Building an ADU in unincorporated Sacramento County

Unincorporated areas only

Sacramento County's zoning rules for ADUs apply only on land outside city limits. The county's ADU standards ask you first to confirm that your property is in the unincorporated area, using the county's General Map.

If your address is inside a city, follow that city's ADU rules instead. We have pages for the City of Sacramento and Elk Grove. For the statewide rules every city and county must follow, see our California page. [1]

What you can build

Any property developed with a primary residential use may have ADUs. The rules are in Sacramento County Zoning Code Section 5.4.5.B, Table 5.11, which the county's Planning and Environmental Review (PER) division reproduces in its ADU and JADU zoning standards (version 8, effective May 21, 2025).

Single-family homes and halfplexes. You can have up to three units in addition to the house:

• one new detached ADU,
• one junior ADU (JADU), and
• one of these three: a new attached ADU, an ADU converted from space in the house, or an ADU converted from a detached building.

Multifamily properties. You can build up to two new detached ADUs, and convert non-living space (storage rooms, attics, basements, garages and similar) into ADUs, up to 25% of the units or one unit, whichever is greater. A property that was multifamily as of January 1, 2025 can instead have up to eight new detached ADUs, but no more than its number of existing units, in addition to conversions.

What isn't an ADU. A guest house with no kitchen is not an ADU. A "Second Dwelling Unit" is a separate category allowed only on lots eligible for SB 9, and it pays full impact and affordable housing fees. RVs and other "homes on wheels" can't be used as dwellings outside a permitted mobile home park; every ADU needs a permanent foundation. [1]

Size, height and setbacks

Size. Every ADU or JADU must be at least 150 sq ft, and the county says it can never be larger than the main house. State law says size limits, including ones based on the size of the house, can't keep you from building at least an 800 sq ft ADU with 4 ft side and rear setbacks, so if your house is small, confirm with PER.

• New detached ADU: up to 1,200 sq ft, with no increases allowed.
• New attached ADU: the greater of 50% of the house's habitable floor area, 850 sq ft for a studio or one bedroom, or 1,000 sq ft for two or more bedrooms.
• Converted space: the size of the existing permitted space, plus 150 sq ft for an entrance.

Height. A detached ADU can be 16 ft to the peak by default, or 18 ft on a multifamily property. It can go to 20 ft if you keep a 10 ft rear setback and 5 ft side setbacks. It can go to 18 ft with a Planning Director's determination if it is within a half mile of a major transit stop or needs the height to match the house's roof pitch. State law says a local agency can't set a height limit below 18 ft, plus 2 ft to match the house's roof pitch, for a detached ADU within a half mile walking distance of a major transit stop or high-quality transit corridor. If your lot may qualify, confirm with PER which process applies. An attached ADU can be 25 ft or the house's height limit, whichever is less.

Stories. The county limits a new detached ADU to one story; a second story needs a Minor Special Development Permit. Attached ADUs can be two stories. State law says a local agency must allow at least two stories if they fit under the applicable height limit and meet building standards, so confirm a two-story detached plan with PER.

Setbacks for new construction. Side and rear: 4 ft. Front: 20 ft. Street side on a corner lot: 12.5 ft. Special planning areas and planned developments may set their own front and street-side setbacks. Setbacks are measured from the wall, and roof overhangs can extend up to 24 inches into them. If you are less than 5 ft from a property line or another building, fire walls or limits on windows may be required. Converted space can stay at its originally permitted setbacks.

If you can't fit the standard. The Planning Director can approve smaller front or street-side setbacks when needed to fit an ADU of up to 800 sq ft. That request is a Planning Director Determination, which the county says costs $495.33 and takes about four weeks. [1][3]

Parking

The county requires one parking space for an ADU, except that none is needed when:

• the ADU is within a half mile walking distance of public transit,
• it is in an architecturally and historically significant historic district,
• it is part of the house or an existing accessory building,
• on-street parking permits are required but not offered to the ADU's occupant,
• a car share vehicle is located within one block,
• it is a new detached ADU of 800 sq ft or less, or
• it is on a multifamily property.

You don't have to replace parking when a garage, carport or parking space is torn down or converted to build an ADU. JADUs never need parking under state law. [1][3]

Fees

The county says ADU fees are project specific and can vary a lot. They can come from the county and from other agencies, such as SMUD, water districts and local fire departments. Expect building permit fees and development impact fees.

Impact fees. State law bars impact fees on an ADU with 750 sq ft of interior livable space or less, and requires any impact fee on a larger ADU to be charged in proportion to the ADU's size compared with the main house. The county's Shelf Ready program likewise notes that ADUs over 750 sq ft are subject to impact fees. For an estimate, send a calculation request to the county's Site Improvement and Permits Section; see the development impact fees page or call (916) 874-6544.

School and utility fees. ADUs and JADUs under 500 sq ft of interior livable space are not subject to school impact fees. Utilities can't treat an ADU or JADU as a new residential use when calculating connection fees or capacity charges, unless it is built at the same time as a new single-family home. Where a connection fee or capacity charge does apply, it must be proportionate to the ADU's size or plumbing fixtures compared with the house.

For building permit fees, call Building Permits and Inspection at (916) 875-5296. For typical costs see our ADU cost guide. [1][2][3][4]

How long it takes

Under state law, the county must tell you within 15 business days whether your application is complete, and approve or deny a complete ADU application within 60 days when there is an existing home on the lot.

Optional extra steps take longer. A Planning Director Determination for a minor setback or height deviation takes about four weeks. A Minor Special Development Permit, for deviations of up to 25% from other standards, runs about $1,337.60 and three to four months. See our ADU permit process guide. [1][3]

Garage conversions and junior ADUs

Converting a garage or other building. You can convert existing permitted space into an ADU, adding up to 150 sq ft for an entrance. The building can stay where it is, but any added entry must meet new-construction setbacks. Converting an accessory building counts as a change of use, so it needs a building permit and must be brought up to current residential building standards. You don't have to replace the lost parking. See our garage conversion guide.

Junior ADUs. A JADU is up to 500 sq ft inside the house, which can include an attached garage or storage area, plus 150 sq ft for an entrance. It needs at least an efficiency kitchen and its own exterior entrance. If it shares a bathroom with the house, it must also have an interior door into the house. The county says the owner must live in the house or the JADU, unless the owner is a government agency, land trust or housing organization. State law now requires owner occupancy only when the JADU shares sanitation facilities with the house, so confirm with PER if your JADU has its own bathroom. You must record a deed restriction that bars selling the JADU separately from the house. See our junior ADU guide. [1][3]

Renting it out and short-term rentals

State law bars owner-occupancy requirements for ADUs, so you can rent out both the ADU and the house. Owner occupancy can apply only to JADUs.

An ADU can't be used as a short-term rental unless it was a legally permitted ADU before January 1, 2020. JADUs and guest houses can never be used as short-term rentals.

SB 9. ADUs and JADUs can be combined with SB 9 projects, but the county caps an existing lot at four units in total, ADUs and JADUs included. With an SB 9 lot split, the cap is four units across both new lots. See our SB 9 guide. [1][3]

Shelf Ready ADU plans

Through a state Local Early Action Planning (LEAP) grant, the county offers free detached ADU plans to residents of the unincorporated area only. There are five models: Laurel and Willow (460 sq ft studio or one bedroom), Redwood (870 sq ft, two bedrooms), Elderberry (1,000 sq ft, two bedrooms) and Magnolia (1,184 sq ft, three bedrooms). Building Permits and Inspection has plan checked them to the 2022 California codes. Download them from the Shelf Ready ADU Program page.

The plans can't be changed beyond adding outlets, lights or switches and the floor plan options provided; you choose exterior colors and interior finishes. The Redwood, Elderberry and Magnolia models need a solar (PV) system, with plans you provide and a separate permit. Standard building fees still apply, and you must also submit to your local fire district, which may charge its own fees. [2]

Permit steps in Sacramento County

1. Confirm you are in the unincorporated county

   Look up your parcel on the county's General Map. If you are inside a city, that city handles your ADU. [1]

2. Check the zoning standards

   Read the county's ADU and JADU zoning standards. To verify setbacks for your lot, email PER at sacplan@saccounty.gov. [1][2]

3. Choose plans

   Use one of the county's free Shelf Ready ADU plans or have custom plans drawn. Shelf Ready applicants also prepare a scaled plot plan, PV plans for the larger models, and a Hold Harmless Agreement. [1][2]

4. Get an impact fee estimate

   Request a development impact fee calculation from the Site Improvement and Permits Section through the development impact fees page. [1][4]

5. Apply online for a building permit

   Submit through the county's online permit portal. For a Shelf Ready plan, put the model name in the description (for example, A1-Laurel). [2]

6. Get fire district review

   Submit to the fire jurisdiction for your area, which may require its own review, permit and fees. [1][2]

7. Build and pass inspections

   For Shelf Ready plans that need solar, the PV plans must be approved and issued before the rough frame inspection. [2]

Pre-approved and sample plans

• Shelf Ready ADU Program

  Five free, plan-checked detached ADU designs from 460 to 1,184 sq ft for unincorporated Sacramento County; standard building fees apply. [2]

Who to call

• Sacramento County Planning and Environmental Review

  ADU zoning rules, setbacks and deviation requests (email sacplan@saccounty.gov)

  [1]

• Sacramento County Building Permits and Inspection

  Building permits, Shelf Ready ADU plans and inspections; Building Assistance Center at 9800 Goethe Road

  916-875-5296

  9800 Goethe Road, Sacramento, CA 95827

  [2][5]

• Site Improvement and Permits Section (County Engineering)

  Development impact fee estimates

  (916) 874-6544

  827 7th Street, Room 102, Sacramento

  [4]

Questions people ask