Best ADU Builder in San Diego | Instant Living

Building an Accessory Dwelling Unit (ADU) in San Diego requires navigating a mix of city zoning and density rules. Homeowners in the City of San Diego can generally build up to 150 to 1,200 square feet, and must abide by strict lot-size-based unit caps that limit properties to 4–6 ADUs depending on the lot size.

Cost & Permitting Average Cost: Expect to invest between $375 to $600+ per square foot for turnkey construction. A standard build typically costs between $300,000 and $450,000+ covering design, permits, site preparation, and utility hookups.

Financial Assistance: The San Diego Housing Commission (SDHC) ADU Finance Program provides up to $250,000 in construction loans and no-cost technical help for eligible low-income homeowners.

Property Taxes: Building an ADU does not trigger a reassessment of your primary home; your property taxes will only increase based on the added assessed value of the new unit.City Size & Density Regulations

Size Limits: Both attached and detached ADUs must be a minimum of 150 sq. ft. and can go up to 1,200 sq. ft.. If you are converting an existing accessory structure or part of your primary residence, the 1,200 sq. ft. cap generally does not apply.