Real ranges by ADU type, and the factors that push a project toward the low or high end.
Accessory dwelling units are one of the most requested projects we get calls about, usually framed as "what would it cost to add a unit for my in-laws" or "can I turn my garage into a rental." The honest answer still depends on which of the three ADU types you're building, but here are the ranges we actually see in Los Angeles.
Garage conversion ADU: converting an existing detached garage into livable space is usually the most affordable path, since the structure, foundation, and roof already exist. In Los Angeles, garage-to-ADU conversions commonly run from the high $70K–s into the $150K range depending on size and finish level.
Attached ADU: building new square footage onto your existing home shares some infrastructure (roofline, sometimes utilities), which can moderate cost compared to a fully detached build, but still requires new foundation work for the addition itself. Expect a range roughly between garage conversions and full detached units.
Detached, new-construction ADU: a standalone unit built from the ground up on your lot is the most flexible option and typically the most expensive, since it needs its own foundation, roof, and full utility connections. In LA, new detached ADUs commonly start around $150K and can move well past $250K for larger units or higher-end finishes.
Square footage. Cost doesn't scale perfectly linearly, but a 600 sq ft unit will cost meaningfully more than a 350 sq ft studio, mostly in kitchen, bathroom, and finish quantities.
Utility connections. Running new electrical, water, sewer, and gas lines to a detached unit, especially one at the back of a deep lot, adds cost that's easy to underestimate before a site visit.
Site conditions. Slope, existing hardscape that needs to be removed, tree removal, and access for equipment all affect a detached build more than a garage conversion.
Permits and Title 24 energy compliance. Every ADU in California needs its own permit set, structural review, and energy compliance documentation before construction starts. See our general permit guide for how that process works.
Finish level. A rental-grade ADU with builder-basic finishes costs meaningfully less than one finished to match a high-end primary home, especially in cabinetry, countertops, and flooring.
Two lots that look similar from the street can have very different ADU costs once you factor in what's underground, how far utilities need to travel, and local setback and easement rules. That's why we walk every property before giving a real number, rather than quoting off a floor plan alone.
We handle ADU design, permitting, and construction as one process rather than handing you off between separate architects, engineers, and contractors. Founder Erica Anenberg and Head of Sales & Operations Beth Benson stay on every project from the first walkthrough through final inspection. See our ADU construction services for what's included, or browse recent projects.
Thinking about an ADU for your property? Schedule a discovery call →, or read our kitchen & bathroom remodel cost guide.
Tell us about your project and we'll set up a discovery call to talk it through. Serving LA and the Valley.