Accessory dwelling units (ADUs) have become one of the smartest ways to add value and living space to a Los Angeles property. Whether you want rental income, a home office, or space for family, the first question is always cost.
The short answer: most ADUs in Los Angeles cost between $150,000 and $450,000 to build in 2026, or roughly $250 to $500 per square foot. A garage conversion sits at the low end, while a new detached ADU with high-end finishes sits at the top.
ADU cost by type
The type of ADU is the biggest driver of cost. Here is how the three main options compare in the LA market:
| ADU type | Typical cost | Notes |
|---|---|---|
| Garage conversion | $100,000 to $250,000 | Uses an existing structure, lowest cost |
| Attached ADU | $180,000 to $350,000 | Built onto the existing home |
| Detached new ADU | $250,000 to $450,000+ | Standalone, most flexible, highest cost |
Cost by size
At a mid-range of about $350 per square foot, here is what different ADU sizes run:
| Size | Estimated cost |
|---|---|
| 400 sq ft (studio) | $120,000 to $180,000 |
| 600 sq ft (1 bed) | $180,000 to $270,000 |
| 800 sq ft (2 bed) | $240,000 to $360,000 |
| 1,000 sq ft (2 bed) | $300,000 to $450,000 |
What drives the price
- Type and size. New detached construction costs more than converting an existing garage.
- Site work. Running new water, sewer, and electrical to a detached unit adds cost, especially on sloped lots.
- Finishes. A rental-grade ADU costs far less than one built to match a high-end main house.
- Kitchen and bath. These are the most expensive rooms per square foot in any ADU.
- Utilities. A separate meter and upgraded electrical panel may be required.
Do ADUs pay for themselves?
In Los Angeles, a well-built ADU can rent for $2,000 to $3,500 or more per month depending on size and location, and it adds significant resale value to the property. For many owners, the unit pays back its construction cost over several years while boosting the home's market value from day one.
Soft costs to budget for
- Design and architectural plans
- Permit and city fees
- Structural engineering
- Utility connections and possible panel upgrade
- A 10 to 15 percent contingency
How long does it take to build an ADU?
From design to move-in, most ADUs in Los Angeles take 8 to 14 months. Permitting typically runs 3 to 6 months and construction another 4 to 8 months, though garage conversions can move faster.
Frequently asked questions
What is the cheapest type of ADU to build?
A garage conversion, because it reuses an existing structure and foundation. It is the fastest and lowest-cost path to a permitted ADU in Los Angeles.
Can I build an ADU on any LA lot?
Most single-family and multifamily lots in Los Angeles can add at least one ADU under current state law, but size and placement depend on your lot. A builder can confirm what your property allows.
Does an ADU increase property taxes?
Yes, the added value of the ADU is assessed and increases your property tax, but the rest of your home is not reassessed. The rental income usually far outweighs the added tax.
Thinking about an ADU?
The right ADU depends on your lot, your goals, and your budget. JJP Construction builds ADUs across Los Angeles, and we can tell you exactly what your property allows and what it will cost before you commit.
