Garage Conversion vs. Ground-Up ADU: Which Is Right for Your LA Home?
Many Los Angeles homeowners have the same question: should we convert the garage, or build a brand-new ADU in the backyard? Both can add a comfortable, permitted living space. But they're different projects, with different trade-offs.
Here's a plain-English comparison to help you think it through before you talk to anyone about numbers.
What Each Option Means
Garage conversion
A garage conversion turns your existing garage into a living unit. The walls, roof and slab are already there. The work focuses on making the space livable: insulation, windows and doors, a kitchen, a bathroom, plumbing, electrical, heating and cooling, and finishes.
Ground-up ADU
A ground-up ADU is a new building, usually detached in the backyard, though it can also be attached to your house. Everything is new, from the foundation to the roof. You have much more freedom in size, layout and placement.
Cost: Starting Prices Side by Side
2-car garage conversion: from $90k.
Ground-up ADU: from $290 per square foot.
Both are build-only starting prices. Design, permits, city fees and utility upgrades are extra. A starting price isn't a quote, and your final price is set in your written estimate.
Because a ground-up ADU is priced per square foot, the total depends heavily on how big you go. A conversion has a fixed starting point because the footprint already exists. In general, reusing a structure means less new construction. But a garage that needs a lot of repair can narrow that gap.
Space and Layout
A garage conversion is limited by the garage you have. A typical two-car garage can work well as a studio or a compact one-bedroom, but the shape and ceiling height are already set.
A ground-up ADU lets you design around your needs. California law says a city can't use certain local rules to block an ADU of at least 800 square feet with four-foot side and rear setbacks, as long as it meets other applicable standards. That gives many LA lots real room to work with. Your lot's size, shape and slope still matter.
Parking
This is a common worry. Under California law, when a garage is converted to an ADU, or demolished to build one, the city cannot require you to replace those parking spaces. You will lose the garage as a parking or storage space, though, so think about where cars, bikes and stored items will go.
With a ground-up ADU, your garage can stay a garage.
Condition of Your Garage
A conversion is only as good as the structure you start with. Before planning one, it helps to know:
Was the garage built with permits? You can research past permits through LADBS property records.
Is the slab level and in good shape?
Are the walls and roof framing sound?
Will the space need a new foundation or major repairs to meet code for a home?
If the answer to that last question is yes, a ground-up ADU may make more sense. We'll tell you honestly which way we'd lean after seeing the structure.
Permits and Timeline
Both options need a permit, and in the City of Los Angeles that goes through LADBS plan review. Under state law, once a city receives a complete ADU application on a lot with an existing home, it must approve or deny it within 60 days. The city makes the final permit decision.
Our build timelines start from about 3 months. A conversion often has less site work than a new build, but every project is different. Design time, plan check corrections and utility work can all affect the overall schedule.
Utilities
Both an ADU and a garage conversion need power, water and a sewer connection. Some houses have enough electrical capacity. Others need a panel or service upgrade. These upgrades are not included in our build-only starting prices, and we can only tell you what your home needs after a look.
Quick Comparison
Garage conversion | Ground-up ADU | |
Starting price (build-only) | From $90k (2-car) | From $290/sq ft |
Size and layout | Set by your garage | Designed around you |
Garage parking | Lost (no replacement required by state law) | Kept |
Biggest unknown | Condition of the garage | Site conditions and size |
How to Decide
Ask yourself a few simple questions:
Do we need the garage for parking or storage?
How much space does this unit really need?
Is our garage in good shape and permitted?
Is there room in the yard for a new building?
There's no single right answer. A retired couple wanting a small guest space may love a conversion. A family planning for grown kids or parents may want the room a new build allows. See more options on our ADU page.
Not Sure Which Way to Go?
Tehran Construction & Remodeling brings 10 years of experience and has helped 237+ clients, serving homeowners across Los Angeles with design in-house or through our partners. We speak English and Farsi. Let's look at your garage and your yard together with a free, no-obligation feasibility review. Call or WhatsApp (818) 818-8366, or reach out through our contact page.
Licensed contractor: Bardia Ekrami, CSLB #1143589.
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