Building an Accessory Dwelling Unit (ADU) is a smart investment, but understanding the costs involved is key to making an informed decision. At Connest, we aim to simplify the process by offering transparent pricing and turn-key solutions. Here’s what you need to know about ADU costs in San Diego, California:

General Cost Estimates

For a turn-key, detached ADU ranging from 500–1,200 sqft, you can expect to pay between $375–$600+ per square foot, depending on design, finishes, and site conditions.

• Vertical building construction (structure and standard finishes) accounts for roughly 80–85% of the total cost.
• Additional costs include design, permitting, site work, and utility upgrades.

Cost Breakdown by ADU Size (All-In Costs)

Additional Costs to Factor In

1. Design Fees: Approximately $12,000
2. Professional design ensures your ADU meets your needs and complies with regulations.
3. Permitting Fees: Roughly $2–$14 per square foot (depending on the city)
4. Streamlined permitting processes in California make this step easier than ever.
5. Sitework: Around $25,000
6. This includes grading, foundation prep, and other site-specific requirements. Challenging properties may incur higher costs.
7. Utility Upgrades: Approximately $30,000–$50,000+
8. Depending on your property’s existing infrastructure, utility connections (water, sewer, electrical) may require upgrades.

Important Considerations

1. Construction Cost Index :
2. The California Construction Cost Index (CCCI) increased by 37% from January 2021 to January 2024. For example, an ADU that cost $300,000 to build in 2021 would now cost approximately $410,000 in 2025.
3. Multiple ADUs :
4. Building a second ADU may cost around 85% of the first unit’s price, but the cost per square foot won’t decrease as much as simply adding square footage to a single ADU.
5. Cost Drivers :
6. Several factors influence the final cost, including:
   • Size of the unit
   • Number of units being built
   • Site conditions (grading, utility locations)
   • Local permitting requirements
7. Sitework Variability :
8. Sitework is often the most variable cost and can exceed tens of thousands of dollars on challenging properties.

Why Choose Connest for Your ADU?

At Connest, we take the guesswork out of ADU construction:

• Pre-Approved Designs: Hassle-free permitting with HCD certification.
• Durable Steel-Frame Construction: Fire-resistant, earthquake-safe, and energy-efficient.
• Turn-key Solutions: From design to installation, we handle everything so you don’t have to.
• Built 3x Faster: Move-in ready in weeks, not months.

Ready to Get Started?

Investing in an ADU is not just about adding value to your property—it’s about creating opportunities for rental income, multi-generational living, or contributing to affordable housing solutions.

Contact us today to learn more about how Connest can help you build a high-quality ADU tailored to your needs and budget.

Building a traditional Accessory Dwelling Unit (ADU) typically takes 10 to 18 months from start to finish. The timeline depends on the complexity of the design, permitting requirements, and site conditions. Here’s how the process generally breaks down:

Design Phase:
The design process takes approximately 3 to 4 months and includes creating architectural plans and the construction documents required for permitting. More complex designs or challenging site conditions can extend this timeline.

Permitting Phase:
Permitting can take 3 to 8 months, depending on the city’s approval process, local jurisdiction requirements, and potential additional reviews from homeowners associations (HOAs) or coastal authorities.

Construction Phase:
Traditional on-site construction typically takes 5 to 7 months. Factors like weather, site conditions, and subcontractor availability can further extend this timeline.

Common Delays in Traditional ADU Construction

Several factors contribute to extended timelines, including:

• Lengthy city permitting and review processes
• Additional approvals required for coastal zones or HOAs
• Utility upgrades, such as sewer or electrical system enhancements
• Material shortages and supply chain delays
• Weather-related interruptions
• Design revisions and plan resubmissions

These factors often create a domino effect, delaying each subsequent phase of the project.

The Connest Modular Advantage

At Connest, we believe that building an ADU shouldn’t take over a year. Our modular construction process significantly reduces build time, offering move-in ready ADUs in as little as 12 weeks with our Fast-Track Program.

Why is Connest faster?

Pre-Approved and Certified:
Our modular ADUs are pre-approved, HCD-certified, and Title 24 compliant, which eliminates months of permitting delays.

Off-Site Manufacturing:
While your site is being prepared, we manufacture your ADU in our controlled facility. This parallel process drastically cuts down the total timeline.

Weather-Resistant Production:
Factory construction prevents weather-related delays that often slow traditional builds.

Rapid Installation:
Our plug-and-play system allows us to complete on-site installation in a matter of days, not months.

Streamlined Permitting Support:
We manage the permitting process, ensuring faster approvals and minimal back-and-forth with city officials.

The Result:
With Connest, you can move into your ADU three times faster than with traditional construction, without sacrificing quality or safety.

Ready to build faster and smarter?

Contact us today to learn how Connest can simplify your ADU project and get you into your new space sooner.

With Connest’s modular approach, ADUs can be completed in as little as three months, far quicker than traditional construction.

Yes, financing options include home equity loans, construction loans, and refinancing. Connest partners with lenders to offer financing solutions tailored to your budget.

Investing in an ADU offers multiple benefits, such as generating rental income, enhancing property value, and providing additional space for your lifestyle needs. It’s a smart, long-term investment for your property.

The process includes site evaluation, design selection, permitting, off-site manufacturing, delivery, and on-site installation. Connest manages each step to simplify your project.