Accessory Dwelling Unit (ADU) City Regulations

Are ADUs allowed in Piedmont:


Number of ADUs allowed:

Limit of one accessory dwelling unit per parcel.

Types of ADUs allowed:

Detached, attached and junior ADUs are allowed.

Lot size:

Refer to the minimum state requirements.

ADU size:

Attached accessory dwelling units may not exceed 50% of the existing living area and are capped at 800 sq. ft. Detached units are limited to 800 sq. ft. However, applicants may seek an exception under section 17.38.070 C.1.


No setback is required for an existing garage that has been converted into an ADU, however, if an accessory dwelling unit is constructed above an existing garage there is a minimum setback of five feet from the side and rear lot lines.


If a garage, carport, or covered parking structure is demolished as part of the construction of an ADU, any replacement parking configuration may be used on the parcel as long as the spaces are not located within the 20-foot street setback. See Gov't. Code ยง65852.2 (a)(1)(D)(xi).

Fire Safety:

ADU fire sprinklers are only required if fire sprinklers are also required for the primary residence.

Shape, materials and style:

Design features, materials and color schemes must match those of the primary dwelling.


ADU height requirements are subject to the underlying zoning code.

Design review:

Must follow ministerial review process as per state minimum standards.


Owner occupancy of either the primary or secondary dwelling is required, except in the case of an exempt ADU. Additionally, the lot owner must record with the County Recorder a declaration of restrictions in a city-provided form.


Exceptions apply. Please check with the Planning Commission to determine if ADU designs meet exception requirements.


Independent, exterior access is required for any ADU. Passageways, however, are not necessary.


ADUs established before 1930 may be confirmed in writing by the City and be classified as exempt accessory dwelling units.

Code / Manual: 

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