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ADU Rules in Woodinville, Washington

Complete guide to building an Accessory Dwelling Unit in Woodinville — zoning, setbacks, permits, costs, and more.

Max Size: 300 to 1,500 sq ft of habitable floor area (WMC 21.41.020(3)(b)), 500 sq ft above the 1,000 sq ft floor in RCW 36.70A.681(1)(f). Habitable floor area is gross floor area minus vehicle parking, covered and open-air floors and space under 5-ft ceilings, so a garage bay or low attic does not count. Building coverage (Table 21.32.050(1)) is the practical cap: R-1 steps from 40% on lots under 5,000 sq ft to 15% at 43,560 sq ft and over; R-4 35%; R-6 50%; R-8 55%; R-12 and R-18 60-65% Setbacks: No separate rear setback: Table 21.32.030(2) sets one "minimum setback from interior property lines", 10 ft in R-1 (5 ft on R-1 lots under 15,000 sq ft, note 2) and 5 ft in R-4, R-6, R-8, R-12 and R-18. A detached ADU "may have the zoning setback reduced to zero from any property line abutting a dedicated public alley" (WMC 21.41.020(3)(c)). Add a 10-ft building setback from the edge of any wetland or riparian buffer (WMC 21.51.050(3)) Parking: 1 Space Verified: 2026-09-20

Researched by ADU Zoning Hub · verified 2026-09-20 against Woodinville planning code and Washington ADU law · methodology · 27 sources cited ↓

ADU Score: 8/10
Very ADU-friendly · how we score

Are ADUs allowed in Woodinville, WA? [1][2][3][4][5][6][7][8][9][10]

Yes. Woodinville allows ADUs on most residential lots. A detached unit can be up to 1,500 sq ft, set 10 ft back from the rear line. One off-street space is required. Owner-occupancy is not required, so the unit can be rented out. A building permit is required and applications are reviewed administratively, without a public hearing.

Maximum size300 to 1,500 sq ft of habitable floor area (WMC 21.41.020(3)(b)), 500 sq ft above the 1,000 sq ft floor in RCW 36.70A.681(1)(f). Habitable floor area is gross floor area minus vehicle parking, covered and open-air floors and space under 5-ft ceilings, so a garage bay or low attic does not count. Building coverage (Table 21.32.050(1)) is the practical cap: R-1 steps from 40% on lots under 5,000 sq ft to 15% at 43,560 sq ft and over; R-4 35%; R-6 50%; R-8 55%; R-12 and R-18 60-65%
SetbacksRear No separate rear setback: Table 21.32.030(2) sets one "minimum setback from interior property lines", 10 ft in R-1 (5 ft on R-1 lots under 15,000 sq ft, note 2) and 5 ft in R-4, R-6, R-8, R-12 and R-18. A detached ADU "may have the zoning setback reduced to zero from any property line abutting a dedicated public alley" (WMC 21.41.020(3)(c)). Add a 10-ft building setback from the edge of any wetland or riparian buffer (WMC 21.51.050(3)) · Side Same interior-line standard: 10 ft in R-1 (5 ft where the R-1 lot is under 15,000 sq ft), 5 ft in every other residential zone (WMC Table 21.32.030(2)). Roof eaves may project 18 in. into an interior setback, chimneys and bay windows 24 in., covered porches 18 in. (WMC 21.32.030(5))
ParkingOne stall per ADU (WMC Table 21.37.060, row "Accessory dwelling unit", Ord. 792 § 22, 2025); tandem stalls assigned to a unit are fine (WMC 21.37.070(6)). Washington's 2025 parking law (SB 5184, RCW 35A.21.445) exempts code cities of 30,000 or fewer people (subsection (6)(a)), so it does not reach Woodinville. RCW 36.70A.681(2)(a)(i) still bars any ADU parking requirement within one-half mile walking distance of a major transit stop, except on lots with critical areas or buffers (subsection (4))
Owner-occupancyNot required. WMC 21.41.020 has no owner-occupancy condition, and RCW 36.70A.681(1)(b) bars a city from requiring the owner to live in the ADU or the main house. On a critical-area lot the state bar switches off (RCW 36.70A.681(4)) but Woodinville's code still imposes nothing. RCW 36.70A.681(1)(k) requires the city to allow an ADU to be sold as a condominium unit (again, not on critical-area lots); WMC 21.41.020 is silent on it, so ask Development Services about the process

Do I need a permit to build an ADU in Woodinville? [11][12][13][14][15][16][17][18][19][20]

Yes. Every ADU in Woodinville needs a building permit. Applications are handled administratively — no public hearing.

Permit fees2026 schedule (Resolution 668): permit fee on valuation ($148.28/sq ft for wood-frame R-3, WMC 21.62.060), plan review 65% of it, fire plan review 13.2% of that, $6.50 state surcharge. A 1,000 sq ft detached ADU comes to about $3,480, plus $119 plus $25 per fixture for mechanical and plumbing
Typical timelineWMC 21.80.210 (Ord. 782, 2025): the city must say whether the application is complete within 28 days and decide a construction permit within 120 days of the completeness date; the clock pauses while it waits for your corrections. Plan review covers two resubmittals; a critical areas report adds time
Official Woodinville links:

Three things to know before you build in Woodinville

  • Order a critical areas screen before you draw anything. WMC 21.51.030(3) lists the reference maps: FEMA flood maps, USGS and DNR hazard and slope maps, the National Wetlands Inventory, WDFW priority habitat maps and the city's own Critical Aquifer Recharge Areas and Geologically Sensitive Areas maps. A stream or wetland buffer plus the 10-ft building setback in WMC 21.51.050(3) will decide where the ADU can physically go
  • Do not let anyone tell you a critical area means no ADU. RCW 36.70A.681(4) removes the state guarantee, not Woodinville's own permission: WMC 21.41.020 has no critical-area exception. You lose the statutory backstop, not the entitlement
  • 1,500 sq ft is habitable floor area: vehicle parking, open-air floors and space under 5-ft ceilings are all subtracted (WMC 21.41.020(3)(b)). A unit with a garage bay and a low storage attic can be considerably bigger than 1,500 sq ft on paper

Last verified 2026-09-20 against Woodinville planning code. How we verify

Yes: Woodinville allows up to two accessory dwelling units on every lot in the R-1, R-4, R-6, R-8, R-12 and R-18 zones under WMC 21.41.020 (Ordinance 792, 2025), each 300 to 1,500 sq ft of habitable floor area, 500 sq ft above the state floor. There is no owner-occupancy rule, one parking stall per unit (Washington's 2025 parking law SB 5184 exempts cities of 30,000 or fewer people, so it does not reach Woodinville), 5-ft interior setbacks (10 ft on larger R-1 lots) and a zero setback on a lot line along a public alley. The permit is a Type 1 building permit with a 120-day decision deadline (WMC 21.80.210); under the 2026 fee schedule city permit fees come to about $3,500 on a 1,000 sq ft unit, the school impact fee is waived outright and the park impact fee is halved. Much of the city carries critical areas (Chapter 21.51 WMC); they decide where on the lot the unit can go, not whether you may build one.

In Woodinville you will also hear an ADU called a DADU — short for detached accessory dwelling unit, the usual term across Washington. The rules on this page apply either way.

Outside city limits? If your property is in unincorporated King County (not within Woodinville's boundaries), different rules apply — see our King County (unincorporated) ADU rules.

Zoning & Size Requirements [1][2][3][4][5][6][7][8][9][10]

Yes — Woodinville allows ADUs. A detached ADU can typically be up to 1,500 sq ft under current Washington and Woodinville zoning rules.

See what this means for your lot — ask Woodinville ADU builders for a quote →

Allowed ZonesPermitted outright (P) in R-1, R-4, R-6, R-8, R-12 and R-18 (WMC Table 21.21.050, row "Dwelling Unit, Accessory", note 1 pointing to WMC 21.41.020). Not listed in R-24, R-48 or any commercial, industrial or other zone, so not allowed there (WMC 21.21.030(2)(g)). Under WMC 21.21.030(3) ADUs count when classifying the residential use: a house plus two attached ADUs reads as a three-unit townhouse or stacked flat, which in R-1 to R-8 brings in the Chapter 21.38 Low-Rise Residential Design Standards
Max Size (Detached)300 to 1,500 sq ft of habitable floor area (WMC 21.41.020(3)(b)), 500 sq ft above the 1,000 sq ft floor in RCW 36.70A.681(1)(f). Habitable floor area is gross floor area minus vehicle parking, covered and open-air floors and space under 5-ft ceilings, so a garage bay or low attic does not count. Building coverage (Table 21.32.050(1)) is the practical cap: R-1 steps from 40% on lots under 5,000 sq ft to 15% at 43,560 sq ft and over; R-4 35%; R-6 50%; R-8 55%; R-12 and R-18 60-65%
Max Size (Attached)Same 300 to 1,500 sq ft of habitable floor area. An ADU "may be fully contained inside a primary dwelling unit, attached or stacked to a primary or accessory dwelling unit, attached or stacked on a building containing an accessory residential use, or may be standalone one-unit dwellings" (WMC 21.41.020(3)(a)). An interior conversion with no exterior expansion is exempt from the Chapter 21.38 design standards (WMC 21.38.010(2))
Max Size (JADU)Washington has no junior ADU category and Woodinville's code has none. A unit carved out inside the house is simply an attached ADU (WMC 21.11B.050) with the same 300 to 1,500 sq ft habitable floor area range
Max Height35 ft in R-1, R-4, R-6, R-8 and R-12; 45 ft in R-18 (WMC Table 21.32.040(2), re-read 20 Sept 2026). WMC 21.41.020(3) applies the zone's standards to an ADU and does not modify height. A pitched roof (hip, gable or shed; not mansard or gambrel) may rise up to 10 ft above the limit if the space is not habitable or opens onto 7-ft walls below and the pitch is 1:2 or flatter (WMC 21.32.040(6)(h)). Height is measured from average finished grade 6 ft out from the walls (WMC 21.32.040(5))
Max UnitsTwo ADUs per parent lot (WMC 21.41.020(1)); "parent lot" is the original lot from which unit lots may be split (WMC 21.11A.170), so a unit lot subdivision does not multiply the allowance. ADUs count toward the maximum dwelling units per lot in Table 21.31.030 (2 in R-1 and R-4, 3 in R-6 to R-18), but the second of two compliant ADUs is excluded from that count (WMC 21.41.020(2)), so a house plus two ADUs works even in R-1

Setback Requirements [1][2][3][4][5][6][7][8][9][10]

Woodinville requires a rear setback of about 10 ft for a detached ADU, and one off-street parking space is required. Owner-occupancy is not required — you can rent it out without living on the property.

Rear SetbackNo separate rear setback: Table 21.32.030(2) sets one "minimum setback from interior property lines", 10 ft in R-1 (5 ft on R-1 lots under 15,000 sq ft, note 2) and 5 ft in R-4, R-6, R-8, R-12 and R-18. A detached ADU "may have the zoning setback reduced to zero from any property line abutting a dedicated public alley" (WMC 21.41.020(3)(c)). Add a 10-ft building setback from the edge of any wetland or riparian buffer (WMC 21.51.050(3))
Side SetbackSame interior-line standard: 10 ft in R-1 (5 ft where the R-1 lot is under 15,000 sq ft), 5 ft in every other residential zone (WMC Table 21.32.030(2)). Roof eaves may project 18 in. into an interior setback, chimneys and bay windows 24 in., covered porches 18 in. (WMC 21.32.030(5))
Front Setback10 ft from a street property line in every residential zone; 20 ft for an attached or detached garage, measured along the driveway centreline from the vehicle door to the street line (WMC Table 21.32.030(2), note 1). If the ADU includes a garage bay, the 20-ft figure governs that part. Eaves may project 24 in. and covered porches 5 ft into a street setback (WMC 21.32.030(5))
Parking RequiredOne stall per ADU (WMC Table 21.37.060, row "Accessory dwelling unit", Ord. 792 § 22, 2025); tandem stalls assigned to a unit are fine (WMC 21.37.070(6)). Washington's 2025 parking law (SB 5184, RCW 35A.21.445) exempts code cities of 30,000 or fewer people (subsection (6)(a)), so it does not reach Woodinville. RCW 36.70A.681(2)(a)(i) still bars any ADU parking requirement within one-half mile walking distance of a major transit stop, except on lots with critical areas or buffers (subsection (4))
Owner OccupancyNot required. WMC 21.41.020 has no owner-occupancy condition, and RCW 36.70A.681(1)(b) bars a city from requiring the owner to live in the ADU or the main house. On a critical-area lot the state bar switches off (RCW 36.70A.681(4)) but Woodinville's code still imposes nothing. RCW 36.70A.681(1)(k) requires the city to allow an ADU to be sold as a condominium unit (again, not on critical-area lots); WMC 21.41.020 is silent on it, so ask Development Services about the process
Min Lot SizeNo ADU-specific minimum. The zone minimums are 35,000 sq ft in R-1, 9,000 in R-4, 6,000 in R-6, 5,000 in R-8, 3,600 in R-12 and 2,400 in R-18 (WMC Table 21.31.030, Ord. 792 § 16, 2025). RCW 36.70A.681(1)(e) requires the city to allow an ADU on any lot that meets the minimum lot size for the principal unit, and Woodinville adds nothing of its own

Permit Process & Fees [11][12][13][14][15][16][17][18][19][20]

An ADU permit in Woodinville goes through a standard permit review. Typical timeline: WMC 21.80.210 (Ord. 782, 2025): the city must say whether the application is complete within 28 days and decide a construction permit within 120 days of the completeness date; the clock pauses while it waits for your corrections. Plan review covers two resubmittals; a critical areas report adds time. Permit fees: 2026 schedule (Resolution 668): permit fee on valuation ($148.28/sq ft for wood-frame R-3, WMC 21.62.060), plan review 65% of it, fire plan review 13.2% of that, $6.50 state surcharge. A 1,000 sq ft detached ADU comes to about $3,480, plus $119 plus $25 per fixture for mechanical and plumbing.

Approval ProcessA building permit processed as a Type 1 administrative decision with no hearing, unless a SEPA threshold determination is needed, which makes it Type 2 (WMC 21.82.010(3)). Apply through the online Permit Portal or at the Development Services Permit Center, 17301 133rd Ave NE, 425-489-2754; the first pre-application meeting is free (2026 fee schedule). Two things add review: a critical area or buffer on the lot, which needs a critical areas report (WMC 21.51.060) and a critical area determination ($618) or alteration review ($2,805) in 2026; and, in R-1 to R-8, a third unit built onto the outside of a building, which triggers Chapter 21.38 design review inside the same Type 1 decision (WMC 21.38.010, 21.38.020). Street frontage improvements are not required for an ADU unless they would be required anyway (WMC 21.63.020(1)(b)). Electrical work is permitted separately; ask the Permit Center which agency issues it
Review TimelineWMC 21.80.210 (Ord. 782, 2025): the city must say whether the application is complete within 28 days and decide a construction permit within 120 days of the completeness date; the clock pauses while it waits for your corrections. Plan review covers two resubmittals; a critical areas report adds time
Permit Fees2026 schedule (Resolution 668): permit fee on valuation ($148.28/sq ft for wood-frame R-3, WMC 21.62.060), plan review 65% of it, fire plan review 13.2% of that, $6.50 state surcharge. A 1,000 sq ft detached ADU comes to about $3,480, plus $119 plus $25 per fixture for mechanical and plumbing
Impact FeesSchool impact fee: ADUs approved under WMC 21.41.020 are fully exempt (WMC 3.38.040(3), Ord. 800, 2025); a new three-bedroom house pays $17,550 (WMC 3.38.060), so the exemption is real money. Park impact fee: an ADU pays 50% of the fee for the largest primary unit on the lot (WMC 3.36.080(2), Ord. 811, 4 Aug 2026); the schedule is $2,054 for a unit of 1,500 sq ft or less, $4,886 from over 1,500 to under 2,300 sq ft and $7,718 at 2,300 sq ft and over (WMC 3.36.060(2)), so an ADU behind a 2,000 sq ft house owes $2,443 and behind a 2,400 sq ft house $3,859. Transportation impact fee: $3,760 per p.m. peak-hour person trip (WMC 3.39.085, Ord. 772, 2024), trips predicted from the ITE Trip Generation manual (WMC 3.39.090(4)); Chapter 3.39 has no ADU exemption, but RCW 36.70A.681(1)(a) caps any ADU impact fee at 50% of the principal unit's, a cap RCW 36.70A.681(4) switches off on a critical-area lot, where only the city's own 3.36.080(2) and 3.38.040(3) apply. You may ask for a non-binding advance calculation (WMC 3.39.090(3)). Fees are fixed at building permit issuance; deferral to final inspection against a recorded lien is written for one-unit dwellings and single-family construction (WMC 3.36.060(3), 3.39.090(2)), so ask whether an ADU permit qualifies
Plan CheckStandard building plan review under Chapter 21.62 WMC. Prefabricated units are allowed on a permanent foundation (WMC 21.41.020(4)(c)). Conversions of existing enclosed structures, detached garages included, are allowed even where the structure breaks current coverage or setback rules, provided it and the nonconformance were legally established (WMC 21.41.020(4)(a)). The Director may approve deviations from zoning standards for accessibility features (WMC 21.41.020(3)(e)). If the lot has a wetland, stream, steep slope, flood area or critical aquifer recharge area, expect a critical areas report (WMC 21.51.060), mitigation sequencing (WMC 21.51.050) and the 10-ft building setback from any riparian zone or wetland buffer (WMC 21.51.050(3)). Structural review sent to an outside consultant is billed at cost, with an advance deposit if it is expected to exceed $5,000 (2026 fee schedule, note 4)
Pre-Approved PlansNone. Woodinville publishes no pre-approved ADU plan set: the city's Permitting and Applications & Forms pages (archived 6 Jan 2026) list none, and the code contains no expedited ADU track, unlike Kirkland's four registered plans. Confirm with the Permit Center at 425-489-2754 whether plans approved elsewhere would shorten review

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Construction Costs [21][22][23][24]

Building an ADU in Woodinville typically costs $325,000-$550,000 ($400-$650 per sq ft); a garage conversion runs $100,000-$225,000.

See what this means for your lot — ask Woodinville ADU builders for a quote →

Average Build Cost$325,000-$550,000
Cost per Sq Ft$400-$650
Garage Conversion$100,000-$225,000
Prefab ADU (Installed)$300,000-$450,000

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Rental Income Potential [25][26]

A 2-bedroom ADU in Woodinville rents for around $2,800-$3,150/mo, an estimated 5-9% gross annual yield on a $325,000-$550,000 detached build renting at $2,400-$3,150/mo, before vacancy, taxes, impact fees and financing; a garage conversion at $100,000-$225,000 yields roughly double.

Avg Rent (1 Bedroom)$2,400-$2,700/mo
Avg Rent (2 Bedroom)$2,800-$3,150/mo
Short-Term RentalNo. "Accessory dwelling units are prohibited from being rented for periods of fewer than 30 consecutive nights" (WMC 21.41.020(5), re-read 20 Sept 2026, pointing to the short-term rental definition in RCW 36.70A.696).
Est. Annual ROI5-9% gross annual yield on a $325,000-$550,000 detached build renting at $2,400-$3,150/mo, before vacancy, taxes, impact fees and financing; a garage conversion at $100,000-$225,000 yields roughly double

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Recent Law Changes

What's Changed Recently

  • 20 Sept 2026 re-verify: every zoning, permit and impact-fee figure re-read from the codified Woodinville Municipal Code (current through Ordinance 811, passed 4 Aug 2026) and the 2026 Development Services fee schedule (Resolution 668). Corrections: the parking rule sits in Table 21.37.060 and tandem parking in WMC 21.37.070(6) (the entry had cited 21.37.030 and 21.37.060); review deadlines added from WMC 21.80.210; permit fee figures added; rents re-anchored to HUD FY2026 and FY2027 Small Area FMRs for ZIP codes 98072 and 98077; build costs aligned to 2026 Seattle-metro guides
  • Ordinance 811 (passed 4 Aug 2026) repealed and replaced Chapter 3.36 WMC, park impact fees: $2,054 / $4,886 / $7,718 by unit size, with an ADU paying 50 percent of the fee calculated for the largest primary unit on the lot (WMC 3.36.080(2)). Ordinance 800 (2025) reset school impact fees (WMC 3.38.060: $17,550 for a detached house with three or more bedrooms) and kept the full ADU exemption at WMC 3.38.040(3)
  • Ordinance 792 (2025) repealed and replaced WMC 21.41.020 (accessory dwelling units), 21.31.030 (residential lot standards) and 21.36.030, added Chapter 21.38 (Low-Rise Residential Design Standards) and amended some thirty further sections including the use table (21.21.050), coverage (21.32.050), parking (21.37.060, 21.37.070) and frontage improvements (21.63.020): the city's middle housing and ADU compliance package, and the reason the ADU cap is 1,500 sq ft rather than the state's 1,000 sq ft floor
  • Ordinance 782 (2025) rewrote the project permit review procedures in Chapter 21.80 WMC, including WMC 21.80.100 (completeness determination within 28 days) and WMC 21.80.210 (decision on a construction permit within 120 days of completeness; Type 1 project permits within 65 days). Ordinance 784 (2025) repealed and replaced Chapter 21.51 WMC, the critical areas regulations
  • Washington HB 1337 (2023 c 334), codified at RCW 36.70A.681, preempts local ADU regulation inside urban growth areas: two ADUs on every lot that allows a single-family home, no owner-occupancy requirement, no floor-area cap under 1,000 sq ft, no roof height limit under 24 ft, no setbacks stricter than the main house, conversions of existing structures including detached garages, siting on a lot line along a public alley, impact fees capped at half the principal unit's, condominium sale allowed, no street improvements and no parking within one-half mile walking distance of a major transit stop. Text unchanged as of 20 Sept 2026
  • The critical-area catch: RCW 36.70A.681(4) provides that the section "does not apply to lots designated with critical areas or their buffers as designated in RCW 36.70A.060." Woodinville designates critical aquifer recharge areas, frequently flooded areas, wetlands, geologically hazardous areas and fish and wildlife habitat conservation areas (Chapter 21.51 WMC), and the Sammamish River and Little Bear Creek run through the city. On such a lot none of the state guarantees apply, but WMC 21.41.020 has no critical-area exception of its own, so the local entitlements (two ADUs, 1,500 sq ft, no owner occupancy, alley lot-line siting, conversion rights, halved park fee, waived school fee) survive
  • Washington SB 5184 (2025 c 204, RCW 35A.21.445), the parking-minimum law that Kirkland implemented on 15 Sept 2026, does not apply to code cities with a population of 30,000 or less (RCW 35A.21.445(6)(a)); Woodinville (about 14,500 people) keeps its one-stall-per-ADU rule. EHB 1345 (Chapter 231, Laws of 2026, effective 11 June 2026) concerns detached ADUs outside urban growth areas and has no effect inside the city

Tips for Building an ADU in Woodinville

  • Order a critical areas screen before you draw anything. WMC 21.51.030(3) lists the reference maps: FEMA flood maps, USGS and DNR hazard and slope maps, the National Wetlands Inventory, WDFW priority habitat maps and the city's own Critical Aquifer Recharge Areas and Geologically Sensitive Areas maps. A stream or wetland buffer plus the 10-ft building setback in WMC 21.51.050(3) will decide where the ADU can physically go
  • Do not let anyone tell you a critical area means no ADU. RCW 36.70A.681(4) removes the state guarantee, not Woodinville's own permission: WMC 21.41.020 has no critical-area exception. You lose the statutory backstop, not the entitlement
  • 1,500 sq ft is habitable floor area: vehicle parking, open-air floors and space under 5-ft ceilings are all subtracted (WMC 21.41.020(3)(b)). A unit with a garage bay and a low storage attic can be considerably bigger than 1,500 sq ft on paper
  • If your lot backs a dedicated public alley, WMC 21.41.020(3)(c) lets a detached ADU go to zero setback on that line, the single biggest gain in usable yard available in this code
  • Permit fee worked example under the 2026 schedule: a 1,000 sq ft wood-frame detached ADU is valued at $148,280 (WMC 21.62.060), giving a $2,000 permit fee, $1,300 plan review, $172 fire plan review and a $6.50 state surcharge, about $3,480; a 1,500 sq ft unit ($222,420) comes to about $4,760. Add $119 plus $25 per fixture for the mechanical and plumbing permit, and $618 for a critical area determination if one is needed
  • Two ADUs on one lot makes the property a three-unit development for classification (WMC 21.21.030(3)). In R-1, R-4, R-6 and R-8 that brings in the Chapter 21.38 design standards for any new construction on the outside of a building: 15 percent windows and doors on the street facade, a 3 ft by 3 ft entry canopy and a walkway to the sidewalk (WMC 21.38.030). Interior conversions are exempt (WMC 21.38.010(2))
  • The impact fee position is genuinely good: the school impact fee ($17,550 for a new three-bedroom house) is waived outright for an ADU, the park impact fee is halved, and both come from Woodinville's own code rather than the state cap that a critical area would switch off. The transportation impact fee ($3,760 per p.m. peak-hour person trip) is the one that remains; ask Public Works for an advance estimate
  • R-1 lots under 15,000 sq ft get a 5-ft interior setback instead of 10 ft under note 2 to Table 21.32.030(2). Check your lot area first; it is worth 5 ft of building width
  • Long-term tenants only. Renting an ADU for under 30 consecutive nights is prohibited outright by WMC 21.41.020(5): no permit, no licence, no exception
  • Cost basis: the build-cost ranges are Seattle-metro 2026 industry figures (four guides dated Nov 2025 to May 2026: $325,000-$550,000 for a new detached unit, $400-$650 per sq ft all-in, $100,000-$225,000 for a garage or basement conversion, $300,000-$450,000 for a prefab unit installed). No Woodinville-specific cost survey exists; Eastside sites with slopes, long utility runs or critical-area work sit at the top of the ranges. Rents are HUD FY2026 and FY2027 Small Area Fair Market Rents for 98072 and 98077 ($2,420-$2,670 for one bedroom, $2,820-$3,120 for two)
  • Cost basis (2026-09-20 re-verification): short term allowed: No. "Accessory dwelling units are prohibited from being rented for periods of fewer than 30 consecutive nights" (WMC 21.41.020(5), re-read 20 Sept 2026, pointing to the short-term rental definition in RCW 36.70A.696). There is no permit or licence route around it: Woodinville's ADU rules are written for long-term tenancy, which is also why the school impact fee is waived and the park fee halved

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Sources & References

All data on this page is sourced from official government records and verified market data. View our full methodology.

  1. Woodinville Municipal Code 21.41.020 — Accessory dwelling unit (Ord. 792 § 27, 2025); Chapter 21.41 Accessory Uses Municipal Code — Accessed 2026-09-20
  2. Woodinville Municipal Code 21.21.030 and Table 21.21.050 — Residential Use Table (Ord. 792 § 14, 2025) Municipal Code — Accessed 2026-09-20
  3. Woodinville Municipal Code Chapter 21.32 — Bulk and Setback Standards (Tables 21.32.030(2), 21.32.040(2), 21.32.050(1); 21.32.030(5); 21.32.040(5)-(6)) Municipal Code — Accessed 2026-09-20
  4. Woodinville Municipal Code 21.31.030 — Residential zoned lot development standards (Ord. 792 § 16, 2025) Municipal Code — Accessed 2026-09-20
  5. Woodinville Municipal Code Chapter 21.37 — Off-Street Parking and Loading (Table 21.37.060 ADU row, Ord. 792 § 22, 2025; 21.37.070(6) tandem; 21.37.080(2)(d)) Municipal Code — Accessed 2026-09-20
  6. Woodinville Municipal Code Chapter 21.38 — Low-Rise Residential Design Standards (21.38.010 applicability; 21.38.020 Type 1 review; Ord. 792 § 26, 2025) Municipal Code — Accessed 2026-09-20
  7. Woodinville Municipal Code 21.11A.170 (parent lot, unit lot) and 21.11B.050 (dwelling unit, accessory; dwelling, one-unit) — Definitions Municipal Code — Accessed 2026-09-20
  8. RCW 36.70A.681 — Accessory dwelling units, limitations on local regulation (2023 c 334 s 4, HB 1337), including parking at (2)(a) and the critical-areas carve-out at (4) state_statute — Accessed 2026-09-20
  9. RCW 35A.21.445 — Minimum parking requirements (2025 c 204 s 3, SB 5184); (6)(a) exemption for code cities of 30,000 or fewer state_statute — Accessed 2026-09-20
  10. Woodinville Municipal Code Chapter 21.51 — Critical Areas Regulations (21.51.030(3) maps; 21.51.050 general requirements and (3) 10-ft building setback; 21.51.060 report; Ord. 784 § 14 (Att. A), 2025) Municipal Code — Accessed 2026-09-20
  11. Woodinville Municipal Code 21.82.010 — Building permit (Type 1 administrative decision; Type 2 with SEPA) Municipal Code — Accessed 2026-09-20
  12. Woodinville Municipal Code Chapter 21.80 — Project Permit Review Procedures (21.80.100 completeness; 21.80.210 review time frames; Ord. 782 §§ 26, 34, 2025) Municipal Code — Accessed 2026-09-20
  13. Woodinville Municipal Code 21.62.060 — Building permit fees and valuation table (R-3 one- and two-family, Type VB $148.28/sq ft; Ord. 775 § 1, 2024) Municipal Code — Accessed 2026-09-20
  14. Woodinville Municipal Code Chapter 21.13 — Development Fees (21.13.040 fee resolution; 21.13.060 advance deposit; 21.13.070 disputes) Municipal Code — Accessed 2026-09-20
  15. Woodinville Municipal Code 21.63.020 — Street frontage improvements, applicability (ADU exemption at (1)(b); Ord. 792 § 33, 2025) Municipal Code — Accessed 2026-09-20
  16. City of Woodinville — 2026 Fee Schedule, Resolution No. 668 (building permit valuation table, plan review 65%, fire plan review 13.2%, critical areas $618/$2,805, SEPA, pre-application, hourly $142); read from the Internet Archive capture of 7 Jan 2026 because woodinville.gov sits behind a Cloudflare bot check Planning Department — Accessed 2026-09-20
  17. City of Woodinville — Permitting; Fees; Applications & Forms (Development Services Permit Center, 17301 133rd Ave NE, 425-489-2754; Permit Portal; no pre-approved ADU plans listed); Internet Archive captures of 6-7 Jan 2026 Planning Department — Accessed 2026-09-20
  18. Woodinville Municipal Code Chapter 3.36 — Park Impact Fees (3.36.060(2) schedule and (3) deferral; 3.36.080(2) ADU 50%; Ord. 811 § 1 (Att. A), 2026) Municipal Code — Accessed 2026-09-20
  19. Woodinville Municipal Code Chapter 3.38 — School Impact Fees (3.38.040(3) ADU exemption; 3.38.060 schedule; Ord. 800 §§ 1-3, 2025) Municipal Code — Accessed 2026-09-20
  20. Woodinville Municipal Code Chapter 3.39 — Transportation Impact Fees (3.39.050 exemptions; 3.39.085 $3,760 per p.m. peak-hour person trip, Ord. 772 § 7, 2024; 3.39.090 ITE basis, deferral, advance calculation) Municipal Code — Accessed 2026-09-20
  21. Cost to Build a DADU in Seattle (2025-2026 Update) | Ballard Backyard Cottages industry — Accessed 2026-09-19
  22. How Much Does It Cost to Build an ADU in Seattle? 2026 Guide (Jan. 8, 2026) | Kolmo industry — Accessed 2026-09-19
  23. Seattle ADU Cost 2026 by Type and Size (updated May 12, 2026) | ADU Glossary industry — Accessed 2026-09-19
  24. Prefab ADU 2026: Brands, True Costs (updated May 19, 2026) | OwnADU industry — Accessed 2026-09-19
  25. HUD FY 2026 and FY 2027 Small Area Fair Market Rents, Seattle-Bellevue, WA HUD Metro FMR Area, ZIP codes 98072 and 98077 Government Data — Accessed 2026-09-20
  26. Woodinville Municipal Code 21.41.020(5) — ADU short-term rental prohibition (fewer than 30 consecutive nights; RCW 36.70A.696 definition) Municipal Code — Accessed 2026-09-20
  27. Woodinville Municipal Code — Ordinance Table (current through Ord. 811, 2026; Ords. 782, 784, 789, 792, 794, 800 of 2025; 804, 807, 811 of 2026) Municipal Code — Accessed 2026-09-20

Frequently Asked Questions

Can I build an ADU in Woodinville?

Yes. ADUs are allowed in Permitted outright (P) in R-1, R-4, R-6, R-8, R-12 and R-18 (WMC Table 21.21.050, row "Dwelling Unit, Accessory", note 1 pointing to WMC 21.41.020). Not listed in R-24, R-48 or any commercial, industrial or other zone, so not allowed there (WMC 21.21.030(2)(g)). Under WMC 21.21.030(3) ADUs count when classifying the residential use: a house plus two attached ADUs reads as a three-unit townhouse or stacked flat, which in R-1 to R-8 brings in the Chapter 21.38 Low-Rise Residential Design Standards in Woodinville. The maximum size for a detached ADU is 300 to 1,500 sq ft of habitable floor area (WMC 21.41.020(3)(b)), 500 sq ft above the 1,000 sq ft floor in RCW 36.70A.681(1)(f). Habitable floor area is gross floor area minus vehicle parking, covered and open-air floors and space under 5-ft ceilings, so a garage bay or low attic does not count. Building coverage (Table 21.32.050(1)) is the practical cap: R-1 steps from 40% on lots under 5,000 sq ft to 15% at 43,560 sq ft and over; R-4 35%; R-6 50%; R-8 55%; R-12 and R-18 60-65%. Owner-occupancy is not required, so you can rent out the ADU.

How much does an ADU cost in Woodinville?

ADU construction in Woodinville typically costs $325,000-$550,000. Garage conversions run $100,000-$225,000, and prefab ADUs cost $300,000-$450,000.

How much can I rent an ADU for in Woodinville?

Average ADU rents in Woodinville are $2,400-$2,700/mo for a 1-bedroom and $2,800-$3,150/mo for a 2-bedroom unit.

Do I need parking for an ADU in Woodinville?

One stall per ADU (WMC Table 21.37.060, row "Accessory dwelling unit", Ord. 792 § 22, 2025); tandem stalls assigned to a unit are fine (WMC 21.37.070(6)). Washington's 2025 parking law (SB 5184, RCW 35A.21.445) exempts code cities of 30,000 or fewer people (subsection (6)(a)), so it does not reach Woodinville. RCW 36.70A.681(2)(a)(i) still bars any ADU parking requirement within one-half mile walking distance of a major transit stop, except on lots with critical areas or buffers (subsection (4)). Check with Woodinville planning department for the latest Washington ADU parking rules, as many states have relaxed requirements in recent years.

How long does it take to get an ADU permit in Woodinville?

The permit review timeline in Woodinville is WMC 21.80.210 (Ord. 782, 2025): the city must say whether the application is complete within 28 days and decide a construction permit within 120 days of the completeness date; the clock pauses while it waits for your corrections. Plan review covers two resubmittals; a critical areas report adds time. Permit fees: 2026 schedule (Resolution 668): permit fee on valuation ($148.28/sq ft for wood-frame R-3, WMC 21.62.060), plan review 65% of it, fire plan review 13.2% of that, $6.50 state surcharge. A 1,000 sq ft detached ADU comes to about $3,480, plus $119 plus $25 per fixture for mechanical and plumbing.

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Woodinville ADU FAQ

Answers to every common question about building an ADU in Woodinville — costs, rules, permits, rental income.

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Woodinville ADU Costs

Detailed cost breakdown: construction $325,000-$550,000, garage conversion $100,000-$225,000, plus ROI analysis.

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Garage Conversion ADU Guide

Complete guide to costs ($80K-$180K), impact fee savings, and permits for garage-to-ADU conversions.

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ADU vs Mother-in-Law Suite

Legal differences that affect what you can build, how you can use it, and rental rights.

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About this information: This page is an informational summary of publicly available regulations - it is not legal, financial, or professional advice, and it is not a substitute for confirming requirements with your local planning department. Rules change frequently; always verify current requirements before designing, budgeting, or building. Last verified: 2026-09-20. Contractors we introduce are independent businesses - verify license and insurance directly before hiring. Spotted an error? Tell us - we verify against primary sources and correct quickly.

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