The True Cost of Building an ADU in San Diego (2025 Guide)
As Accessory Dwelling Units (ADUs) continue to gain popularity in San Diego, one of the biggest questions homeowners and investors ask is: How much does it cost to build an ADU? Understanding the financial investment required for an ADU can help you plan wisely and maximize your property's value and rental income potential.
Breaking Down the Costs of an ADU in San Diego
The cost of building an ADU depends on size, design, materials, and site conditions, but here’s a general breakdown of what you can expect in 2025:
1. Design & Permitting Costs ($10,000 - $35,000+)
Feasibility Study: $1,500 - $3,500 (recommended before starting)
Architectural & Engineering Plans: $5,000 - $15,000
City Permits & Fees: $5,000 - $20,000+ (varies by location and unit size)
✅ Tip: Streamlining the permitting process with experts can help you avoid unnecessary delays and added costs.
2. Construction Costs ($150,000 - $400,000+)
The biggest portion of your budget goes toward materials and labor. On average, expect to pay:
Garage Conversion ADU (400-600 sq. ft.): $150,000 - $200,000
Detached ADU (600-1,200 sq. ft.): $250,000 - $400,000+
High-End ADUs (custom finishes & smart home features): $300,000 - $500,000
✅ Tip: Costs per square foot typically range from $300 - $500+, depending on finishes and complexity.
3. Utility Connections & Site Prep ($10,000 - $50,000+)
Water, sewer, and electrical hookups: $10,000 - $30,000
Foundation work, grading, and soil testing: $5,000 - $20,000
Energy-efficient requirements (Title 24 compliance): $2,000 - $5,000
✅ Tip: If your main home’s utilities are outdated, additional upgrades may be needed, increasing costs.
Ways to Reduce ADU Costs
Choose Standardized ADU Designs – Custom ADUs cost more due to extra design and engineering work.
Build Smaller – A JADU (Junior ADU) or studio ADU requires fewer materials and permits.
Utilize Existing Structures – Garage conversions are often the most cost-effective option.
Explore Financing Options – Consider HELOCs, construction loans, or government ADU grants to offset costs.
Is an ADU Worth the Investment?
Yes! ADUs increase property value and provide passive rental income, making them one of the best real estate investments in San Diego’s high-demand rental market. Many ADUs generate $2,000 - $4,000+ per month in rental income, allowing homeowners to recoup costs in 5-10 years.
Start Your ADU Project Today!
At Life House Design & Construction, we specialize in turnkey ADU solutions, from feasibility studies to full construction. Let’s maximize your property’s potential and create a profitable ADU that fits your needs.
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