Danville Zoning and ADU Guide for Homeowners

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Last updated November 13, 2026. Reviewed by the Cash Home Buyers CA team.

Danville regulates accessory dwelling units in Municipal Code chapter 32-76, most recently amended by Ordinance 2025-04, and its ADU FAQ says up to three units can be added to a single-family lot: an attached or converted ADU, a junior ADU and a detached ADU of up to 800 square feet. This guide summarizes the Town’s published rules for homeowners: unit counts, size, setbacks, height, parking, owner occupancy, rentals and what happens when you sell a house that already has a second unit. Confirm the current text with the Planning Division before you design anything.

Danville ADU rules at a glance

Code	Danville Municipal Code section 32-76, Accessory Dwelling Units (amended by Ordinance 2025-04)
Units allowed	Up to three units added to a single-family lot: one attached or converted ADU, one junior ADU and one detached ADU not over 800 square feet
JADU size	Up to 500 square feet, created from existing floor space
ADU size	Up to 1,200 square feet where the zoning district’s minimum lot size is under 40,000 square feet, and up to 2,000 square feet above that; attached units may not exceed 50 percent of the primary home
Setbacks	Front setback as required by the zoning district; side and rear setbacks of 4 feet if the unit sits back from the front line by the district minimum
Height	Detached: 16 feet with reduced setbacks or 24 feet if the unit meets the primary home’s setbacks; attached: up to 25 feet or the primary home’s height
Parking	One added space generally required, with exceptions such as transit within a half mile or a converted garage
Owner occupancy	None required for ADUs; required for a JADU, recorded by deed notice
Rentals	Terms of 30 days or more only; short-term rentals are prohibited
Contact	Planning Division, (925) 314-3310, planning@danville.ca.gov

How many units you can build

On a lot with a single-family home, the Town’s FAQ allows up to three units in addition to the primary residence: an attached ADU built within a proposed new home or converted from existing space, one junior ADU and one detached ADU not exceeding 800 square feet.

State law separately gives owners the right to build an ADU of at least 800 square feet, and the Town’s ordinance says setbacks are reduced to the extent needed to allow an 800 square foot unit.

Multifamily lots have their own limits, including at least one attached ADU and up to 25 percent of existing units, and up to two or up to eight detached ADUs depending on the lot.

Size, setbacks and height

A junior ADU is capped at 500 square feet. A full ADU can reach 1,200 square feet in districts with lots under 40,000 square feet and 2,000 square feet in larger-lot districts, but an attached unit cannot exceed half of the primary home. A garage attached to a detached ADU does not count against the ADU’s square footage and can be up to 20 by 22 feet.

The Town’s table sets front yard setbacks by zoning district, for example 20 feet for the R-6 through R-15 districts and 25 feet for R-20 through R-65, with larger figures for R-100. Side and rear setbacks are 4 feet when the unit meets those front setbacks.

Setbacks are measured to the furthest projecting feature, including eaves and gutters. An ADU built in the same place and size as an existing nonconforming structure such as a detached garage does not have to meet the side and rear setbacks.

Detached ADUs are limited to 16 feet in height with the reduced setbacks, or 24 feet if they meet the primary home’s setbacks.

Parking, owner occupancy and rentals

One added parking space is required unless an exception applies.

The Town lists exceptions including a location within a half mile walk of public transit, a historic district, a unit that is part of the existing home or an accessory structure, and a garage or carport demolished or converted for the ADU.

The ADU has no owner-occupancy requirement, but a junior ADU does: the owner must live in either the remaining home or the JADU, and a deed notification recording that requirement is required. Rentals must be for terms longer than 30 days.

How the approval process works

The Town describes a six-step path. You can talk to staff first, then submit a building permit application with all required plans and documents, including a lot survey if proposed setbacks are under 5 feet.

Planning, Building and, where needed, Engineering staff review the application at staff level, you pick up the permit and pay fees when the Permit Technician contacts you, you schedule inspections during construction, and you pick up the Certificate of Occupancy at the Permit Center.

The Town also offers permit-ready ADU designs, such as a Garden Cottage plan, with an expedited review path for plans submitted in person.

Older units, garage conversions and legalization

Many older homes have a garage conversion or backyard room built without permits. Such a structure may or may not qualify under today’s rules, which are more permissive than they were when it was built.

Planning staff can tell you whether it could be approved, and the Building Division can explain which plans, corrections and inspections would be needed. That information lets you compare the cost and delay of legalizing the unit with the option of selling the house as it stands.

ADUs, garage conversions and selling a Danville house

A permitted ADU can add rental income and buyer appeal, while an unpermitted one can complicate financing and appraisal. Because an ADU generally cannot be sold separately from the main home, its value comes only through the sale of the whole property. See our unpermitted work guide and Prop 13 guide. If you own a Danville house with an old backyard unit or garage conversion:

Find out what the city has on file for each structure.
Ask whether current ADU rules would allow what is there.
Get a rough cost to correct and permit it.
Decide whether legalizing first or selling as-is fits your timeline.

How to sell a house in Danville

Check which additions, conversions and structures on the property have Town permits.
Collect permits, plans and any Town notices.
Request a no-obligation cash offer for the house as it stands.
Choose your closing date.
Close with no repairs, permit cleanup or showings required.

Our local pages cover related situations in Danville, including selling as-is, selling an inherited house and selling during a divorce. See also our Danville page and the Contra Costa County hub.

Own a Danville home with an ADU or garage conversion? Sell as-is for cash.

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Frequently asked questions

How many ADUs can I build in Danville?

On a single-family lot, the Town’s FAQ allows up to three added units: one attached or converted ADU, one junior ADU and one detached ADU of up to 800 square feet.

How big can a Danville ADU be?

A junior ADU is up to 500 square feet. An ADU can be up to 1,200 square feet in districts with lots under 40,000 square feet and up to 2,000 above that, and an attached unit cannot exceed 50 percent of the primary home.

What setbacks apply to a Danville ADU?

Side and rear setbacks are generally 4 feet, provided the unit meets the front setback for its zoning district. The Town’s table sets those front setbacks by district.

Can I rent my Danville ADU short term?

No. The Town says short-term rentals are prohibited and rentals must be for terms longer than 30 days.

Do I have to live on the property if I add an ADU?

Not for a full ADU. A junior ADU requires the owner to occupy either the home or the junior unit, recorded by a deed notification.

Can I sell my Danville house with an unpermitted ADU or garage conversion?

Yes. You can disclose it and sell as-is, including to a cash buyer. Our statewide guide explains the disclosure rules.

More guides

Sources

This guide is general information from public sources, not legal advice. Confirm current rules, fees and hours with the city.