Building an ADU in the City of Riverside

What you can build in Riverside

The city's rules are in Riverside Municipal Code Chapter 19.442, last amended in 2025. ADUs, junior ADUs (JADUs) and movable ADUs (MADUs) are permitted in all residential zones, including multifamily and mixed-use zones with an existing or proposed home. There is no minimum lot size, and an ADU's floor area doesn't count toward lot coverage.

Single-family lots. Besides the house you can have one attached or converted ADU, one detached new-construction ADU or MADU, and one JADU. Lots developed under SB 9 follow the two-unit development chapter instead; see "Lot splits" below.

Multifamily lots. You can convert non-living space such as storage rooms, attics, basements or garages into ADUs: at least one, and up to 25% of the existing units. You can also build up to eight new detached ADUs on a lot with an existing apartment building (no more than the number of existing units), or two on a lot with a proposed one. MADUs aren't allowed on multifamily lots. The city's 2022 ADU FAQ still says two detached ADUs on a lot with existing apartments; the current code allows eight.

City or county? These rules apply only inside the City of Riverside. If your address is in unincorporated Riverside County, the county's Building & Safety department ((951) 955-1800) handles it. Statewide rules are on our California page. [1][4][5]

Size, height and setbacks

Size.

• Detached ADU: up to 1,200 sq ft.
• Attached ADU (including converted space in the house): up to 50% of the house or 1,200 sq ft, whichever is less, but never less than 850 sq ft for a unit with one bedroom or less, or 1,000 sq ft with more bedrooms. The city's FAQ gives an example: a 2,000 sq ft house can have a 1,000 sq ft attached ADU or a 1,200 sq ft detached ADU.
• JADU: up to 500 sq ft.
• MADU: 150 to 430 sq ft.
• Every ADU or JADU must be at least the size of an efficiency unit under the building code.

Height. Attached ADUs follow the zone's height limit. A one-story detached ADU (or MADU) can be 20 feet tall. A two-story detached ADU, or an ADU on the second floor of an existing accessory building, can be 30 feet. In the RC zone, detached ADUs are limited to 20 feet and one story.

Setbacks.

• Converting an existing structure: no additional setback. Adding a new second story to an existing structure: the zone's setbacks for the house.
• New one-story ADUs and MADUs under 16 feet tall: at least 4 feet from side and rear lot lines. The FAQ adds 4 feet from other buildings.
• New ADUs over 16 feet tall, and second-floor ADUs in new buildings: the zone's side and rear setbacks for the house.
• Front and street-side yards: the zone's setbacks apply in full. The FAQ says ADUs aren't allowed in front yards.

State law says a city can require a setback of "no more than four feet from the side and rear lot lines" for an attached or detached ADU, and that front setbacks can't block an ADU of at least 800 sq ft. If the zone's larger setbacks would affect your two-story ADU or your only buildable spot is in front, ask Planning how these rules apply. More on the state rules on our California page. [1][4][6]

Parking

Riverside requires no parking for any ADU, MADU or JADU. If you convert a garage, carport or covered parking for the house into an ADU, you don't have to replace those spaces. [1][4]

Dwell Riverside permit-ready plans

Dwell Riverside offers four pre-reviewed, single-story detached ADU plans, each in Craftsman, Ranch and Spanish styles:

• 746 sq ft, 1 bedroom, 1 bathroom
• 800 sq ft, 2 bedrooms, 2 bathrooms
• 1,020 sq ft, 2 bedrooms, 2 bathrooms
• 1,200 sq ft, 3 bedrooms, 2 bathrooms

Who qualifies. Your lot must be zoned single-family (R-1, RE, RR, RC or RA-5) with an existing or proposed house, must not be in a flood hazard area (check the FEMA flood map site), and must not be a designated or eligible cultural resource under Title 20. Planning reviews a signed eligibility form, and the city notes that approval of the form "does not guarantee eligibility."

What you fill in. The cover sheet (T1.1) of the plan set, a preliminary site plan marking where the ADU goes, a hold harmless agreement, and the clearance form, where you choose the elevation style and match the ADU's wall, roof, window and trim colors to the house. Properties in Very High Fire Hazard Severity Zones must use the plan's wildfire (WUI) specifications.

Speed. The first building plan review takes 3 business days, and any later reviews 10 business days. Plan sets and instructions are on the Permit-Ready ADU Plans page. See also our prefab ADU guide. [2][3][7]

Fees

City impact fees. The code says no city impact fees apply to ADUs under 750 sq ft. ADUs of 750 sq ft and over pay impact fees in proportion to the size of the house. State law exempts ADUs of 750 sq ft of interior livable space "or less," so ask the city how it treats an ADU of exactly 750 sq ft.

Utility connection fees. An ADU isn't treated as a new residential use for water and sewer connection fees or capacity charges, unless it's built with a new house. No new connection or capacity charge can be required for an ADU inside the existing house. A new detached ADU on a lot with an existing house may pay a connection fee or capacity charge proportionate to its burden, based on its size or number of plumbing fixtures. MADUs must be connected to water, sewer and electricity.

Other fees. Plan check and permit issuance fees apply, and the city says ADUs pay "some – but not all" of the impact and utility fees a new house pays, depending on the property. Under state law, ADUs and JADUs under 500 sq ft of interior livable space aren't subject to school impact fees. For a fee estimate call the One Stop Shop at (951) 826-5800. Our ADU cost guide covers typical budgets. [1][4][6]

How long it takes

State law requires the city to tell you within 15 business days whether your ADU application is complete, and to approve or deny a complete application within 60 days when a home already exists on the lot. A denial must come with a full list of what's deficient and how to fix it.

With a Dwell Riverside plan, the first plan review is 3 business days and later reviews 10 business days. After review, you download a conditions report from the permit portal; meeting those conditions may take extra steps and meetings with other departments. See our ADU permit process guide.

Historic properties. On a designated or eligible cultural resource, any property in a historic district, or a contributor in a neighborhood conservation area, you also need a Certificate of Appropriateness. The city's ADU design standards for historic properties (adopted February 19, 2025) are mandatory there unless staff grants an exemption, and Planning staff review these applications administratively. MADUs aren't allowed on historic properties. [1][2][6][8]

Garage conversions and junior ADUs

Garage conversions. Garages, workshops, guest quarters and parts of the house can be converted to an ADU or JADU. A converted structure needs no additional setback, you don't have to replace the garage parking, and no actions to correct zoning nonconformities related to physical improvements are required. Structures not built for living may need upgrades to meet the building code. See our garage conversion guide.

Junior ADUs. A JADU must be inside the walls of an existing or proposed house; an attached garage or other attached non-living space can be converted, but not a freestanding building. It can be up to 500 sq ft and needs cooking facilities (appliances, a food prep counter, refrigeration and storage) and either its own bathroom or a shared one. An attached ADU or JADU needs its own exterior entrance.

Owner occupancy conflict. Riverside's code (and its FAQ) allows a JADU only if the owner lives in the house or the JADU, recorded in a deed restriction that also bars selling the JADU separately. Under 2025 changes to state law (in effect by January 1, 2026), HCD says owner occupancy is required only if the JADU shares a bathroom with the house. Ask Planning which rule the city is applying before you record anything. More in our junior ADU guide. [1][4][6]

Renting, selling and lot splits

Renting. ADUs and MADUs can be rented separately from the house, and you don't have to live on the property. Any ADU, MADU or JADU that is rented must be rented for more than 30 days, so vacation rentals aren't allowed.

Selling. An ADU can't be sold separately from the house, except when the house and ADU were developed by a 501(c)(3) housing nonprofit or faith-based organization working with the Housing Authority to provide homes to low-income households.

Lot splits (SB 9). Two-unit developments are allowed in the R-1, RE, RR, RC, DSP-RES and NSP-MDR zones. An undivided single-family lot can have up to four homes in total, including up to two ADUs and JADUs. A lot created by an urban lot split can have up to two homes of any kind, including ADUs. Units built under these rules must be rented for more than 30 days, and unless the lot came from an urban lot split, the owner must live in one of the units. See our SB 9 guide. [1][4][9]

Permit steps in Riverside

1. Confirm you're in the city and check your zone

   Make sure your address is in the City of Riverside, not unincorporated Riverside County, and check your zoning and any historic designation with the Planning Division through the One Stop Shop. [2][5]

2. Choose custom or permit-ready plans

   Hire a licensed design professional for custom plans, or use a Dwell Riverside permit-ready plan if your single-family lot qualifies. For permit-ready plans, submit the Planning ADU eligibility and clearance form. [2][3][4][7]

3. Get a Certificate of Appropriateness if historic

   If the property is a cultural resource, is in a historic district, or contributes to a neighborhood conservation area, the ADU must meet the city's historic ADU design standards and needs a Certificate of Appropriateness. [8]

4. Apply on the Public Permit Portal

   Create an account on the Public Permit Portal and upload your plans and forms (for permit-ready plans: the plan set with completed T1.1, preliminary site plan, hold harmless agreement and clearance form). [2][3]

5. Review and conditions

   Each department reviews the application. When review is done you get an email, and you download a conditions report from the portal that explains what's still needed, including visits to the One Stop Shop. [2]

6. Record the JADU deed restriction if needed

   For a junior ADU, the city requires a recorded deed restriction barring separate sale and stating the owner-occupancy rule. Confirm the wording with Planning, since state law on JADU owner occupancy changed in 2025. [1][6]

7. Pay fees and get the permit

   Once all conditions are met and fees are paid in full, the building permit is issued and you can download the approved plans. [2]

Pre-approved and sample plans

• Dwell Riverside permit-ready ADU plans

  Four pre-reviewed single-story detached plans (746 to 1,200 sq ft) in Craftsman, Ranch and Spanish styles, with a 3-business-day first plan review. [2][3]

Who to call

• City of Riverside One Stop Shop (Community & Economic Development)

  Planning and Building & Safety questions, ADU eligibility and fees (CDDINFO@riversideca.gov)

  951-826-5800

  City Hall, 3900 Main Street, 3rd Floor, Riverside, CA 92522

  [3][4]

• City of Riverside Building & Safety Division

  Plan check, permits and inspections (B&SInfo@RiversideCA.gov)

  (951) 826-5697

  3900 Main Street, 3rd Floor, Riverside, CA 92522

  [5]

Questions people ask