Merced, CA Accessory Structures: ADU Rules (2026)

030 of the Merced Municipal Code lays out where and how big an accessory dwelling unit can be. ADUs are permitted in any district zoned for single-family or multi-family residential or mixed use. On a single-family lot, the city allows one attached ADU, one detached ADU, and one junior ADU simultaneously; on a multi-family lot, converted ADUs are capped at 25 percent of the existing dwelling units and no more than two detached ADUs are allowed. There is no minimum parcel size for an ADU, and the code carves out a 'Statewide Exemption ADU' that cannot be blocked by lot coverage, floor area ratio, open space, or minimum lot size rules as long as it stays at or under 800 square feet, 16 feet tall, and keeps four-foot side and rear setbacks.

Outside that exemption, an attached or converted ADU is capped at 50 percent of the primary home's living area or 1,200 square feet, whichever is smaller, while a detached ADU is capped flat at 1,200 square feet. Height for a detached ADU tops out at 16 feet in most cases, rising to 18 feet (or 20 feet for a matching roof pitch) within a half-mile of a major transit stop, and standard setbacks are four feet on the side and rear except where an existing accessory structure is simply converted in place, which requires no additional setback.

Parking is capped at one space per ADU or per bedroom, whichever is less, and is waived entirely within a half-mile of public transit, in historic districts, or when a car-share vehicle sits within a block.