Garage Conversion vs. Detached ADU. What’s the Difference?

Accessory Dwelling Units (ADUs) are quickly becoming one of the most strategic investments for Los Angeles homeowners. Whether you're building for family, looking to increase resale value, or creating a guest space to generate income, ADUs offer flexibility that few other improvements match.

Thanks to statewide housing reforms and a growing demand for rental units, constructing an ADU is now more accessible than ever. But the first major decision is often the most important: should you convert an existing garage, or build a brand-new detached unit?

Both paths have clear advantages. A garage conversion can be faster and more affordable. A detached unit, on the other hand, gives you more design freedom and long-term potential for rental income. In this guide, we’ll explore both options how much they cost, how they rent, what zoning hurdles you’ll face, and which fits best with your property and goals.

All information is specific to Los Angeles as of 2025 and draws from data provided by the California Department of Housing and Community Development (HCD), the Los Angeles Department of Building and Safety (LADBS), and active rental listings.

Cost Comparison: What You’ll Spend (and Why)

Garage Conversion

For many owners, converting an existing garage is the most direct route to building an ADU. In Los Angeles, costs typically range from $95,000 to $135,000, depending on garage condition and interior finish. Since the structure already exists, you may save on foundation work, rough utilities, and framing.

However, many garages built before the 1980s may not meet current code. If the slab is cracked, the ceiling too low, or electrical panels outdated, those issues must be corrected before the city will approve the unit for habitation. This can add time and cost to your project.

Garage conversions are generally exempt from parking replacement rules if located within a half-mile of public transit, per state law [California HCD, 2022]. Still, homeowners should budget for upgrades that often go overlooked until construction begins.

Detached ADU

Building a detached ADU involves more complexity and more opportunity. These projects require a new foundation, full utility connections, and full-scale residential finishes. Costs typically range from $180,000 to over $300,000.

Per-square-foot costs often fall between $300 and $400, depending on the level of finish and whether the lot is flat or sloped. Larger units mean more space to work with more storage, more natural light, and the ability to add a full kitchen or a second bedroom.

Detached ADUs are more likely to attract high-quality long-term tenants or higher-paying guests, and they tend to add more resale value over time.

Permitting, Zoning, and Fire Access

Garage Conversions

Garage conversions are relatively simple to permit in most Los Angeles neighborhoods. Because the structure already exists, you’re often exempt from setback requirements and can move through the process more quickly. If the garage is within transit proximity, replacement parking is not required under California Government Code §65852.2.

Since fire access was already established with the original garage, LADBS rarely flags these projects for path-of-travel issues. As long as you’re not expanding the footprint, zoning conflicts are minimal.

Detached ADUs

Detached ADUs come with more code layers. The Los Angeles Fire Code requires a clear, level path of 3 to 4 feet from the street to the ADU entrance. This is non-negotiable. If your side yard is too narrow or blocked, the project may require redesign.

Detached units must comply with at least 4-foot setbacks from rear and side property lines and maintain a 6-foot separation from the main home. Hillside lots and Specific Plan areas may impose additional restrictions, which can impact both size and placement.

This is why early design due diligence is critical. Without it, you could end up paying for plans that cannot be permitted as submitted.

Design Flexibility, Privacy, and Guest Experience

Garage Conversions

Garage conversions are ideal for compact spaces studios or one-bedroom layouts under 400 square feet. They’re efficient, quick to build, and perfect for budget-conscious projects.

But the location can be a drawback. Garages are often set near driveways or lot edges, which limits privacy and natural light. If your goal is to host guests or tenants who value a standalone feel, you may find a conversion too constrained. These units are best for shorter stays, transitional housing, or supplementary income.

Detached ADUs

Detached units offer total design control. Whether you’re creating a private rental suite or a multigenerational home, you can tailor the space to your audience.

Units between 500 and 850 square feet support multiple bedrooms, full kitchens, vaulted ceilings, and open layouts. Detached structures allow for more outdoor integration think fenced yards, patios, or private entries.

For guests staying long-term or tenants seeking independence, the experience is closer to living in a second home than an extension of the main house. That kind of space typically rents faster and commands higher rates.

Rental Income and Return on Investment

Garage Conversions

Garage ADUs rent for $1,800 to $2,400 per month depending on neighborhood and design quality. Units in West Adams, Highland Park, and El Sereno consistently exceed $2,000 per month, according to May 2025 listings from Zillow and Apartments.com.

When well-executed, garage conversions can recoup their cost in 4 to 6 years, particularly when financed through home equity or paired with the CalHFA ADU grant program. The lower cost also means faster ROI and less upfront financial risk.

Detached ADUs

Detached units rent for $2,400 to $3,800 per month, with two-bedroom layouts in Mar Vista or Culver City occasionally topping $4,000. While these units cost more to build, they offer stronger long-term upside.

Here’s how the math plays out:

Type	Cost Range	Rent Range	Annual Income	Payback Timeline
Garage Conversion	$95K – $135K	$1,800 – $2,400	$21,600 – $28,800	4–6 years
Detached Studio	$140K – $180K	$2,000 – $2,700	$24,000 – $32,400	5–7 years
Detached 1-Bedroom	$180K – $230K	$2,400 – $3,200	$28,800 – $38,400	5.5–8 years
Detached 2-Bedroom	$240K – $300K	$3,000 – $3,800	$36,000 – $45,600	6.5–8.5 years

These figures reflect gross income. Net returns will vary based on utilities, financing, and vacancy rates.

Detached units also tend to appraise higher at resale, especially if they are permitted, metered separately, and finished to a high standard.

Which Option Is Right for You?

Choose a Garage Conversion If:

• You have a detached, code-compliant garage in good condition

• You want to build quickly with a modest budget

• You plan to host guests, students, or family for short- to mid-term stays

Choose a Detached ADU If:

• Privacy, square footage, and layout matter

• You plan to rent long-term or create a permanent secondary residence

• Your lot meets fire access and zoning requirements

Final Thoughts

Whether you're building an ADU for rental income, family support, or to expand your hospitality offerings, your choice of structure will shape the experience and the return. Garage conversions are accessible, efficient, and relatively fast. Detached units are more flexible, private, and valuable over time.

Start with a clear understanding of your goals, your lot’s limitations, and what you want the ADU to deliver whether that’s privacy, profit, or a space designed for hosting.

Before you commit to plans or permits, a zoning review or feasibility study can confirm what’s possible on your lot and ensure your project moves forward with confidence.