What Types of ADUs Are There?

If you're thinking about building an Accessory Dwelling Unit (ADU), one of the first decisions you'll face is what type of ADU to build. The right option depends on your budget, lot size, goals, and local regulations.

Here’s a breakdown of the most common ADU types, with pros and cons for each:

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🏡 1. Detached ADU

Description: A standalone structure, usually built in the backyard.

Pros:

• Maximum privacy for tenant and homeowner
• High rental value potential
• Easier to convert into a short-term rental

Cons:

• Most expensive to build
• Requires more space and permitting
• Often needs new utility connections

Great For: Income-producing rentals, multi-generational housing, guesthouses

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🧱 2. Attached ADU

Description: Built as an addition to the main home, sharing at least one wall.

Pros:

• Lower construction costs than detached
• Uses existing utility hookups
• Good for keeping family close

Cons:

• Less privacy than detached
• May require structural changes to the main house

Great For: Aging parents, extended family, live-in caregivers

🚪 3. Garage Conversion ADU

Description: Converts an existing garage (detached or attached) into a livable unit.

Pros:

• Uses existing structure = lower cost
• Ideal for small or narrow lots
• Fast-track permitting in many cities

Cons:

• Structural upgrades often required
• You lose covered parking or storage

Great For: Urban lots, cost-conscious homeowners

🧭 4. Interior Conversion (Basement or Spare Room)

Description: Builds out an existing part of the home into a separate unit.

Pros:

• Most affordable ADU option
• Minimal exterior changes
• Easier utility tie-ins

Cons:

• Limited square footage
• May feel less independent

Great For: Short-term guests, adult children, rental on a budget

🏘️ 5. Junior ADU (JADU)

Description: A compact unit (≤500 sq ft) located within the main home, often sharing a bathroom.

Pros:

• Easier approval process in many cities
• Lower build cost
• Great for studios, offices, or family use

Cons:

• Space is limited
• Limited to owner-occupied homes in some jurisdictions

Great For: Downsizing, boomerang kids, hybrid office/guest space

Choosing the Right ADU

Every type of ADU comes with tradeoffs. Start with your goals, your lot layout, and your city’s rules.

📥 Want help deciding? Download our “ADU Type Decision Guide” and compare side-by-side.

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