How to Choose Between Detached, Attached, and Garage Conversion ADUs

As homeowners look for smart ways to expand living space, accommodate family, or generate extra income, accessory dwelling units (ADUs) have become an increasingly attractive solution. But deciding which type of ADU—detached, attached, or garage conversion—best fits your goals and property requires careful consideration. Each option comes with its own set of benefits, challenges, and design possibilities. Here’s how to weigh your choices based on lifestyle, budget, and future plans.

Detached ADUs: Maximum Privacy and Long-Term Value

Detached units are fully independent structures, typically built in the backyard. They offer the greatest separation from the main home, making them perfect for renters, long-term guests, or multigenerational families who want their own space. Because you’re building from the ground up, you have full control over layout, size, and design. However, detached ADUs are usually the most expensive option due to the need for new foundations, utility hookups, and permits. You’ll also need enough lot space and must comply with local zoning setbacks.

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Best for:

• Maximizing privacy

• Hosting long-term guests or tenants

• Increasing property value

• Homeowners with large yards and flexible budgets

Attached ADUs: Close Connection with Lower Costs

Attached ADUs are built as additions to the main house and share at least one wall. They’re ideal for families who want to stay connected—such as aging parents or adult children—while still providing some independence. These units are generally more affordable than detached builds because they often use the home’s existing infrastructure for plumbing, electricity, and heating. While privacy may be less than with a detached unit, separate entrances and thoughtful design can create comfortable boundaries.

Best for:

• Multigenerational households

• Budget-conscious expansions

• Shared access and utilities

• Homes with existing side or rear expansion potential

Garage Conversions: Efficient Use of What You Have

Garage conversions turn an existing space into a livable unit, making them one of the most cost-effective ADU options. Since no new foundation is needed, construction is usually faster and more affordable. This solution is ideal for smaller households or rental income, particularly in urban areas where lot space is limited. Keep in mind that these units often require upgrades to insulation, ventilation, and structural integrity to meet building codes, and their compact size may limit layout flexibility.

Best for:

• Maximizing existing square footage

• Quick, cost-effective builds

• Homeowners with unused garages

• Smaller units like studios or guest suites

Matching the ADU to Your Long-Term Goals

When choosing between ADU types, consider not just the current use, but how your needs might evolve. Detached units offer independence and future rental value. Attached additions support family closeness and flexibility. Garage conversions make the most of existing space without a major build. Think about who will live there, how private the space needs to be, and what level of investment you’re ready for.

Ultimately, the best ADU is one that meets your needs today and adds lasting function and value to your property. With the right plan, any type—detached, attached, or converted—can become a valuable extension of your home.