Merced County, CA Accessory Structures: ADU Rules (2026)
ADU rules in Merced County, CA, also called accessory dwelling unit regulations or granny flat ordinances, cover setbacks, owner-occupancy, parking, and permit requirements.
Key Facts
- Single-family parcel max
- 1 JADU + 1 attached + 1 converted + 1 detached ADU
- Multi-family converted ADU cap
- 25% of existing units
- Multi-family detached ADU cap
- Up to 8 units
- Governing section
- Zoning Code Section 18.62.070
- Review type
- Ministerial Zoning Clearance, 60-day timeline
Summary
Unincorporated Merced County allows up to four accessory dwelling units on a single-family parcel: one junior ADU, one attached ADU, one converted ADU, and one detached ADU, under Zoning Code Section 18.62.070. Multi-family parcels get a different formula, capping converted ADUs at 25% of existing units and detached ADUs at eight.
For parcels meeting the requirements of Section 18.62.020 (Applicability), the following type and number of accessory dwelling units (ADUs) may be allowed: A. Parcels with a Single-Family Dwelling. 1. The following ADU types shall be allowed per parcel with an existing or proposed single-family dwelling: a. One junior accessory dwelling unit (JADU); and b. One attached ADU; and c. One converted ADU; and d. One detached ADU. B. Parcels with Multi-Family Dwelling(s). 1. Converted ADUs. The number of converted ADUs, on a parcel with an existing multi-family dwelling, shall not exceed 25% of the total number of dwelling units. 2. Detached ADUs. Up to eight detached ADUs, as long as the number of ADUs does not exceed the number of existing units on the property. (SB1211)
Official source re-checked September 7, 2026: no newer edition of the code had been published (publisher’s edition: rev 4930839; v8 updated 2026-06-02).
Full Breakdown
020 states that where the two conflict, state law supersedes. 070. For a parcel with a single-family dwelling, the county allows one junior accessory dwelling unit, one attached ADU, one converted ADU, and one detached ADU, meaning up to four separate accessory units can exist alongside the primary home. For a parcel with multi-family dwellings, the formula changes: converted ADUs cannot exceed 25% of the total number of existing dwelling units, while up to eight detached ADUs are allowed, so long as the number of ADUs does not exceed the number of existing units on the property.
040 grants ADUs and JADUs several protections: they are deemed an accessory use consistent with the existing General Plan or zoning designation, they do not count toward density limits or growth-control ordinances, and they cannot be required to correct nonconforming zoning conditions as a condition of ministerial approval. 050 requires the county to act on a complete ADU application within 60 days. 050(C).
Violations & Fines
Building or operating an accessory dwelling unit that exceeds the type-and-number limits of Section 18.62.070, or that otherwise fails to comply with Chapter 18.62 and the Building Code, is a Zoning Code violation under Section 18.154.070(D), carrying infraction fines up to $100 for a first violation, $200 for a second within a year, and $500 for each additional violation, plus potential Stop Work Order issuance under Section 18.154.070(G) for unpermitted construction.
Frequently Asked Questions
How many ADUs can I build on a single-family lot in unincorporated Merced County?
How many detached ADUs are allowed on a multi-family parcel in Merced County?
Is off-street parking required for a Merced County ADU?
Sources & Official References
Other rules in Merced County
How Merced County compares: Easiest Cities to Build an ADU·California rules heatmap·Compare Merced County to another location·View the California accessory structures overview
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