Detached ADU Construction San Diego
Build a detached ADU in San Diego, CA with one local company for design, permits, and construction, from the first idea to the final walkthrough.
Get Free ConsultationWhat Homeowners Say About the Process
Homeowners work with IL Total Design and Build for clear ADU planning, permit support, design help, and construction guidance.
“I utilized IL Total Design and Build to design and build a custom ADU here in San Diego. I cannot imagine having a better experience or final house.”
nursenancyfoster · ADU design-build
“Rummy drove this to the end for the permit to finally be granted to us. The design itself is beautiful. She is talented, honest, and dependable.”
Leah T. · ADU permit and design
“Rummy walked us through multiple different design ideas and came out to the property to understand the current layout, landscape, and how the sun hit our home.”
Blair S. · ADU design
A Private Home Built Around Your Property
A detached ADU is a separate living space on the same property as the main home. It can work for family, guests, long-term rental use, an adult child, aging parents, or simply more private living space.
Unlike a garage conversion or attached ADU, a new detached structure gives you more freedom to plan the footprint, rooms, roofline, windows, and outdoor connection around the lot.
IL Total Design and Build handles property review, ADU design, permit planning, city submittals, construction, and project coordination from the first consultation to the final walkthrough.
Design, Permits, and Construction Under One Roof
A detached ADU should be planned around the property before construction starts.
Property Review First
We review the lot, existing home, access, utilities, slope, local rules, fire requirements, and other site conditions before the project moves forward.
One Coordinated Process
Design, permit planning, and construction stay connected, which means fewer handoffs and one company responsible for moving the project forward.
Find Out What May Fit on Your Property
Start with the lot, the space you have, your goals, and a realistic project scope.
Why Homeowners Choose a Detached ADU
A detached ADU gives the new living space its own identity while keeping it on the same property as the main home.
More Privacy
No shared wall with the main house. Family members, guests, or long-term tenants can have a more independent place to live.
Custom Layout
The new structure can be planned around your lot, access, views, outdoor space, room needs, and the way the ADU will be used.
Long-Term Flexibility
The same ADU can support changing needs over time, from family housing to guest space, work space, or a long-term rental.
Real Detached ADU Project Costs
These examples come from completed IL Total Design and Build projects. They show why size alone does not determine cost. Site work, structure, finishes, utilities, and added scope all matter.
Custom Detached ADU for Family
A high-end custom detached ADU built for family use. Finish level, cabinetry, flooring, tile, appliances, and other selections pushed this project toward the top of the cost range.
View Poway Detached ADU Project
580 Sq Ft Detached ADU
A compact detached ADU on a flatter lot with good utility access. The smaller footprint and simpler site conditions helped keep the full project cost lower.
640 Sq Ft ADU With Added Main-Home Scope
This total covered more than the detached ADU. The project also included a 380 sq ft home addition and structural garage or storage work. The supplied project record lists the detached ADU portion at about $310,000.
What Does a Detached ADU Cost in San Diego?
Based on the completed-project records supplied for this page, the cost range changes with the size of the ADU, the lot, the finish level, and the amount of site work.
| Project Type | Typical All-In Range |
|---|---|
| Compact detached ADU, about 500–650 sq ft, standard finishes | $200,000–$300,000 |
| Mid-size detached ADU, about 650–900 sq ft, mid-range finishes | $280,000–$400,000 |
| Large detached ADU, about 900–1,200 sq ft, higher-end finishes | $400,000–$600,000+ |
| Sloped-lot work, retaining walls, or deeper excavation | Can add $20,000–$60,000 |
| Coastal-area project conditions | Can add roughly 5–10% |
The older completed-project record also puts many standard detached ADUs around $350–$500 per sq ft, with more difficult sites and luxury finishes running higher. For a deeper breakdown, see the San Diego ADU cost guide.
How We Build a Detached ADU
Each phase stays connected, from the first property review through final inspections.
Property Feasibility
We review the lot, setbacks, zoning, access, utilities, slope, and the space available for a detached ADU.
Custom Design
We develop the layout, elevations, and design around the property and the way you plan to use the new space.
Engineering and Energy
Structural calculations, energy documents, and the required technical information are prepared for the permit set.
Permits and City Review
We prepare the submittal, respond to plan-check comments, and help move the project through the required city review.
Ground-Up Construction
Construction covers the foundation, framing, utilities, mechanical work, insulation, drywall, finishes, fixtures, and exterior work in the approved scope.
Final Inspections
We coordinate the final inspection steps and project close-out so the completed ADU is ready for use.
Detached ADU Rules to Know in 2026
ADU rules depend on the property, zone, height, fire area, coastal location, and project type. These are useful starting points, not a substitute for a property review.
Up to 1,200 Sq Ft
The City of San Diego defines an attached or detached ADU as 1,200 square feet or less. Floor-area and site rules can still affect what fits on a specific lot.
Two Stories in Single-Family Zones
For lots that allow single-family development but not multifamily development, the City allows detached ADU structures up to two stories, subject to the base and overlay-zone height rules.
Setbacks Are Property-Specific
Front, side, and rear requirements depend on the structure height, base zone, adjacent uses, fire conditions, building code, and other site limits. Some ADUs can encroach into side or rear setback areas.
No ADU Owner-Occupancy Requirement
The City states that the property owner is not required to live on-site for an ADU. JADUs follow different rules.
31-Day Minimum Rental Term
City guidance states that an ADU may not be leased for less than 31 consecutive days.
Coastal and Fire Areas Need Extra Review
Coastal overlays, fire hazard areas, brush management, and building-code requirements can add site-specific conditions to the project.
For current city guidance, see San Diego Information Bulletin 400.
Detached ADU vs. Other ADU Types
A detached ADU is not the right fit for every lot or budget. Here is a simple way to compare the main options before deciding what to plan.
| Factor | Detached ADU | Garage Conversion | Above-Garage ADU | Attached ADU |
|---|---|---|---|---|
| Typical project cost from the older page records | $200K–$585K+ | $100K–$180K | $200K–$320K | $180K–$320K |
| Design freedom | Highest | Limited by existing garage | Moderate | Moderate |
| Privacy from main home | Highest | Good if garage is detached | Good | Shared connection or wall |
| Yard impact | Uses buildable yard area | Uses existing structure | Uses existing footprint | Usually smaller footprint impact |
| Typical total timeline from the older page records | 10–12 months | 6–9 months | 9–12 months | 8–12 months |
If you already have a garage, a garage conversion may use the existing footprint and reduce the amount of new construction. If you want a separate structure with more layout freedom, a detached ADU may make more sense.
Explore Other ADU Services
If a detached ADU is not the right fit, there may be another way to add living space on your property.
Attached ADU
Add an ADU connected to the existing home when the lot or project goals make an attached layout a better fit.
Explore Attached ADUsGarage Conversion
Turn an existing garage into permitted living space while keeping more of the yard available.
Explore Garage ConversionsADU Design
Start with property review, custom plans, permit drawings, and design support before the construction phase begins.
View ADU Design ServicesBuild With a San Diego ADU Company
Detached ADU construction depends on the lot, local review, utilities, design, and the approved scope.
Keeping design and construction connected helps the project move forward with fewer handoffs and clearer responsibility.
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Areas We Serve
IL Total Design and Build helps homeowners across San Diego and nearby communities plan, permit, and build detached ADUs.
Our San Diego Location
IL Total Design and Build is located in San Diego, CA, and helps homeowners across San Diego County with detached ADUs, ADU design, permit planning, garage conversions, attached ADUs, JADUs, and accessory dwelling unit construction.
- IL Total Design and Build
- 9655 Granite Ridge Dr #200, San Diego, CA 92123
- (619) 404-0125
Detached ADU Questions From San Diego Homeowners
Simple answers about cost, timeline, lots, rental use, city rules, and other ADU options.
How much does a detached ADU cost in San Diego?
Based on the completed-project records supplied for this page, compact detached ADUs can start around $200,000, while larger or higher-end projects can reach $400,000 to $600,000 or more. Many mid-size projects fall around $280,000 to $400,000. Site work, utilities, engineering, finishes, slope, and added scope can change the final price.
How long does a detached ADU project take?
The older project records use about 10 to 12 months as a typical full-project range. That includes design, permit review, construction, and final inspection steps. The actual schedule depends on the property, city review, utilities, design changes, and construction scope.
How much space do I need for a detached ADU?
There is not one simple lot-size answer. The usable building area depends on the lot, zone, existing structures, access, setbacks, fire conditions, utilities, and the size of ADU you want to build. We review those conditions during the property feasibility step.
Can I rent out a detached ADU in San Diego?
City guidance states that the property owner is not required to live on-site for an ADU and that an ADU may not be leased for less than 31 consecutive days. Other rental, financing, deed, or program restrictions may still apply to a specific property or project.
Can a detached ADU be sold separately from the main home?
San Diego has adopted rules that can allow separate sale or conveyance of an ADU under qualifying circumstances. This is not automatic. It involves subdivision or condominium requirements and should be reviewed for the specific property before the project is designed around that goal.
What is the difference between a detached ADU and a JADU?
A detached ADU is a separate structure away from the main home. A JADU is a smaller unit created within an existing or proposed single-family home or certain attached space, and it follows different size and occupancy rules. See our JADU construction page for that option.
Bring Your Detached ADU to Life
Tell us about your property. We’ll help you understand the size, scope, design path, and next steps that may make sense for your lot.
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