How Much Does It Cost to Build an ADU in Los Angeles? (2026 Guide)

A new detached ADU in Los Angeles costs between $219,000 and $459,000 depending on the size, configuration, and site conditions of your project. A garage conversion runs $140,000 to $245,000+ depending on the condition of the existing structure and whether you are adding square footage.

Those are real numbers from real projects — not industry averages pulled from a national database, and not the lowball estimates you will find on sites that have never built anything.

After designing and building over 100 ADUs across Los Angeles County, I have seen the full spectrum of what an ADU costs — from straightforward garage conversions on flat lots to complex detached new construction on hillside properties with challenging access. And the single biggest mistake I see homeowners make is starting the process without understanding where the money actually goes.

In this guide, I am going to give you the most transparent ADU cost breakdown you will find anywhere online. I will walk you through what every ADU type costs, show you a line-by-line budget from an actual project, explain what drives costs up (and what keeps them down), and help you understand how to get the most value for your construction dollar.

If you have already read this and want to understand how to pay for your ADU, head over to our complete ADU Financing Guide for Los Angeles.

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ADU Cost by Type and Size

Not all ADUs cost the same. The type of ADU you build — garage conversion, single-story detached, or two-story detached — has a massive impact on your total budget. Here is what each category costs in Los Angeles as of 2026.

Garage Conversion ADUs: $140,000 – $245,000+

Garage conversions are typically the most affordable path to a permitted ADU because the basic structure — walls, roof, foundation — already exists. You are converting existing space rather than building from scratch, which eliminates a significant portion of the construction cost.

What determines where you land in that range: The single biggest variable in a garage conversion is the condition of the existing garage. A well-built, newer garage with a solid foundation and proper framing can be converted with minimal structural upgrades — saving tens of thousands compared to an older garage that needs to be partially or fully rebuilt. Electrical panel capacity, sewer connection distance, and whether the city requires a seismic retrofit also move the needle.

Detached New Construction ADUs: $219,000 – $459,000

A detached ADU is a brand new, standalone home built from the ground up in your backyard. This is the premium ADU option — and for good reason. Detached ADUs offer the most design flexibility, the highest rental income potential, the greatest property value increase, and complete privacy for both the homeowner and the ADU occupant.

We offer nine architect-designed Signature Home models across two collections — six single-story and three two-story — all at fixed, all-inclusive pricing.

Single-Story Collection: $219,000 – $389,000

Our single-story models work on virtually any lot that meets setback and lot coverage requirements. They are the most straightforward to permit and the fastest to build.

The Wilshire is our most compact model — a studio layout with a corner shower that fits the tightest backyards. The Lincoln is our largest single-story, delivering the full feel of a standalone house with three bedrooms and two baths in 1,000 sqft. It is ideal for families or multigenerational living.

Two-Story Collection: $339,000 – $459,000

This is our primary competitive differentiator. No prefab ADU company — not Samara, not Abodu, not Villa — offers two-story models. Factory and transport constraints make it impossible for prefab. Because we are site-built and LA-based, we can build vertically, which means you get significantly more living space on a much smaller building footprint.

Look at The Fairfax: you get 840 sqft of living space — two bedrooms and a half bath downstairs — on a footprint of just 448 sqft. That is critical on narrow lots where setbacks and lot coverage eat into your buildable area. The Venice is our most popular two-story configuration, and The Culver at 1,200 sqft is comparable in size to a small single-family home.

All nine models are fixed-price, all-inclusive, and turnkey. Every price listed above includes design, engineering, permit processing, construction, interior finishes, and a move-in-ready home — including utility trenching and installation up to 75 linear feet for electrical, water, and sewer.

For full pricing details including what is and is not included, visit our ADU Pricing page.

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You Choose the Look: À La Carte Design Configurator

One of the things that sets our Signature Homes apart from other productized ADU companies is that every model is fully customizable in appearance. Rather than choosing from a handful of pre-set design packages, you build your ADU’s look piece by piece through our à la carte configurator — selecting one option per category across both exterior and interior finishes.

The result: over 15,000 unique design combinations per model — all at fixed, predictable pricing.

Exterior Selections

You choose from five exterior categories, and your selections are combined to create a cohesive look:

• Roof form: Flat roof with TPO membrane or gable roof with dimensional shingles — included in the fixed price at no additional cost.
• Siding: Sand finish stucco is standard. Upgrades include smooth stucco, James Hardie HardiePlank horizontal lap, and James Hardie HardiePanel vertical board-and-batten.
• Windows: White Milgard Trinsic windows are standard. Matte black Milgard Trinsic is available as an upgrade.
• Color scheme: Warm or cool palette included in the fixed price. A custom Sherwin-Williams color match is available as an upgrade.

Exterior lighting, front door style, and trim details are auto-assigned based on your roof and color scheme selections — so everything coordinates without you having to specify every detail.

Interior Selections

Inside, you choose from five finish categories. Every option at the base level is included in your fixed price — no option costs more than another:

• Cabinets: Walnut slab, bleached oak slab, charcoal black slab, or white shaker — all solid wood RTA cabinets.
• Countertops: Warm white/cream, white/light gray, or charcoal/dark — all Bedrosians quartz.
• Plumbing hardware: Champagne bronze, matte black, or brushed nickel — all Delta Nicoli.
• Flooring: Barrel, Whitelock, or Driftwood — all Daltile Bellamy Place luxury vinyl plank.
• Backsplash: Zagora mosaic, ice white subway, or black large format — all Bedrosians tile.

Cabinet hardware, shower glass finish, vanity, and lighting are auto-assigned based on your plumbing and cabinet selections. Bathroom finishes follow the kitchen, so the entire home feels cohesive without requiring dozens of individual decisions.

There is no upcharge for any interior selection and no upcharge for your roof form choice. Exterior siding, window color, and custom paint are the only categories with optional upgrades — and upgrade pricing is published per model so you know exactly what any change costs before you commit.

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Where Does the Money Actually Go? A Real Cost Breakdown

This is the section most ADU websites skip — a line-by-line accounting of where your construction dollars are actually spent. The following is a real cost breakdown from a Westwood Signature Home we built in the North Hills neighborhood of Los Angeles — a 550 sqft, 1-bedroom, 1-bath detached ADU priced at $259,000 turnkey.

This was a flat, corner lot with easy vehicle access — an ideal building scenario. The client made a minor plan modification, removing one window for additional privacy on the side of the home facing the neighbor. The sewer tie-in was a long distance from the ADU location, using the full 75 linear feet of utility trenching included in our pricing. The HVAC system was a 2-zone mini-split with dedicated zones for the main living area and the bedroom, giving the client independent temperature control throughout the home.

Note: City permit and plan-check fees are not included in this total. These fees vary by jurisdiction and are paid directly by the homeowner to the city. In the City of Los Angeles, expect approximately $3,000 to $6,000 for a standard ADU. We handle the entire permit submission and coordination process on your behalf — you just pay the city’s fees at cost.

A few things worth noting about this budget.

Plumbing and electrical are the biggest single line items at a combined $60,000 — roughly 23% of the total budget. This is typical for ADUs because you are building a complete home with a full kitchen and full bathroom in a relatively small footprint. Unlike a larger home where bedrooms and living areas dilute the per-square-foot cost, an ADU is kitchen-and-bathroom-dense, which drives these trades higher on a percentage basis.

The sewer connection used the full 75-foot utility allocation included in our Signature Home pricing. On this North Hills project, the city sewer line was a long run from the ADU location in the backyard. That distance added cost to the plumbing line item — but it was fully covered within the fixed price. Our pricing includes utility trenching and installation up to 75 linear feet for electrical, water, and sewer/drain. If your project requires longer runs, we identify that during pre-construction and bid it separately before the project starts — so there are no mid-project surprises.

The 2-zone HVAC system was a smart upgrade for a 1-bedroom. Rather than a single-zone mini-split, this client opted for dedicated zones in the living area and bedroom. That means you can keep the bedroom cool at night without overcooling the living space, or heat the living area during the day without wasting energy on an empty bedroom. It added roughly $2,500 over a single-zone system but meaningfully improves daily comfort and energy efficiency.

The window modification cost almost nothing. The client wanted to eliminate one window on the side of the home facing their neighbor for privacy. Because we caught this during design — before construction documents were finalized — the change was simple and had virtually no impact on the budget. This is one of the advantages of working with a design-build firm: design decisions and construction costs are coordinated from the start, not discovered after the fact.

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The Cost-Per-Square-Foot Question

I know many of you are already doing the math. The Westwood project above comes out to approximately $471 per square foot. Before you react to that number, let me explain why it is both accurate and potentially misleading.

An ADU is a complete, self-contained home — with a full kitchen, full bathroom, plumbing, electrical, HVAC, and all the infrastructure that comes with any residence. Kitchens and bathrooms are the most expensive rooms to build per square foot, and in a 400–500 sqft ADU, they represent a much larger percentage of the total floor area than they would in a 2,000 sqft house. There are no large, inexpensive-to-build bedrooms or living rooms to dilute the average.

This is why a 400 sqft ADU does not cost half of what an 800 sqft ADU costs. The fixed costs — foundation, sewer connection, electrical service, permit fees, HVAC — are similar regardless of size. What scales with square footage is primarily framing, drywall, flooring, and roofing. The expensive stuff stays roughly the same.

A better way to evaluate ADU cost is by the value it creates. In most Los Angeles neighborhoods, a new detached ADU adds $300,000 or more to the resale value of your property — often far exceeding the cost to build it. Combine that with rental income of $2,000 to $3,500+ per month depending on size and neighborhood, and the return on investment is difficult to match with any other real estate strategy available to homeowners.

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What Drives ADU Costs Up (and What Keeps Them Down)

Every property is different, and site conditions can push your budget in either direction. Here are the most common factors that affect your final cost.

Things That Increase Cost

Challenging site access. If your backyard is only accessible through a narrow side yard, materials and equipment have to be carried in by hand rather than delivered by truck or crane. This adds labor time and cost to virtually every phase of construction.

Sloped lots. A hillside property may require retaining walls, stepped foundations, or specialized grading that can add $15,000 to $40,000+ to your budget compared to a flat lot.

Long utility runs beyond 75 feet. Our Signature Home pricing includes utility trenching up to 75 linear feet. If your ADU sits farther from the existing sewer, water, and electrical connections, the additional distance is identified during pre-construction and bid separately — always before the project starts, never as a surprise mid-build.

Required upgrades to the main house. Some jurisdictions require you to upgrade the main house’s electrical panel, replace an aging sewer lateral, or install a new water meter as a condition of your ADU permit. These costs are not part of the ADU itself but are triggered by the project and are not included in our base pricing.

Soil conditions. Expansive soil, high water tables, or poor load-bearing capacity can require deeper footings, engineered fill, or specialized foundation systems.

Custom design. Moving beyond our pre-designed Signature Home models into fully custom architecture increases design fees, engineering complexity, and often construction cost. Our Custom Design-Build tier starts at $300,000 and can exceed $600,000+ depending on scope and complexity.

Things That Keep Costs Down

Flat, accessible lots. A level backyard with truck access from a driveway or alley is the ideal scenario. Site prep is minimal, foundation costs are lower, and trades can work efficiently.

Pre-Designed Signature Homes. Using a pre-engineered model eliminates weeks of custom design work and the uncertainty that comes with it. All nine of our models are architect-designed, structurally pre-engineered, and priced before you sign — compared to $15,000 to $25,000+ for a fully custom design from an independent architect, plus the risk of construction budget overruns.

Fixed-price contracts. A guaranteed, fixed-price construction contract protects you from the change orders and budget overruns that plague custom construction. Generic contractors typically come in 20–40% over their initial estimates by the time the project is finished. Our pricing is non-negotiable by design — what we quote is what you pay.

Newer main house infrastructure. If your electrical panel, sewer lateral, and water service are modern and adequate, you avoid the forced upgrades that can add $5,000 to $15,000 to your project.

Two-story models for tight lots. If your lot has limited buildable area due to setbacks or lot coverage rules, a two-story Signature Home like The Fairfax lets you get 840 sqft of living space on just a 448 sqft footprint — potentially avoiding expensive variances or a smaller-than-desired ADU.

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How ADU Options Compare in Los Angeles

If you are researching ADU companies in Los Angeles, you will likely come across a few different approaches — prefab builders like Samara and Abodu, site-built specialists like us, and independent general contractors. Each has trade-offs, and the right choice depends on your property, your priorities, and your budget. Here is a side-by-side comparison to help you evaluate:

A few things worth noting. Samara and Abodu both offer quality products with fixed pricing, which we respect — fixed pricing protects homeowners and we think every ADU company should offer it. Where we differ is in construction method and model selection. Prefab units are factory-built and transported to your property, which means they are limited in size by what can fit on a truck and cannot be built as two-story structures. Our Signature Homes are site-built on your property by LA-based crews, which gives us the flexibility to offer two-story models, larger floor plans, and designs that adapt to the specific conditions of your lot

With independent contractors, pricing is typically open-ended. The initial quote may look lower, but without a fixed-price contract, change orders and unforeseen costs can push the final number 20–40% higher by the time the project is complete. Our pricing is guaranteed before construction begins — what we quote is what you pay.

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Is an ADU Worth the Investment?

This is the question behind the question. You are not just asking what an ADU costs — you are asking whether it is worth spending that money.

Here is the math, using our Westwood Signature Home (1-bed, 1-bath, 550 sqft) — the same model we broke down in detail above — as an example:

A $259,000 investment that immediately adds $300,000+ in property value — creating over $41,000 in equity the day it is finished — while generating $26,000 to $33,000 per year in rental income. And if you finance the project with a HELOC, the rental income more than covers your monthly payment from the very first month.

This is why we say an ADU is not a cost — it is a leveraged real estate investment. And it is one of the best investments available to Los Angeles homeowners in 2026.

For a complete walkthrough of every financing option available to you, read our ADU Financing Guide for Los Angeles.