Home Addition vs ADU: Which Is Right for You?
Two of the most popular ways to add living space in San Jose are a home addition and an Accessory Dwelling Unit (ADU). While both expand your property's usable space, they serve different purposes and have distinct legal, financial, and practical differences.
Quick Comparison: Home Addition vs ADU
Connected to Main Home
Addition: Yes — shares walls, HVAC, utilities. ADU: Usually separate, with its own entrance and facilities.
Independent Rental
Addition: Cannot be independently rented. ADU: Can be rented as a separate unit — generates income.
Cost Range
Addition:$200–$650/sq ft. ADU:$250–$450/sq ft (detached); higher total cost for larger units.
Permitting Complexity
Addition: Standard building permit. ADU: Building + separate utility meters, separate address.
When to Choose a Home Addition
- You need connected extra space (bedroom, family room, office) integrated with your home
- You want to add a master suite or expand the kitchen
- You don't need (or want) rental income from the space
- Your lot doesn't have room for a detached structure
See our Home Addition Construction and Room Addition services. For cost details, check our Room Addition Cost Per Square Foot guide.
When to Choose an ADU
- You want to generate rental income ($2,000–$3,500/month in San Jose)
- You want a private, fully independent space for family
- You want to maximize your property's long-term value
- Your lot has space for a backyard structure or garage conversion
See our ADU Building and ADU Construction Service pages. Need pricing? Read How Much Does an ADU Cost in San Jose CA?
Not Sure? We'll Help You Decide
Our team offers free consultations to evaluate your property, goals, and budget — then recommend the best path forward. Call (650) 900-8598 or visit our contact page. Learn more about us.