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Can I build an ADU in Danville, California?

Danville, Contra Costa County · Ordinances checked 2026-10-05 · Reviewed · 16 cited sections

Allowed with a permit

Yes. Danville allows ADUs and junior ADUs on residential lots through a staff-level (ministerial) building permit review, with up to three extra units per single-family lot. A detached ADU can be up to 1,200 sq ft (2,000 sq ft in districts with 40,000 sq ft minimum lots), 16 feet tall with 4-foot side and rear setbacks, and the owner doesn't have to live on site.

Review processMinisterial (staff review) if standards are met [1]
Where allowedAny residential or mixed-use district [2]
Max units added to a single-family lot3 (attached ADU + JADU + detached ADU up to 800 sq ft) [3]
Max size, detached ADU1,200 sq ft; 2,000 sq ft in 40,000+ sq ft lot districts [4]
Max size, attached ADU1,200 sq ft (2,000 in large-lot districts) and no more than 50% of the house [5]
Side/rear setback4 feet [6]
Max height, detached ADU16 ft (24 ft if it meets primary-home setbacks) [7]
Max height, attached ADU25 ft [8]
Junior ADU sizeUp to 500 sq ft inside the house [9]
Owner occupancyNot required for ADU; required for JADU under local code (state law may limit this) [10]
Parking1 space, with exemptions (e.g., within 1/2 mile of transit) [11]
RentalsTerms longer than 30 days only [12]

Where and how

Danville's ADU ordinance (Sec. 32-76, as amended by Ord. 2025-04) allows ADUs and junior ADUs (JADUs) in any residential or mixed-use district [2]. Units that meet the ordinance's standards get ministerial (staff-level) review [1]; units that don't meet them go through an administrative review with neighbor notice. Any attached or detached ADU of 800 sq ft or less is allowed on residentially zoned land and is subject only to the state's limited standards [13].

How many and how big

On a single-family lot you can add up to three units: an attached ADU built from existing or proposed floor space, one JADU, and one detached ADU of no more than 800 sq ft [3]. A detached ADU can be up to 1,200 sq ft in districts with lots under 40,000 sq ft, and 2,000 sq ft in R-40, R-65 and R-100 districts [4]. Attached ADUs have the same caps but can't exceed 50% of the house's conditioned area, though an 850 sq ft unit (1,000 sq ft with more than one bedroom) is always allowed [5]. A JADU is up to 500 sq ft inside the house [9]. Converting existing space in the house or an accessory structure isn't subject to the setback, height or size limits [15].

Setbacks and height

Side, rear and secondary-front setbacks are 4 feet, and the front setback is the same as for the house [6]. Detached ADUs can be 16 feet tall, or 24 feet if they meet the primary home's setbacks [7]; attached ADUs can be 25 feet [8]. The exterior must match the house's paint colors, siding and roof materials [14].

Occupancy, parking and rentals

The owner doesn't have to live in the house or the ADU; for a JADU the owner must live on site and record a deed restriction [10]. State law now lets cities require owner-occupancy only for a JADU that shares a bathroom with the house, so state law may override this rule for a JADU with its own bathroom. One parking space is required unless an exemption applies, such as being within half a mile of transit or inside the house [11]. ADUs and JADUs may only be rented for more than 30 days [12].

Older code text

The 2019 printout of the single-family zoning chapter still lists ADUs only up to 1,000 sq ft as allowed uses [16]; the 2025 ADU ordinance (Sec. 32-76) sets the current size limits.

Coming in 2027

Starting January 1, 2027, state law (AB 956) will require cities to approve two new detached ADUs on a single-family lot, which may override Danville's limit of one detached ADU in the three-unit combination.

See how Danville compares with 8+ other California towns on accessory dwelling units (adus) →

Next steps

  1. Optionally meet with the Danville Planning Division (925-314-3310, 500 La Gonda Way) to discuss attached vs. detached and placement.
  2. Submit a building permit application with complete plans; a lot survey is required if setbacks under 5 feet are proposed.
  3. Expect ministerial review by Planning, Building and (if grading is involved) Engineering, plus EBMUD, Central San and San Ramon Valley Fire sign-offs.
  4. For a JADU, record the owner-occupancy deed restriction and give the Town confirmation before the permit is issued.

Common questions

Can I build an ADU in Danville, California?
Yes. Danville allows ADUs and junior ADUs in any residential or mixed-use district. Units that meet the ordinance's standards get ministerial, staff-level review through a building permit; units that don't meet them go through an administrative review with neighbor notice.
How big can an ADU be in Danville, California?
A detached ADU can be up to 1,200 sq ft in districts with lots under 40,000 sq ft, and 2,000 sq ft in R-40, R-65 and R-100 districts. Attached ADUs have the same caps but can't exceed 50% of the house, though an 850 sq ft unit (1,000 sq ft with more than one bedroom) is always allowed. A JADU can be up to 500 sq ft.
How many ADUs can I have on my lot in Danville, California?
On a single-family lot you can add up to three units: an attached ADU, one JADU, and one detached ADU of no more than 800 sq ft. Starting January 1, 2027, state law (AB 956) will require cities to approve two new detached ADUs on a single-family lot, which may override Danville's limit.
What are the ADU setbacks and height limits in Danville, California?
Side, rear and secondary-front setbacks are 4 feet, and the front setback is the same as for the house. Detached ADUs can be 16 feet tall, or 24 feet if they meet the primary home's setbacks; attached ADUs can be 25 feet.
Do I have to live on site or provide parking for an ADU in Danville, California?
The owner doesn't have to live on site for an ADU. For a JADU the local code requires it, though state law may override that for a JADU with its own bathroom. One parking space is required unless an exemption applies, such as being within half a mile of transit. ADUs may only be rented for more than 30 days.

California's statewide ADU law

California's ADU law (Gov. Code §§66310–66342, recodified from §65852.2; latest amendments effective January 1, 2026) overrides conflicting city rules, including in charter cities. Cities must approve ADUs ministerially (no hearing) within 60 days of a complete application, or the permit is deemed approved.

What cities cannot require or do:

  • Owner-occupancy for an ADU.
  • A minimum lot size.
  • Side or rear setbacks over 4 feet for a new ADU, or any setback for a converted existing structure.
  • Size, lot coverage or floor-area rules that block an ADU of at least 800 sq ft. Size caps can't be under 850 sq ft (1,000 for 2+ bedrooms).
  • Parking within half a mile walking distance of public transit, or replacement parking for a garage converted to an ADU.
  • Impact fees on ADUs of 750 sq ft or less.

By right on a single-family lot: one converted ADU plus one junior ADU (JADU, up to 500 sq ft inside the house), plus one new detached ADU (up to 800 sq ft, 16 ft tall). Owner-occupancy may be required only for a JADU that shares a bathroom.

Short-term rentals: cities may bar ADU rentals under 30 days, and must for by-right ADUs, JADUs and SB 9 units.

Coming January 1, 2027: AB 956 raises the by-right count to two new detached ADUs per single-family lot.

SB 9 (§§65852.21, 66411.7) allows two homes on a single-family lot, or a split into two lots of at least 1,200 sq ft (with a 3-year owner-occupancy affidavit).

State sources: Gov. Code §66314 (ADU ordinance standards) · Gov. Code §66315 (no owner-occupancy requirement) · Gov. Code §66317 (ministerial review, 60-day deadline) · Gov. Code §66321 (size, setback and height limits on local rules) · Gov. Code §66322 (parking exemptions) · Gov. Code §66323 (by-right ADUs and JADUs) · Gov. Code §66333 (junior ADUs) · Gov. Code §66311.5 (impact fees) · AB 956 (2026), Stats. 2026, ch. 791 · Gov. Code §65852.21 (SB 9 two-unit projects) · Gov. Code §66411.7 (SB 9 urban lot splits) · HCD, Accessory Dwelling Units (ADU Handbook, updated March 2026)

What the ordinance says

Exact text from Danville's published ordinances. Section numbers are as printed in the source.

  1. Sec. 32-76.3(a), Municipal Code Sec. 32-76 Accessory Dwelling Units (as amended by Ord. 2025-04), p. 2
    Accessory dwelling units and junior accessory dwelling units which are consistent with the development and design standards contained within this section shall be subject to the Town's ministerial review process.
  2. Sec. 32-76.4(a), Municipal Code Sec. 32-76 Accessory Dwelling Units (as amended by Ord. 2025-04), p. 2
    Accessory dwelling units and junior accessory dwelling units shall be allowed in any residential or mixed-use General Plan land use district.
  3. Sec. 32-76.7(e)(2), Municipal Code Sec. 32-76 Accessory Dwelling Units (as amended by Ord. 2025-04), p. 3
    For three (3) additional units, an attached accessory dwelling unit constructed from existing or proposed floor space subject to the size restrictions under subsection 32-76.6.d, one (1) junior accessory dwelling unit, and one (1) detached accessory dwelling unit not exceeding eight hundred (800) square feet.
  4. Sec. 32-76.7(d), Municipal Code Sec. 32-76 Accessory Dwelling Units (as amended by Ord. 2025-04), p. 3
    For residential zoning districts allowing a maximum lot size less than forty thousand (40,000) square feet, the maximum size shall be one thousand two hundred (1,200) square feet. For lots that are within a zoning district requiring a minimum forty thousand (40,000) square foot lot size or larger, the maximum size shall be two thousand (2,000) square feet.
  5. Sec. 32-76.6(d), Municipal Code Sec. 32-76 Accessory Dwelling Units (as amended by Ord. 2025-04), p. 2
    For residential zoning districts allowing a maximum lot size less than forty thousand (40,000) square feet, the maximum size shall be one thousand two hundred (1,200) square feet, but shall not exceed fifty percent (50%) of the conditioned square footage of the existing or proposed primary residence. However, a minimum of eight hundred fifty (850) square foot or one thousand (1,000) square foot accessory dwelling unit with more than one (1) bedroom shall be allowed. For lots that are within a zoning district requiring a minimum forty thousand (40,000) square foot lot size or larger, the maximum size shall be two thousand (2,000) square feet, but shall not exceed fifty percent (50%) of the conditioned square footage of the existing or proposed primary residence.
  6. Sec. 32-76.7(a), Municipal Code Sec. 32-76 Accessory Dwelling Units (as amended by Ord. 2025-04), p. 3
    Setbacks, secondary front yard, side yard, and rear yard. Four (4)-foot minimum setback to the property line, measured to the closest part of the structure, including eves and other architectural projections.
  7. Sec. 32-76.7(c), Municipal Code Sec. 32-76 Accessory Dwelling Units (as amended by Ord. 2025-04), p. 3
    Height. The maximum height shall be sixteen (16) feet. If located within one-half (½) mile walking distance of a major transit stop or high quality transit corridor, the maximum height shall be eighteen (18) feet, with an allowance of two (2) additional feet (total maximum height of 20 feet) to accommodate roof pitch aligned with the primary dwelling unit. If the accessory dwelling unit maintains the minimum setbacks applicable to the primary residence, the maximum height shall be twenty-four (24) feet.
  8. Sec. 32-76.6(c), Municipal Code Sec. 32-76 Accessory Dwelling Units (as amended by Ord. 2025-04), p. 2
    Height. The maximum height shall be twenty-five (25) feet. If the accessory dwelling unit maintains the minimum setbacks applicable to the primary residence, the maximum height shall be the height applicable to the primary residence.
  9. Sec. 32-76.2(h), Municipal Code Sec. 32-76 Accessory Dwelling Units (as amended by Ord. 2025-04), p. 1
    Junior accessory dwelling unit shall be defined as a unit that is no more than five hundred (500) square feet in size and contained entirely within the floor space of an existing or proposed residence.
  10. Sec. 32-76.12, Municipal Code Sec. 32-76 Accessory Dwelling Units (as amended by Ord. 2025-04), p. 4
    a. The property owner is not required to occupy either the primary residence or an accessory dwelling unit. b. For a junior accessory dwelling unit, the property owner must occupy either the remaining portion of the structure or the newly created junior accessory dwelling unit.
  11. Sec. 32-76.14(a), Municipal Code Sec. 32-76 Accessory Dwelling Units (as amended by Ord. 2025-04), p. 5
    Except for the circumstances listed below, one (1) off-street parking space shall be provided for all new accessory dwelling units: 1. The accessory dwelling unit is located within one-half (½) mile walking distance of public transit.
  12. Sec. 32-76.16, Municipal Code Sec. 32-76 Accessory Dwelling Units (as amended by Ord. 2025-04), p. 5
    If an accessory dwelling unit or junior accessory dwelling unit is rented, it shall be rented for terms longer than thirty (30) days.
  13. Sec. 32-76.13, Municipal Code Sec. 32-76 Accessory Dwelling Units (as amended by Ord. 2025-04), p. 5
    Any attached or detached accessory dwelling unit which is eight hundred (800) square feet or less in size shall be allowed on lands zoned to allow or conditionally allow residential use.
  14. Sec. 32-76.5(e), Municipal Code Sec. 32-76 Accessory Dwelling Units (as amended by Ord. 2025-04), p. 1
    Architectural compatibility will be determined to exist where the accessory dwelling unit incorporates similar paint colors, siding, and roof materials as the primary residence.
  15. Sec. 32-76.11(a), Municipal Code Sec. 32-76 Accessory Dwelling Units (as amended by Ord. 2025-04), p. 4
    The conversion or reconstruction in the same location within the dimensions of existing floor space within a single family residence or detached accessory structure to an accessory dwelling unit shall not be subject to setback height or size requirements under subsections 32-76.6 and 32-76.7.
  16. Sec. 32-22.3(a)(15), Municipal Code Sec. 32-22 Single Family Residential Districts (printed 11/15/2019, with illustrations), p. 7
    15. Accessory dwelling units that have one thousand (1,000) square feet or less of conditioned living space and comply with Section 32-76 (Accessory Dwelling Unit Ordinance);
This page summarizes Danville's posted ordinances as of 2026-10-05. Ordinances are amended, and individual lots can have overlays, subdivision covenants, or HOA rules that are stricter. Confirm with Development Services - Building Division / Code Enforcement, 500 La Gonda Way (925-314-3330 (Building); Code Enforcement 925-314-3361) before you build. Spot an error?