Prefab ADUs in San Diego
San Diego permits more ADUs than any California city except Los Angeles — and rents are up 38% since 2021. We deliver an all-in prefab ADU from our factory in Lathrop — permits, foundation, delivery and installation included — at one fixed price.
Free lot check · zoning, coastal & fire maps · reply with a fixed price
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Quick answer
ADUs in San Diego — key facts for 2026
Most San Diego homeowners can add a detached ADU of up to 1,200 sq ft with no parking and no city impact fees under 750 sq ft. San Diego is #2 in California for ADU permits, and Bay Modular delivers a factory-built ADU all-in for $124,900–$271,900 — the same price anywhere in California.
- Can I build an ADU in San Diego?
- Yes, on most single-family lots: one detached ADU up to 1,200 sq ft, plus a conversion ADU and a JADU. A one-story ADU (16 ft or lower) outside fire zones can sit at 0 ft from side and rear lines.
- How long does a San Diego ADU permit take?
- A building permit is always required. State law gives cities 60 days to decide on a complete application; city-listed preapproved plans get a 30-day review.
- What fees does San Diego charge?
- No city impact fees under 750 sq ft (and the first two ADUs on a lot are exempt at any size). An inclusionary housing fee can apply. SDUSD charges $5.38 per sq ft from 500 sq ft.
- How much does a prefab ADU cost in San Diego?
- Bay Modular: $124,900–$271,900 all-in, the same price as anywhere in California, permits and installation included.
- How many ADUs does San Diego build?
- 2,165 ADU permits in 2025 — about 1 in 4 new homes in the city and #2 in California after Los Angeles.
- What does an ADU rent for in San Diego?
- Average asking rent in San Diego was $3,036 a month in August 2026 (Zillow), up 38% since January 2021.
Sources: HCD APR 2025, San Diego Municipal Code §141.0302 (Sep 2026 ed.), City of San Diego DSD ADU page, Zillow ZORI Aug 2026. Last reviewed October 2026.
San Diego in numbers
San Diego builds ADUs at scale
ADU permits more than doubled since 2021, and ADUs now make up about a quarter of all new homes permitted in the city.
ADU permits issued in the City of San Diego
Source: California HCD Annual Progress Report data (Table A2), City of San Diego, permits issued per year. Percent = ADUs among all housing units permitted in the city that year.
average San Diego asking rent since January 2021 ($2,198 → $3,036)
Zillow Observed Rent Index, City of San Diego, Aug 2026more ADU permits in 2025 than in 2021 (870 → 2,165)
HCD APR data, 2021–2025Can I build in San Diego?
Most San Diego lots with a house can add an ADU
San Diego’s ADU rules (Municipal Code §141.0302) are among the most generous in California. Here is what matters for most homeowners:
A detached ADU can be 150–1,200 sq ft. Up to 800 sq ft it's exempt from lot-coverage, floor-area and front-setback limits.
0 ft from side and rear lines for an ADU 16 ft or lower outside fire zones; 4 ft if taller or in a High/Very High fire zone.
One ADU plus one conversion ADU and one JADU on a single-family lot. No owner-occupancy rule for the ADU.
None required — except in the Beach Impact Area outside transit areas, where some ADUs need one space.
Near the coast, Coastal Overlay rules and sometimes a Coastal Development Permit apply. We check your lot first.
Extra 'bonus' ADUs are now limited in many single-family zones. A standard backyard ADU isn't affected.
Based on San Diego Municipal Code §141.0302 (Sep 2026 edition, incl. O-21989 effective Aug 22, 2025) and the City’s DSD ADU page (Oct 2026). Not legal advice — rules depend on your exact lot. More in our San Diego ADU guide.
New in 2027: under AB 956 (Chapter 791, Statutes of 2026), from January 1, 2027 state law lets you build two detached ADUs on a lot with a single-family home, and HOA rules can’t block an ADU on a lot zoned to allow one.
Costs & fees in San Diego
What an ADU costs in San Diego
Same all-in price as anywhere in California. Our models are all under 750 sq ft, so none pays San Diego impact fees — and four of five pay no school fee.
| Model | All-in price | School fees | City impact fees |
|---|---|---|---|
| Backyard Studio120 sq ft · home office or guest studio, not a rentable ADU | $75,900 | $0 | $0 |
| Small Studio256 sq ft | $124,900 | $0 | $0 |
| Large Studio ADU320 sq ft | $154,900 | $0 | $0 |
| 1 Bedroom ADU480 sq ft | $214,900 | $0 | $0 |
| 2 Bedroom ADU640 sq ft | $271,900 | $3,443 | $0 |
Sources: SDMC §142.0640 (DIF, Jul 2026 ed.); City of San Diego DSD ADU page (Oct 2026); San Diego Unified developer fees (eff. May 10, 2026); Gov. Code §66311.5. Launch pricing runs through December 31, 2026. Comparison is general — every project differs.
Renting in San Diego
Renting out an ADU in San Diego
average asking rent for all homes in San Diego — up 38% since 2021. HUD's 2027 fair rent for a 2-bedroom here is $2,823.
Zillow Observed Rent Index, City of San Diego, Aug 2026 · HUD FY2027 FMR ADU for rental incomeSan Diego doesn't allow an ADU to be rented for less than 31 days — no Airbnb or vacation rentals.
San Diego's 2023 Residential Tenant Protections Ordinance adds local eviction rules; a new ADU is exempt from the statewide rent cap (AB 1482) for 15 years.
San Diego lets most ADUs become condos and be sold on their own (SDMC §141.0302(f)); bonus ADUs are excluded.
Same money, other options
Yearly income per dollar, before taxes and costs. An ADU wins because you already own the land. Full comparison →
Sources: SDMC §141.0302(a)(8) and (f); DSD Information Bulletin 400 (Aug 2026); City of San Diego Residential Tenant Protections Ordinance (2023); Civil Code §1947.12. Comparison: HUD FY2027 2-bedroom Fair Market Rent, San Diego-Chula Vista-Carlsbad area ($2,823) × 12 ÷ $271,900; U.S. Treasury (Oct 6, 2026); FTSE Nareit (Sep 2026); Zillow ZORI ÷ ZHVI, San Diego metro (Aug 2026); FDIC (Sep 2026). Not legal or investment advice.
Permits in San Diego
How your San Diego permit works — we handle it
Free lot check
Zoning, coastal and fire maps, setbacks, sewer and power for your San Diego address.
Plans & submittal
Our HCD-approved plans plus your site plan, submitted to San Diego Development Services.
City review
Building permit review; coastal lots may also need a Coastal Development Permit. We answer comments for you.
Decision in 60 days
State law requires a decision on a complete application within 60 days. Your ADU is built in our factory meanwhile.
Install & move in
Delivered from our Lathrop factory, installed in about a week, inspected, then your Certificate of Occupancy.
Based on the City of San Diego DSD ADU page (Oct 2026) and Gov. Code §66317. San Diego also gives city-listed preapproved ADU plans a 30-day review.
Why now
Start your San Diego ADU with zero risk
Lock in launch pricing, see exactly what you get, and only decide once you have a fixed price for your lot.
All-in from $75,900 — everything included
- Backyard Studio (home office)$75,900All-in · fixed in writing
- Small Studio$124,900All-in · fixed in writing
- Large Studio ADU$154,900All-in · fixed in writing
- 1 Bedroom ADU$214,900All-in · fixed in writing
- 2 Bedroom ADU$271,900All-in · fixed in writing
Zero-risk start
- Free lot check & quoteNo obligation, no credit card.
- One fixed all-in priceDesign, permits, delivery and install — one number.
- HCD-approved plansState approval #1585366, financed and appraised like a home.
- 2-year warrantyOn materials and workmanship.
Visit our factory in Lathrop, CA and walk through a finished ADU.
San Diego ADU questions
Read the full San Diego ADU guide, see all of California, or call (209) 214-6845.
Can I build an ADU on my lot in San Diego?
Most San Diego single-family lots can add one ADU up to 1,200 sq ft, plus a conversion ADU and a JADU. A one-story ADU outside fire zones can sit right at the side and rear lot lines. Coastal and fire-zone lots have extra rules — we check your address for free.
How much does an ADU cost in San Diego?
Our all-in prices are the same as anywhere in California: from $124,900 for a Small Studio to $271,900 for a 2 Bedroom ADU, with launch pricing through December 31, 2026. San Diego charges no impact fees under 750 sq ft; an inclusionary housing fee can apply, and SDUSD's school fee starts above 500 sq ft.
How long does an ADU permit take in San Diego?
Every ADU needs a building permit, and state law requires a decision on a complete application within 60 days. Your ADU is built in our factory at the same time, so most projects take 4–6 months from signing to keys.
Do I need parking for an ADU in San Diego?
Usually no. Parking is only required for some ADUs in the Beach Impact Area outside transit priority areas.
Can I rent my San Diego ADU on Airbnb?
No. San Diego doesn't allow an ADU to be rented for less than 31 consecutive days.
Can I sell my ADU separately in San Diego?
Yes. San Diego allows most ADUs to be converted to condos and sold separately; bonus-program ADUs are excluded, and the unit must first be offered to owner-occupants for 30 days.
What changed with San Diego's ADU Bonus program in 2025?
Since August 22, 2025, extra 'bonus' ADUs are restricted in many single-family zones and capped by lot size. A standard backyard ADU (plus a conversion ADU and JADU) is still allowed.
Is an ADU a better investment than a rental property in San Diego?
For most homeowners with room on their lot, yes: you don't buy land. A 2 Bedroom ADU at HUD's 2027 fair rent for a 2-bedroom ($2,823) earns about 12.5% a year on its price before costs, vs. about 3.9% for a typical San Diego-area rental home (Zillow, Aug 2026). Not investment advice.
Free · no obligation
Can you build an ADU on your San Diego lot?
Send your San Diego address. We'll check zoning, coastal and fire maps and utilities, and send a fixed all-in price — permits included.
HCD-approved plans (#1585366) · 2-year warranty · factory in Lathrop, CA
Sources: California HCD Annual Progress Report data, Table A2 (City of San Diego, 2021–2025, updated Oct 2026); Zillow Observed Rent Index, City of San Diego (Aug 2026); HUD FY2027 Fair Market Rents; San Diego Municipal Code §141.0302 (Sep 2026 ed.) and §142.0640; City of San Diego DSD ADU page and Information Bulletin 400; San Diego Unified developer fees (May 2026); Civil Code §1947.12; HCD ADU Handbook (2026). General information, not legal or investment advice. Updated October 2026.