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Building an ADU in Sunnyvale, CA

Checked against the city's ADU pages on Oct 18, 2026.

Can I build one?
Yes, up to 1,000 sq ft A new ADU can be 1,000 sq ft. Up to 800 sq ft needs only a building permit; larger ones need a planning permit first. No parking required.[1][2][3]
What will the city charge?
8 fee lines The city's ADU Calculator gives rough estimates. See every fee[4][2]
Who builds here?
13 licensed builders Each lists Sunnyvale on its own site and holds an active CSLB license. See the list
See 13 builders Get quotes

Licensed ADU builders in Sunnyvale

Ranked by a public score anyone can check: license, years licensed, ADU types and cities shown on their own sites, a local office, and published prices. Nobody pays to move up. Quote requests go to our team with the builder you picked. How we rank

What Sunnyvale allows

  • Detached ADU, max size[1][2]

    150 to 1,000 sq ft; over 800 sq ft needs a planning permit (MPP) first

  • Attached ADU, max size[1]

    150 to 1,000 sq ft

  • Conversion of existing space[1]

    No size cap

  • Junior ADU (inside the house)[2][1]

    Up to 500 sq ft

  • Height[1]

    Detached: 16 ft, or 18 ft within 1/2 mile of major transit; +2 ft to match the main roof pitch. Attached: 25 ft

  • Side and rear setbacks[1]

    4 ft side and rear. Over 800 sq ft: front setbacks too, and 5 ft from the main home and other buildings

  • Floor area and lot coverage[1]

    Up to 800 sq ft of each ADU doesn't count

  • Units on a single-family lot[2][1]

    Up to 3: 1 new ADU + 1 conversion + 1 JADU. You can't pair a conversion inside the house with an attached new ADU

  • Parking[3]

    None. Covered parking you remove doesn't need replacing

  • Owner must live on site[1]

    No for an ADU. A JADU needs an owner deed restriction only if it shares a bathroom with the house
  • Short-term rentals are banned for ADUs approved after Jan 1, 2020, and you can't sell an ADU separately.[1]
  • A detached ADU needs fire sprinklers if the main home has them, or if hoses can't reach every part of it within 150 ft.[1]
  • A JADU is not allowed on a lot with 2 or more detached homes.[2]
ADU rules in Sunnyvale drawn on a typical lot Detached ADU, single-family lot: up to 1,000 square feet, 4 feet from side and rear lot lines, 16 feet tall. Parking: None required. Rear lot line Street Main house ADU up to 1,000 sq ft 16 ft tall 4 ft 4 ft Parking: none required
Detached ADU, single-family lot. Not to scale.

City fees for an ADU in Sunnyvale

Fee lines for an ADU in Sunnyvale
Building permit, by valuation $2,445 for the first $100,000 of valuation, plus $13.50 per $1,000 up to $500,000[4] The Building Division sets valuation from its own tables. FY 2026/27 fees, effective Aug 18, 2026.
Plan check, energy and fire Plan check 70%, energy plan check 10% and fire permit 70% of the building permit fee[4]
Issuance and trade permits $42.50 issuance; 5% technology surcharge; electrical, mechanical and plumbing $0.15 per sq ft each ($130 minimum)[4]
Construction tax and General Plan fee 0.54% plus 0.15% of valuation[4]
Transportation impact fee $0 at 750 sq ft and under; larger ADUs pay a share of $5,095 per single-family home[1][5][3] Rate for south of Route 237. The ADU's share is set in proportion to the main home.
Park in-lieu fee $0 under 750 sq ft[5][6] The impact fee sheet has no ADU line. State law bars impact fees under 750 sq ft.
School fees New ADUs 500 sq ft and up; $1.72 to $5.38 per sq ft by district[1][5][7][8][9][10] Sunnyvale SD charges $3.32 and Fremont Union HSD $2.06 in its Sunnyvale area. You pay both your elementary and high school district, directly to them, before the permit is issued.
Sewer and water connection (City of Sunnyvale) $0; incremental connection fees are exempt for single-family ADUs[1] Once the ADU is finaled, your lot is billed at two-unit multifamily utility rates. More than 5 toilets on site means a 4-inch sewer line.
School fee rates for districts in Sunnyvale (7)

Five elementary districts and two high school districts serve Sunnyvale. If your lot is in both an elementary and a high school district, you pay both.[5]

  • Sunnyvale School District[7][11] $3.32/sq ft
  • Fremont Union High School District[12]500 sq ft or less is exempt. $2.15/sq ft
  • Santa Clara Unified School District[10]No fees on ADUs or additions under 500 sq ft. $5.38/sq ft
  • Cupertino Union School District[13] $3.23/sq ft
  • Mountain View Whisman School District[14]Applies at 500 sq ft or more. $3.45/sq ft
  • Los Altos School District[15][16] $3.58/sq ft
  • Mountain View-Los Altos Union High School District[9] $1.72/sq ft
Total cost in Sunnyvale, fees plus building

How the permit works

  1. 1

    Check if your ADU is streamlined

    New ADUs up to 800 sq ft on a single-family lot, conversions and JADUs need only a building permit.[2]

  2. 2

    Over 800 sq ft: get a Miscellaneous Plan Permit

    Apply at the Online Permit Center. A planner sends an invoice, and review takes 2 to 4 weeks from payment.[1]

  3. 3

    Apply for the building permit

    Use your own plans or a plan from the city's pre-approved ADU Plans Gallery.[2]

  4. 4

    Pay fees, including school fees

    School fees are paid directly to the districts before the building permit is issued.[5]

  5. 5

    Build and get final sign-off

    Utility billing switches to two-unit rates the day the ADU is signed off.[1]

Review time: The planning permit for an ADU over 800 sq ft typically takes 2 to 4 weeks from fee payment.[1]

State deadline: Sunnyvale's code gives the city 15 business days to say if your application is complete and 60 days to approve or deny it, matching state law.[3][6]

Preapproved plans

Sunnyvale lists pre-approved plans in its ADU Plans Gallery. You buy a plan from the designer and get streamlined permitting.[2][1]

The gallery is at sunnyvale.aduaccelerator.org/gallery. We could not read its plan list, and the city publishes no prices.

Common questions

What are the ADU requirements in Sunnyvale?

A new ADU can be 150 to 1,000 sq ft with 4 ft side and rear setbacks. A detached ADU can be 16 ft tall, or 18 ft near major transit. Up to 800 sq ft needs only a building permit.[1][2]

How big can an ADU be in Sunnyvale?

1,000 sq ft for a new ADU on a single-family lot. A conversion has no size cap, and a junior ADU can be up to 500 sq ft.[1]

Do I need parking for an ADU in Sunnyvale?

No. The ADU code requires no parking, and you don't have to replace covered parking you remove.[3]

How much is the Sunnyvale ADU permit cost?

The city publishes no total. The building permit comes from a valuation table, with plan check and fire each adding 70% of that fee. ADUs of 750 sq ft or less pay no transportation impact fee, and sewer and water connection fees are exempt.[4][1]

How many ADUs can I build in Sunnyvale?

Up to 3 on a single-family lot: one new ADU, one conversion and one junior ADU.[2]

Nearby cities

What we couldn't confirm

  • The parking rule comes from a code mirror (GoCodebook); the official code host blocked automated reads.
  • Pre-approved plan list and prices not captured.
  • Online Permit Center URL not recorded.
  • How the city sizes the transportation impact fee for an ADU over 750 sq ft is not published.
  • School district lines within the city not checked against district maps.

Sources

Every fact on this page links to one of these. We read each one on the date shown.

  1. 1. City of Sunnyvale ADU brochure: new construction 150 to 1,000 sq ft (SFH) Checked Oct 18, 2026
  2. 2. City of Sunnyvale Single-family lot: max 1 new construction + 1 conversion + 1 JADU (3 total) Checked Oct 18, 2026
  3. 3. GoCodebook (third-party mirror) Section structure, parking, impact fee and timeline rules Checked Oct 18, 2026
  4. 4. City of Sunnyvale Building Permit Fees FY 26/27, effective August 18, 2026: issuance $42.50 Checked Oct 18, 2026
  5. 5. City of Sunnyvale Development Impact Fees FY 2026-27, effective August 18, 2026: park in-lieu low density $80,858.25/unit Checked Oct 18, 2026
  6. 6. California Department of Housing and Community Development (HCD) All state ADU/JADU rules used in state_baseline.md (sizes, heights, setbacks, parking, owner-occupancy, JADU, Checked Oct 18, 2026
  7. 7. Sunnyvale School District Statutory $5.38/sf Checked Oct 18, 2026
  8. 8. Fremont Union HSD All Other Residential $2.15 (Cupertino area) / $2.06 (Sunnyvale area) Checked Oct 18, 2026
  9. 9. Mountain View-Los Altos Union HSD MVLA share $1.72/sf Checked Oct 18, 2026
  10. 10. Santa Clara Unified School District Residential $5.38/sf effective 8/24/2026 Checked Oct 18, 2026
  11. 11. Sunnyvale School District $3.32/sf residential listed Checked Oct 18, 2026
  12. 12. Fremont Union HSD $2.15 (Cupertino area) / $2.06 (Sunnyvale area) eff Checked Oct 18, 2026
  13. 13. Cupertino Union SD $3.23/sq ft residential eff Checked Oct 18, 2026
  14. 14. Mountain View Whisman SD $3.45/sf residential effective July 1, 2024 Checked Oct 18, 2026
  15. 15. Los Altos School District $3.58/sf residential Checked Oct 18, 2026
  16. 16. Los Altos School District Adopted Dec 15, 2025 Checked Oct 18, 2026