Breaking Down the Costs of Building an ADU: What to Expect

Building an Accessory Dwelling Unit (ADU) can be one of the smartest investments you make—whether it's for rental income, a guest house, or extra space to work or live. But as someone who's been deep in the world of prefab homes and modular solutions for years, I can tell you that understanding the true cost of building an ADU is a crucial first step.

In this guide, we’ll go through a comprehensive ADU cost breakdown, including initial planning, permits, construction, and even some unexpected add-ons. Whether you're going all-in on a custom build or curious about prefab options like the Autonomous WorkPod, this is everything you should know before you break ground.

Initial Planning and Design Costs

Before construction starts, there’s a lot of groundwork—literally and figuratively.

Architectural and Design Fees

One of the first costs you’ll encounter is the design process. If you're going the traditional route with a custom ADU, you’ll likely hire an architect or designer. How much do ADU plans cost? Typically, between $2,000 to $15,000, depending on complexity. That cost includes conceptual designs, construction drawings, and often a few rounds of revisions.

• A simple garage conversion may be on the lower end.
• A detached, two-story ADU with a unique layout and high-end finishes could easily push the budget higher.

Many cities (especially in California) offer pre-approved ADU plans to cut down on time and fees. And if you go prefab, design fees are often bundled into the cost—saving you thousands upfront.

Permits and Approvals

Once you’ve got your plans, it’s time to get them approved. Permit costs vary depending on your city and the scope of your project. You may be dealing with:

• Building permits
• Electrical, plumbing, and mechanical permits
• Plan review fees
• School impact fees (in some districts)

Total permit costs typically land in the $1,000 to $3,000 range, but some cities can charge more. Delays and revisions during the permitting process can also drive up costs and stress, so it's smart to have a clear plan from the start.

Site Surveys and Soil Tests

These are the less glamorous parts of the process, but they’re essential. A site survey confirms your property boundaries, helps avoid future legal issues, and ensures your ADU fits within zoning setbacks. A soil test may be required to determine if the ground can support a new foundation. These costs typically range from $500 to $2,000.

If your site has slope issues, drainage challenges, or unusual soil conditions, costs can go up due to engineering requirements.

Construction Costs

The construction phase is where the bulk of your budget will be spent. ADU building cost can vary significantly based on factors such as location, materials, and labor. On average, the construction costs can range from $100,000 to $300,000, translating to an ADU cost per square foot of $150 to $300.

• Building a solid foundation and structure is essential. This can cost between $30,000 and $50,000, depending on the size and complexity of the ADU.
• Framing and roofing typically cost between $20,000 and $40,000, depending on the materials used and the size of the ADU.
• The cost of exterior finishes (such as siding and painting) and interior finishes (such as drywall, flooring, and painting) can range from $25,000 to $70,000.
• Installing windows and doors can add another $10,000 to $20,000 to the construction budget.
• The overall ADU cost breakdown will depend on your design choices and quality of materials, influencing the final building ADU cost.
• Connecting your ADU to utilities like water, electricity, and sewer systems is another essential aspect of the project. These costs can be substantial, ranging from $10,000 to $30,000.
• Water and Sewer Connections can cost between $5,000 and $15,000, depending on the distance from existing lines and local fees.
• Wiring the ADU for electricity, including the installation of a new meter if needed, can cost between $3,000 and $10,000.
• Installing plumbing for kitchens and bathrooms typically costs between $2,000 and $5,000.
• Utility connection costs are crucial to factor into your overall ADU construction cost per square foot, ensuring your new space is fully functional and compliant with local codes.

Additional Costs

Beyond the primary categories, there are other potential costs to consider:

Landscaping: Adding or modifying landscaping around your ADU can cost between $2,000 and $10,000.

Furniture and Appliances: Outfitting your ADU with necessary furniture and appliances can range from $5,000 to $15,000, depending on your preferences.

Insurance: Updating your homeowner's insurance to include the new structure can add another $500 to $1,000 annually.

Prefabricated ADUs: In some regions, such as Los Angeles, opting for a prefab ADU can significantly influence costs. The prefab ADU cost in LA can range from $50,000 to $150,000, offering a potentially more affordable and quicker alternative to traditional construction.

Understanding these additional expenses will give you a comprehensive view of how much building an ADU costs.

Custom, stick-built ADUs are often the most expensive because of labor, timeline, and material management. They also require more inspections, on-site coordination, and subcontractors.

Prefab ADUs, on the other hand, are manufactured in a controlled environment and delivered for on-site installation, which dramatically cuts down construction time (and usually costs). Depending on the size and features, prefab models can save you 10–30% over custom builds.

Cost-Saving Tips for Building an ADU

When planning and constructing an Accessory Dwelling Unit (ADU), it's crucial to manage your budget efficiently. Here are eight detailed cost-saving tips to help you minimize expenses while ensuring a high-quality build.

1. Plan Efficiently

Efficient planning is the cornerstone of a successful ADU project. By investing time and resources into the planning phase, you can identify potential issues early, which helps prevent costly changes and delays during construction. Work with experienced architects and contractors who understand local building codes and regulations. They can help you create a comprehensive plan that covers everything from design and materials to permits and utilities. Detailed planning ensures that every aspect of your project is accounted for, reducing the likelihood of unexpected expenses.

2. Simplify Design

Choosing a simple and efficient design can significantly cut down on your construction costs. Complex designs with custom features and irregular shapes often require more materials and labor, driving up the overall expense. By opting for a straightforward layout, you streamline the construction process. Standard sizes for windows and doors are typically less expensive than custom sizes, as they are mass-produced and readily available. Simplifying your design not only saves money but also shortens the construction timeline.

3. Choose Prefab Options

Prefabricated ADUs are manufactured off-site and assembled on your property, which can lead to significant savings in both time and money. The controlled environment of a factory reduces waste and ensures higher quality construction. In areas like Los Angeles, prefab ADU costs can be much lower than traditional builds due to reduced labor and material costs. Additionally, prefab ADUs often come with streamlined permitting processes, further cutting down on expenses and construction time.

4. DIY Where Possible

Taking on some of the work yourself can substantially reduce labor costs. Tasks like painting, landscaping, or even installing fixtures can be managed by homeowners with the right skills and tools. However, it's essential to be realistic about your abilities and time commitment. While DIY can save money, mistakes can be costly to fix. Focus on tasks that match your skill level and leave more complex work, such as electrical or plumbing, to licensed professionals.

Plug-and-Play ADUs That Actually Look Good

If prefab is on your radar, let’s talk about the Autonomous WorkPod line. These aren’t just "sheds with insulation"—they’re purpose-built, modern structures that ship ready to install. They’re great if you want to avoid the long lead times and unknowns of traditional construction.

WorkPod

The original WorkPod is a compact yet thoughtfully designed unit, perfect for turning unused backyard space into something meaningful. Whether you're building a dedicated home office pod, music room, or meditation retreat, the WorkPod offers a quiet, insulated environment you can count on year-round.

• Fully insulated and sound-dampened
• Weather-resistant for all seasons
• Ready to use in few days—just plug in and go

It’s one of the fastest, most functional ways to add livable square footage to your property.

WorkPod

Next-level WFH.

97 reviews

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Specifications

Overall size	8.5’W x 12’L x 11’H
Floorspace	102 square feet
Ceiling height	6.8’ to 9.3’
Weight capacity	2.9 tons
Door & Window dimensions, material (include glass)	Main door: 7.5’W x 6.8'H 3 windows: 1.1’W x 7.9’H Window material: Wooden frame, 5/16” tempered glass, composite wood cover Door material: Anodized aluminum frame, 5/16” tempered glass
Siding, roof, floor & balcony material	Siding: Plywood 1/2”, wooden frame, honeycomb paper, plywood 3/8”, bitume, housewrap, vinyl siding Roof: Roof shingles Floor: Plywood Balcony: Composite wood
Electrical devices	1 RCB (Residual current breaker) 3 Wall outlet (Universal wall sockets) 1 Ceiling light switch 1 Ceiling light 1 Ventilator switch 1 Ventilator 66ft power cable with 2 connectors
Power input	Maximum voltage: 110V AC (US standard) Maximum current: 25A Maximum power dissipation: 2750W
Interior furniture	Unfurnished option: 1 Bookshelf, 1 Electrical Cabinet Furnished option: 1 SmartDesk Connect, 1 Autonomous Chair Ultra, 1 Monitor Arm, 1 Cable Tray, 1 Filing Cabinet, 1 Anti-Fatigue Mat, 1 Bookshelf, 1 Electrical Cabinet
Compatible with	Portable air conditioner: A/C units with dimensions smaller than 22” L x 20” W x 88” H and a 5.9” vent hole diameter will fit well. Heater: A small personal heater is more than sufficient.

• 

  "The WorkPod has made an incredible difference in my productivity. I now have a dedicated backyard workspace that's both comfortable and efficient." - Tyler M.
• 

  "I'm impressed by the WorkPod's design and functionality." - William H.
• 

  "The WorkPod's privacy features make it easy to take important calls or have virtual meetings without interruptions."

  - Ben D.

WorkPod Versatile

Need more room or flexibility? The WorkPod Versatile delivers a larger footprint and opens the door to a wider range of uses—think guest room or art studio. It’s designed for those who want a multi-use space that evolves with their needs.

• Spacious enough to add a bed, desk, or workout setup
• Strong enough to handle year-round use
• Flexible layout with easy customization options

This model is ideal if you're looking to blend lifestyle, function, and a little future-proofing.

WorkPod Versatile

For work and play.

54 reviews

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Specifications

Overall size	8’4”W x 12’6”L x 9’10”H
Floorspace	105 square feet
Ceiling height	7’3”
Weight capacity	2.9 tons
Pedestal	18”W x 43”L x 7”H
Door & Window dimensions, material (include glass)	Main door: 39”W x 89”H Large window: 59”W x 81”H Small window: 39”W x 39”H Window & door material: Powder coated aluminum, 5/16” tempered glass
Siding, roof, floor & balcony material	Siding: Plywood 1/2”, steel frame, honeycomb paper, plywood 3/8”, bitume, housewrap, vinyl siding Roof: Roof shingles Floor: Plywood Pedestal: Steel frame & wood plastic composite
Electrical devices	1 RCB (Residual current breaker) 5 Wall outlet (Universal wall sockets) 1 Ceiling light switch 4 Ceiling light 1 Ventilator switch 1 Ventilator 2 Ethernet wall port 66ft power cable with 2 connectors
Power input	Maximum voltage: 110V AC (US standard) Maximum current: 25A Maximum power dissipation: 2750W
Furniture (optional)	Cabinet, Desk, Small & Big Bookshelf, TV Shelf, Foldable Sofa Table & Electrical Cabinet* (*Electrical Cabinet always included)

• 

  "The StudioPod has been a remarkable addition to my backyard. Its design and functionality create an inspiring workspace that's truly a game-changer."

  - Keith H.
• 

  "What I really love about the StudioPod is it's multi-purpose. You can use it for work, it has a good desk, plenty of storage space. You can use it for playing video games, watching games, being noisy without disturbing family life. You can also extend it and use for having people sleeping over!" - Jaime H.
• 

  "Excellent customer service for StudioPod. Quick responses."

  - Matthew C.
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  "The StudioPod's ergonomic chair provides excellent support for long hours of work."

  - Marcus D.

WorkPod mini

Not every yard can handle a big structure—and not every use case needs one. That’s where the WorkPod mini shines. It brings the same level of craftsmanship and comfort, just in a tighter, more budget-friendly package. Think of it as your personal escape pod.

• Space-saving design for small or narrow yards
• Ideal for solo work, study, or quiet focus zones
• Minimal setup time and lower upfront cost

This is a great entry point into prefab ADUs, especially for homeowners with limited space or minimalist needs.

WorkPod mini

For small yards and budgets.

8 reviews

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Specifications

Dimension	Overall size: 8’7"W x 9’L x 9’3"H Floorspace: 80 square feet Ceiling height: 7’3" Weight capacity: 2.3 tons (including Pod body) Pedestal: 24"W x 103"L x 9"H
Door & Window dimensions, material (include glass)	Main door: 37"W x 89"H (open side) & 33"W x 89"H (fixed side) Window: 43"W x 20"H Window & door material: Powder coated aluminum, 5/16" tempered glass
Siding, roof, floor & balcony material	Siding: Plywood 1/2" , steel frame, honeycomb paper, plywood 3/8", bitume, housewrap, vinyl siding Roof: Metal roofing Floor: Plywood Balcony & Pedestal: Steel frame & wood plastic composite
Electrical devices	1 RCB (Residual current breaker) 2 Wall outlet (Universal wall sockets) 1 Ceiling light switch 1 Ceiling light 1 Wall light 1 Ethernet wall port 66ft power cable with 2 connectors
Power input	Maximum voltage: 110V AC (US standard) Maximum current: 25A Maximum power dissipation: 2750W

• 

  "Would prefer it. Love the way it fits right into my backyard space. Actually the material & design looks better than my expectation. Would prefer it to my network."

  - Alejandro B.
• 

  "A perfect fit for our tight backyard space. We love how this allowed us to get extra space without the headache of going through permits or renovation costs. The Pod Lite is small enough to not be considered an ADU that requires permitting and clearance from the city, which is amazing. Such an innovative solution, especially as more people are working from home now. It’s going to be our new office space!" - Katie S.
• 

  "Very worth it. The WorkPod Lite surpassed my expectations with its faithful resemblance to the website's depiction. Its design is not only visually consistent but also surprisingly spacious. The material is also very sturdy and weather resistance."

  - Hee-Sang L.
• 

  "The WorkPod Lite is a fantastic buy! Despite a slightly delayed delivery, it effortlessly nestled into my compact backyard. Quick assembly had it up and running within days. Highly recommended!"

  - Meredith H.

WorkPod Solar

For those aiming to build smarter and greener, the WorkPod Solar brings eco-conscious design into the mix. It comes equipped with integrated solar panels, helping you offset energy use and reduce long-term operating costs.

• Lower environmental impact
• Ideal for remote locations with limited access to utilities
• Great for those seeking a self-sustaining ADU option

Over time, the Solar version can help pay for itself—making it one of the most forward-thinking prefab options available today.

WorkPod Solar

118 reviews

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Specifications

Solar panel	System size: 70.7" x 138.5" x 4.7"~5.5" Number of solar panels: 3pcs Solar panel size: 67.8" × 44.6" × 1.18" Solar panel weight: 46.7lbs Solar Cell: 108pcs Maximum Rating Power: 430W Module Efficiency: 0.22 Operating Temperature: −40 °F to +185 °F
Inverter	Inverter size: 17.9" x 13.8" x 5.1" Inverter weight: 25.4lbs Maximum Rating Power: 3000W Maximum Efficiency: 0.93 AC output: 120V Output frequency: 50/60Hz Operating Temperature: 32 °F to +132 °F
Battery Cabinet	Battery cabinet size: 15.8" x 23.7" x 21.7" Number of Battery: 2pcs Battery size (1pc): 5.6" x 18.5" x 17.2" Battery weight (1pc): 99lbs Battery capacity: 10.2kWh Voltage: 48V Cell type: LiFePo4 Internal resistance: ≤ 40mΩ Operating Temperature: −4 °F to +140 °F
Dimension	Overall size: 8.5’W x 12’L x 11’H Gross floor area - GFA (Including external walls): 102 square feet Ceiling height: 6.8’ to 9.3’ Weight capacity: 2.9 tons
Door & Window dimensions, material (include glass)	Main door: 7.5’W x 6.8'H 3 Windows: 1.1’W x 7.9’H Window material: wooden frame, 5/16” tempered glass, composite wood cover Door material: anodized aluminum frame, 5/16” tempered glass
Siding, roof, floor & balcony material	Siding: plywood 1/2”, wooden frame, honeycomb paper, plywood 3/8”, bitume, housewrap, vinyl siding Roof: roof shingles Floor: plywood Balcony: composite wood
Electrical devices	1 RCB (Residual current breaker) 3 (Universal wall sockets) Wall outlet 1 Ceiling light switch 1 Ceiling light 1 Ventilator switch 1 Ventilator 66ft power cable with 2 connectors
Power input	Maximum voltage: 110V AC (US standard) Maximum current: 25A Maximum power dissipation: 2750W
Interior furniture	Unfurnished option: 1 Bookshelf 1 Electrical Cabinet Furnished option: 1 SmartDesk 5 1 ErgoChair Ultra 2 1 Monitor Arm 1 Cable Tray 1 Filing Cabinet 1 Anti-Fatigue Mat 1 Bookshelf 1 Electrical Cabinet
Compatible with	Dreo Portable Air Conditioner: The best choice for WorkPod with: 12000 BTU fast cooling 16 feet long-range cooling 35-80° wide-angle auto swing 65-85°F cool 30%-80% humidity setting 4 levels of fan 46 dB quiet working Drainage-free in cool mode 3-in-1 mode with cool, fan, and dehumidifier Large LED display Touchpad/APP/Voice/Remote control Works with Alexa & Google Assistant White color Heater: A small personal heater is more than sufficient.

• 

  Optimize every square foot of your 102 sq. ft. WorkPod Solar for maximum productivity and comfort.
• 

  Go green and achieve more with a workspace that works as hard as you do—all powered by the sun.
• 

  Ergonomic design meets functional innovation. Feel at ease and focused in your personal office.
• 

  From energy systems to installation, WorkPod Solar is designed to let you focus on what you do best.

Whether you’re planning to use your ADU as a home office, guest suite, or creative space, the Autonomous WorkPod series offers something traditional builds can’t: speed, predictability, and peace of mind. Instead of waiting months for permits and construction, you can have your pod delivered, installed, and ready for use in a fraction of the time—and often at a much lower total cost.

If you're serious about adding space without adding stress, a WorkPod might be your smartest move yet.

Conclusion

So, what’s the bottom line on the cost of an ADU?

Depending on your location, design choices, and whether you go custom or prefab, you’re looking at a price tag anywhere from under $20,000 to $300,000+ (for large, luxury detached units). But if you approach it strategically—choosing the right team, sticking to a clear plan, and considering prefab options—you can absolutely build an ADU that fits your needs and your budget.

Whether you're exploring the ADU cost in the Bay Area, the cost of ADU in California, or the ADU cost in San Diego, being well-informed about each aspect of the process will help you manage your project efficiently. By taking a strategic approach to your ADU build, you can create a high-quality living space that meets your needs while staying within your budget.

Thinking about a no-fuss option with a fast timeline and a modern aesthetic? The Autonomous WorkPod lineup is one of the easiest ways to bring an ADU to life without the stress of traditional building.

Whether you're building a guestroom, renting out a studio, or adding your dream backyard office, now you’ve got the details (and a few ways to save while you’re at it).