The Timeline for Building an ADU in San Diego: What to Expect from Start to Finish

Introduction

One of the biggest questions homeowners ask when considering an Accessory Dwelling Unit (ADU) is: "How long will it take to build?"

While ADUs are smaller than traditional homes, the process of designing, permitting, and constructing one still takes careful planning and coordination. A realistic timeline helps homeowners set expectations, avoid unnecessary delays, and ensure a smooth build.

In this post, we’ll break down the typical timeline for building an ADU in San Diego—step by step—so you know exactly what to expect before starting your project.

How Long Does It Take to Build an ADU?

On average, the entire ADU process takes 8 to 18 months from start to finish. This includes:

Pre-construction (3-6 months) – Feasibility study, design, and permitting.
Construction (4-9 months) – Site preparation, foundation, framing, utilities, and finishing touches.
Final inspections & move-in (1-3 months) – City approvals, utility connections, and occupancy readiness.

The actual timeline depends on several factors, including ADU size, design complexity, and city approval processes. Below, we’ll break down each phase so you can plan accordingly.

Phase 1: Feasibility & Planning (1-2 Months)

Before designing your ADU, you’ll need to assess your property’s suitability. This phase includes:

Zoning & Property Evaluation – Checking local regulations, setbacks, and utility connections.
Budget Planning – Determining financing options and estimating construction costs.
Choosing an ADU Builder or Architect – Partnering with experts who can guide you through the process.

Phase 2: Design & Architectural Plans (1-3 Months)

Once you confirm your ADU is feasible, the next step is designing it. During this phase:

Work with an architect or designer to create floor plans and elevations.
Decide on ADU type – Detached, attached, garage conversion, or JADU (Junior ADU).
Finalize materials & finishes to align with your budget and aesthetic preferences.

Phase 3: Permitting Process (2-4 Months)

San Diego has streamlined its ADU permitting process, but approval times can vary based on project complexity. Key steps include:

Submit plans to the city for zoning and building code review.
Receive plan check comments (if required) and make necessary revisions.
Secure all required permits (building, electrical, plumbing, mechanical).

Phase 4: Construction Process (4-9 Months)

Once permits are secured, construction can begin! The timeline varies based on factors like ADU size, site conditions, and weather, but generally includes:

A. Site Preparation & Foundation (1-2 Months)

• Clearing the area, grading the land, and pouring the foundation.

B. Framing & Roofing (1-2 Months)

• Constructing the walls, roof, and installing windows/doors.

C. Utilities & Systems (1-2 Months)

• Installing plumbing, electrical wiring, HVAC, and sewer connections.

D. Interior Finishing (2-3 Months)

• Drywall, flooring, cabinetry, painting, and final appliance installation.

Phase 5: Final Inspections & Move-In (1-3 Months)

Before you can officially use your ADU, the city must approve it through final inspections. This includes:

Building Inspection – Ensuring construction meets code requirements.
Utility Hookups – Finalizing water, sewer, gas, and electricity connections.
Certificate of Occupancy – The final approval needed before move-in.

What Can Delay an ADU Project?

Even with a well-planned timeline, certain factors can cause delays:

Permit processing delays – If city offices are backlogged, approvals may take longer.
Design changes mid-project – Altering plans after permits are issued can cause setbacks.
Material shortages – Some building materials may have long lead times.
Weather conditions – Rain or extreme heat can slow down construction.
Contractor availability – High demand for ADU builders can lead to scheduling challenges.

Conclusion: Plan Your ADU with Confidence

Building an ADU in San Diego is a rewarding investment, but it’s essential to have realistic expectations about the timeline. By understanding each phase—from feasibility to move-in—you can better prepare for the process and avoid unexpected setbacks.

At ADU Pals, we guide homeowners through every step of the ADU journey, ensuring a smooth and efficient build.