ADU Construction Cost in California: San Diego 2025

Planning an accessory dwelling unit (ADU) in San Diego? You’re not alone. With California’s 2019 ADU laws making construction easier, homeowners are increasingly turning to ADUs for rental income, multi-generational housing, or long-term equity. However, costs vary widely by region, design, and finishes. This guide breaks down the real costs of ADU construction in San Diego and how to plan your budget effectively.

Typical ADU Costs in San Diego

Mid-range ADU construction in San Diego typically costs $300–$400 per square foot. High-end ADUs with custom finishes can reach $500–$600 per square foot. These prices include design, permits, construction, and finishes.

What’s Included in the ADU Cost

• Design and architectural plans
• Permits and city fees
• Site preparation, foundation, framing, and utilities
• Interior and exterior finishes
• Landscaping and hardscaping

ADU Cost Breakdown by Type

• Detached ADUs: $350–$450/sq ft
• Attached ADUs: $250–$350/sq ft
• Converted garage ADUs: $200–$300/sq ft
• Second-story ADUs: $350–$450/sq ft

How to Reduce ADU Construction Costs

• Choose a simple design with fewer custom features
• Use cost-effective materials without sacrificing durability
• Plan early to avoid permit delays and labor spikes
• Consider a shared-walls or garage-conversion ADU instead of a detached one

ADU Financing Options

• Home equity loans and HELOCs
• FHA 203(k) loans
• Construction loans
• Personal savings or investor partnerships

Conclusion

ADUs in San Diego are a smart investment, but costs vary based on size, design, and finishes. Work with a reputable ADU builder to get an accurate estimate and avoid costly surprises.

Ready to start your ADU project? Call Cali Dream Construction for a free consultation at (858) 434-7166.