1200 Sq Ft ADU Cost in San Diego, CA
A 1200 sq ft ADU in San Diego, CA costs roughly $605,000–$1,029,000 all-in for 2026, including permits, utilities, and soft costs. Adjust the slider to see other sizes.
Cost Breakdown (Mid-Range)
| Category | Amount | Share of Mid Total |
|---|---|---|
| Hard construction (labor + materials) | $660,000 | 85% |
| Soft costs (design, engineering, PM) | $79,200 | 10% |
| Permit and impact fees | $21,000 | 3% |
| Utility hookups | $12,000 | 2% |
| Mid-range total | $772,200 | 100% |
Last updated April 2026.
Building a 1200 Sq Ft ADU in San Diego: What's Specific Here
San Diego's Affordable Homes Bonus Program ('Bonus ADU') lets you stack multiple units on a single lot if you deed-restrict one as affordable, and the city's no-impact-fee policy for ADUs under 750 sq ft (per AB 681) makes sub-750 builds noticeably cheaper. Lots inside the Coastal Zone face a separate Coastal Development Permit through California Coastal Commission review, which can add 3-6 months to the timeline. For a 1200 sq ft build specifically, expect 12-18-week plan review through City of San Diego Development Services Department and a build sequence shaped by the city's mild coastal climate and Title 24 energy compliance, CalGreen Tier 1, San Diego Municipal Code §141.0302 requirements.
What a 1200 Sq Ft ADU Actually Gets You
At 1,200 sq ft you hit the San Diego ADU maximum on most lots and trigger the full structural review path. Expect the highest plan check bracket, supplemental energy modeling, and on lots under 7,000 sq ft, careful FAR (Floor Area Ratio) math to make sure the build still pencils.
Cost by Build Method
| Build method | Low | Mid | High | Notes |
|---|---|---|---|---|
| Stick-built (custom) | $605,370 | $772,200 | $1,029,030 | Most common path; highest cost, most layout flexibility |
| Prefab / panelized | $532,726 | $710,424 | $987,869 | 15-25% faster, 5-10% cheaper; limited layout options |
Realistic Build Timeline for 1200 Sq Ft in San Diego
| Milestone | Typical duration |
|---|---|
| Design + construction documents | 4-8 weeks |
| San Diego, CA permit submission + review | 12-18 weeks |
| Site prep + foundation | 4-6 weeks |
| Framing + rough-ins (MEP) | 8-12 weeks |
| Finishes + final inspection | 10-14 weeks |
| TOTAL (design → certificate of occupancy) | 38-58 weeks |
Financing a $772,000 1200 sq ft ADU in San Diego, CA
Most San Diego, CA homeowners stack a cash or HELOC down payment with a construction-to-perm loan. Sample scenario for a mid-range 1200 sq ft build:
| Total project cost (mid) | $772,200 |
| 20% down payment (cash or HELOC) | $154,440 |
| Loan principal (80%) | $617,760 |
| Estimated rate (May 2026) | 7.5% (30-year) |
| Estimated monthly payment | $5,399 |
| Estimated rent (1200 sq ft in San Diego, CA) | $2,310–$3,910/mo |
| Break-even rent target | $5,399/mo |
Sample scenario only — your actual rate, term, and rent will vary. Use the loan calculator to plug in your numbers.
San Diego Permit Fee Detail
| Plan check | $1,000–$2,500 |
| Building permit | $1,500–$4,000 |
| Impact fees | Waived (<750 sf) / $4,000–$8,000 (>750 sf) |
| School fees | $2.85–$4/sf |
| Utility hookups | $2,500–$7,000 |
Questions to Ask San Diego ADU Contractors
Before signing with a contractor for your 1200 sq ft ADU in San Diego, CA, ask:
- How many full 1- and 2-bedroom ADUs have you completed in San Diego in the last 24 months?
- What's your average permit timeline with City of San Diego Development Services Department, and how do you handle plan-check correction cycles?
- Do you handle Title 24 energy compliance docs and HERS rater verification in-house or sub it out?
- What's specifically included vs. excluded in your turnkey quote — soft costs, utility tap fees, landscaping, driveway repair?
- What's your payment schedule, and what triggers a change order vs. an allowance overrun?
- Can you provide addresses for 2-3 completed San Diego ADU projects I can drive by?
How We Calculate This
These are 2026 all-in market estimates. Hard costs scale linearly with square footage using a low/mid/high per-sq-ft band calibrated to recent build data in each metro. Soft costs (design, engineering, project management) are applied at ~12% of hard costs. Permit and utility hookup fees are set to local base amounts and lightly adjusted for size. For an itemized estimate tied to your lot, finish level, and specific city jurisdiction, use our Cost Estimator.
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Frequently Asked Questions
How much does a 1200 sq ft ADU cost in San Diego, CA?
A 1200 sq ft ADU in San Diego, CA typically costs $605,000–$1,029,000 all-in for 2026. The mid-range estimate is $772,000, which includes hard construction ($660,000), soft costs ($79,200), permit fees ($21,000), and utility hookups ($12,000).
What is the price per square foot for ADUs in San Diego, CA?
For a 1200 sq ft build in San Diego, CA, expect $504–$858/sq ft all-in. The mid-range is roughly $644/sq ft. Per-sq-ft cost falls slightly at larger sizes because permit and utility fees amortize over more square footage.
How long does a 1200 sq ft ADU take to build in San Diego, CA?
Total timeline runs 38-58 weeks from design start to certificate of occupancy in San Diego, CA. Permits alone take 12-18 weeks through City of San Diego Development Services Department, followed by 22+ weeks of construction. Pre-approved plans and prefab paths can shorten the permit phase.
Can I finance a $772,000 ADU in San Diego, CA?
Yes. For a $772,000 mid-range build, common options are construction-to-permanent loans, HELOC, cash-out refinance, or RenoFi. At current ~7.5% rates, a fully-financed build is roughly $5,399/month on a 30-year term. Use the ADU loan calculator to compare products side by side.
What size of ADU is allowed in San Diego, CA?
San Diego, CA permits detached ADUs up to 1200 sq ft on most lots. A 1200 sq ft unit is within the typical limit, so the standard ADU permit path applies.
What rent can I expect from a 1200 sq ft ADU in San Diego, CA?
In San Diego, CA, 1200 sq ft ADUs rent for approximately $2,310–$3,910/month based on 2026 market rents for comparable units. Newer construction with separate parking and a private entrance lands at the high end of that range.
What's the difference between a 1200 sq ft and a 1500 sq ft ADU in San Diego, CA?
A 1200 sq ft San Diego, CA ADU comes in around $772,000 mid-range, while the next bucket up at 1500 sq ft runs about $959,000 — roughly $186,000 more. The bigger size adds a bedroom or larger living area but still falls within the city ADU size cap.
What's the most common mistake when building a 1200 sq ft ADU in San Diego, CA?
Underestimating the title 24 energy compliance docs and hers rater verification requirement — many homeowners get bids from contractors who don't price these into the quote, then face change orders mid-build. Always confirm in writing how title 24 energy compliance docs and hers rater verification is handled before signing.
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