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An ADU in San Diego typically costs between $180,000 and $420,000 for a detached unit in 2026, while garage conversions run $90,000 to $180,000. The final number depends on size, site conditions, and whether you go prefab or custom stick-built. Most San Diego homeowners land somewhere around $250,000 to $300,000 for a 500 to 700 square foot detached ADU with permits included.
Key Takeaways
- Detached ADU: $180,000 to $420,000 all-in for San Diego permits, construction, and finishes
- Garage conversion: $90,000 to $180,000, the most affordable path to rental income
- Prefab units from brands like Abodu and Cover often land 15 to 25% below custom builds
- San Diego permit fees and utility hookups add $15,000 to $35,000 on top of construction
- Lodgewick ADU San Diego gives a written price before any work starts, every time
ADU Cost Breakdown (2026)
Here’s what a detached, 500 square foot, one-bedroom ADU costs in San Diego as of 2026. These numbers reflect real bid data from projects across Clairemont, North Park, Chula Vista, La Mesa, and El Cajon.
| Cost Item | Typical Range (San Diego, 2026) |
|---|---|
| Architecture and structural engineering | $8,000 – $18,000 |
| San Diego permit fees and school impact fees | $6,000 – $15,000 |
| Site prep and foundation (flat lot) | $12,000 – $25,000 |
| Site prep on sloped lot (common in La Mesa, Mount Helix) | $25,000 – $50,000 |
| Framing, roofing, and exterior | $45,000 – $80,000 |
| Plumbing, electrical, HVAC rough-in and finish | $30,000 – $55,000 |
| Drywall, paint, flooring, trim | $25,000 – $45,000 |
| Kitchen (cabinets, counters, appliances) | $15,000 – $35,000 |
| Bathroom (fixtures, tile, shower) | $10,000 – $25,000 |
| Utility connections (new water and electrical panel upgrades) | $8,000 – $20,000 |
| Landscape and hardscape repair after construction | $4,000 – $12,000 |
| Builder overhead and profit | $18,000 – $40,000 |
| Total for 500 sq ft detached ADU | $181,000 – $420,000 |
Garage conversions cost less because the shell foundation, roof, and exterior walls already exist. In San Diego, a 400 square foot garage conversion lands between $90,000 and $180,000 including finishes, the new kitchen and bath, and the electrical panel upgrade the city requires for most conversions. A JADU, which stands for Junior Accessory Dwelling Unit, runs $50,000 to $90,000 because California caps these at 500 square feet and allows them to share a bathroom with the main house, cutting plumbing work roughly in half.
What drives the spread? Two ADUs on the same block in Normal Heights can differ by $100,000 based on soil, sewer line location, panel amperage, and finish choices. A flat lot with 200 amp service and a stub-out for sewer is the ideal build site. A 1930s bungalow in Kensington with a 60 amp panel, cast-iron drain lines, and a steep driveway is a different budget entirely.
What Affects ADU Pricing in San Diego
These six factors move the number more than anything else in the San Diego market.
- Garage conversion vs. detached build. Converting an existing garage saves $40,000 to $80,000 in structural costs. The trade-off is ceiling height: many San Diego garages built before 1980 have 7-foot ceilings that need work to meet the 7-foot-6 minimum for living space.
- Slope and soil conditions. Neighborhoods like Mount Soledad, La Mesa foothills, and parts of El Cajon sit on decomposed granite or clay that shifts with winter rains. A sloped lot can triple foundation costs. We regularly see spring soil issues in East County that require caissons or additional grading.
- Prefab vs. custom construction. Prefab ADUs from manufacturers we know well, including Abodu, Cover, Dvele, Mighty Buildings, and Boxabl, typically cost 15 to 25% less than a comparable custom build and shave 3 to 6 months off the timeline. The savings come from factory production and faster on-site assembly, not from cheaper materials.
- Panel capacity and utility runs. San Diego Gas & Electric connection fees and panel upgrades add $5,000 to $15,000 when the existing panel is under 100 amps. Homes in older neighborhoods like Golden Hill and South Park often need a full service upgrade before an ADU can pass inspection.
- Finishes and appliances. A kitchen with stock cabinets, laminate counters, and a basic appliance package runs about $15,000. The same footprint with custom cabinetry, quartz, and a panel-ready appliance package pushes $35,000. That $20,000 swing is a choice, not a construction cost.
- Coastal zone and historic district requirements. Parts of Ocean Beach, Point Loma, and Mission Hills trigger coastal development permits or historic review, adding $8,000 to $20,000 in consultant and processing fees before a shovel breaks ground.
Prefab vs. Custom ADU Costs in San Diego
The prefab route is worth understanding because it changes the shape of the budget. Prefab manufacturers deliver the ADU to your lot in modules or flat-packed panels, and a local contractor handles site work, foundation, utilities, and finishing.
What you can expect in San Diego right now: a 480 to 600 square foot one-bedroom from Abodu usually lands between $220,000 and $290,000 turnkey in the city of San Diego. A comparable custom stick-built ADU runs $260,000 to $340,000. Dvele and Plant Prefab skew higher, $350,000 to $500,000+, because those are architect-designed, high-performance homes. Mighty Buildings and Boxabl target lower entry points, roughly $150,000 to $220,000 for their smallest models, but the factory price excludes your local site work, which often adds $60,000 to $90,000 in San Diego.
Lodgewick ADU San Diego works with both approaches and with all these manufacturers. Our team has hands-on familiarity with Abodu, Cover, Dvele, Mighty Buildings, Boxabl, Plant Prefab, Tuff Shed, and James Hardie for exterior finishes. The right choice depends on your lot, your timeline, and what your budget tolerates. We’ll tell you straight what each option costs in writing before you commit.
One note: Tuff Shed structures are not permitted as dwellings in the city of San Diego. They work as storage or a studio shell in some jurisdictions, but they do not meet California building code for occupancy. A real ADU requires engineered foundation, insulation, electrical, plumbing, and a certificate of occupancy.
San Diego Permits and Fees: The Honest Numbers
Permit costs in San Diego are not hidden extras, but they feel like it when the bid lands. Here are the line items to plan for.
- City of San Diego building permit: $3,000 to $8,000 based on valuation
- School impact fees (SDUSD or local district): $4 to $5 per square foot, roughly $2,000 to $3,500 for a 600 sq ft unit
- SDG&E gas and electric connection: $2,000 to $8,000 depending on trenching and panel
- Water and sewer connection fees: $3,000 to $10,000
- Plan check and review fees: $2,000 to $5,000 across building, fire, and zoning
- School fee waiver (owner-occupied JADU in some cases): $0 with proper filing
Here’s the local nuance that shows up on San Diego job sites but rarely on a generic cost blog. The city’s ADU bonus program allows a second ADU on the same lot if one is deed-restricted affordable for very low income tenants, but that deed restriction runs for 30 years and meaningfully caps rents. Also, in neighborhoods covered by the Coastal Commission overlay, including most of Pacific Beach and La Jolla, expect 3 to 6 additional months of processing time and $8,000 to $15,000 in added fees. That’s real money and real time that should be in the budget from day one.
If you’re looking at a garage conversion in a home built before 1978, San Diego requires lead paint and asbestos testing before demolition. That adds $1,500 to $4,000. It’s standard, and a contractor who skips it cuts corners that the city inspector will catch.
How Much Does a Garage Conversion Cost in San Diego?
A garage conversion in San Diego costs $90,000 to $180,000 in 2026 for a legal, permitted unit. The range runs from a one-bedroom, one-bath budget build at the low end to a two-bedroom with custom finishes at the top.
The advantage in San Diego is the mild climate. Because the structure already exists, you avoid foundation and most framing costs. The work shifts to floor insulation (slab or raised), wall insulation, electrical, plumbing for the new bathroom and kitchen, drywall, windows and doors, and finishes. Ceiling height is the number one conversion killer: a 7-foot garage ceiling requires either raising the roof structure or lowering the slab, and both paths add $15,000 to $30,000. If your garage is attached with a 9-foot ceiling and the main electrical panel is nearby, you have the cheapest possible ADU path in San Diego.
ADU Financing Options in San Diego
Most San Diego homeowners pay for an ADU with one of these four vehicles. The right choice depends on home equity, timeline, and whether the ADU will generate rental income.
- Home equity line of credit (HELOC): usually the lowest rate, variable, draw as you build
- Cash-out refinance: fixed rate, but resets your existing mortgage
- Renovation construction loan (FHA 203k or Fannie Mae HomeStyle): wraps ADU costs into one mortgage
- California HCD CalHFA ADU Grant Program: up to $40,000 for pre-construction costs, when funds are available, with income limits that apply
The San Diego Housing Commission also periodically offers ADU financing and technical assistance for low and moderate income homeowners in specific council districts. These programs shift year to year, so ask when you call. Lodgewick can point you toward the current path, even if you’re just exploring.
ADU Rental Income in San Diego: What You Can Recoup
San Diego rents make ADU economics work faster than almost anywhere in California. A one-bedroom ADU in Clairemont or City Heights rents for roughly $1,800 to $2,300 per month in 2026. A two-bedroom ADU near SDSU or in North Park rents for $2,400 to $3,000.
Run the math: a $250,000 garage conversion renting at $2,100 per month grosses $25,200 a year. That’s a gross yield of about 10%, which beats most local rental property purchases before you even account for property tax impacts. The property tax reality is worth knowing: an ADU triggers a supplemental assessment, but only on the ADU itself, not the whole property. San Diego County assessors typically value the addition at construction cost, so a $250,000 ADU adds roughly $2,500 to $3,000 per year in property taxes.
One caution from actual projects: short-term vacation rental of an ADU is banned for most new ADUs in the city of San Diego. The city’s Short-Term Residential Occupancy ordinance prohibits new ADUs from being used as vacation rentals unless the property was already a permitted STRO before the ADU was built. Build for long-term rental or family housing, not AirBnB revenue.
How to Save on ADU
Saving money on an ADU in San Diego is about making decisions before the plans are drawn, not shopping for a cheaper faucet after construction starts.
- Convert before you build. A garage conversion or an attached addition costs 40 to 50% less per square foot than a detached ADU. If the existing garage works structurally, start there.
- Keep it under 500 square feet. That threshold avoids some fee escalation and keeps you in JADU territory if you’re willing to share a bathroom wall. Staying compact saves $30,000 to $60,000 on most lots.
- Choose a prefab shell with local finishes. Brands like Cover and Abodu do the heavy lifting in the factory. Local crews handle foundation and finishes. Total cost usually drops 15 to 25% versus custom framing on-site.
- Build on a flat, accessible portion of the lot. Every foot of trenching, retaining wall, and pier costs. A site that works with a standard slab foundation is the single biggest cost control lever in San Diego.
- Use standard window and door sizes. Custom openings trigger custom ordering, which adds weeks and 20 to 40% to the fenestration budget.
- Get a written price before you sign anything. This one isn’t about materials. It’s about protecting everything above. When a contractor puts the number in writing up front, the number doesn’t change at the door. Lodgewick ADU San Diego provides a written price before any work starts on every project. It’s how the Kingswell family has run the company since 2010. Call (619) 376-2760 for a free estimate and we’ll send a written number, not a ballpark phone quote.
How Long Does ADU Construction Take in San Diego?
Plan on 8 to 14 months from first meeting to move-in for a custom detached ADU in the city of San Diego. A prefab ADU cuts that to 5 to 9 months. Garage conversions land in the middle, usually 6 to 10 months, because they still require full plumbing and electrical work.
The timeline breaks down this way for a typical custom build: design and engineering 1 to 2 months, city plan check 2 to 4 months (longer in the coastal zone), site preparation and foundation 1 to 2 months, vertical construction 3 to 4 months, finishes and inspections 1 to 2 months. The waiting time on permits is what pushes San Diego builds past the one-year mark in some cases.
Should You Repair or Build an ADU?
This question comes up when a garage or bonus room already exists and is in rough shape. Here’s the comparison. Repairing an existing non-permitted room to make it legal living space costs $40,000 to $80,000 when the existing shell is sound, which is less than a conversion. But most non-permitted San Diego rooms lack proper foundation tie-downs, insulation, and electrical, so the “repair” effectively becomes a rebuild. If the goal is a rentable unit with its own kitchen and bath, a permitted ADU conversion is usually the better investment because the rental income recovers the cost in 4 to 6 years in San Diego’s rental market.
Lodgewick ADU San Diego will give you both numbers in writing: repair versus convert versus build new. Then you decide with the real figures in front of you.
The Kingswell Way: What We Put in Writing
Here’s what we do differently, and why it matters when you’re spending $200,000 to $400,000 on your property.
Every Lodgewick project starts with a written price. Not a range, not a handshake, not a “we’ll see how it goes.” A written price, delivered before any work starts, and that price does not change at the door. Every project includes a defined arrival window so our crew shows up when we say we will. Every job site is left clean at the end of the day, not just the end of the project. Every project includes the 365-Day Done Right Promise: if the work isn’t right, we come back and make it right, in writing, with a free return visit if the work fails within the guarantee period.
Our technicians are background-checked and uniformed, which means you always know who is on your property. And when you call (619) 376-2760, a live person answers. Not a voicemail, not a chatbot, not a phone tree. The name Lodgewick comes from the idea of a lodge: a small house on a larger property. That’s literally what an ADU is, and building them well is all we do.
FAQs – ADU Cost
Is it cheaper to build an ADU or buy a house in San Diego?
Building an ADU is dramatically cheaper. The median San Diego home price sits around $900,000 in 2026, so a $250,000 detached ADU costs about 72% less than buying a second property. You also avoid acquiring new land, new property tax base on a separately assessed parcel, and any HOA fees.
How much does a 2-bedroom ADU cost in San Diego?
A 2-bedroom ADU in San Diego runs $280,000 to $480,000 for a detached 700 to 900 square foot unit in 2026. A 2-bedroom garage conversion in a larger existing garage lands between $150,000 and $220,000. Call (619) 376-2760 for an exact quote based on your lot and existing structure; estimates are free.
Can you build an ADU in San Diego for under $150,000?
For under $150,000 in San Diego, the realistic path is a JADU conversion under 500 square feet sharing the main house bath, or a shell-only delivery that you finish yourself. A fully permitted, turnkey detached ADU under $150,000 is not realistic in 2026 with current labor and material prices in San Diego County.
Do ADUs increase property taxes in California?
Yes. San Diego County assesses the ADU at construction cost and applies the base 1% rate plus local assessments. A $250,000 ADU typically adds $2,500 to $3,000 per year in property taxes. The assessment applies to the ADU only, not to the existing home.
How much does a garage conversion cost per square foot in San Diego?
Garage conversions in San Diego run $225 to $450 per square foot in 2026, depending on finishes and how much structural work the existing garage needs. Detached ADUs run $360 to $600 per square foot. The lower cost per square foot of conversions reflects the free shell.
Can Lodgewick come to my house today for an estimate?
Yes. We offer free estimates and a live person answers the phone 24/7. Call (619) 376-2760 and we’ll schedule a time to walk your lot, measure your garage, and give you a written price before any work starts.
Get Your ADU Price in Writing
If you’re in San Diego and want to know what an ADU or garage conversion will cost on your specific lot, call Lodgewick ADU San Diego at (619) 376-2760. You’ll get a free estimate, a written price before any work begins, and the 365-Day Done Right Promise in writing on every project. Russ Delmar and the team are ready to walk your property and give you real numbers, not ballpark ranges.
Pricing reflects the San Diego market as of 2026. Lodgewick ADU San Diego offers free estimates – call (619) 376-2760.
Written by Russ Delmar, Owner at Lodgewick ADU San Diego, serving San Diego since 2010.
What Our Customers Say
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