How Much Does a 500 Sq Ft ADU Cost in California? [2026 Price Guide]
Building a 500 square foot ADU in California? Complete cost breakdown from $150,000-$250,000+ including permits, design, and construction.
A 500 square foot ADU is one of the most popular sizes in California—large enough for a comfortable one-bedroom unit, yet efficient to build. Here's what you can expect to pay in 2026.
500 Sq Ft ADU Cost Breakdown
The total cost for a 500 square foot ADU in San Diego typically ranges from $150,000 to $250,000, depending on design, finishes, and site conditions.
Cost Per Square Foot Analysis
- Budget Build: $300-$350/sq ft = $150,000-$175,000
- Mid-Range: $350-$400/sq ft = $175,000-$200,000
- Premium/Custom: $400-$500/sq ft = $200,000-$250,000
Detailed Cost Categories
Pre-Construction Costs: $15,000-$25,000
- Architectural plans: $5,000-$12,000
- Structural engineering: $2,000-$4,000
- Title 24 energy compliance: $500-$1,500
- Site survey: $500-$1,000
- Soils report (if required): $1,500-$3,000
- Permit fees: $5,000-$8,000
Site Preparation: $10,000-$25,000
- Demolition/clearing: $2,000-$5,000
- Grading and excavation: $3,000-$8,000
- Foundation: $8,000-$15,000
Structure and Shell: $50,000-$75,000
- Framing: $15,000-$25,000
- Roofing: $8,000-$15,000
- Windows and doors: $5,000-$12,000
- Exterior siding/stucco: $10,000-$18,000
- Insulation: $3,000-$5,000
Mechanical Systems: $25,000-$40,000
- Electrical: $8,000-$15,000
- Plumbing: $8,000-$15,000
- HVAC: $5,000-$10,000
Interior Finishes: $35,000-$60,000
- Drywall: $5,000-$8,000
- Flooring: $5,000-$12,000
- Kitchen cabinets and counters: $10,000-$20,000
- Bathroom fixtures and tile: $8,000-$15,000
- Paint: $2,000-$4,000
- Lighting fixtures: $2,000-$5,000
Utility Connections: $10,000-$20,000
- Sewer/septic connection: $3,000-$8,000
- Water line: $2,000-$5,000
- Electrical service: $3,000-$6,000
- Gas line (if applicable): $1,500-$3,000
What Affects ADU Costs?
Several factors can push your 500 sq ft ADU cost higher or lower:
- Site Access: Difficult access = higher labor costs
- Slope: Hillside construction adds $20,000-$50,000+
- Utility Distance: Long runs to connections increase costs
- Design Complexity: Custom designs cost more than standardized plans
- Finish Level: Luxury finishes vs. builder-grade materials
500 Sq Ft ADU Rental Income Potential
In San Diego, a well-designed 500 sq ft one-bedroom ADU can rent for:
- Coastal areas (La Jolla, Pacific Beach): $2,500-$3,500/month
- Central San Diego: $2,000-$2,800/month
- East County: $1,800-$2,500/month
Get an Accurate Estimate
Every property is different. Contact One Stop Builders at (858) 567-0007 for a free site visit and detailed cost estimate for your specific ADU project.