Building an ADU in the City of Davis

What you can build here

Davis's ADU rules are in Municipal Code Section 40.26.450. The city rewrote it with Ordinance 2693, dated September 1, 2026. The section says that where it conflicts with state law, "state law shall prevail."

The city's ADU webpage still says that "Since the last update to the City's ADU requirements in 2021, certain City zoning regulations in Chapter 40 may be different due to State updates to ADU laws." That note predates the September 2026 update, so rely on the current code and confirm with the city.

Davis has two ministerial (no-hearing) paths:

• Building permit only. ADUs and junior ADUs that meet state Gov. Code 66323 need only a building permit and are exempt from the local standards below. On a single-family lot, state law lets you combine one converted ADU, one junior ADU and one new detached ADU of up to 800 sq ft with 4 ft side and rear setbacks. On a lot with an existing apartment building, it allows up to eight detached ADUs (no more than the existing units) and conversions of non-living space. See our California page.
• Local standards. Other ADUs follow the city's own size, height, setback and design rules. One ADU is allowed under this path on a lot zoned for single-family or multifamily use with a proposed or existing home.

ADUs that meet neither path may be approved as "non-ministerial" ADUs with an administrative use permit, which requires the director to make findings.

Every ADU also needs a building permit. ADUs don't count toward the lot's density limit. For lot splits, see our SB 9 lot split guide. [1][2][3]

Size, height and setbacks

Local-standards ADUs:

• Attached ADU: up to 50% of the gross floor area of the existing house.
• Detached ADU: up to 850 sq ft of interior livable space with zero or one bedroom, or 1,000 sq ft with two or more bedrooms. Minimum 150 sq ft.
• Height: 18 ft for a detached ADU (including 2 ft for roof pitch); 25 ft or the zone's limit for the house, whichever is lower, for an attached ADU. An attached ADU can be a second story on the house or over the garage.
• Setbacks: 4 ft from side and rear lot lines for new ADUs; none for an ADU inside an existing structure or rebuilt in the same place and size. Front setbacks apply unless they would prevent an 800 sq ft ADU.
• Separation: a detached ADU must be at least 5 ft from the house, unless that would prevent an 800 sq ft ADU.
• Lot coverage, floor area ratio and open space: the zone's rules apply, but no local standard may block an ADU of at least 800 sq ft with 4 ft side and rear setbacks.

Building-permit-only ADUs under Gov. Code 66323(a)(4) may be 18 ft tall plus 2 ft for roof pitch.

Non-ministerial ADUs (administrative use permit): up to 1,200 sq ft and 30 ft tall, with 5 ft interior side and 10 ft rear setbacks (3 ft next to an alley, park or greenbelt), 50% maximum lot coverage and 20% usable open space.

Design (local standards). The ADU must have the same roof pitch as the house, give or take 2/12, with matching eave details, and a separate exterior entrance. On historic or conservation-overlay properties it can't require changes to the street-facing facade, and ADUs that could affect a California Register property must follow the federal Secretary of the Interior's Standards.

Confirm the standards for your lot with Community Development at (530) 757-5610. [1][4]

Parking

Davis's code says: "No additional vehicle parking space is required for an ADU." That applies to non-ministerial ADUs too.

If you convert or demolish a garage, carport or covered parking to build an ADU, you don't have to replace those spaces as long as the ADU stays a legal ADU. State law also bars parking requirements for junior ADUs. [1][2]

Fees

The code says ADUs "that are less than seven hundred fifty square feet of interior livable space shall not be subject to impact fees," and larger ADUs "shall be charged impact fees that are proportional in relation to the square footage of the primary dwelling unit." State guidance says the exemption covers ADUs of "750 square feet of interior livable space or less," so ask the city before designing at exactly 750 sq ft.

Utility connections. An ADU may use the house's water and sewer connections. For a new ADU that isn't a conversion, the city may require a separate utility connection, with a connection fee or capacity charge proportionate to the ADU's burden.

Monthly bills. The city's Cost of Building an ADU handout says four charges on your utility bill go up once the ADU is finaled: the municipal service tax, public safety charge, sanitation and sewer. In the city's example the monthly bill rose by $59.06. Rates change, so check the city's current utility rates.

State guidance says school districts may charge ADUs over 500 sq ft, and ADUs under 500 sq ft of interior livable space are not subject to school impact fees. Building permit fees are set when staff process your application. See our ADU cost and ADU financing guides. [1][2][4][5]

How long it takes

The code says the director reviews and approves a complete ADU permit application ministerially, with no public hearing, within the timelines in state Gov. Code 66317.

For building permits, the city's Building Division says "Typical processing times vary between 20 and 35 business days from the date of submittal," and applications are reviewed in the order received.

State law says a city must tell you within 15 business days whether your application is complete, and must approve or deny a complete ADU application within 60 days when there is already a home on the lot. See our ADU permit process guide. [1][2][4]

Pre-designed and pre-approved plans

The city runs a program, under state law AB 1332, where designers can have ADU plans plan-checked by the city at their own cost. Once accepted as a "master plan," the designs are posted on the city's ADU webpage. The city says those posted plans are "for reference only" and are not construction drawings; owners can view the elevations and floor plans, and review time is shorter because the plans were already checked. Each project still needs site plan review by Planning before a building permit.

The city also offers free Pre-Designed ADU Plans in three sizes: a 300 sq ft studio, a 565 sq ft one-bedroom and a 740 sq ft two-bedroom, each in Adobe, Agrarian or Mid-Mod style. The city says they were plan-checked in advance, so review is quicker and plan check fees are reduced, but changes to the plans are not accepted. To get the official plan set, you submit a site plan and a signed Hold Harmless and Indemnification Agreement in person at Community Development. The city says a California licensed general contractor is required before the building permit is issued for these plans. [3][6]

Garage conversions and junior ADUs

You can convert a garage or other existing structure into an ADU. No new setback is required inside the existing structure, and you don't have to replace the lost parking. If a garage conversion goes through the non-ministerial (use permit) path, the garage door must be removed and replaced with walls, windows and trim that match the house. See our garage conversion guide.

A junior ADU (JADU) can be up to 500 sq ft inside a single-family home and is approved with a building permit only. Before the certificate of occupancy, you record a declaration of restrictions: the JADU can't be sold separately, can't be rented for less than 31 consecutive days, and, unless it has its own bathroom, the owner must live in the JADU or the house. That matches the state's 2026 rule. See our junior ADU guide.

Fire sprinklers. The code says ADUs and JADUs must have sprinklers if the house is required to have them. Building an ADU doesn't trigger sprinklers in an existing apartment building.

Guest houses are different: living space in an accessory building with no kitchen, which can't be rented as a separate home. [1][2][3]

Renting or selling your ADU

ADUs and JADUs approved with a building permit only "shall be rented only for terms longer than thirty days." Ask the city about rental rules for local-standards ADUs.

State law bars cities from requiring owners to live on a property because it has an ADU. An ADU can be sold separately from the house only under the state's nonprofit, affordable-housing exception (Gov. Code 66341), which the Davis code spells out.

The code also says the city won't deny an ADU because of a nonconforming zoning condition, building code violation or unpermitted structure on the lot that doesn't threaten health and safety. An ADU may raise your property taxes; see our ADU property tax guide. [1][2]

State review of Davis's ADU rules

On October 8, 2025, the state housing agency (HCD) sent Davis a letter of technical assistance. It said the most recent ADU ordinance HCD had on file for the city was from 2019 and "may be outdated and out of compliance with State ADU Law," and asked for a response by November 7, 2025.

The city's code shows ADU amendments in 2020 and 2021 and a rewrite by Ordinance 2693 on September 1, 2026. We did not find an HCD review of the 2026 ordinance. [1][7]

Permit steps in Davis

1. Choose your path

   Decide whether your ADU fits the state's building-permit-only combinations or the city's local standards in Section 40.26.450. Ask Community Development at (530) 757-5610 if unsure. [1][4]

2. Design the ADU

   Hire a designer or check the city's ADU webpage for plans already checked by the city. Planning reviews the site plan for each project. [3]

3. Apply

   Download the building forms, then email the application and documents to OnlinePermits@cityofdavis.org. Owner-builders may apply. Staff contact you with timelines, any extra documents and fees. [4]

4. Plan review

   Applications are reviewed in the order received, typically in 20-35 business days. [4]

5. Pay fees and get the permit

   Fees of $1,000 or less can be paid online with your permit number; otherwise pay by check. For a junior ADU, record the declaration of restrictions before the certificate of occupancy. [1][4]

6. Build and pass inspections

   Schedule inspections with the Building Division. Once the ADU is finaled, your city utility charges will increase. [4][5]

Pre-approved and sample plans

• City Pre-Designed ADU Plans

  Free city plans (300 sq ft studio, 565 sq ft one-bedroom, 740 sq ft two-bedroom) in three styles, with quicker review and reduced plan check fees; no changes allowed, and a licensed contractor is required. [6]

Who to call

• Community Development and Sustainability, Building Division

  Building permits, plan review and inspections; email OnlinePermits@cityofdavis.org or cddweb@cityofdavis.org

  (530) 757-5610

  23 Russell Blvd, Suite 2, Davis, CA 95616 (8 a.m. to 4 p.m.)

  [4]

Questions people ask