1. Allowed Zones & Locations

• Zoning: ADUs are allowed in all zoning districts that allow single-family or multi-family dwelling residential uses.

• Lot Size: There is no minimum lot size required to build an ADU.

• Number of Units:

  • Single-Family Lots: You are generally allowed one ADU (attached or detached) AND one JADU (Junior ADU) per lot, provided specific requirements are met.

  • Multi-Family Lots: You may be allowed to convert non-livable space (like storage rooms) into at least one ADU, or build up to two detached ADUs on the lot.

2. Types of Units & Size Limits

A. Detached ADU

• Maximum Size: Up to 1,200 square feet.

• Statewide Exemption: You are guaranteed the right to build at least an 800 sq. ft. ADU, 16 feet tall, with 4-foot side and rear setbacks, regardless of other local zoning limits (like Lot Coverage or Floor Area Ratio).

B. Attached ADU

• Maximum Size: The lesser of 50% of the primary dwelling's living area OR 1,200 square feet.

• Minimum: State law prevents the city from denying an attached ADU that is at least 850 sq. ft. (or 1,000 sq. ft. for 2+ bedrooms).

C. Junior ADU (JADU)

• Definition: A unit created largely within the walls of the proposed or existing primary residence.

• Size: Maximum 500 square feet.

• Entrance: Must have a separate exterior entrance.

• Kitchen: Must have an "efficiency kitchen" (cooking facility with appliances and a food preparation counter and storage cabinets).

• Bathroom: May share a bathroom with the main house or have its own.

3. Setbacks and Height

Lafayette must comply with state maximums regarding restrictions:

• Side and Rear Setbacks: 4 feet.

• Front Setback: Subject to standard zoning, unless adhering to the front setback would prevent you from building an 800 sq. ft. unit. In that case, the front setback can be encroached upon.

• Height:

  • 16 feet: Generally allowed.

  • 18 feet: Allowed if the lot is within ½ mile of major transit or on a multi-family lot.

  • 25 feet: Often allowed for attached ADUs (to match the main house roofline) or if the ADU is above a garage.

4. Parking Requirements

• Standard Requirement: One parking space per ADU or bedroom (whichever is less).

• Parking Exemptions (Very Common in Lafayette): No parking is required if:

  • The ADU is within ½ mile walking distance of public transit (This covers a massive portion of Lafayette due to BART and bus lines).

  • The ADU is part of the proposed or existing primary residence or an accessory structure (conversion).

  • The ADU is located within one block of a car-share vehicle pick-up location.

• Replacement Parking: If you convert a garage, carport, or covered parking structure into an ADU, you do not need to replace the lost parking spaces for the main house.

5. Design & Architectural Standards

Lafayette applies "Objective Design Standards." They cannot use subjective criteria (like "neighborhood character") to deny a permit, but they can enforce specific objective rules:

• Materials: The exterior materials and colors should generally match or be compatible with the primary residence.

• Privacy: If a second-story ADU is built, the city may require windows to have high sills or obscure glass to protect neighbor privacy.

• Historic Constraints: If your home is on a historic register, additional reviews apply.

6. Owner Occupancy

• Standard ADUs: As of 2025, California law generally prohibits local agencies from requiring owner occupancy for ADUs permitted between Jan 1, 2020, and Jan 1, 2025 (and likely extended). This effectively allows you to rent out both the main house and the ADU.

• JADUs: Owner occupancy is required. The owner must reside in either the remaining portion of the primary residence or the newly created JADU.

7. Fire Safety (Crucial for Lafayette)

Lafayette has many High Fire Severity Zones (HFSZ).

• Sprinklers: If the primary residence requires fire sprinklers, the ADU requires them. If the primary residence does not, the ADU generally does not (unless it is a detached ADU of a certain size/location necessitating it for safety).

• Access: In very narrow hillside streets, Fire Department access can be a hurdle. While they cannot deny the ADU solely on zoning, they can enforce fire code regarding road width and hydrant proximity.

8. Utilities and Fees

• Solar Panels: Newly constructed detached ADUs require solar panels. Conversions usually do not.

• Separate Meters: Not required for ADUs (can be sub-metered), but usually required for the main house and ADU to be rented separately long-term.

• Impact Fees:

  • < 750 sq. ft.: Exempt from Impact Fees (Park fees, traffic fees, etc.).

  • > 750 sq. ft.: Fees must be charged proportionally to the size of the primary dwelling.

9. Rentals

• Short-Term Rentals: Lafayette (and most of CA) generally prohibits ADUs from being used for short-term rentals (less than 30 days, i.e., Airbnb/VRBO). They are intended for long-term housing.

Steps to Move Forward in Lafayette

1. Check the GIS Map: Verify your lot lines, easements, and Fire Severity Zone status using the Lafayette or Contra Costa County GIS maps.

2. Pre-Application Meeting: Contact the Lafayette Planning Department. Ask specifically about "Ministerial Review for ADUs" (this means over-the-counter approval without a public hearing).

   • Phone: (925) 284-1968

   • Location: 3675 Mt. Diablo Blvd #210, Lafayette, CA 94549

3. Site Plan: You will need a professional site plan showing the proposed footprint, setbacks from property lines, and utility connections.