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

Accessory Dwelling Units (ADUs) have become a central feature of housing expansion in Los Angeles. As more homeowners explore how to add value and flexibility to their properties, two common options stand out: converting an existing garage or constructing a new detached ADU.

Both approaches can improve property utility and generate rental income, but they involve distinct permitting paths, costs, and design constraints. Understanding these differences can help homeowners and professionals make the right decision before engaging an architect or contractor.

Cost Comparison: What You’ll Spend and Why

Garage Conversion

Garage conversions typically cost between $95,000 and $135,000 in Los Angeles, according to local builder estimates and the California Department of Housing and Community Development (HCD) [HCD, 2022 ADU Handbook]. These projects often benefit from existing infrastructure, including a slab foundation and utility lines, which can reduce costs.

However, savings are not guaranteed. Many garages in Los Angeles were built before current building codes were adopted. Common issues include cracked or unreinforced slabs, outdated electrical wiring, insufficient ceiling height, or framing that does not meet modern structural requirements. These deficiencies can trigger costly upgrades or even require partial demolition.

Detached ADU

Detached ADUs involve ground-up construction and generally range from $180,000 to over $300,000, based on size, location, finish level, and site complexity. The California Residential Cost Guide places most detached ADU projects between $300 and $400 per square foot, although premium finishes or hillside conditions can raise that figure.

This type of unit requires new foundation work, trenching for utilities, and full mechanical, plumbing, and electrical systems. These elements make detached builds more expensive, but they also allow for greater flexibility in size, layout, and design features such as private entries, full kitchens, and multiple bedrooms.

Permitting, Zoning, and Fire Access

Garage Conversions

Garage conversions are typically simpler to permit. Under California Government Code §65852.2, replacement parking is not required if the property is located within half a mile of public transit, which covers a substantial portion of Los Angeles. Converted garages often fall within existing building footprints and are therefore exempt from side and rear setback requirements under the state’s ADU law.

Additionally, fire access is rarely an issue because the structure already exists and has been part of the original permitted site plan. Plan review tends to focus on life-safety upgrades, energy compliance, and conversion to residential use, making this one of the most efficient approval paths.

Detached ADUs

Detached ADUs are subject to more extensive review. One of the most important requirements is compliance with Los Angeles Fire Code Section 503.1.1, which mandates a clear, unobstructed path from the street to the ADU entrance. This path must be a minimum of 3 to 4 feet wide and cannot be blocked by fences, utilities, or landscaping.

Setback requirements also apply. The state mandates a minimum of 4 feet from rear and side property lines, but local regulations may impose additional limits depending on zoning overlays, lot size, or hillside location. Detached ADUs must also maintain appropriate building separation, often 6 feet, to meet Title 24 fire safety standards.

Common permitting challenges include:

• Easements that limit where the unit can be placed

• Slope or drainage conditions that require grading or retaining walls

• Inadequate fire access paths

• Overbuilt garages that are not up to code

Before proceeding, it is essential to review property surveys and consult with LADBS or a qualified planning professional.

Design Flexibility, Privacy, and Livability

Garage Conversions

Garage conversions are ideal for smaller units such as studios or compact one-bedrooms. Most detached garages in Los Angeles offer 300 to 400 square feet of usable space, which restricts the range of possible layouts. While they can be efficient, they may lack privacy, natural light, or outdoor access if not thoughtfully designed.

Due to their location near the main home, garage conversions may also introduce noise or privacy concerns, particularly for long-term tenants. These limitations can be addressed through smart design choices but remain a factor when evaluating livability.

Detached Units

Detached ADUs allow for fully customized design and orientation. Units between 500 and 850 square feet are common and can support multiple bedrooms, vaulted ceilings, and full kitchens. Detached layouts support more natural light, cross ventilation, and outdoor integration through patios or private yards.

Because they are separate from the main house, detached units also offer superior privacy. This makes them ideal for long-term tenants, family members, or use as a home office. Detached ADUs tend to perform better in the rental market and may be more appealing to appraisers and future buyers.

According to Freddie Mac (2020), homes with legally permitted detached ADUs generally see higher appraisal values compared to similar properties without them.

Rental Income and ROI

Garage Conversions

Rents for garage conversions in Los Angeles generally range from $1,800 to $2,400 per month, depending on location and finishes. In neighborhoods like West Adams, Highland Park, and North Hollywood, converted units consistently rent above $2,000 per month [Apartments.com and Zillow listings, May 2025].

Given the relatively low construction cost, these units often generate gross yields of 18 to 25 percent annually. This allows many homeowners to recoup their investment in under six years, particularly when paired with financing options like a HELOC or the CalHFA $40,000 ADU grant.

Detached Units

Detached ADUs rent for $2,400 to $3,800 per month, with some two-bedroom units in high-demand areas reaching or exceeding $4,000. These higher rents reflect better privacy, livability, and curb appeal.

Despite the higher build cost, the long-term ROI often surpasses that of garage conversions. Detached units can be depreciated over time, rented at higher rates, and typically increase the appraised value of the property more substantially.

Here’s a simplified ROI breakdown:

Type	Build Cost	Monthly Rent	Annual Gross	Est. Payback
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

Figures based on Los Angeles 2025 market data. Actual performance may vary based on loan terms, maintenance, and local vacancy.

Final Thoughts

There is no universal answer when it comes to choosing between a garage conversion and a detached ADU. Each project type has its strengths and limitations.

Garage conversions are faster, simpler, and less expensive, making them ideal for homeowners with an existing structure in good condition. Detached ADUs require a larger investment but offer greater flexibility, privacy, and long-term value.

For most property owners, the right choice depends on:

• Site-specific constraints like fire access or easements

• Budget and financing options

• Intended use: rental, family housing, or resale enhancement

Before starting design or submitting permits, The Code Solution recommends a site feasibility review. Identifying zoning restrictions, infrastructure conflicts, and buildable area early in the process can prevent costly redesigns and help align your ADU with both your goals and the city’s requirements.