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

Folsom says a building permit is required to construct an accessory dwelling unit, and that its ADU rules in Chapter 17.105 of the Municipal Code were updated by Ordinance No. 1361, effective May 14, 2026. If you own a house with a backyard unit, a converted garage or plans for one, this is what the city lays out.

Folsom ADU rules at a glance

What types of ADU does Folsom recognize?

The city describes three types. An attached ADU shares a structural wall with the main home and may be created by converting space or adding space. A detached ADU is a stand-alone unit, which may come from converting a shed or garage or building a new structure.

A junior ADU, or JADU, is a conversion of up to 500 square feet within the primary residence; it may share a bathroom with the home and use an efficiency kitchenette. The city offers separate checklists for each type, and JADUs have a deed restriction template.

How does the Folsom ADU permit process work?

The city’s process has four stages: research and planning with the ADU Design Workbook and checklists, plan preparation using the Residential Projects Checklist, application through the ePermit Center, and permit issuance and construction. After issuance, a new address for the ADU is assigned by request to the Planning Division.

ADUs in the Historic District have additional design requirements, so contact Planning first. The city also runs an ADU Master Plan program in which pre-reviewed detached ADU plans can get a streamlined review, as long as the approved plan is not changed.

How an ADU affects selling a house in Folsom

A permitted ADU can be a selling point. An unpermitted conversion is the opposite: a buyer’s inspector or lender may ask for proof that the space was built legally, and sellers generally must disclose known unpermitted work. Because the city requires a building permit for ADUs, check your permit history first; our Folsom building permits guide explains how.

Junior ADUs, Rentals and Who to Call

Folsom’s ADU page says a junior ADU, also called a JADU, is limited to 500 square feet. It also states that ADUs cannot be used as vacation rentals, meaning rentals of fewer than 30 days, which matters if a unit has been listed on a short-term rental site.

The city offers an ADU Master Plan Program and an ADU Parking Requirement Map, and design review includes an additional plan review fee. Questions go to the Planning Division at 916-461-6202 or the Building Division at 916-461-6201, and applications are submitted through the Folsom ePermit Center.

Before you list a house with a garage conversion or backyard unit, ask Building Services whether a permit was issued and finaled, and keep the answer in writing. A finaled permit is the clearest proof a buyer’s lender will accept.

California Disclosure Rules for Unpermitted Units

California Civil Code 1102 and following requires most sellers of one-to-four-unit homes to deliver a Transfer Disclosure Statement. It asks about additions or alterations made without permits and about notices from agencies. A garage conversion or backyard unit built without approval belongs on that form, and it can complicate financing for a buyer using a loan.

A cash buyer can purchase a property with an unpermitted unit as-is, so you do not have to legalize it before closing. If you would rather keep the property and bring the unit into compliance, the city’s four-step process is where to start. We do not quote fee totals or review timelines here because the city page does not state them.

How to sell a house in Folsom with an ADU or unpermitted unit

1. Confirm the permit. Ask Building Services whether a permit was issued and finaled.
2. Know the rental rules. If tenants live in the unit, read how selling a tenant-occupied house in Folsom works.
3. Compare options. Legalize it, sell with a credit, or sell as-is for cash.
4. Disclose honestly. A cash offer does not change what you must disclose.

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

Have a unit and are not sure what to do? Call (424) 435-2326 or request a cash offer. There is no cost and no obligation.

Folsom ADU FAQ

Do I need a permit for an ADU in Folsom?

Yes. The city says a building permit is required to construct an ADU, and some larger ADUs also need design review.

Can I rent my Folsom ADU on a short-term basis?

No. The city says ADUs cannot be rented for less than 30 days.

What is a junior ADU in Folsom?

A conversion of up to 500 square feet within the primary residence, which may share a bathroom with the home and use an efficiency kitchenette.

Can I sell a Folsom house with an unpermitted ADU?

Yes. It can slow a traditional sale, but a cash buyer can purchase the property as it is.

How big can a junior ADU be in Folsom?

The city’s page says a junior ADU is limited to 500 square feet.

Can I rent my Folsom ADU on a short-term basis?

No. The city says ADUs cannot be used as vacation rentals, meaning rentals for less than 30 days.

Can I sell a Folsom home with an unpermitted ADU?

Yes, though California’s Transfer Disclosure Statement asks about unpermitted additions and alterations, so it should be disclosed. A cash buyer can purchase as-is without requiring you to legalize the unit first.

Sources

• City of Folsom: Accessory Dwelling Units

This guide is general information, not legal advice. ADU rules change often; confirm requirements with the City of Folsom.