Planning an ADU in San Diego: What to Know Before You Build

Accessory dwelling units — ADUs — have become one of the most popular ways San Diego homeowners add value and flexibility to their property. Whether you want rental income, a place for aging parents, or a quiet home office, an ADU can be a smart investment. Here's what to think through before you start.

1. Decide what the ADU is for

How you'll use the space shapes the whole design:

• Rental income points toward a full, self-contained unit with its own entrance.
• Multigenerational living often means single-level, accessible layouts.
• A home office or studio can be smaller and simpler.

2. Know your ADU options

There's more than one way to add an ADU:

• Detached ADU — a standalone backyard cottage.
• Attached ADU — added onto the existing home.
• Garage conversion — turning existing square footage into living space.

The right choice depends on your lot, your goals, and your budget. We'll help you weigh them.

3. Understand what drives cost and timeline

ADU cost depends on size, site conditions, utility connections, and finish level. Detached units generally cost more than conversions because they need their own foundation and utilities. Permitting timelines vary, so it pays to work with a team that knows the local process.

4. Work with a design-build team

Because an ADU is a small building in its own right — foundation, framing, plumbing, electrical, finishes — a design-build firm can take you from concept through permits to completion with one point of contact. That's exactly how we approach every ADU at Stel Builders.

Curious what's possible on your property? Request a consultation and we'll take a look.