ADU Pass
Washington
ADU Pass helps homeowners in Washington, Nevada County, California navigate the permit paperwork for building an accessory dwelling unit. This area covers 1 ZIP code.
Map
ADU details
ADU legality: allowed-with-restrictions
ADUs are by-right under Nevada County's ministerial pathway (Section L-II 3.19.1). However, Washington sits at ~2,612 ft on the South Yuba River, surrounded by Tahoe National Forest, in a CAL FIRE Very High Fire Hazard Severity Zone (WUI). Practical constraints: defensible-space and ignition-resistant construction (CRC Chapter 7A / Part 7 Title 24), septic feasibility (no public sewer), and Washington County Water District capacity for new connections.
Cost scenarios
| Scenario | Sq ft | Permit | Build | Total |
|---|---|---|---|---|
| minimum | 150 | $5,800 | $87,000 | $92,800 |
| 600 | 600 | $7,200 | $348,000 | $355,200 |
| midpoint | 675 | $7,800 | $391,500 | $399,300 |
| 1000 | 1,000 | $16,400 | $570,000 | $586,400 |
| maximum | 1,200 | $19,400 | $666,000 | $685,400 |
Fee breakdown (as of 2026-04)
Permitting process
Viability (permitted uses)
- Long-term rental: yes Long-term rental (30+ days) explicitly permitted per state preemption (AB 976). Owner-occupancy not required.
- Short-term rental: with-restrictions Nevada County regulates short-term rentals separately from ADU permitting. STR registration, TOT remittance, and FHSZ-area defensible-space verification apply. Washington has emerging STR demand from South Yuba River recreation tourism (rafting, swimming holes).
- Office rental: with-restrictions Standalone commercial office rental of an ADU is not a permitted ADU use. Home occupations within an owner-occupied ADU are allowed.
- Home office: yes Home occupation permitted with traffic / employee / signage limits per Nevada County Code.
- Studio / workshop: yes Personal artist studio / workshop is a permitted accessory residential use.
- Agriculture: with-restrictions Many Washington parcels carry AE (Agriculture Exclusive) or AG zoning where agricultural support buildings are explicitly allowed alongside ADUs. Livestock subject to zoning-district-specific limits.
- Relative support: yes Family-occupancy ADU explicitly permitted; common Washington use is multigenerational rural housing for aging parents who want to stay near the South Yuba canyon.
Incentives
Contacts
Utilities
- Water: Washington County Water District (WCWD) · 60d connect · $8,500
WCWD is a small rural water district with limited capacity; new ADU connections require district board review. Some Washington parcels rely on private wells outside the WCWD service area. - Sewer: On-site septic (no public sewer) · 90d connect · $28,000
Washington has no public sewer. Every ADU requires either an existing septic with proven capacity for the additional load, or new/expanded system designed by a Registered Environmental Health Specialist and permitted through Nevada County Environmental Health. Slope and soil conditions in the South Yuba canyon often force engineered systems. - Electric: Pacific Gas & Electric Company (PG&E) · 45d connect · $3,800
PG&E serves Washington for electric. Service drops to remote canyon parcels are often longer than urban runs and may require Public Safety Power Shutoff (PSPS) consideration; many residents pair grid with solar + battery storage. - Gas: No piped gas — propane only · 21d connect · $2,200
PG&E does not extend natural gas to Washington. ADUs use propane (AmeriGas, Suburban Propane local providers) for cooking/heat or all-electric heat pumps.
Property values & taxes
Construction timeline
Realistic total: best 9mo · typical 14mo · worst 22mo
Sierra winter weather (Nov-Mar) compresses the Washington build season. GC pool is shallow; most contractors are based in Grass Valley / Auburn / Nevada City and charge mileage premiums. Septic permitting can extend timeline by 4-8 weeks beyond the building permit.
Modular pathway inspectors are novice with modular
Financing
State ADU loans:
- CalHFA ADU Grant Program up to $40,000
- HCD ADU Funding index
Insurance impact
Washington is in a Very High Fire Hazard Severity Zone. Many California carriers (State Farm, Allstate, Farmers) have non-renewed or paused new business in this area; owners increasingly use the California FAIR Plan with a Difference In Conditions (DIC) wrap. Premium delta is substantially above urban California ADU norms.
HOA prevalence & preemption
Washington is rural unincorporated land with virtually no HOAs. The few covenant communities are small private road associations with no enforceable ADU prohibition under AB 670 / AB 3182. State preemption applies fully.
Regulatory overlays (5)
- wui-fire-zone
Most of the Washington area is mapped as Very High Fire Hazard Severity Zone (CAL FIRE). Triggers CRC Chapter 7A / Part 7 Title 24 ignition-resistant construction (Class A roof, ember-resistant vents, non-combustible cladding within 5 ft) and 100-ft defensible-space requirement. Sierra Nevada Conservancy funded a $1.0M fuel-thinning project on Tahoe National Forest land surrounding Washington (172 acres, 5.5 mi containment line, Washington Road / Alpha Road). - historic-district
Washington is recognized as a California Point of Historic Interest as a remaining Gold Rush hydraulic-mining village. The Washington Hotel (1857) is a contributing structure. While there is no formal local historic-preservation ordinance (no city government), proposed development on Main Street and the Washington Mining District core may attract Nevada County and Office of Historic Preservation review attention. - flood-zone
Parcels along the South Yuba River corridor in Washington sit in FEMA Special Flood Hazard Areas (SFHA). Riverine flooding from snowmelt-driven spring flows is the dominant hazard. - seismic-retrofit-zone
All of Nevada County is in California seismic design category D for the IBC/CRC. Mountain-foothill geology and steep canyon slopes can elevate site-specific design demand. - other
South Yuba River is federally designated Wild & Scenic. The river corridor itself is protected; parcels adjacent to or above the SFHA may face additional setback or visual-resource conditions where the Tahoe National Forest abuts private land.
Technical envelope (climate & building code)
Climate & energy code
Building code
Amendments:
- Amendment
- Amendment
Contractor market (aggregate)
Legal history (timeline)
Current ordinance: Nevada County Code Section L-II 3.19.1 — Accessory and Junior Accessory Dwelling Units, adopted 2017-04-25, last amended 2023-12-12
- 2017-04-25 — Nevada County Ordinance 2440 — initial AB 2299/SB 1069 ADU conformance (county-ordinance)
Nevada County Board of Supervisors adopted the first ADU conformance ordinance to comply with the 2017 California ADU statute changes.
Effect: Established Section L-II 3.19 ADU framework in Nevada County's Land Use & Development Code; applied to all unincorporated communities including Washington. - 2020-02-25 — Nevada County ADU update conforming to AB 68/881/587/671/SB 13/AB 670 (county-ordinance)
Conforming amendments to align Section L-II 3.19 with the 2020 California ADU statute package.
Effect: Adopted statewide design / setback / parking standards. Aligned plan check and fee structure with state preemption. Workshop January 24-25, 2018 led to this update. - 2023-12-12 — Nevada County 2023 Housing Ordinance Amendments (PLN23-0059 / ORD23-1 / GPT23-0001) (county-ordinance)
Comprehensive housing-element amendments to Section L-II 3.19.1 and related zoning sections.
Effect: Expanded ministerial ADU eligibility to RA, R1, R2, AE, AG, FR, and TPZ districts regardless of minimum parcel size and zoning density, in line with the 2023 California ADU statute package (SB 897, AB 2221). - 2024-04-12 — Nevada County Regional Pre-Approved ADU Plans launch (Jackson and Sands Engineering) (county-ordinance)
Nevada County partnered with Jackson and Sands Engineering, Inc. on a Regional Partnership for Achievable Housing offering pre-approved ADU plans available across Nevada County, Town of Truckee, and surrounding jurisdictions.
Effect: Owners pay $1,200 per use to the design consultant; plans then route through standard county permitting at reduced plan-check effort. Available to all unincorporated parcels including Washington.
Known issues (2)
- other — Washington is in a Very High Fire Hazard Severity Zone with active wildfire-prevention work funded by Sierra Nevada Conservancy and CAL FIRE (Tahoe National Forest fuel thinning, Washington Road / Alpha Road). Insurance availability is materially impaired; owners often rely on the California FAIR Plan.
- other — Washington County Water District has limited capacity (~122 connections, gravity-flow). New ADU connections require district board review; some parcels rely on private wells. Septic feasibility is the single most common project killer.
Nevada County — county ADU rules and overlays
County ADU ordinance
Nevada County (population ~102,000) is a Sierra Nevada gold-country county on the western slope between the Sacramento Valley foothills and the Sierra crest at Donner Summit. Incorporated cities are Grass Valley (the largest, ~13,000), Nevada City (the historic county seat, a registered National Historic Landmark District), and the Town of Truckee (which incorporated in 1993 and includes a small slice of the Lake Tahoe Basin north of the lake). Major unincorporated communities include Penn Valley, Rough and Ready, Washington (a Gold Rush ghost town), Lake of the Pines, North San Juan, Cedar Ridge, and the Donner Summit cabin districts. The county is dominated by the Tahoe National Forest (over 60% of land area) and is one of the highest-percentage Williamson Act counties in the Sierra foothills. The Board of Supervisors administers ADU permitting in unincorporated territory under California Government Code Sec. 65852.2 and 65852.22 (state ADU preemption). Practical permitting frictions are dominated by very high fire severity zone coverage following the 2017 Lobo Fire, 2020 Jones Fire, and 2021 River Fire, plus septic/well dependence and TRPA jurisdiction along the small Tahoe Basin segment north of Truckee.
- Nevada County Land Use and Development Code (Title L-II) - Accessory Dwelling Units
- Cal. Gov't Code Sec. 65852.2 (Accessory Dwelling Units)
- Cal. Gov't Code Sec. 65852.22 (Junior Accessory Dwelling Units)
- Tahoe Regional Planning Compact (Pub. Law 96-551)
- Nevada County General Plan Housing Element (6th Cycle, 2021-2029)
State-floor overlay: California state ADU preemption applies in full to unincorporated parcels. Tahoe Basin parcels (the small north-of-Truckee slice in the Tahoe hydrologic basin) are subject to TRPA review, which is discretionary and can override the state ministerial preemption. AB 976 prohibits owner-occupancy mandates on detached ADUs through 2025 expiry. AB 1033 condo-conversion election: not adopted by the county as of last check. HCD oversight: any county ordinance amendment must be submitted to HCD within 60 days per Sec. 65852.2(h). The Tahoe National Forest federal land (over 60% of county acreage) is outside county zoning - Forest Service in-holdings (recreation residences under Forest Service special-use permits) are governed by USFS, not county code.
County regulatory overlays
Nevada County overlays of consequence: CAL FIRE State Responsibility Area / Very High FHSZ across virtually all unincorporated foothills (post-2022 FHSZ map update extended coverage); recent burn footprints (2017 Lobo Fire ~822 acres in Penn Valley, 2020 Jones Fire ~705 acres near Nevada City, 2021 River Fire ~2,600 acres in the Bear River corridor); FEMA SFHA along the Yuba River, Bear River, and Truckee River drainages; Williamson Act on agricultural parcels in Penn Valley and the foothills; TRPA jurisdiction over the small Tahoe Basin slice north of Truckee; Nevada City National Historic Landmark District (the only Gold Rush town with that federal designation); SR-49 (Mother Lode highway) state scenic corridor; and Tahoe National Forest federal land covering more than 60% of county acreage.
- CAL FIRE State Responsibility Area / Very High FHSZ (post-2022 update)
- Recent burn footprints - Lobo (2017), Jones (2020), River (2021)
- Tahoe Regional Planning Agency (TRPA) jurisdiction - Tahoe Basin north of Truckee
- FEMA SFHA - Yuba River / Bear River / Truckee River
- Williamson Act agricultural preserve contracts
- Nevada City National Historic Landmark District
- California Scenic Highway System - SR-49 / SR-20
- Tahoe National Forest federal land
County permitting (unincorporated parcels)
Nevada County Planning Department issues all ADU permits for unincorporated parcels; the County Building Department handles plan check and inspections. Practical permitting frictions: CAL FIRE State Responsibility Area covers nearly all rural foothills (Very High to High FHSZ across most of unincorporated territory); 2017 Lobo Fire, 2020 Jones Fire, and 2021 River Fire burn-footprint parcels carry post-fire defensible-space and access-road conditions of approval; septic/well dependence outside the Nevada Irrigation District (NID) and small community service districts (Penn Valley, Lake Wildwood, Lake of the Pines); steep-slope grading review in foothill terrain; oak woodland habitat considerations; short-term-rental tension in the Donner Summit cabin districts and historic Nevada City periphery. The county's housing element commits to ADU streamlining as a key infill strategy.
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 Code
- 95986
Post Office
- 15274 Washington Rd, 95986