An ADU is the rare project that pays you back — in rental income, in flexibility for family, and in permitted value that stays with your property. But the first question every homeowner asks is the right one: what will it actually cost?
Here are honest 2026 numbers for Los Angeles and Orange County, from a team that designs and builds ADUs end to end.
The short answer: $150K to $450K+
Most ADUs in Los Angeles land between $150K and $450K+, and the spread comes down to one thing more than any other: how much structure you're building from scratch.
- Garage conversion ADU — typically $150K–$250K. The structure already exists; the work is converting it into a legal, conditioned dwelling with a kitchen and bath.
- Junior ADU (JADU) — often the most affordable path. Capped at 500 sq ft within your existing home, sharing systems with the main house.
- Attached ADU — typically $200K–$350K. A new addition that shares at least one wall with the main home.
- Detached ADU — typically $300K–$450K+. A ground-up backyard home, up to 1,200 sq ft — the most expensive path, and the one that lives and rents best.
What's inside the number
A trustworthy ADU budget isn't one line — it's five. When you compare bids, make sure each of these is actually included:
- Design, engineering and permits — architectural plans, structural engineering, city plan check and fees.
- Site work and utilities — trenching, sewer and water connections, and any electrical panel upgrade the added load requires.
- The shell — foundation, framing, roofing, windows and doors.
- Systems — electrical, plumbing and HVAC for a complete, independent dwelling.
- Finishes — kitchen, bathroom, flooring, tile and paint. This is where budgets swing most, because it's where taste lives.
The drivers people don't see coming
Three things move an ADU budget more than any material selection: your electrical panel (older homes often need an upgrade to carry a second dwelling), your lot (slope, access and how far utilities have to travel), and your finish level (a rental-grade interior and an owner-grade interior can differ by six figures on the same floor plan).
Decide what the ADU is for before you design it. A unit built to rent and a unit built for your mother should not be specified the same way.
Timelines in 2026
California law requires cities to review a compliant ADU application within 60 days. Realistically, plan for 6–12 months from first design conversation to keys — design and permitting up front, then roughly 4–8 months of construction depending on type.
How to keep the budget predictable
The ADUs that stay on budget are the ones where every decision was made before construction started. That's our entire process: design first, lock the plans and selections, then build to a number you approved. The most expensive change order is the one made on a job site.
If you're weighing an ADU for your property, start with the honest question — what your lot allows and what your goal is worth. We'll give you a straight answer either way.