What the City of Sunnyvale allows in 2026: sizes, heights, parking, fees, rentals, JADUs, permit timelines, and how a factory-built ADU fits.
Yes. A single-family lot can add a new ADU up to 1,000 sq ft plus a junior ADU. No parking is required, and the city has 60 days to act on a complete application.
What size ADU can you build in Sunnyvale?
In Sunnyvale, square footage decides your paperwork and your fees. Sunnyvale rewrote its ADU rules in April 2025 and updated them on July 28, 2026.
800 sq ft or less needs a building permit only. 750 or less pays no city impact fee. At 500 sq ft and up, your school district charges a fee. Detached ADUs can be 16 ft tall, with 4 ft side and rear setbacks.
Deep lot? Check fire access first. A detached ADU needs fire sprinklers if the main house has them, or if fire hoses can't reach every part of it within 150 ft. And check your title report: no ADU can sit on an easement that bans permanent structures.
How much does an ADU cost in Sunnyvale?
Under 500 sq ft, you skip both the city impact fee and the school fee. Our price is one all-in number, permit fees included.
Launch price through Dec 31, 2026. Everything from permits to keys. Not included: solar, furniture, upgrades. What's included
Call PG&E early. The city's standard is a 100-amp subpanel at the ADU and 200-amp service at the main house, so ask about upgrade availability before you lock the budget.
How long does it take?
The city has 15 business days to confirm your application is complete and 60 days to decide. Our projects take 4 to 6 months in total, from first call to keys, permits included.
Our homes are factory-built to HCD-approved plans (HCD #1585366) in our Lathrop factory. The city inspects the site work: foundation and utility hookups. What factory-built means
Sunnyvale ADU FAQ
Sunnyvale ADU rules in full›
What fits: on a single-family lot, one new ADU (detached or attached, 150 to 1,000 sq ft, no bedroom limit), one conversion ADU (no maximum size), and one junior ADU up to 500 sq ft. You can't combine a conversion inside the house with an attached addition.
Height: 16 ft for a detached ADU; 18 ft within a half-mile walk of major transit, such as the Sunnyvale Caltrain station; 25 ft for an attached ADU, or the main house's limit if lower. Setbacks: 4 ft from side and rear lot lines.
Over 800 sq ft: a Miscellaneous Plan Permit (MPP) first, the zoning front setback, at least 5 ft from the house, and extra design rules. The city says MPP review typically takes 2 to 4 weeks from fee payment. No ADU can sit on an easement that bans permanent structures.
Source: Sunnyvale Municipal Code Ch. 19.79 (Table 19.79.030); ADU Toolkit, January 2026.
Sunnyvale fees to plan for›
750 sq ft or less: no city impact fees. Over 750, the Transportation Impact Fee applies, in proportion to the main house's size. School fee: for 500 sq ft or more of living area; the 2026 state maximum is $5.38 per sq ft, so a 640 sq ft ADU pays at most $3,443. Sewer and water connection: exempt. MPP (only over 800 sq ft): $281.40.
Building permit fees follow a valuation table, plus plan check (70% of the permit fee), energy plan check (10%), a 0.54% construction tax, and a 0.15% general plan fee. Try the city's free ADU Calculator or our California ADU cost guide.
Sources: City ADU brochure (Aug. 2026); ADU Toolkit (Jan. 2026); FY 2026/27 fee schedules; Gov. Code § 66311.5; Office of Public School Construction.
Renting, junior ADUs, and local surprises›
Renting: owner-occupancy is not required for an ADU (Gov. Code § 66315). You can't sell the ADU separately from the house. JADU: up to 500 sq ft inside the house, with an efficiency kitchen and its own exterior entrance; you must live on site only if it shares a bathroom with the house, and then a deed restriction is recorded before the permit.
Deep lots: a detached ADU needs fire sprinklers if the main house has them, or if fire hoses can't reach every part of it within 150 ft. Power: the city's standard is a 100-amp subpanel at the ADU and 200-amp service at the house; check with PG&E early. Size floor: the 150 sq ft minimum means our 120 sq ft Backyard Studio can't be permitted there as a separate ADU.
How to choose a Sunnyvale ADU builder: 5 checks›
1. License. Look up the contractor on the CSLB license check. 2. Size strategy. A good builder designs to the 500, 750, and 800 sq ft lines. 3. Factory approval. A factory-built ADU should carry California HCD approval; ours is HCD #1585366. 4. Price in writing. One number for design, permit fees, foundation, delivery, hookups, and installation, plus what isn't included. 5. Payment schedule. Payments follow finished milestones.
Do I need a parking space for my ADU in Sunnyvale?›
No. Sunnyvale requires no off-street parking for an ADU and no replacement for garage spaces you remove (SMC 19.79.040).
Can I Airbnb my ADU in Sunnyvale?›
Not if it was approved on or after January 1, 2020. Those ADUs can't be rented for 30 consecutive days or less. Longer-term rentals are allowed, and you don't have to live on the property.
Does Sunnyvale have pre-approved ADU plans?›
Yes. The city's ADU Plans Gallery lists plans already reviewed for the building code, and the city says they're processed within 30 days. You still need a site plan and a permit for your lot.
Will an ADU raise my property taxes in Sunnyvale?›
Only on the value the ADU adds. The Santa Clara County Assessor treats an ADU like a home addition: "The existing home will not be reassessed."
We check your lot, tell you which model fits, and give you a fixed all-in price. You decide after that.
About Julia B. Julia B is a marketing specialist at Bay Modular, a licensed California ADU builder (CSLB #1112074) with its own factory in Lathrop. She writes about what ADUs really cost and how to avoid surprises.
Sources, city contacts, more guides
More: Models · Building in Sunnyvale · San Jose · Palo Alto · San Mateo guides
- City of Sunnyvale, Accessory Dwelling Units page; ADU Brochure (August 2026); ADU Toolkit (January 2026). Accessed October 8, 2026.
- Sunnyvale Municipal Code Chapter 19.79, Accessory Dwelling Units (Ord. 3240-25, April 8, 2025; Ord. 3258-26, July 28, 2026) and Chapter 19.76, Short-Term Rentals. Accessed October 8, 2026.
- City of Sunnyvale, FY 2026/27 fee schedules, effective August 18, 2026; Permit Center.
- City of Sunnyvale ADU Plans Gallery and ADU Calculator, October 8, 2026.
- California Government Code § 66311.5 (fees), § 66315 (owner-occupancy), § 66317 (review deadlines); HCD, Accessory Dwelling Unit Handbook, March 2026.
- Office of Public School Construction, Developer Fee History: residential Level 1 maximum $5.38 per sq ft, adopted January 28, 2026.
- U.S. Department of Housing and Urban Development, FY 2026 Fair Market Rents, Santa Clara County. Accessed October 8, 2026.
- Santa Clara County Office of the Assessor, Granny Units / ADUs; Caltrain, Sunnyvale station.
- Bay Modular Pricing & Financing, October 2026 (model sizes and prices).
Sources checked October 8, 2026. City of Sunnyvale One-Stop Permit Center, City Hall, 456 W. Olive Ave. · Planning: (408) 730-7440, planning@sunnyvale.ca.gov · Building: (408) 730-7444, building@sunnyvale.ca.gov
General information, not legal, tax, or financial advice. Confirm details for your address with the City of Sunnyvale Planning and Building Divisions.
