ADU fees in Sunnyvale: $2,353–$8,701 in modeled fees for 1,000 sq ft, plus valuation-based permits
Sunnyvale's building permit comes from a valuation table, with plan check and fire review each at 70% of it and a 0.54% construction tax, so the biggest costs depend on your project's valuation. Trade permits are $0.15 per sq ft each. Above 750 sq ft, the transportation impact fee applies. New ADUs over 800 sq ft on single-family lots also need a planning permit.
14 fee lines · 4 official sources · checked Oct 18, 2026 · Sources · Calculator
Totals leave out valuation-based building fees. Enter a construction valuation in the calculator to include them.
Modeled fees by ADU size
Detached ADU, 2,000 sq ft main home (example assumption), law in force today. Bars: solid = fees that apply, hatched = fees that may apply.
Each fee with its official source (numbers link to the source list). Est. = computed by us from the official rate; May apply = high total only; Up to = statewide cap, district may charge less.
Fee
499 sq ft
750 sq ft
1,000 sq ft
1,200 sq ft
Planning & zoning
Miscellaneous Plan Permit (new ADU over 800 sq ft, incl. 5% surcharge)3
Building permit (valuation table)1Valuation is set by the Building Division from its adopted valuation tables, which aren't in the fee schedule; enter your valuation in the calculator.
Transportation impact fee (south of Route 237)2The schedule lists $5,095 per single-family home and $3,158 per multifamily unit but no ADU rate. We show that range, prorated by ADU ÷ main-home size as state law requires. North of Route 237 and plan areas have other rates.
Exempt
Exempt
Est.$1,579–$2,548
Est.$1,895–$3,057
School district fee
School fees (your elementary and high school districts)5District rates not captured yet; shown at the 2026 statewide Level 1 maximum as an upper bound.
Exempt
Up to$4,035
Up to$5,380
Up to$6,456
Modeled total
$432
$432–$4,468
$2,353–$8,701
$2,759–$10,377
Rules
What you can build in Sunnyvale
Maximum size
State floor: cities must allow at least 850 sq ft (1,000 sq ft with 2+ bedrooms); detached ADUs can be capped at 1,200 sq ft. Local rule not captured yet.6
Height
State floor: 16 ft detached (18 ft near transit or on a multifamily lot, +2 ft for roof pitch); 25 ft attached. Local rule not captured yet.6
Setbacks
State limit: no more than 4 ft side and rear. Local rule not captured yet.6
Parking
State limit: at most 1 space per ADU or bedroom, and none within ½ mile of transit and in other cases. Local rule not captured yet.6
Owner occupancy
State law: cities can't require the owner to live on site for an ADU (JADUs: owner on site if sanitation is shared). Local rule not captured yet.6
Pre-approved plans
The City runs a Pre-approved ADU Plans Gallery with a streamlined permit process. 4
Approval process
New ADUs up to 800 sq ft on single-family lots, conversions and JADUs need only a building permit. Larger new ADUs on single-family lots need a Miscellaneous Plan Permit first. 4
State law
Why a 750 sq ft ADU pays no impact fees
California bars impact fees on ADUs of 750 sq ft or less of interior livable space. Above that, they must be proportional to the main home’s size; we assume 2,000 sq ft unless you enter yours. School fees start at 500 sq ft. From January 1, 2027, SB 1117 limits impact fees to the area over 750 sq ft. How the state rules work →
ADU permits issued
Sunnyvale issued 107 ADU building permits in 2025
515 from 2018 to 2025, as the jurisdiction reported to the state in its Housing Element Annual Progress Reports (Table A2, ADU rows; may include JADUs). “–” means no ADU rows were reported that year.
The building permit and the fees based on it (plan check, fire, energy, technology) plus the construction tax and general plan fee depend on valuation from the City's own tables, so modeled totals leave them out. Enter a valuation in the calculator.
Park in-lieu fees are listed for residential projects by density; whether the City charges them on ADUs isn't stated on the fee sheet, so they aren't included.
Size, height, setback and parking standards aren't captured yet (the City's code is Chapter 19.79); state minimums are shown.
Sewer and water connection charges aren't included. School district rates not captured; shown at the statewide cap.
The Governor approved SB 1117 (Chapter 809, Statutes of 2026) on September 29, 2026. It amends Gov. Code 66311.5: on lots with up to two ADUs, impact fees on an ADU over 750 sq ft must still be proportional to the primary home, and may only be charged on the area over 750 sq ft. Regular 2026 statutes take effect January 1, 2027. Until then, fees on a larger ADU are figured on its full size. Our calculator has a 2027 setting that shows the difference.
The Department of Housing and Community Development updated its ADU Handbook to reflect the laws that took effect January 1, 2026. Its proportional-fee example: a 1,000 sq ft ADU next to a 2,000 sq ft home pays 50% of the fee a new home would pay. Our models use 2,000 sq ft as the example primary-home size unless you enter your own.
On January 28, 2026 the State Allocation Board raised the statewide maximum Level 1 developer fee for residential construction from $5.17 to $5.38 per sq ft (+4.06%). School districts collect it on ADUs of 500 sq ft or more, at their own adopted rate up to this cap (higher Level 2/3 fees need extra findings). Where we haven't confirmed a district's rate, we use $5.38 as the upper bound.
SB 543 (Chapter 520, Statutes of 2025) took effect January 1, 2026. It restates the impact-fee rule in Gov. Code 66311.5: no impact fees on an ADU of 750 sq ft of interior livable space or less, or a JADU of 500 sq ft or less; above that, fees must be proportional to the primary home. It also caps JADUs at 500 sq ft of interior livable space. Many city documents still cite the older section numbers (65852.2 or 66324).
For a detached ADU with a 2,000 sq ft main home (an example assumption), our model of Sunnyvale’s official fee schedules comes to $432–$4,468 at 750 sq ft and $2,353–$8,701 at 1,000 sq ft. These totals leave out valuation-based building fees. Ranges show fees that may or may not apply to your project.
Does Sunnyvale charge impact fees on a 750 sq ft ADU?
No. California Government Code section 66311.5 bars impact fees on an ADU of 750 sq ft of interior livable space or less (500 sq ft or less for a JADU). Above 750 sq ft, impact fees must be proportional to the size of the main home. At 1,000 sq ft, the impact fees we model for Sunnyvale come to at most $2,548.
Do school fees apply to an ADU?
Only at 500 sq ft or more. School districts charge their adopted developer fee per sq ft, capped at the State Allocation Board’s Level 1 maximum ($5.38 per sq ft since January 28, 2026) unless they qualify for higher levels.
A local agency, special district, or water corporation shall not impose any impact fee upon the development of an accessory dwelling unit that has 750 square feet of interior livable space or less