ADU Ledger
ADU Ledger / Washington
State hub · 16 cities

Washington ADU rules, city by city

HB 1337 (2023): HB 1337 required every Washington city over 25,000 people to allow two ADUs per residential lot, drop owner-occupancy requirements, cap size limits no lower than 1,000 sq ft, cap height limits no lower than 24 ft, and stop requiring parking near major transit — with compliance due June 30, 2025 for larger cities.

The statute set a floor, not the rules. Each city adopted its own ordinance — some more generous, some barely compliant, several already amended again. Compare cities directly below, or browse rule by rule. Every value cites the municipal code section it comes from; city pages carry the detail, quirks, and pending amendments.

Statewide questions

How many ADUs can I build in Washington? · What is HB 1337? · Do I need parking for an ADU in Washington? · Can cities require me to live on the property? · How big can an ADU be in Washington? · Can I sell an ADU separately in Washington? · Which WA cities have pre-approved ADU plans? · When did WA ADU rules change? · How tall can an ADU be in Washington? · How close to my property line can an ADU be built? · Will I have to pay impact fees on an ADU in Washington? · How long does it take to get an ADU permit in Washington?

Compare cities

RuleBellevueBothellBurien
ADUs allowed per lotTwo ADUs per lot in any district that allows a single-family dwelling — attached, detached, or a mix. No new ADU on a unit lot created by unit-lot subdivision.LUC 20.20.120.C.1, .C.7Two ADUs per lot, in any mix. Exceptions: one ADU on lots developed with middle housing, and one on lots constrained by critical areas or their buffers.BMC 12.14.135(A)–(C)Two ADUs per lot, with no restriction on the attached/detached mix — allowed accessory to a single detached home in any zone, or to middle housing in a Residential zone.BMC 19.17.070(2)(A)–(B)
Maximum size1,200 sq ft maximum per ADU. Up to 300 sq ft of parking or unheated storage per ADU is excluded. The Director may approve more for a single-floor attached ADU, an addition to an existing detached accessory structure, or a conversion; guest-cottage conversions are exempt from the cap.LUC 20.20.120.C.31,200 sq ft. Conversions of existing space may exceed that with director approval, capped at 40% of the primary dwelling's gross floor area.BMC 12.14.135(D)(1)–(2)1,000 sq ft for internal, attached, AND detached ADUs. The director may grant size exceptions to better use existing spaces in buildings at least five years old. (The 800 sq ft detached cap in the city's old handout is the pre-2025 rule.)BMC 19.17.070(2)(C)
Detached ADU height24 ft to the highest point for a detached ADU; 28 ft when built as an addition over an existing accessory structure. (Principal units get 32–35 ft.)LUC 20.20.120.E.1; Table 20.20.538.C.1 fn 930 ft for a detached ADU — 33 ft when built over an existing accessory structure. (Other accessory buildings are capped at 20 ft.)BMC 12.14.135(E); 12.14.130No ADU-specific height limit. Residential accessory structures are capped at 10 ft above the primary residence's existing height or the zone's maximum height (35 ft in residential zones), whichever is less — and the code doesn't expressly say whether that formula binds DADUs. On a low single-story house it could compute below the state's 24-ft floor, an unresolved conflict we're tracking.BMC 19.17.060(2)(B); RCW 36.70A.681
Detached ADU setbacksSame dimensional standards as middle housing: side 5 ft; rear 15 ft (LL-1 through SR-2 districts) or 10 ft (SR-3 through MDR-2); front 10–25 ft by district. A DADU may be sited at a lot line that abuts an alley. Conversions of existing structures are allowed despite nonconforming setbacks.LUC 20.20.120.E.2, .C.4; Table 20.20.538.C.1Side: 5 ft in all residential zones. Rear: a DADU matches the primary structure's rear setback (R-C 35 ft; R-L1/R-L2 15 ft; R-M1/R-M2 10 ft), except on alleys, where alley-structure standards apply (down to 0 ft at the alley line; vehicle access needs 25 ft clear to the alley's far edge).BMC 12.14.070(B); 12.14.030(A); 12.14.060New DADUs meet zone standards (front 20 ft, interior 5 ft in RS-7,200) — except a detached ADU may sit at the rear lot line where it abuts an unplowed public alley. Conversions of existing structures are exempt from setbacks and lot coverage.BMC 19.17.070(2)(D)(i)–(ii)
Off-street parkingNone for ADUs under 1,000 sq ft; none within a half mile of a major transit stop; otherwise one space per ADU in addition to the primary structure's spaces.LUC 20.20.120.C.5, .B.1None. Bothell repealed minimum off-street parking citywide in 2025 — 'there is no required minimum number of off-street parking spaces.'BMC 12.16.030 (Ord 2461 §2, 2025)None. 'No parking is required for ADUs' — unconditional, citywide, beyond what HB 1337 required.BMC 19.20.045(1)(C) (enacted at (1)(D) by Ord 868, re-lettered by Ord 881, 2025)
Owner-occupancyNone. Removed by Ordinance 6746 in July 2023 — owners are not required to live on site, and the separate ADU registration was abolished at the same time.Ord 6746 §1None. The pre-2024 code required owner or family occupancy more than six months a year plus a recorded covenant — all struck by Ordinance 2415.BMC 12.14.135 (current); Ord 2415None — Burien removed owner-occupancy back in 2019 (Ord 724), and the current code carries no trace of it.BMC 19.17.070 (verified absence)
Lot coverage / floor areaLot coverage 40–45% by district (the middle-housing table applies to DADUs). FAR treatment is asymmetric: attached ADUs are fully exempt from FAR and unit counts, while detached ADUs count toward both — making attached units 'cheaper' in zoning currency.LUC 20.20.390.A–.B; Table 20.20.538.C.1 fns 5, 10No FAR. Hard-surface coverage is capped by zone (35% in R-C up to 75% in R-M2). DADUs that meet the ADU size limit are exempt from the 5%-of-lot-area cap that binds other accessory buildings.BMC 12.14.030(A), (B)(8); 12.14.135(D)(2)70% impervious-surface coverage in RS-7,200; accessory structures are limited to the lesser of 15% of lot area or 80% of the primary structure's footprint (minor deviations allowed). ADU conversions are exempt from lot coverage.BMC 19.15.005; 19.17.060(2)
Permit path & timelinePermitted use — no conditional use permit and no ADU registration. Built under a standard building permit. The city publishes no ADU-specific review timeline; secondary sources suggest roughly 4–6 months for custom single-family-track review (estimate only).LUC 20.20.120.C.2, .C.4Single-family building permit with the city's ADU submittal checklist — no separate land-use permit. No published review timeline. An amnesty path lets unpermitted existing ADUs be legalized through application and inspection.BMC 12.14.135(F); city handout 3f (rev. Dec 2025)Building permit under Title 15 — an attached ADU is reviewed as a duplex for building-code purposes. Sewer and water availability certificates plus Fire Marshal flow review are submitted with the application. No published timeline (secondary sources suggest 3–4 months).City ADU handout (building-code items); BMC Title 15

Every city, rule by rule

The full corpus, one rule at a time — how all 16 cities answer each question.

ADUs allowed per lot
  • BellevueTwo ADUs per lot in any district that allows a single-family dwelling — attached, detached, or a mix. No new ADU on a unit lot created by unit-lot subdivision.LUC 20.20.120.C.1, .C.7
  • BothellTwo ADUs per lot, in any mix. Exceptions: one ADU on lots developed with middle housing, and one on lots constrained by critical areas or their buffers.BMC 12.14.135(A)–(C)
  • BurienTwo ADUs per lot, with no restriction on the attached/detached mix — allowed accessory to a single detached home in any zone, or to middle housing in a Residential zone.BMC 19.17.070(2)(A)–(B)
  • EdmondsTwo ADUs per detached single-family principal dwelling — one attached plus one detached, two attached, or two detached. Not available on townhouse, duplex, plex, or cottage-housing lots.ECDC 16.20.060(B)
  • EverettTwo ADUs per lot in all zones except industrial — attached, detached, or a combination, with no minimum lot size.EMC 19.08.100 Table 8-6
  • IssaquahTwo ADUs in any combination of attached or detached, with a single-family residence or with middle housing (the lot must meet density and minimum lot size for the principal unit; nonconforming lots also qualify for up to two).LUC 18.500.090(F)(1), (C)
  • KentTwo ADUs per lot, in any mix — one attached plus one detached, two attached, or two detached. An ADU connected to the house only by a breezeway or shared roof (or attached to a garage) counts as detached.KCC 15.08.350(B)(1)–(2)
  • KirklandTwo ADUs per single-family dwelling — one attached plus one detached, or two of either type. ADUs don't count as 'dwelling units' for one-unit-per-lot limits.KZC 115.07 (introductory)
  • LynnwoodNo ADU-specific cap — the units-per-lot rules govern: RN zones allow 3 units per lot base (a house plus two ADUs), 4 with one affordable unit or within a quarter-mile walk of a major transit stop. ADUs are a permitted use in the RN, RM-45, NC, and CDM zones.LMC 8.30 Table 8.30.03; Table 8.35.01
  • OlympiaTwo ADUs per residential lot in all residential districts — added to, created within, or detached from the principal unit; an ADU may even attach to a garage, shop, or another ADU.OMC 18.04.060(A)(1)–(4)
  • RedmondTwo ADUs or tiny homes per residential lot — attached (within or added to the primary home) or detached, in any mix.RZC 21.04.1110.C.1, C.2.a
  • RentonTwo ADUs per legal lot as accessory to a principal dwelling — one attached plus one detached, two attached, or two detached. In the lower-density zones, the second ADU must meet the principal dwelling's location and setback standards.RMC 4-2-110C
  • SammamishTwo ADUs per lot with a single-family home — two attached, two detached (in one or two structures), one of each, or conversions of existing structures like a detached garage.SMC 21.05.010.C(5)(a)(i)–(ii)
  • SeattleTwo ADUs per lot, in addition to the principal unit(s) — attached, detached, or stacked, in any combination. Two detached ADUs may even stack in one structure.SMC 23.42.022.C–.D
  • ShorelineTwo ADUs per lot, attached and/or detached — subject to the zone's units-per-lot density (NR3: 3 dwellings per lot, 4 within a half mile of a major transit stop; NR2: 4; NR1: no unit cap).SMC 20.40.210(A)–(B); Table 20.50.020(1)
  • TacomaTwo ADUs per residential lot, on any legally established lot regardless of size or width, in any zone permitting residential use — attached, detached, or a mix. All dwellings must be in single ownership.TMC 13.06.080.A.4.a, A.5.a
Maximum size
  • Bellevue1,200 sq ft maximum per ADU. Up to 300 sq ft of parking or unheated storage per ADU is excluded. The Director may approve more for a single-floor attached ADU, an addition to an existing detached accessory structure, or a conversion; guest-cottage conversions are exempt from the cap.LUC 20.20.120.C.3
  • Bothell1,200 sq ft. Conversions of existing space may exceed that with director approval, capped at 40% of the primary dwelling's gross floor area.BMC 12.14.135(D)(1)–(2)
  • Burien1,000 sq ft for internal, attached, AND detached ADUs. The director may grant size exceptions to better use existing spaces in buildings at least five years old. (The 800 sq ft detached cap in the city's old handout is the pre-2025 rule.)BMC 19.17.070(2)(C)
  • EdmondsGross floor area of 1,200 sq ft in the LDR-L and LDR-M zones, 1,000 sq ft in LDR-S. GFA counts interior habitable area including basements and attics but excludes unconditioned space such as a garage.ECDC 16.20.060(C); 21.35.013
  • Everett1,000 sq ft of gross floor area, excluding garage and accessory-structure space. No size cap for an ADU located within one floor of the principal dwelling.EMC 19.08.100 Table 8-6 row 3; EMC 19.04.030
  • Issaquah1,000 sq ft each, excluding nonliving areas like garages, storage sheds, and decks (unless the ADU is located in them). Internal conversions and existing-structure conversions may exceed 1,000 sq ft if no exterior expansion is needed. One catch: the principal home must have gross floor area at least 25% larger than the largest ADU.LUC 18.500.090(F)(2)(a)–(c)
  • Kent1,000 sq ft per ADU (no transferring square footage between the two). Excluded from the count: areas under 7-ft ceilings, up to 200 sq ft of covered decks and porches, and the host structure's floor area when the DADU is built within, above, or as an addition to an existing garage or accessory building.KCC 15.08.350(B)(6)
  • Kirkland1,200 sq ft of gross floor area per ADU. Excluded: floor area under 5-ft ceilings, uncovered rooftop decks and at-grade patios, and up to 200 sq ft of exterior elements. The Planning Director may allow a larger attached ADU occupying an entire existing floor.KZC 115.07(4)(a)–(c)
  • Lynnwood1,000 sq ft — written into the ADU definition itself (a cap added by Ord 3492 in November 2025; the original UDC had none). No garage or storage exclusion is stated.LMC 8.99.0250 (Ord 3492 §18)
  • Olympia1,000 sq ft of gross floor area each. Covered porches up to 120 sq ft per ADU don't count, and an ADU may combine with an accessory structure of up to 800 sq ft. The director may allow an entire single floor of an existing home.OMC 18.04.060(A)(3)–(7)
  • Redmond1,000 sq ft total (the state-law floor, exactly). The Administrator may allow more if the ADU occupies an entire single floor of the primary unit, or on lots over 10,000 sq ft where the ADU is affordable or provides a public benefit. Tiny homes max 400 sq ft.RZC 21.04.1110.C.3.a–d
  • Renton1,000 sq ft of gross floor area and 1,000 sq ft of building area (GFA excludes garages, porches, exterior stairs; building area includes attached garages). Converting an entire single floor of the house may reach 1,250 sq ft.RMC 4-2-110C; 4-2-110I fns 40–41, 25
  • Sammamish1,000 sq ft; an ADU entirely within the existing residence may be the larger of 50% of the home's floor area or 1,000 sq ft.SMC 21.05.010.C(5)(a)(iii)
  • Seattle1,000 sq ft of gross floor area for an ADU with up to 2 bedrooms; 1,200 sq ft with 3+ bedrooms; up to 1,500 sq ft in Lowrise zones in frequent-transit areas (with an anti-speculation condition). Up to 250 sq ft of attached garage, underground stories, and up to 35 sq ft of bike parking don't count.SMC 23.42.022.G.1–.2
  • Shoreline1,200 sq ft. An ADU inside the residence may exceed the limit if it occupies a separate floor sharing a common roof with the primary home. No garage/storage exclusion is stated in code.SMC 20.40.210(C)
  • Tacoma1,000 sq ft of habitable living area, excluding garage and other non-living areas. An ADU occupying a single floor of an existing building may exceed this to use the whole floor efficiently.TMC 13.06.080.A.5.b
Detached ADU height
  • Bellevue24 ft to the highest point for a detached ADU; 28 ft when built as an addition over an existing accessory structure. (Principal units get 32–35 ft.)LUC 20.20.120.E.1; Table 20.20.538.C.1 fn 9
  • Bothell30 ft for a detached ADU — 33 ft when built over an existing accessory structure. (Other accessory buildings are capped at 20 ft.)BMC 12.14.135(E); 12.14.130
  • BurienNo ADU-specific height limit. Residential accessory structures are capped at 10 ft above the primary residence's existing height or the zone's maximum height (35 ft in residential zones), whichever is less — and the code doesn't expressly say whether that formula binds DADUs. On a low single-story house it could compute below the state's 24-ft floor, an unresolved conflict we're tracking.BMC 19.17.060(2)(B); RCW 36.70A.681
  • Edmonds24 ft for detached ADUs; attached ADUs follow the 25-ft primary-dwelling limit.ECDC 16.20.060(C)
  • EverettContested in the current code. The 2023 ADU ordinance allowed 24 ft (28 ft on alley lots), but the 2025 rewrite's Table 22-2 caps detached accessory buildings in NR zones at 18 ft on non-alley lots (24 ft on alley lots with a steep roof), with the 24/28 allowance surviving only in the UR4/UR7 zones. This sits in tension with the state-law height minimums — confirm your specific lot with Everett planning before designing.EMC 19.22.020, Tables 22-1/22-2; RCW 36.70A.681
  • IssaquahNo separate DADU cap — ADUs comply with the principal unit's height per Ch. 18.404 (roughly 30 ft in most single-family zones).LUC 18.500.090(F)(3)
  • Kent24 ft; chimneys, antennas, and railings may extend 4 ft above that.KCC 15.08.350(B)(4)
  • KirklandThe zone's single-family height applies: 25 ft above average building elevation in RS/PLA 3C/PLA 6E, 30 ft in RSX/RSA/PLA 16. A DADU sited within the reduced 5-ft rear yard is capped at 15 ft.KZC 115.07(5); 15.30.060; 115.115(3)(o)(3)
  • LynnwoodNo ADU-specific limit — a proposed 24-ft ADU cap was dropped at adoption. Detached units fall under the RN detached-configuration maximum of 35 ft.LMC 8.30 building-form tables
  • Olympia24 ft for detached ADUs — an exception carved out of every district's height row, including districts that otherwise allow 35–60 ft.OMC 18.04.080 Table 4.05
  • RedmondStructures containing ADUs may go to the underlying zone maximum — 38 ft base in Neighborhood Residential — rather than the 22-ft cap that applies to other accessory structures.RZC 21.04.1120.C.1; Table 21.08.200.B
  • Renton24 ft to the highest ridge, with shed-roof averaging allowed. PRADU pre-approved plans are exempt from the height cap.RMC 4-2-110C; fns 23, 42
  • Sammamish24 ft for detached ADUs in every residential zone (the primary residence gets 35 ft in R-1 through R-8, 60 ft in R-12/R-18).SMC 21.04.030.C height table
  • SeattleDetached ADUs follow the same height standards as the main house: 32 ft in Neighborhood Residential zones, plus 5 ft for a pitched roof ridge (4:12 or steeper).SMC 23.42.022.E; 23.44.070
  • ShorelineNo ADU-specific limit — base zone heights apply: 23 ft in NR3 (28 ft with a pitched roof), 30 ft in NR2 (35 pitched), 35 ft in NR1 (40 pitched).Table 20.50.020(1)
  • TacomaNo ADU-specific cap — zone and housing-type limits apply: 35 ft in UR zones, but 25 ft within the rear 25 ft of UR-1 lots (where most DADUs sit). The old 18-ft DADU cap was repealed.TMC 13.06.080.A.5.c; 13.06.020.F.1
Detached ADU setbacks
  • BellevueSame dimensional standards as middle housing: side 5 ft; rear 15 ft (LL-1 through SR-2 districts) or 10 ft (SR-3 through MDR-2); front 10–25 ft by district. A DADU may be sited at a lot line that abuts an alley. Conversions of existing structures are allowed despite nonconforming setbacks.LUC 20.20.120.E.2, .C.4; Table 20.20.538.C.1
  • BothellSide: 5 ft in all residential zones. Rear: a DADU matches the primary structure's rear setback (R-C 35 ft; R-L1/R-L2 15 ft; R-M1/R-M2 10 ft), except on alleys, where alley-structure standards apply (down to 0 ft at the alley line; vehicle access needs 25 ft clear to the alley's far edge).BMC 12.14.070(B); 12.14.030(A); 12.14.060
  • BurienNew DADUs meet zone standards (front 20 ft, interior 5 ft in RS-7,200) — except a detached ADU may sit at the rear lot line where it abuts an unplowed public alley. Conversions of existing structures are exempt from setbacks and lot coverage.BMC 19.17.070(2)(D)(i)–(ii)
  • EdmondsStreet/side setbacks per zone (LDR-L 25/10 ft; LDR-M 25/7.5; LDR-S 20/5). DADU rear setbacks: 25 ft in LDR-L; 15 ft in LDR-M (reducible to 10 if the DADU is 15 ft or shorter); 10 ft in LDR-S (reducible to 7.5). Zero rear setback where the rear lot line abuts a public alley.ECDC 16.20.060(C) + footnotes
  • EverettDetached ADUs use the principal-building setbacks: front 10 ft; interior side 5 ft (none where the side lot line abuts an alley); rear 5 ft (none on alley lots).EMC 19.06.020(F) Table 6-4; Table 6-2
  • IssaquahStandard zone setbacks — with one exception: new ADUs face no rear-yard setback where the rear yard abuts an alley (unless the city routinely plows snow on it).LUC 18.500.090(F)(4)(a)(1)
  • KentZone setbacks apply generally — but a DADU in the rear half of the lot may come within 2 ft of the side and rear lot lines, and may sit on the lot line where it abuts a public alley (unless the alley is routinely plowed). The planning director may modify setbacks where lot shape makes an ADU infeasible.KCC 15.08.350(B)(3)(a)–(d)
  • KirklandZone single-family setbacks apply (RS: front 20 ft, sides 5 ft each, rear 10 ft). A DADU without alley access may come within 5 ft of the rear line (with the 15-ft height cap), and may extend to the rear lot line where it abuts an alley. Conversions of existing structures are exempt from setbacks and coverage if the nonconformity isn't increased.KZC 115.07(5)–(6); 115.115(3)(o)(3)–(4)
  • LynnwoodRN detached configuration: 10 ft from the street, 5 ft interior side and rear, 10 ft between buildings. No reduced alley setback — but where an alley exists, vehicle access must come from it.LMC 8.30 Tables 8.30.04–05
  • OlympiaSide: the zone's required side yard (typically 5 ft). Rear: 5 ft, reduced to zero where the lot abuts an alley. Any garage attached to the ADU must also conform.OMC 18.04.080(H)(5)(a)–(b)
  • RedmondZone setbacks apply (NR: front 10 ft, street side 10 ft, interior side 3 ft, rear 5 ft, alley 2 ft) — and a detached ADU may sit immediately on a lot line that abuts a public alley or right-of-way. No accessory structures in the front setback.Table 21.08.300.A; RZC 21.04.1120.C.4–5
  • RentonRear: 5 ft (zero at an alley; a DADU within 10 ft of the rear line must keep 25% of the rear yard's length clear). Side: 25 ft in RC/R-1, 5 ft in R-4 through R-8, 4 ft in R-10/R-14. A detached unit within 4 ft of another residential structure counts as attached.RMC 4-2-110C
  • SammamishSide 5 ft and rear 5 ft in every residential zone — but only for stand-alone DADUs; a DADU combined with another structure (garage, pool house) takes standard structure setbacks. Accessory-structure front setbacks run 10–20 ft by zone (30 ft on arterials).SMC 21.04.030.C + conditions (4), (7)
  • SeattleSide: 5 ft average, 3 ft minimum (a flat 3 ft on lots under 5,000 sq ft in frequent-transit areas). Rear: 5 ft, or zero where the rear lot line abuts an alley. Structures containing floor area need 5 ft between them.Table A for SMC 23.44.090 fn 3; 23.44.100.A
  • ShorelineSide 5 ft; rear 10 ft (NR3/NR2) or 5 ft (NR1); front 10 ft. A DADU's side or rear setback drops to zero where it abuts an alley.Table 20.50.020(1) + Exception (25)
  • TacomaSide: 5 ft (8 ft where a main entrance faces the side lot line). Rear: 15 ft in UR-1, 10 ft in UR-2/UR-3 — and none from alleys (rear may be measured from the alley centerline). Attached ADUs use the primary structure's setbacks.TMC 13.06.020.F.1; 13.06.100.F
Off-street parking
  • BellevueNone for ADUs under 1,000 sq ft; none within a half mile of a major transit stop; otherwise one space per ADU in addition to the primary structure's spaces.LUC 20.20.120.C.5, .B.1
  • BothellNone. Bothell repealed minimum off-street parking citywide in 2025 — 'there is no required minimum number of off-street parking spaces.'BMC 12.16.030 (Ord 2461 §2, 2025)
  • BurienNone. 'No parking is required for ADUs' — unconditional, citywide, beyond what HB 1337 required.BMC 19.20.045(1)(C) (enacted at (1)(D) by Ord 868, re-lettered by Ord 881, 2025)
  • EdmondsFirst ADU: no parking. Second ADU: one off-street space (tandem allowed) — waived within a half mile of a major transit stop. A Level-II EV circuit is required for the second ADU's space.ECDC 16.20.060(C); 17.50.020
  • EverettEffectively none: every dwelling unit under 1,200 sq ft is exempt from off-street vehicle parking, which covers every conforming ADU, citywide, with no transit test. Bicycle parking is required.EMC 19.34.050(C); 19.34.160
  • IssaquahZero minimum — and a maximum of one space per ADU. Tandem parking satisfies any space you choose to provide.Table 18.604.080(A) (Ord 3093); LUC 18.500.090(F)(5)
  • KentZero within a half-mile walking distance of a major transit stop; one space per ADU beyond that, with director waivers available for special circumstances.KCC 15.05.040(A) parking chart (rev. 1/26)
  • KirklandNone within a half mile of a major transit stop. Beyond that, one space is required only when there's more than one ADU — and even that is waived if on-street parking exists within 600 ft or frequent transit is within a half mile. The first ADU never requires parking.KZC 115.07(7)(a)–(b)
  • LynnwoodZero. Dwelling units under 1,200 sq ft of gross floor area require no parking — which covers every conforming ADU, citywide, with no transit test.LMC 8.40.0720(A); Table 8.40.70
  • OlympiaZero. No off-street parking is required for ADUs anywhere in Olympia — and that has been true since 2019 (Ord 7187), not just since the 2025 package. Optional parking is allowed if the owner wants it.OMC 18.38.100 (most recently amended by Ord 7444)
  • RedmondZero. The parking table sets ADU minimums at 0 in all three location categories — near transit, in centers, and everywhere else. No transit-proximity condition needed.RZC 21.40.010 Table D
  • RentonOne space per ADU — but zero within a half-mile walking distance of a major transit stop, and lots partially inside that walkshed count as entirely inside.RMC 4-2-110C; fn 20
  • SammamishNo additional space required when the parcel already has four or more; and no minimum parking at all for homes, ADUs, and middle housing within a quarter mile of an existing or planned transit stop — counting planned stops is unusually generous.SMC 21.05.010.C(5)(a)(iv); 21.06.030
  • SeattleNone. No off-street parking is required for an ADU anywhere in Seattle — no transit-proximity condition.SMC 23.42.022.I
  • ShorelineZero. Shoreline repealed minimum vehicle parking citywide in August 2025 — not just for ADUs, for everything.Ord 1043 §1; SMC 20.50.390 (repealed)
  • TacomaNone. No off-street parking is required for ADUs anywhere in Tacoma — a local rule since 2019, not a transit-conditioned waiver. You may not remove the primary dwelling's required parking unless it's replaced.TMC 13.06.080.A.4.d
Owner-occupancy
  • BellevueNone. Removed by Ordinance 6746 in July 2023 — owners are not required to live on site, and the separate ADU registration was abolished at the same time.Ord 6746 §1
  • BothellNone. The pre-2024 code required owner or family occupancy more than six months a year plus a recorded covenant — all struck by Ordinance 2415.BMC 12.14.135 (current); Ord 2415
  • BurienNone — Burien removed owner-occupancy back in 2019 (Ord 724), and the current code carries no trace of it.BMC 19.17.070 (verified absence)
  • EdmondsNone. Ordinance 4360 repealed the old owner-occupancy chapter entirely, barred enforcement of previously recorded ADU covenants, and authorized staff to release them.Ord 4360 §§8, 10
  • EverettNone. The Everett 2044 rewrite deleted the owner-occupancy requirement effective July 8, 2025. (It existed as recently as the 2023 ordinance, so pre-2025 sources will say otherwise.)EMC 19.08.100 (current); Ord 3963-23 §5 (former rule)
  • IssaquahNone — Ordinance 3092 struck the owner-occupancy criterion and covenant. ADUs can be sold and owned separately, and the code bars prohibiting condominium conveyance.Ord 3092 Exh. C; LUC 18.500.090(F)(8)
  • KentNone — the code affirmatively states an owner-occupancy covenant 'is not required,' and old recorded covenants can be released by the planning director (applicant pays the recording cost).KCC 15.08.350(B)(9)
  • KirklandNone. The code affirmatively allows the ADU to be segregated in ownership from the house, and ADUs (except stacked ones) may be subdivided via unit-lot subdivision.KZC 115.07(2)–(3)
  • LynnwoodNone — no owner-occupancy requirement exists anywhere in the adopted UDC. (Pre-UDC city guides described one; they're obsolete.)LMC Title 8 (verified absence)
  • OlympiaNone — and ADUs may be sold separately from the main house via condominium or unit-lot subdivision.OMC 18.04.060(A)(8)
  • RedmondNone. No owner-occupancy provision exists anywhere in the current chapter.RZC 21.04.1110 (absence verified)
  • RentonNone. The city confirms both units may be rentals — no on-site owner required.RMC 4-2-110C (absence); city HB 1337 page
  • SammamishNone — no owner-occupancy condition appears anywhere in the adopted ADU regulations.SMC 21.05.010.C(5)(a) (verified absence)
  • SeattleNone. Seattle removed owner-occupancy in 2019, six years before the state required it.Ord 125854 (2019)
  • ShorelineNone. Ordinance 1027 struck the owner-occupancy requirement, the deed covenant, and the ban on selling the ADU separately.Ord 1027 §1 (Exh. A)
  • TacomaNone — removed by Tacoma's 2019 ADU ordinance. One exception: using an ADU (or the main house) as a short-term rental requires the owner to occupy one of the dwellings.TMC 13.06.080.A.4.g; Ord 28576 (2019)
Lot coverage / floor area
  • BellevueLot coverage 40–45% by district (the middle-housing table applies to DADUs). FAR treatment is asymmetric: attached ADUs are fully exempt from FAR and unit counts, while detached ADUs count toward both — making attached units 'cheaper' in zoning currency.LUC 20.20.390.A–.B; Table 20.20.538.C.1 fns 5, 10
  • BothellNo FAR. Hard-surface coverage is capped by zone (35% in R-C up to 75% in R-M2). DADUs that meet the ADU size limit are exempt from the 5%-of-lot-area cap that binds other accessory buildings.BMC 12.14.030(A), (B)(8); 12.14.135(D)(2)
  • Burien70% impervious-surface coverage in RS-7,200; accessory structures are limited to the lesser of 15% of lot area or 80% of the primary structure's footprint (minor deviations allowed). ADU conversions are exempt from lot coverage.BMC 19.15.005; 19.17.060(2)
  • Edmonds35% structural lot coverage on all lots — the council cut it from the proposed 45%. No FAR.ECDC 16.20.030 (Ord 4397)
  • Everett50% maximum lot coverage in NR (35% NR-C), plus 5% for two-unit lots, plus an additional ADU-specific bonus: up to 5% more of the lot's ground area may be used for up to two ADUs. No FAR limit in NR.EMC 19.06.010 Table 6-1; Table 8-6 row 4
  • IssaquahADUs don't count toward lot density when associated with a detached single-family home (they do count with middle housing). Standard zone impervious-surface and coverage limits apply.LUC 18.500.090(D)(2)
  • KentUnderlying zone standards apply (maximum site coverage runs 30–55% by residential zone under the April 2026 charts). Note: ADUs count as dwelling units in Kent's density calculations.KCC 15.08.350(B)(8); 15.04.170 (Ord 4536)
  • KirklandZone lot coverage applies (50% in RS/RSA). FAR applies per zone, but the first 500 sq ft (lots under 8,500 sq ft) or 800 sq ft (8,500+ sq ft) of a DADU located behind the main structure is excluded from FAR — a real design lever.KZC 115.42(1)(c)–(d); 15.30.060
  • LynnwoodRN zones use FAR by unit count — 0.6 for one unit, 0.8 for two, 1.0 for three, 1.2 for four — plus building-footprint standards instead of lot coverage, and required amenity space (shared 10% of the lot or 120 sq ft private per unit at grade).LMC 8.30 building-form tables
  • OlympiaADUs meet the same lot-coverage and tree-density standards as a single-family residence in the zone. They're exempt from maximum density except in zones capped at 12 units/acre or less. Structures built before December 22, 2025 (or 10+ years old) may convert even if nonconforming.OMC 18.04.060(A)(5)–(6); 18.04.080(E)(3)
  • RedmondThe DADU and the primary unit must each meet zone lot coverage (NR 50%; 60% for lots ≤18,000 sq ft with 3+ units). NR also caps total gross floor area of all structures by unit count — 4,500 sq ft for one unit, 6,000 for two, 7,500 for three — which effectively binds the combined house-plus-ADU size.Table 21.08.200.B–.C; RZC 21.04.1120.C.2.a
  • RentonZone lot-coverage caps apply; detached accessory structures may exceed coverage by 5%. ADUs are excluded from density calculations. Structures existing before June 30, 2025 that convert to ADUs are exempt from coverage, setback, and size rules.RMC 4-2-110A; 4-2-110I fns 15, 17, 25
  • SammamishADUs are exempt from FAR and hardscape-coverage calculations on single-family lots — a significant design lever. The 3,000 sq ft per-building footprint cap still applies, and the two ADUs together count as one dwelling unit for density.SMC 21.04.030.C ('Exempt' row) + condition (10); 21.05.010.C(5)(a)(v)
  • SeattleLot coverage is capped at 50% in NR zones (60% for stacked-unit and certain courtyard developments). Important 2026 change: ADU floor area now counts toward the floor-area ratio (FAR), and ADUs count toward density — the interim ADU FAR exemption was struck effective January 21, 2026.SMC 23.44.080; 23.42.022.J; 23.44.050 Table A
  • ShorelineNo building-coverage cap in the NR zones; hardscape is capped at 50% for one unit, rising with unit count (NR3 50% / NR2 60% / NR1 75% for 2+ units). No FAR.Table 20.50.020(1) + Exception (6)
  • TacomaUR zones use floor-area ratio rather than lot coverage: UR-1 max 0.6 (1–2 units) / 0.8 (3+); UR-2 0.8/1.0; UR-3 1.0/1.2, higher with affordability bonuses. At least 10% of the lot must remain usable yard space.TMC 13.06.020.F.1, F.7
Permit path & timeline
  • BellevuePermitted use — no conditional use permit and no ADU registration. Built under a standard building permit. The city publishes no ADU-specific review timeline; secondary sources suggest roughly 4–6 months for custom single-family-track review (estimate only).LUC 20.20.120.C.2, .C.4
  • BothellSingle-family building permit with the city's ADU submittal checklist — no separate land-use permit. No published review timeline. An amnesty path lets unpermitted existing ADUs be legalized through application and inspection.BMC 12.14.135(F); city handout 3f (rev. Dec 2025)
  • BurienBuilding permit under Title 15 — an attached ADU is reviewed as a duplex for building-code purposes. Sewer and water availability certificates plus Fire Marshal flow review are submitted with the application. No published timeline (secondary sources suggest 3–4 months).City ADU handout (building-code items); BMC Title 15
  • EdmondsResidential building permit only — the old conditional use permit is gone. Apply via MyBuildingPermit.com. No published review timeline.Ord 4360 §7; city B2 handout
  • EverettPermitted outright with no discretionary review (except historic-overlay DADUs, which get historical commission review). Residential building permit plus trade permits; no published typical timeline.EMC Table 5-1; Table 8-6 row 8
  • IssaquahLevel 1 (administrative) review plus a building permit, e-submittal only via MyBuildingPermit.com. Published target review times: four weeks for first review, three for second, one for third and later — targets start when fees are paid.LUC 18.500.090(B)–(C); city Target Review Times handout (April 2026)
  • KentAn ADU permit through Economic & Community Development plus the building permit; attached and internal ADUs in existing homes are exempt from residential design review. No published review timeline.KCC 15.08.350(B)(10); 15.04.180(10)
  • KirklandPermitted outright. Requires an ADU permit with owner affidavit, a registration covenant recorded with King County, and a standard building permit (via MyBuildingPermit.com). Expedited review is available; pre-approved plans use a reduced submittal list. No published timeline — secondary sources suggest 8–12 weeks standard.KZC 115.07(9)
  • LynnwoodAn ADU Permit is a Type 1a ministerial decision processed with the building permit — no notice, no hearing. Completeness review within 28 days; no codified final-decision deadline.LMC 8.90.0330; 8.90.0320
  • OlympiaPermitted outright in all residential districts — a building permit, with design review folded into it inside the Infill & Design Review District (the ADU must reflect the primary home's character; every unit needs a lit, 3-ft paved walkway). No published review timeline; the city urges early pre-application contact.OMC 18.04.060(A); Table 4.01; city ADU page
  • RedmondPermitted outright in NR, NMF, NMU and mixed-use zones — a residential building permit only, no land-use permit. No city-published ADU timeline; secondary sources suggest roughly 4–8 weeks.RZC 21.04.0100; redmond.gov/469
  • RentonPermitted outright — building permit only, no discretionary land-use review. The city states PRADU pre-approved-plan permits can issue in about a week. No street improvements or sidewalks required.RMC 4-2-060; 4-2-080A.7; city PRADU materials
  • SammamishBuilding permit via MyBuildingPermit.com. No published review timeline (secondary sources suggest roughly 8–14 weeks for single-family-class review).City Permit Center page
  • SeattlePermitted outright — no land-use or design review, no MHA contribution. Standard construction permit through SDCI. Pre-approved DADU plans through the ADUniverse program permit in roughly 2–6 weeks; no published timeline for custom designs.SMC 23.42.022.A; SDCI
  • ShorelineType A ministerial decision (staff-level, no hearing) plus a building permit — and Type A decisions are due within 65 calendar days, with the clock running from the completeness determination.Table 20.30.040; SMC 20.30.140(A)(1)
  • TacomaPermitted outright — building permit only, no discretionary land-use review. The city's stated issuance goal for residential new-building permits is 8 weeks.TMC 13.06.080.A.3.a; tacomapermits.org

City pages

Bellevue · Bothell · Burien · Edmonds · Everett · Issaquah · Kent · Kirkland · Lynnwood · Olympia · Redmond · Renton · Sammamish · Seattle · Shoreline · Tacoma

Verified 2026-08-19 against codified municipal code and adopted ordinance text. See methodology and the changelog.