Martinez, CA Accessory Structures: Garage Conversions (2026)

Under Martinez Municipal Code Chapter 22.43, an existing attached or detached garage may be converted to an ADU or JADU on a single-family lot. The City may not require replacement of off-street parking eliminated by the conversion under state law. The existing garage footprint and setbacks are preserved; any added square footage beyond the original walls must meet the 4-foot side and rear setbacks for new construction. A JADU created within an attached garage is capped at 500 sq ft, must be within the walls of the primary single-family dwelling, and requires owner-occupancy of either the primary or JADU recorded by deed restriction. State law and Chapter 22.43 require the City to allow up to 800 sq ft for any ADU and up to 1,200 sq ft for a detached or 2-bedroom attached ADU. ADU/JADU submissions are processed through Martinez Planning Division on a 60-day ministerial timeline; building permits and plan review are handled by Martinez Building Division under the California Residential Code (egress, 7-foot ceiling height, light/ventilation, smoke and CO alarms, fire separation).