Accessory Structures in Martinez, CA: What Residents Actually Need to Know

If you live in Martinez or are thinking about moving there, accessory structures are one of those things you probably won't think about until they affect you directly. Martinez has 3 specific rules on the books covering different aspects of accessory structures, and some of them might surprise you.

ADU Rules

Martinez complies with California Gov Code §65852.2 (statewide ADU law). One ADU and one JADU (up to 500 sq ft) are permitted per single-family lot. Detached ADUs up to 1,200 sq ft; attached up to 1,000 sq ft or 50% of primary home. 4-ft rear/side setbacks for new detached ADUs. ADUs under 750 sq ft exempt from impact fees. ADUs cannot be used as STRs per city's STR prohibition.

Key details: Max Size (Detached): 1,200 sq ft. Max Size (Attached): 1,000 sq ft or 50% of primary home. Setbacks: 4 ft rear and interior side (new detached ADU). STR Use: Prohibited — city bans all STRs.

Cities cannot deny conforming ADU applications. Unpermitted ADU construction: standard building code enforcement.

Shed Rules

Accessory structures in Martinez require building permits unless very small, non-habitable, and under ~120 sq ft with no utilities. Structures must comply with setback requirements (typically 5 ft from side/rear property lines in residential zones). Maximum height is governed by Title 22 zoning code.

Key details: Permit Required: Yes for most sheds; ~120 sq ft threshold for exemption. Setbacks: Typically 5 ft from side/rear property lines. Height Limit: Per Title 22 Zoning Code. Design: Should complement primary home architecture.

Unpermitted structure: retroactive permit with penalty. Non-compliant setback: modification or removal. Habitation violation: immediate correction.

Garage Conversions

Martinez regulates ADU and JADU development under Martinez Municipal Code Chapter 22.43, consistent with California Government Code §65852.2. Garage conversions are by-right with no replacement parking required, no minimum lot size, and existing garage setbacks preserved for the conversion footprint.

Key details: Code: Martinez MC Ch. 22.43. Replacement Parking: Not required. Existing Setbacks: Preserved for conversion. JADU Cap: 500 sq ft. Review Timeline: 60-day ministerial.

Converting a Martinez garage to habitable space without a building permit is a violation of Martinez Municipal Code Chapter 22.43 and the California Residential Code, with stop-work orders, administrative citations, and required after-the-fact permits or restoration. Operating a post-2020 conversion-ADU as a short-term rental violates state law and the recorded deed restriction.

Martinez is more permissive than most cities when it comes to garage conversions. That said, there are still limits.

The Bottom Line

Martinez's accessory structures rules are a mixed bag. Some areas are strict, others are relaxed, and the details matter. The best approach is to check the specific rule that applies to your situation rather than assuming Martinez is broadly strict or permissive.

Keep in mind that Martinez can amend these rules at any council meeting. For the most current version of any rule mentioned here, check the specific ordinance page, where we track updates as they happen.