How Much Does an ADU Cost in San Diego in 2026?
Building an ADU in San Diego typically costs between $150,000 and $350,000 for a complete project including design, permits, and construction. On a cost per square foot basis, expect to pay $250 – $400 per sq ft depending on construction type and finish level.
Garage conversions start around $100,000 ($200–$300/sq ft), while detached new-build ADUs average $200,000 to $320,000 ($300–$400/sq ft).
At Subworkit Contracting, we handle the entire ADU process — from architectural drawings and permits to construction and final inspection. Here's everything you need to know about ADU costs in San Diego County.
ADU Cost Per Square Foot in San Diego (2026)
The cost to build an ADU per square foot in San Diego varies by construction type, finish level, and site conditions:
| Construction Type | Cost Per Sq Ft | 500 Sq Ft ADU | 800 Sq Ft ADU | 1,200 Sq Ft ADU |
|---|---|---|---|---|
| Garage conversion (budget) | $200 – $280/sq ft | $100,000 – $140,000 | N/A | N/A |
| Garage conversion (mid-range) | $280 – $350/sq ft | $140,000 – $175,000 | N/A | N/A |
| Attached ADU (addition) | $270 – $350/sq ft | $135,000 – $175,000 | $216,000 – $280,000 | N/A |
| Detached new-build (standard) | $300 – $370/sq ft | $150,000 – $185,000 | $240,000 – $296,000 | $360,000+ |
| Detached new-build (premium) | $370 – $420/sq ft | $185,000 – $210,000 | $296,000 – $336,000 | $444,000+ |
| Junior ADU (JADU) | $150 – $250/sq ft | $75,000 – $100,000 | N/A | N/A |
Why does per-sq-ft cost matter? When comparing bids from ADU contractors, per-square-foot pricing makes it easy to compare apples to apples — even when ADU sizes differ between proposals.
San Diego ADU Cost Breakdown by Type
| ADU Type | Size Range | Cost Range | Timeline |
|---|---|---|---|
| Garage conversion | 400–600 sq ft | $100,000 – $180,000 | 3–5 months |
| Interior conversion (basement, attic) | 300–500 sq ft | $80,000 – $150,000 | 2–4 months |
| Above-garage ADU | 400–800 sq ft | $150,000 – $250,000 | 4–7 months |
| Attached ADU (addition) | 500–800 sq ft | $150,000 – $280,000 | 5–8 months |
| Detached new-build ADU | 600–1,200 sq ft | $200,000 – $350,000 | 6–12 months |
| Junior ADU (JADU) | 150–500 sq ft | $50,000 – $100,000 | 2–3 months |
Garage Conversion ADU: San Diego's Most Affordable Option
Converting an existing garage into an ADU is the most cost-effective way to add a rental unit in San Diego. Because the shell, foundation, and roof already exist, you save $50,000–$100,000 compared to a new-build.
What a garage conversion includes:
- Insulation and drywall (the garage walls typically have no insulation)
- New flooring (garage slabs need moisture barrier + flooring)
- Full kitchen and bathroom rough-in and finish
- Electrical sub-panel, new circuits, outlets, and lighting
- Plumbing for kitchen, bath, and water heater
- HVAC — mini-split systems are most common for garage ADUs ($3,000–$6,000 installed)
- Exterior door and window modifications
- Title 24 energy compliance (insulation, windows, water heater efficiency)
Above-garage ADUs cost more ($150,000–$250,000) because they require structural reinforcement of the existing garage, a staircase, and fire-rated separation between the garage and living space. However, they preserve your parking while adding a full second-story unit — a popular option in neighborhoods like North Park and Hillcrest where lot space is limited.
What's Included in ADU Construction Costs?
A full ADU project in San Diego includes these cost components:
- Design & architecture: $5,000 – $15,000 for architectural drawings, structural engineering, and Title 24 energy compliance
- Permits & fees: $3,000 – $12,000 for City of San Diego plan check, building permit, school impact fees, and utility connections
- Site preparation: $5,000 – $20,000 for demolition, grading, and foundation work
- Framing & structure: $20,000 – $50,000
- Electrical: $8,000 – $20,000 for new panel, wiring, outlets, and lighting (licensed electricians)
- Plumbing: $8,000 – $25,000 for kitchen, bathroom, water heater, and sewer connection (licensed plumbers)
- Roofing: $5,000 – $15,000 (roofing contractors)
- Interior finishes: $15,000 – $40,000 for drywall, painting, flooring, cabinets, countertops
- Exterior & landscaping: $5,000 – $15,000 for siding, landscaping, walkways
City of San Diego ADU Permit Fees (2026)
Understanding San Diego ADU permit fees upfront prevents budget surprises. Here's what the City of San Diego charges:
| Fee Type | Cost | Notes |
|---|---|---|
| Building permit | $1,500 – $5,000 | Based on project valuation |
| Plan check fee | 65% of building permit fee | Covers DSD review |
| School impact fee | $0 – $4,000 | Waived for ADUs under 750 sq ft per state law |
| Sewer capacity charge | $3,000 – $5,000 | For new sewer connections only |
| Water meter fee | $0 – $4,000 | Required only if separate meter installed |
| Fire sprinkler plan review | $300 – $600 | Required for ADUs in some zones |
| Grading permit (if applicable) | $500 – $2,000 | For sites requiring earthwork |
Total permit & fee costs: Budget $3,000 – $12,000 depending on your project. California has waived many local ADU impact fees to encourage housing production. Our permit team applies all available waivers to minimize your fees.
San Diego ADU Permit Process
San Diego has been one of California's most ADU-friendly cities. Here's the current permit process:
- Feasibility check: Verify your lot meets zoning requirements (most single-family lots in San Diego qualify)
- Architectural design: Our architectural team creates plans that meet San Diego's building code and Title 24 energy requirements
- Plan submission: Submit to City of San Diego Development Services Department. Current review time is 4–8 weeks.
- Permit issuance: Once approved, we pull permits and begin construction
- Inspections: Foundation, framing, electrical, plumbing, and final inspection
- Certificate of Occupancy: Final sign-off makes your ADU legal and rentable
For a deeper dive, see our San Diego Building Permit Guide covering the full DSD process, common mistakes, and timelines.
ADU Size & Zoning Rules in San Diego (2026)
California state law (AB 68, AB 881, SB 9) sets minimum requirements, but the City of San Diego has its own rules on top:
- Maximum ADU size: 1,200 sq ft for detached ADUs on single-family lots; 1,000 sq ft on multi-family lots
- Junior ADU (JADU): Up to 500 sq ft, must be within the existing home footprint. You can build both a JADU and a full ADU on the same lot.
- Setbacks: 4-foot rear and side setbacks for new-build ADUs. Garage conversions in the existing footprint require no additional setbacks.
- Height: Up to 16 feet for detached ADUs (single story). Up to 18 feet if within ½ mile of transit. Two-story ADUs allowed on multi-family lots.
- Parking: No additional parking required for ADUs in San Diego (state law override).
- Owner occupancy: Not required for ADUs permitted after January 1, 2025. Both the main home and ADU can be rented.
- Lot coverage: ADUs cannot cause lot coverage to exceed 60%, but state law allows at least an 800 sq ft ADU regardless of lot coverage.
How to Finance an ADU in San Diego
Most homeowners don't pay cash for an ADU. Here are the most common ADU financing options available in San Diego:
| Financing Option | Typical Rate | Loan Amount | Best For |
|---|---|---|---|
| Home Equity Line of Credit (HELOC) | 7–9% variable | Up to 85% of equity | Homeowners with significant equity |
| Cash-out refinance | 6.5–8% fixed | Up to 80% LTV | Locking in a rate for the full project |
| Construction loan | 8–11% | Project cost | New-build ADUs, converts to permanent loan |
| ADU-specific loan (RenoFi, etc.) | 7–10% | Based on after-renovation value | Borrowing against future ADU value |
| CalHFA ADU Grant | 0% (grant) | Up to $40,000 | Pre-development costs (design, permits, soil tests) |
| Personal loan / line of credit | 8–15% | $50,000 – $100,000 | Smaller projects, fast approval |
CalHFA ADU Grant Program: California's Housing Finance Agency offers up to $40,000 in forgivable grants for ADU pre-development costs — architectural plans, permits, soil tests, and impact fees. The grant is forgiven after 5 years if the ADU remains as housing. This is one of the best ways to offset the upfront design and permit costs of your San Diego ADU project.
ROI tip: If your ADU rents for $2,200/month ($26,400/year) and cost $220,000 to build, your gross yield is 12%. Even after financing costs, most San Diego ADUs cash-flow positive within 1–2 years.
ADU ROI in San Diego: Is It Worth the Investment?
San Diego's rental market makes ADUs one of the best real estate investments in Southern California:
- Rental income: A 1-bedroom ADU in San Diego rents for $1,800 – $2,800/month depending on location and finish level
- Property value increase: ADUs typically add $150,000 – $300,000 to property value in San Diego — often more than the construction cost
- Payback period: Most San Diego ADUs pay for themselves in 5–8 years through rental income
- Tax benefits: Depreciation, mortgage interest deductions, and potential tax-free capital gains
- Prop 13 protection: ADU construction in California triggers only a partial reassessment of the new improvement — not your entire property
ADU Costs by San Diego Neighborhood
| Neighborhood | Avg ADU Cost | Cost/Sq Ft | Avg Monthly Rent | Notes |
|---|---|---|---|---|
| La Jolla / Del Mar | $280,000 – $350,000 | $350 – $420 | $2,500 – $3,500 | Premium finishes expected, strict HOA rules |
| North Park / Hillcrest | $200,000 – $280,000 | $300 – $370 | $2,000 – $2,800 | High rental demand, walkable areas |
| Chula Vista / National City | $180,000 – $250,000 | $270 – $340 | $1,800 – $2,400 | Growing market, good ROI |
| El Cajon / Santee / La Mesa | $160,000 – $230,000 | $250 – $320 | $1,600 – $2,200 | Lower land costs, larger lots |
| Escondido / Poway | $170,000 – $250,000 | $260 – $330 | $1,700 – $2,300 | Suburban lots, family-friendly |
| Oceanside / Carlsbad | $220,000 – $300,000 | $310 – $380 | $2,200 – $3,000 | Coastal premium, strong vacation rental |
2026 California ADU Law Updates Affecting San Diego
California continues to expand ADU-friendly legislation. Key changes affecting San Diego homeowners in 2026:
- AB 1033 (ADU condo conversion): Cities can now allow ADUs to be sold separately from the main home as condominiums. San Diego has not yet opted in, but the law opens the door for future ADU sales.
- SB 9 lot splits: Combined with ADU laws, homeowners on single-family lots can now potentially build up to 4 units (2 per lot after splitting). This dramatically increases development potential in San Diego.
- No owner-occupancy requirement: For ADUs permitted after January 1, 2025, the state no longer requires owner occupancy. Both the main home and ADU can be tenant-occupied.
- Streamlined approvals: Cities must approve conforming ADU applications within 60 days. San Diego DSD has been meeting this timeline consistently.
- Impact fee protections: State law continues to prohibit local impact fees on ADUs under 750 sq ft and limits fees on larger units.
Frequently Asked Questions
How much does it cost to build an ADU in San Diego?
A typical ADU in San Diego costs $150,000 – $350,000 depending on type (conversion vs new-build), size, and finish level. On a per-square-foot basis, expect $250 – $400/sq ft. Garage conversions start around $100,000, while detached new-build ADUs average $200,000 – $320,000.
How much does a 500 sq ft ADU cost in San Diego?
A 500 sq ft ADU in San Diego costs $100,000 – $175,000 for a garage conversion or $150,000 – $200,000 for a detached new-build. The per-square-foot cost for a 500 sq ft unit runs $200 – $400 depending on construction type and finishes.
What is the cost per square foot to build an ADU in San Diego?
ADU construction in San Diego runs $250 – $400 per square foot on average. Garage conversions are the most affordable at $200 – $300/sq ft, while premium detached new-builds can reach $370 – $420/sq ft in coastal neighborhoods.
How long does it take to build an ADU in San Diego?
From design to move-in, expect 6–12 months for a detached ADU or 3–5 months for a garage conversion. The City of San Diego permit review process currently takes 4–8 weeks.
Do I need a permit to build an ADU in San Diego?
Yes. All ADUs in San Diego require a building permit from the City of San Diego Development Services Department. Our permit team handles the entire process including architectural drawings, engineering, and plan submission.
How much are ADU permit fees in San Diego?
Total ADU permit and development fees in San Diego range from $3,000 to $12,000 depending on project size. This includes building permit, plan check, and any utility connection fees. School impact fees are waived for ADUs under 750 sq ft under state law.
Can I build an ADU on any property in San Diego?
Most single-family residential lots in San Diego qualify for at least one ADU under California's AB 68 and SB 9 laws. Some HOAs have additional restrictions. We assess feasibility during our free consultation.
Can I convert my garage into an ADU in San Diego?
Yes. Garage conversions are the most popular and affordable ADU type in San Diego, costing $100,000 – $180,000. No replacement parking is required under state law, even if you convert your only garage.
How much can I rent an ADU for in San Diego?
ADU rental rates in San Diego range from $1,600/month in inland areas to $3,500/month in coastal neighborhoods like La Jolla and Del Mar. A well-built 1-bedroom ADU in central San Diego typically rents for $2,000 – $2,500/month.
Does San Diego charge impact fees for ADUs?
San Diego waived many ADU impact fees under state legislation. School fees and utility connection fees may still apply depending on your project. Our team provides a detailed cost breakdown during the estimate process.
Can I finance an ADU in San Diego?
Yes. Common ADU financing options include HELOCs, cash-out refinances, construction loans, and ADU-specific lenders. California's CalHFA program offers up to $40,000 in forgivable grants for ADU pre-development costs. Most San Diego ADUs cash-flow positive within 1–2 years even with financing.
Can I sell my ADU separately from my house?
Under AB 1033 (effective 2024), California cities can allow ADUs to be sold as separate condominiums. San Diego has not yet opted in, but the legal framework is in place. For now, ADUs add value to the entire property when you sell.
Ready to build your ADU in San Diego? Get a free cost estimate or book a consultation with our ADU construction team. We handle everything from permits to foundation to finish — licensed California contractor (Lic #945572).
Ready to Start Your Project?
Contact Subworkit Contracting today for a free consultation. We serve San Diego County.