What you can build
Modesto ADU Regulations & Zoning
KEY RULES AT A GLANCE
Size and Separation
Maximum size: 1200 square feet
Side/rear setbacks: 4 feet
Two story: Allowed in some cases
Building separation: 0 feet
Additional Requirements
Soils Report: Required for ADUs over 750 sq ft
Building Verification Survey: No
Coastal permit: (in some areas) Required in coastal zones
Stormwater Mitigation: No
Number of ADUs Allowed
In most residential zones, you can build one ADU per lot, in addition to the main dwelling. Depending on zoning and property specifics, you may also be permitted to build one Junior ADU (JADU) within the primary residence.
ADU Size & Building Constraints
Detached ADUs can be as large as 1,200 square feet, though the exact size allowed may vary depending on the lot size and zoning regulations.
The typical maximum height for a single-story ADU is 16 feet. A 2-story ADU may be permitted if it meets specific zoning and building codes, although additional factors like privacy and shading might need to be considered.
Attached ADUs can be as large as 50% of the square footage of the existing home, with a maximum size of 1,200 square feet.
The exterior of the ADU must align with the architectural style and materials of the primary dwelling. This includes matching the roof pitch, siding, and colors to ensure the ADU complements both the main house and the surrounding neighborhood.
ADU Setbacks
The minimum setback for detached ADUs is 4 feet from the side and rear property lines. For ADUs that involve converting existing structures (such as garages), the setback requirements may be more flexible, particularly if the current footprint of the structure is maintained.
The ADU must generally be separated by a minimum distance from other structures to meet fire safety regulations. Exact requirements will depend on the building codes and the layout of the lot.
Additional Requirements
Modesto permits the submission of ADU plans through their online permit system, eTRAKiT. This system streamlines the application process by allowing online submissions, tracking, and fee payments. However, it is advisable to have an in-person consultation with the Planning Division at City Hall for more complex projects or to address specific zoning issues.
Make sure your ADU project adheres to both local ordinances and California state regulations. The California Department of Housing and Community Development has evaluated Modesto’s ADU ordinance to confirm it aligns with state standards.
Parking
A parking space is not required for an ADU in any of the following instances:
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Within an established historic district.
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Within an established historic district.
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Converted from the existing space of a primary residence or accessory structure, or are attached to an existing or proposed primary residence.
Effective Jan 2025: When a garage, carport, covered parking structure, or uncovered parking space is demolished or converted for construction of an ADU, replacement parking will not be required.
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If a parking space is needed, it can be placed within the setbacks or in an existing driveway as tandem parking. There is no need to replace parking spaces when a garage, carport, or covered parking structure is demolished or converted for the construction of an ADU.