ADU Pass
Sunnyvale
Santa Clara County portion
Also in: No County
ADU Pass helps homeowners in Sunnyvale, Santa Clara County, California navigate the permit paperwork for building an accessory dwelling unit. This area covers 3 ZIP codes.
Map
ADU details
ADU legality: allowed
Sunnyvale has gone further than the state minimum on streamlining — same-day plan check for compliant single-story detached ADUs ≤800 sqft, and 2025 ordinance amendments waiving historic-resources and tree-removal permit triggers that previously caused delay.
Cost scenarios
| Scenario | Sq ft | Permit | Build | Total |
|---|---|---|---|---|
| minimum | 150 | $1,700 | $90,750 | $92,450 |
| 600 | 600 | $1,700 | $363,000 | $364,700 |
| midpoint | 675 | $1,700 | $408,375 | $410,075 |
| 1000 | 1,000 | $4,200 | $605,000 | $609,200 |
| maximum | 1,200 | $4,500 | $726,000 | $730,500 |
Fee breakdown (as of 2026-04)
Permitting process
Viability (permitted uses)
- Long-term rental: yes Long-term rental (30+ days) explicitly permitted; AB 976 permanently removed owner-occupancy requirement effective 2024-01-01.
- Short-term rental: no Sunnyvale prohibits short-term rentals (under 30 days) of ADUs per state law: California Government Code §65852.2(a)(6) prohibits cities from approving STR use of ADUs. Sunnyvale enforces this prohibition.
- Office rental: with-restrictions Detached commercial office rental to outside tenants is not a permitted ADU use; ADUs are residential. Home occupation by the property owner is allowed.
- Home office: yes Home occupation permitted under SMC zoning with restrictions on signage, employees, and customer traffic.
- Studio / workshop: yes Personal artist/maker studio is a permitted accessory use of an ADU.
- Agriculture: with-restrictions Limited urban agriculture and small-animal keeping (chickens, etc.) permitted in single-family zones per SMC; check current district standards.
- Relative support: yes Family-occupancy ADU explicitly permitted; no relationship requirement under California state law.
Incentives
- CalHFA ADU Grant Program — predevelopment grant up to $40,000
- Same-day plan check for ADUs ≤800 sqft (single-story detached)
Pre-approved plans Pre-approved plans
Contacts
Utilities
- Water: City of Sunnyvale Water Utility (wholesale supply from Santa Clara Valley Water District and San Francisco Hetch Hetchy) · 21d connect · $4,500
Sunnyvale operates its own retail water utility; wholesale water comes from SCVWD and SFPUC Hetch Hetchy. ADUs typically share the primary residence's meter unless larger than 750 sqft and separately metered. - Sewer: City of Sunnyvale Department of Public Works — Water Pollution Control Plant (WPCP) · 21d connect · $5,500
Sunnyvale operates its own WPCP serving Sunnyvale, Mountain View, and parts of Santa Clara. Sewer lateral capacity check required for new ADU connection. - Electric: Pacific Gas & Electric (PG&E) · 30d connect · $1,800
Sunnyvale is in PG&E service territory. Service upgrade required for many ADUs; PG&E lead times for service upgrades have been a known bottleneck running 30-90+ days. - Gas: Pacific Gas & Electric (PG&E) · 21d connect · $1,500
PG&E gas service. Title 24 2025 incentivizes all-electric ADU designs to avoid gas connection altogether.
Property values & taxes
Construction timeline
Realistic total: best 9mo · typical 14mo · worst 22mo
Silicon Valley contractor market is tight; lead times for ADU specialists run 5-7 months. PG&E service-upgrade lead time can extend total timeline materially.
Modular pathway inspectors are experienced with modular
Financing
State ADU loans:
- CalHFA ADU Grant Program up to $40,000
- HCD ADU Funding index
Insurance impact
HOA prevalence & preemption
Most of Sunnyvale's single-family housing stock predates HOA-formation patterns; HOA prevalence concentrated in newer townhome and condo developments. California's AB 670 / AB 3182 Davis-Stirling preemption voids any HOA covenant prohibiting ADUs on single-family lots. Residual HOA design-standards authority remains.
Regulatory overlays (2)
- airport-noise-zone
Moffett Federal Airfield ALUC noise contours touch southern Sunnyvale (north of US-101); some residential parcels in the 60-65 dB CNEL contour require disclosure and may require sound attenuation measures. - seismic-retrofit-zone
Hayward Fault and Calaveras Fault systems within 15 miles; ASCE 7-22 Seismic Design Category D applies. Standard CRC seismic detailing required; no special retrofit overlay for new ADUs beyond code.
Technical envelope (climate & building code)
Climate & energy code
Building code
Amendments:
- Amendment
- Amendment
Contractor market (aggregate)
Legal history (timeline)
Current ordinance: Sunnyvale Municipal Code Chapter 19.79 — Accessory Dwelling Units, adopted 2017-12-12, last amended 2025-03-01
- 2017-12-12 — Sunnyvale Ordinance 3104-17 — initial ADU code update (city-ordinance)
First substantial Sunnyvale ADU ordinance update aligning local code to AB 2299 / SB 1069 (2016 California ADU reforms).
Effect: Established the modern Sunnyvale ADU framework: removed owner-occupancy requirements, eliminated additional parking for ADUs within ½ mile of transit, and reduced setbacks consistent with state minimums. - 2020-04-21 — Sunnyvale ADU code refresh — SMC Chapter 19.79 reorganization (city-ordinance)
Local conforming amendments to align with AB 68 / AB 881 / SB 13 (2020 statewide overhaul).
Effect: Codified by-right ministerial track for ADUs ≤800 sqft, prohibited impact fees on ADUs <750 sqft, waived owner-occupancy for new ADUs through 2025. - 2022-12-09 — HCD review letter — Sunnyvale ADU ordinance compliance findings (city-ordinance)
California HCD reviewed Sunnyvale's then-current ADU ordinance and issued findings.
Effect: Triggered Sunnyvale to amend specific provisions HCD flagged as inconsistent with state law, including height standards and fee proportionality. - 2025-03-01 — Sunnyvale ADU amendment — front-yard ADUs and OTC approvals (city-ordinance)
Council-adopted amendment expanding eligibility for over-the-counter ministerial review and waiving historic-resources / tree-removal permit triggers.
Effect: Front-yard ADUs allowed under specified conditions; OTC plan check available same-day for compliant single-story detached ADUs ≤800 sqft; tree-removal and historic-resources alteration permits no longer triggered when the action is necessary to enable an otherwise-compliant ADU.
Known issues (1)
- other — PG&E electric service-upgrade lead times have been a chronic bottleneck across PG&E territory (including Sunnyvale), routinely adding 30-90+ days to ADU project timelines for ADUs requiring service-panel upgrades.
Santa Clara County — county ADU rules and overlays
County ADU ordinance
California state — ADU law and programs
State ADU law
California has the most aggressive statewide ADU preemption regime in the US, built from ~15 bills passed 2019-2025 and enforced by the Department of Housing and Community Development (HCD). The 2026 HCD ADU Handbook addendum (in effect with the 2025 Title 24 code cycle) is the operative state-level reference. The regime does four things at once: (1) preempts local zoning that would ban or unreasonably restrict ADUs; (2) imposes by-right ministerial approval with short statutory deadlines; (3) caps fees and utility-connection charges; and (4) empowers HCD to void non-compliant local ordinances.
State HOA preemption
California has the strongest statewide HOA-preemption regime in the US for accessory dwelling units, built from two bills: AB 670 (2019) voided ADU-prohibiting covenants on single-family residential lots, and AB 3182 (2020) extended and codified the preemption into the Davis-Stirling Common Interest Development Act (Civil Code §§ 4740 / 4741). The combination prohibits common-interest communities from banning ADUs, restricting rentals below 25% of separate interests, or treating ADUs as separate HOA interests. Limits remain: HOAs retain authority over reasonable design standards and statutory height limits, and the 2026 Carlsbad case (CalMatters coverage) established that an HOA's documented design-standards regime can effectively delay or constrain ADU approval short of outright prohibition.
State financing programs
California's flagship state-level ADU financing program — the CalHFA ADU Grant Program — is paused and has not been refunded since the original $100 million allocation was fully deployed 2023-12-28. The program provided up to $40,000 per qualifying homeowner for pre-construction and non-recurring closing costs and financed approximately 2,500 ADUs in two rounds. As of 2026-04, no new funding round has been announced in the state budget. CalHFA continues to publish anti-scam warnings because bad actors actively solicit homeowners claiming access to grant funds that no longer exist. State-level financing activity has shifted to local pilot programs (San Francisco, San Jose, Los Angeles, San Diego) and private financing products (Fannie Mae ADU mortgage, HELOC, construction-to-permanent).
State housing programs
California's state-level ADU programs are concentrated at HCD (technical guidance, ordinance review, enforcement) and the paused CalHFA grant pipeline (covered under stateFinancing). The state does not operate a central pre-approved ADU plan library — instead, AB 1332 (2024) created a preemption framework for local pre-approved plans with a 30-day ministerial-approval deadline, and major cities (Los Angeles, San Diego, San Jose, Sacramento, Berkeley) have rolled out their own plan catalogs. The California YIMBY coalition and other housing-policy organizations play an influential role in bill drafting; they are not state agencies but effectively drive much of the ADU legislative agenda. The Title 24 code cycle (now 2025, in effect for 2026 permits) is the authoritative building-code baseline.
Federal (United States) — ADU-relevant rules and programs
Federal ADU law
The United States has no federal statute that directly regulates accessory dwelling unit entitlement or design. Land-use authority over ADUs resides with states and local governments under the traditional police power. Federal engagement is limited to financing (Fannie/Freddie/FHA/VA/USDA), flood insurance (FEMA/NFIP), and discretionary housing programs (HUD), which are recorded in sibling sections of this file.
Federal financing programs
Federal housing-finance agencies and GSEs set nationwide underwriting rules that govern whether an ADU can be financed, appraised, and counted toward mortgage qualifying income. The relevant actors are Fannie Mae, Freddie Mac, FHA (HUD), VA, and USDA Rural Development.
Federal tax credits
There is no ADU-specific federal tax credit. ADUs may incidentally qualify for existing federal energy-efficiency and clean-energy tax credits when the ADU construction includes qualifying measures.
Federal housing programs
HUD administers several discretionary programs that can fund ADU-related activity at the grantee's election, but none is an ADU-specific program.
ZIP Codes
- 94086
- 94087
- 94089
Post Office
- 209 E Java Dr, 94089
- 510 E El Camino Real Ste C, 94087
- 526 W Fremont Ave, 94087