Woodinville is one of the more generous ADU codes in King County, and — unusually — it does not lean on state law to get there. Ordinance 792 (2025) rewrote WMC 21.41.020 to allow two accessory dwelling units per parent lot, permitted outright in the R-1, R-4, R-6, R-8, R-12 and R-18 zones, at up to 1,500 sq ft of habitable floor area each. That is 500 sq ft above the floor Washington's HB 1337 guarantees. There is no owner-occupancy requirement, no design-matching requirement, one parking stall per unit, a detached unit may sit right on a property line abutting a public alley, garage conversions are expressly allowed even where the existing structure breaks current setbacks, prefabricated units on a permanent foundation are fine, and street frontage improvements are waived. School impact fees are waived entirely for an ADU and park impact fees are halved. Why that local generosity matters: RCW 36.70A.681(4) switches off every state ADU protection on a lot designated with critical areas or their buffers, and Woodinville has a great deal of critical area — Little Bear Creek, the Sammamish River, wetlands, steep slopes and aquifer recharge areas. On those lots the statute stops protecting you, but Woodinville's own code keeps going. What critical areas cost you here is not permission; it is where on the lot you may build, and a critical areas report to prove it.
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.
Zoning & Size Requirements [1][2][3][4][5][6]
Yes — Woodinville allows ADUs. A detached ADU can typically be up to 1,500 sq ft under current Washington and Woodinville zoning rules.
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| Allowed Zones | Permitted (P) in the R-1, R-4, R-6, R-8, R-12 and R-18 residential zones (Woodinville Municipal Code Table 21.21.050, row "Dwelling Unit, Accessory"). Not listed — and therefore not allowed — in R-24, R-48 or in any commercial, industrial or other zone. Special development conditions are at WMC 21.41.020. Note the Woodinville quirk in WMC 21.21.030(3): all ADUs count in determining the type of residential land use, so a primary unit plus two attached ADUs is interpreted as a three-unit townhouse or stacked flat, which pulls in the Low-Rise Residential Design Standards in Chapter 21.38 WMC |
| Max Size (Detached) | 1,500 sq ft of habitable floor area, with a minimum of 300 sq ft (WMC 21.41.020(3)(b)) — 500 sq ft above the 1,000 sq ft floor RCW 36.70A.681(1)(f) guarantees. "Habitable floor area means the gross floor area of a building reduced by subtracting floor areas for vehicle parking, covered and uncovered outdoor open-air floors, and floor areas having less than five-foot-high ceilings," so a garage bay and a low attic do not count against you. The real limit on most lots is building coverage under Table 21.32.050(1), which in R-1 steps down as the lot gets bigger — from 40% on lots under 5,000 sq ft to 15% on lots of 43,560 sq ft and over, with bands at 35%, 28%, 22% and 20% in between — while minimum landscaping coverage climbs to as much as 75% on the largest R-1 lots. Check your own band with Woodinville Development Services at (425) 489-2700 before sizing the building |
| Max Size (Attached) | Same 1,500 sq ft habitable floor area cap. 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)) — stacked units are expressly on the menu, which many Washington codes still do not allow |
| Max Size (JADU) | Not a category in Washington, and Woodinville has no junior ADU designation. An ADU carved out inside the house is simply an attached ADU and gets the same 300 to 1,500 sq ft range |
| Max Height | 35 feet in R-1, R-4, R-6, R-8 and R-12; 45 feet in R-18 (WMC Table 21.32.040(2)) — an ADU takes the zone's standard, since WMC 21.41.020(3) subjects ADUs to the development standards of the underlying zone except as it modifies them, and it does not modify height. A pitched roof may go up to 10 feet above that limit where the space it creates is not designed for habitation and the slope does not exceed one foot of rise over two feet of run (WMC 21.32.040(6)(h)). Height is measured from average designated grade six feet out from the outer walls (WMC 21.32.040(5)(b)) |
| Max Units | Two accessory dwelling units per parent lot (WMC 21.41.020(1)), matching RCW 36.70A.681(1)(c). "Parent lot" means the initial lot establishing the exterior boundary from which unit lots may be created by a unit lot subdivision (WMC 21.11A.170), so a unit lot split does not multiply your ADU 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 through R-48 — except that if you build two ADUs complying with WMC 21.41.020, the second one is excluded from that count (WMC 21.41.020(2)) |
Setback Requirements [1][2][3][4][5][6]
Woodinville requires a rear setback of about 10 ft for a detached ADU, and parking requirements vary by unit size or location. Owner-occupancy is not required — you can rent it out without living on the property.
| Rear Setback | Woodinville does not use a separate rear setback — Table 21.32.030(2) sets a single "minimum setback from interior property lines": 10 feet in R-1, and 5 feet in R-4, R-6, R-8, R-12, R-18, R-24 and R-48. Note 2 to the table cuts the R-1 figure to 5 feet on R-1 lots smaller than 15,000 sq ft. And WMC 21.41.020(3)(c) goes to zero: "A detached accessory dwelling unit may have the zoning setback reduced to zero from any property line abutting a dedicated public alley" |
| Side Setback | The same interior-property-line standard — 10 feet in R-1 (5 feet where the R-1 lot is under 15,000 sq ft), 5 feet in every other residential zone (WMC Table 21.32.030(2)). Roof eaves may protrude 18 inches into an interior setback and covered decks, patios and porches 18 inches (WMC 21.32.030(5)) |
| Front Setback | 10 feet from a street property line in every residential zone, but 20 feet for an attached or detached garage, measured along the driveway centreline from the vehicle door to the street property line (WMC Table 21.32.030(2)). If your ADU includes a garage bay, the 20-foot figure governs that part of the building |
| Parking Required | One stall per accessory dwelling unit (WMC Table 21.37.030, row "Accessory dwelling unit") — half what a three-bedroom house on a 6,000 sq ft lot must provide. Tandem parking is allowed for residential developments where assigned to individual dwelling units (WMC 21.37.060(6)). Woodinville's code contains no major-transit-stop parking exemption; if your site is within one-half mile walking distance of a major transit stop, RCW 36.70A.681(2)(a)(i) bars any off-street parking requirement at all — but that protection, like the rest of the statute, does not reach a lot designated with critical areas or their buffers. Confirm with Development Services at (425) 489-2700 |
| Owner Occupancy | Not required. WMC 21.41.020 imposes no owner-occupancy condition, and RCW 36.70A.681(1)(b) separately bars a city from requiring "the owner of a lot on which there is an accessory dwelling unit to reside in or occupy the accessory dwelling unit or another housing unit on the same lot." This is one of the places where Woodinville's local code matters most: on a critical-area lot the state bar switches off under RCW 36.70A.681(4), and Woodinville still does not impose owner-occupancy |
| Min Lot Size | No ADU-specific minimum. The district minimum lot area governs: 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, 2,400 in R-18 (WMC Table 21.31.030). RCW 36.70A.681(1)(e) requires a city to allow an ADU on any lot meeting the minimum lot size for the principal unit, and Woodinville adds none of its own |
Permit Process & Fees [7][8][9][10][11]
An ADU permit in Woodinville goes through a standard permit review. Confirm with Woodinville Development Services at (425) 489-2700 — no published ADU review timeline was found in a city source, and the city's website could not be reached from this research session. Budget additional weeks if a critical areas report or a SEPA determination is required. Permit fees: Confirm current amounts with Woodinville Development Services at (425) 489-2700. Development fees are set by City Council resolution rather than in the code (WMC 21.13.040), the city publishes a 2026 Development Services fee schedule, and the Director may require an advance deposit for outside consultant review — which is common where a critical areas report has to be peer-reviewed (WMC 21.13.050 and 21.13.060). A disputed fee estimate is appealable to the Hearing Examiner (WMC 21.13.070).
| Approval Process | A building permit, processed as a Type 1 administrative decision — no hearing — unless a SEPA threshold determination is required, in which case it becomes a Type 2 decision (WMC 21.82.010(3), 21.80.050). There is no conditional use permit and no design review hearing for an ADU. Two things will pull your project off the simple track: a critical area or buffer on the lot, which triggers a critical areas report under WMC 21.51.060, and building three units on one lot, which brings in the Low-Rise Residential Design Standards in Chapter 21.38 WMC by way of WMC 21.21.030(3). Street frontage improvements do not apply to an ADU unless they would have been required without it (WMC 21.41.020(4)(b); WMC 21.63.020) |
| Review Timeline | Confirm with Woodinville Development Services at (425) 489-2700 — no published ADU review timeline was found in a city source, and the city's website could not be reached from this research session. Budget additional weeks if a critical areas report or a SEPA determination is required |
| Permit Fees | Confirm current amounts with Woodinville Development Services at (425) 489-2700. Development fees are set by City Council resolution rather than in the code (WMC 21.13.040), the city publishes a 2026 Development Services fee schedule, and the Director may require an advance deposit for outside consultant review — which is common where a critical areas report has to be peer-reviewed (WMC 21.13.050 and 21.13.060). A disputed fee estimate is appealable to the Hearing Examiner (WMC 21.13.070) |
| Impact Fees | Better than most Washington cities. School impact fees: an accessory dwelling unit approved under WMC 21.41.020 is fully exempt (WMC 3.38.040(3), Ord. 800 § 2, 2025). Park impact fees: an ADU pays only 50 percent of the park impact fee calculated for the largest primary dwelling unit it is associated with (WMC 3.36.080(2), Ord. 811, 2026). The park fee itself runs $2,054 for a unit of 1,500 sq ft or less, $4,886 from 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 attached to a 2,000 sq ft house owes about $2,443. Transportation impact fees are assessed at $3,760 per p.m. peak-hour person trip (WMC 3.39.085, Ord. 772, 2024) with no ADU exemption in Chapter 3.39. RCW 36.70A.681(1)(a) caps ADU impact fees at 50 percent of the principal unit's — but that cap is one more thing RCW 36.70A.681(4) switches off on a critical-area lot, so cite Woodinville's own WMC 3.36.080(2) and 3.38.040(3) instead, which carry no such carve-out. Payment may be deferred to final inspection or certificate of occupancy against a recorded lien (WMC 3.36.060(3)) |
| Plan Check | Standard building plan review under Chapter 21.62 WMC. Prefabricated units are allowed provided they sit on a permanent foundation (WMC 21.41.020(4)(c)). Conversions of existing enclosed structures, detached garages included, are allowed even where the structure does not comply with current building coverage or setback standards, provided the structure and the nonconformance were legally established (WMC 21.41.020(4)(a)). If the lot has a wetland, stream, geologically hazardous area, frequently flooded area or critical aquifer recharge area, expect a critical areas report under WMC 21.51.060, mitigation sequencing under WMC 21.51.050, and a minimum 10-foot building setback from the edge of any riparian management zone or wetland buffer under WMC 21.51.050(3) |
| Pre-Approved Plans | No city pre-approved ADU plan library was found in a Woodinville source — unlike neighbouring Kirkland and Redmond. Confirm with Development Services at (425) 489-2700, and note that Washington State Department of Commerce maintains a statewide pre-approved plan effort you may be able to draw on |
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Construction Costs [12]
Building an ADU in Woodinville typically costs $250,000-$450,000 ($300-$500 per sq ft); a garage conversion runs $120,000-$250,000.
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| Average Build Cost | $250,000-$450,000 |
| Cost per Sq Ft | $300-$500 |
| Garage Conversion | $120,000-$250,000 |
| Prefab ADU (Installed) | $180,000-$350,000 |
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Rental Income Potential [13][14]
A 2-bedroom ADU in Woodinville rents for around $2,400-$3,100/mo, an estimated 5-8% annual return.
| Avg Rent (1 Bedroom) | $1,900-$2,400/mo |
| Avg Rent (2 Bedroom) | $2,400-$3,100/mo |
| Short-Term Rental | No. "Accessory dwelling units are prohibited from being rented for periods of fewer than 30 consecutive nights" (WMC 21.41.020(5), which points to the short-term rental definition in RCW 36.70A.696). Woodinville's ADU rules are built for long-term tenancy — which, given the school impact fee exemption and the halved park impact fee, is clearly the point |
| Est. Annual ROI | 5-8% annual return |
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Recent Law Changes
What's Changed Recently
- Woodinville Ordinance 792 (2025) repealed and replaced WMC 21.41.020 (accessory dwelling units), 21.31.030 (residential lot development standards), 21.31.040, 21.31.050, 21.20.030, 21.36.030 and 21.42.210, added Chapter 21.38 (Low-Rise Residential Design Standards) and amended some thirty further sections — the city's middle housing and ADU compliance package. It is the reason the ADU cap is 1,500 sq ft rather than the 1,000 sq ft floor the state requires
- Washington HB 1337 (2023 c 334), codified at RCW 36.70A.681, preempts local ADU regulation in Growth Management Act cities: two ADUs on every lot in a zoning district inside an urban growth area that allows single-family homes, no owner-occupancy requirement, no maximum floor area under 1,000 sq ft, no roof height limit under 24 feet, no setback or yard coverage rules more restrictive than for the principal house, mandatory conversion of existing structures including detached garages, siting at a lot line abutting a public alley, impact fees capped at half the principal unit's, no public street improvements as a condition, and no off-street parking within half a mile walking distance of a major transit stop
- THE CRITICAL-AREA CATCH: RCW 36.70A.681(4) provides that "the provisions of this section do 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 above apply. The good news, and it is genuinely unusual: WMC 21.41.020 contains no critical-area exception of its own, so Woodinville's local entitlements — two ADUs, 1,500 sq ft, no owner occupancy, alley lot-line siting, conversion rights — survive on those lots even though the state backstop does not
- Woodinville Ordinance 784 (2025) repealed and replaced Chapter 21.51 WMC, the critical areas regulations, in the city's periodic GMA update. Ordinance 811, passed August 4, 2026, repealed and replaced Chapter 3.36 WMC and reset the park impact fee schedule; Ordinance 800 (2025) amended the school impact fee chapter that exempts ADUs
- The Woodinville Municipal Code is current through Ordinance 811, passed August 4, 2026 (Code Publishing / General Code). Note that www.woodinville.gov itself was unreachable from this research session behind a Cloudflare country block (error 1009), so the code text here comes from the city's official codifier rather than the city's own website, and permit fee amounts could not be read
Tips for Building an ADU in Woodinville
- Order a critical areas screen before you draw anything. Woodinville's critical area maps, the National Wetlands Inventory, the Critical Aquifers Recharge Areas map and the Geologically Sensitive Areas map are all listed in WMC 21.51.030 — and a stream or wetland buffer plus the extra 10-foot building setback under 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, and parking, open-air floors and space under five-foot ceilings are all subtracted. 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
- Two ADUs on one lot turns the property into a three-unit development for interpretation purposes under WMC 21.21.030(3), which brings the Chapter 21.38 Low-Rise Residential Design Standards into play. Ask about that before committing to the second unit
- The impact fee position is genuinely good: school impact fees are waived outright for an ADU, park impact fees are halved, and both come from Woodinville's own code — not from the state cap that a critical area would switch off
- R-1 lots under 15,000 sq ft get a 5-foot interior setback instead of 10 under Note 2 to Table 21.32.030(2). Check your lot area first; it is worth five feet 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
ADU Builders in Woodinville
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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.
- Woodinville Municipal Code 21.41.020 — Accessory dwelling unit (Ord. 792 § 27, 2025) Municipal Code — Accessed 2026-09-01
- Woodinville Municipal Code Table 21.21.050 — Residential Use Table Municipal Code — Accessed 2026-09-01
- Woodinville Municipal Code Chapter 21.32 — Bulk and Setback Standards (Tables 21.32.030(2), 21.32.040(2), 21.32.050(1)) Municipal Code — Accessed 2026-09-01
- Woodinville Municipal Code 21.31.030 — Residential zoned lot development standards Municipal Code — Accessed 2026-09-01
- RCW 36.70A.681 — Accessory dwelling units, limitations on local regulation (2023 c 334 s 4, HB 1337), including the critical-areas carve-out at subsection (4) state_statute — Accessed 2026-09-01
- Woodinville Municipal Code Chapter 21.51 — Critical Areas Regulations (Ord. 784 § 14 (Att. A), 2025) Municipal Code — Accessed 2026-09-01
- Woodinville Municipal Code 21.82.010 — Building permit (Type 1 administrative decision) Municipal Code — Accessed 2026-09-01
- Woodinville Municipal Code Chapter 3.36 — Park Impact Fees (Ord. 811 § 1 (Att. A), 2026) Municipal Code — Accessed 2026-09-01
- Woodinville Municipal Code Chapter 3.38 — School Impact Fees (ADU exemption at 3.38.040(3); Ord. 800 § 2, 2025) Municipal Code — Accessed 2026-09-01
- Woodinville Municipal Code Chapter 3.39 — Transportation Impact Fees (3.39.085 rate; Ord. 772 § 7, 2024) Municipal Code — Accessed 2026-09-01
- City of Woodinville — 2026 Development Services Fee Schedule (not readable from this session; city site geo-blocked) Planning Department — Accessed 2026-09-01
- Angi — ADU Construction Cost Data Market Data — Accessed 2026-09-01
- Zillow Rental Manager — Market Rent Data Market Data — Accessed 2026-09-01
- U.S. Census Bureau QuickFacts — Woodinville city, Washington (population, median gross rent) Government Data — Accessed 2026-09-01
- Woodinville Municipal Code — Ordinance Table (current through Ord. 811, passed August 4, 2026) Municipal Code — Accessed 2026-09-01
Frequently Asked Questions
Can I build an ADU in Woodinville?
Yes. ADUs are allowed in Permitted (P) in the R-1, R-4, R-6, R-8, R-12 and R-18 residential zones (Woodinville Municipal Code Table 21.21.050, row "Dwelling Unit, Accessory"). Not listed — and therefore not allowed — in R-24, R-48 or in any commercial, industrial or other zone. Special development conditions are at WMC 21.41.020. Note the Woodinville quirk in WMC 21.21.030(3): all ADUs count in determining the type of residential land use, so a primary unit plus two attached ADUs is interpreted as a three-unit townhouse or stacked flat, which pulls in the Low-Rise Residential Design Standards in Chapter 21.38 WMC in Woodinville. The maximum size for a detached ADU is 1,500 sq ft of habitable floor area, with a minimum of 300 sq ft (WMC 21.41.020(3)(b)) — 500 sq ft above the 1,000 sq ft floor RCW 36.70A.681(1)(f) guarantees. "Habitable floor area means the gross floor area of a building reduced by subtracting floor areas for vehicle parking, covered and uncovered outdoor open-air floors, and floor areas having less than five-foot-high ceilings," so a garage bay and a low attic do not count against you. The real limit on most lots is building coverage under Table 21.32.050(1), which in R-1 steps down as the lot gets bigger — from 40% on lots under 5,000 sq ft to 15% on lots of 43,560 sq ft and over, with bands at 35%, 28%, 22% and 20% in between — while minimum landscaping coverage climbs to as much as 75% on the largest R-1 lots. Check your own band with Woodinville Development Services at (425) 489-2700 before sizing the building. 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 $250,000-$450,000. Garage conversions run $120,000-$250,000, and prefab ADUs cost $180,000-$350,000.
How much can I rent an ADU for in Woodinville?
Average ADU rents in Woodinville are $1,900-$2,400/mo for a 1-bedroom and $2,400-$3,100/mo for a 2-bedroom unit.
Do I need parking for an ADU in Woodinville?
One stall per accessory dwelling unit (WMC Table 21.37.030, row "Accessory dwelling unit") — half what a three-bedroom house on a 6,000 sq ft lot must provide. Tandem parking is allowed for residential developments where assigned to individual dwelling units (WMC 21.37.060(6)). Woodinville's code contains no major-transit-stop parking exemption; if your site is within one-half mile walking distance of a major transit stop, RCW 36.70A.681(2)(a)(i) bars any off-street parking requirement at all — but that protection, like the rest of the statute, does not reach a lot designated with critical areas or their buffers. Confirm with Development Services at (425) 489-2700. 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?
Woodinville does not publish a standard ADU review timeline — confirm with Woodinville Development Services at (425) 489-2700 — no published ADU review timeline was found in a city source, and the city's website could not be reached from this research session. Budget additional weeks if a critical areas report or a SEPA determination is required. Permit fees: Confirm current amounts with Woodinville Development Services at (425) 489-2700. Development fees are set by City Council resolution rather than in the code (WMC 21.13.040), the city publishes a 2026 Development Services fee schedule, and the Director may require an advance deposit for outside consultant review — which is common where a critical areas report has to be peer-reviewed (WMC 21.13.050 and 21.13.060). A disputed fee estimate is appealable to the Hearing Examiner (WMC 21.13.070).
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