell a house in Petaluma with an unpermitted unit

1. Confirm what is permitted. Call the Building Department at (707) 778-4469 about the address.
2. Weigh legalizing against selling. Legalizing takes plans, fees and inspections.
3. Compare your options. Legalize and list, sell with a credit, or sell as-is to a cash buyer.
4. Disclose honestly. A cash offer does not change what you must disclose.

We buy Petaluma houses as they are. Read how selling a house as-is in Petaluma works, or see our Petaluma cash-offer process.

What Petaluma’s zoning ordinance says about ADUs

Petaluma’s municipal code allows an ADU in a residential or mixed-use zone, including planned unit developments. On a lot with a proposed or existing single-family home, one detached ADU is permitted, or alternatively one ADU or junior ADU inside the existing or proposed home or an accessory structure.

Any addition beyond the existing structure to make room for the unit is limited to 150 square feet for ingress and egress.

On a multifamily lot, one ADU is permitted, and up to two detached ADUs are allowed if each is limited to 16 feet in height with four-foot side and rear setbacks.

The maximum living area of an ADU is 1,000 square feet. An attached ADU may not exceed 50 percent of the main home’s living area, unless it is no larger than 800 square feet, no taller than 16 feet and has four-foot side and rear setbacks.

The city’s ADU page lists 16 feet for a detached unit (18 feet within one-half mile of a major transit stop) and 25 feet or the height limit of the main home, whichever is lower, for an attached unit. ADUs must be permanent structures on a permanent foundation.

No setback is required to convert existing living area or to rebuild a non-complying detached structure in the same location, footprint and height. No additional parking is required for a new ADU, but the lot must have at least 100 square feet of usable open space for the occupants.

Junior ADUs and short-term rental limits

A junior ADU is capped at 500 square feet, needs a separate exterior entry, and only one is allowed within a single-family home. The code says no additional parking is required and no sewer connection fee applies to a junior ADU. It also says an ADU permitted after September 7, 2017 cannot be used as a short-term vacation rental, which matters if you are selling a property that was marketed on that income.

California disclosure rules for ADUs and hazard zones

An unpermitted unit is a material fact you should raise with your agent or escrow officer, since an as-is sale does not excuse non-disclosure under Civil Code section 1102.1. Sellers also disclose whether the parcel sits in any of six natural hazard zones listed in section 1103, and any waiver of that disclosure is void. See our natural hazard disclosure guide for the zones.

Need to talk it through? Call (424) 435-2326 or request a cash offer. There is no cost and no obligation.

Petaluma ADU FAQ

How big can a detached ADU be in Petaluma?

The city says up to 1,000 sq ft for a detached ADU, up to 50 percent of existing residential square footage for an attached ADU, and up to 500 sq ft for a JADU.

What setbacks apply to a Petaluma ADU?

The city says attached and detached ADUs need 4 ft minimum side and rear setbacks. Internal conversions have no setback requirement if the footprint does not change.

Can I rent my Petaluma ADU short term?

No. The city says ADUs permitted after September 7, 2017 may only be rented for terms longer than 30 days.

Can I sell a Petaluma house with an unpermitted unit?

Yes. It does not legally stop a sale, but it can slow a traditional one. A cash buyer can purchase the house as it is.

How big can an ADU be in Petaluma?

The municipal code sets a maximum of 1,000 square feet of living area. An attached ADU may not exceed 50 percent of the main home’s living area unless it is 800 square feet or less, no taller than 16 feet, with four-foot side and rear setbacks.

Does Petaluma require extra parking for an ADU?

No. The code says no additional parking is required for new ADUs or junior ADUs, though the lot must have at least 100 square feet of usable open space for ADU occupants.

Can a Petaluma ADU be a short-term rental?

The code says an ADU permitted after September 7, 2017 cannot be used as a short-term vacation rental.

Sources

• City of Petaluma: Accessory Dwelling Units

This guide is general information, not legal advice. Rules change; confirm requirements with the City of Petaluma.