ADUs and home additions in San Diego
We design, permit and build junior ADUs, garage conversions, detached ADUs and room additions across San Diego County. Every project starts with a feasibility review, so you know what your lot allows before you pay for drawings.
Junior ADU from $50,000 · Garage conversion from $80,000 · Detached ADU from $250,000 · Additions from $250 per sq ft
ADUs and additions at a glance
| Starting price | Junior ADU from $50,000. Garage conversion from $80,000. Attached ADU from $150,000. Detached ADU from $250,000. |
|---|---|
| Room additions | From $250 per square foot |
| Construction time | Depends on the size and the site; a written schedule once the plans are approved |
| Permits | Always required. We prepare the plans and handle the city or county review. |
| First step | A feasibility review of setbacks, utilities, access and slope before you pay for design |
| Warranty | 1 year on workmanship, in writing in your contract. Manufacturers' warranties pass on to you |
| Where | San Diego County, including the City of San Diego, Poway, Escondido, San Marcos, Carlsbad and Encinitas |
ADU or addition?
A room addition makes your house bigger: a bedroom, a primary suite, a larger kitchen and family room, or a second story. It shares your walls, your utilities and your front door.
An ADU is a separate home on the same lot, with its own entrance, kitchen and bathroom. Families use them for a parent, a grown child or long-term rental income.
A junior ADU is a smaller unit, up to 500 square feet, created inside the existing house or an attached garage. It’s usually the lowest-cost way to add a legal second unit. Read our junior ADU guide.
If you need more room for your own household, that’s an addition. If you need a second household on the property, that’s an ADU. When it could go either way, we price both.
How long it takes
Room additions: 3 to 5 months of construction.
ADUs: Construction time depends on the size of the ADU and the site. Design, engineering and city review come first, and we don’t promise a date for that part because the city’s review time is out of anyone’s control. Once the plans are approved, you get a written construction schedule. When you compare builders, check whether their schedule counts permits or only construction.
What ADUs and additions cost
Our 2026 starting prices. Your lot has a lot to do with where you land, which is why we start with feasibility.
JADU (up to 500 sq ft, inside the home)
A junior ADU carved out of existing space, with its own entrance and an efficiency kitchen.
Garage conversion ADU
Turning an attached or detached garage into a legal living unit.
Attached ADU
A new unit built onto the existing house.
Detached ADU
A standalone backyard home, from foundation to finish.
Every project is scoped and quoted individually. City permits and fees are billed separately.
Additions and new homes
Room additions
Bedrooms, primary suites, family rooms and second-story additions.
New construction
Ground-up homes on your lot.
Every project is scoped and quoted individually. City permits and fees are billed separately.
Why two ADUs the same size can cost very different amounts
Converting or building new
A garage conversion starts with a slab, walls and a roof you already own. A detached unit needs all three.
Utilities
How far the unit sits from water, sewer and power, and whether your electrical panel can carry a second home. A long trench through a finished yard adds up.
Access, slope and foundation
A flat lot with a wide side yard is simple. A slope, or a spot machinery can’t reach, changes the foundation and the labor.
What the feasibility review covers
| Your lot | Setbacks, slope and the buildings already on it |
|---|---|
| How you’ll use it | More room for your own household points to an addition. A second household, such as a parent, a grown child or a long-term tenant, points to an ADU. |
| Access | Side-yard width, and whether machinery can reach the spot |
| Utilities | Water, sewer and power connections, and what your electrical panel can carry |
| Which rules apply | Plans go to the City of San Diego, the County or your own city, depending on where you live. State law sets the basics and local rules add detail, so we confirm what applies to your property. |
You find out what your lot will cost to build on before you commit to design.
A detached ADU we’re building in Del Mar
This backyard ADU is under construction now. It has a butterfly roof and a covered entry porch.
The photo at the top of this page shows it framed and sheathed. We’ll add the finished photos when it’s done.
From feasibility to move-in
Consultation
We visit and talk through what the new space needs to do.
Feasibility
Setbacks, utilities, access and slope, checked before anyone pays for drawings.
Design and engineering
Architectural plans, structural engineering and 3D renderings.
Permits
We submit the plans and answer plan-check comments until they’re approved.
Construction
Foundation, framing, utilities, inspections and finishes.
Final inspection
We see it through sign-off and walk the finished unit with you.
ADU and addition questions
How much does an ADU cost in San Diego?
Our junior ADUs start at $50,000, garage conversions at $80,000, attached ADUs at $150,000 and detached ADUs at $250,000. Utilities, access, slope and foundation work are the biggest variables. Permit and plan-check fees are billed separately.
How long does it take to build an ADU?
Construction time depends on the size of the ADU and the site. Design, engineering and city review come first, and we don’t promise a date for that part because the city’s review time is out of anyone’s control. Once the plans are approved, you get a written construction schedule.
How big can my ADU be?
It depends on your lot, setbacks, existing structures and the rules where you live. We work it out in the feasibility review, before you commit to a design.
Is a garage conversion cheaper than a detached ADU?
Usually. The slab, walls and roof are already there. A detached unit gives you more freedom over layout and privacy. We can price both during feasibility.
Will an ADU raise my property taxes?
In California, generally only the value of the new construction is added to your assessment. Your existing home isn’t reassessed from scratch. Check the details with a tax professional.
Can I rent out my ADU?
Long-term rental is the most common reason our clients build one. Short-term rentals are regulated separately in San Diego, and we’ll point you to the rules that apply to your property.
What warranty do you offer?
Every project comes with our written warranty: 1 year on our workmanship, starting when the work is substantially complete. If a defect in our work shows up in that year, let us know in writing and we’ll fix it at no charge. Materials, fixtures and appliances carry their manufacturers' warranties, which we pass on to you. The full terms, including what isn’t covered, are in your contract. You can read the current wording on our client care and warranty page.
Do you build new homes from the ground up?
Yes, starting at $300 per square foot. Construction usually takes 8 to 12 months. Design and city review come first, and we give you a written construction schedule once the plans are approved.
Find out what your lot allows
Send us a few details about the project and we’ll set up a visit to look at the space.
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