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Kirkland, WA Accessory Structures: ADU Impact Fees (2026)

Some Restrictions
Compiled from the official code textEditor Martyn O'NeillLast verified September 2026

Key Facts

ADU fee cap
50% of principal-unit impact fee
Small-ADU exemption
800 sq ft or less pays no fee
Deferral admin fee
$240 per building permit
Independent fee study fee
$100 per calculation
Deferral deadline
18 months after permit issuance
Administering department
Kirkland Public Works Department

Summary

Kirkland caps the transportation impact fee on a new accessory dwelling unit at fifty percent of the fee that would apply to the principal house on the same lot. The cap, set by KMC 27.04.030(m) to comply with the state ADU statute, applies once an ADU exceeds 800 square feet, the point where the city's separate small-ADU exemption stops covering it.

To ensure compliance with RCW 36.70A.681(1)(a), the impact fee assessed on the construction of an accessory dwelling unit regulated in Chapter 115 KZC will not be greater than fifty percent of the impact fee that would be imposed on the principal unit.

View official code

Official source re-checked September 8, 2026: no newer edition of the code had been published (publisher’s edition: current through Ordinance 4945, passed July 21, 2026).

Full Breakdown

030(a). 681(1)(a). 050(a)(1); the 50 percent cap is what governs ADUs larger than that threshold. 040, paying a $100 administrative processing fee, and the director may set an alternative fee based on that study. 030(g); the deferred fee is then due before final inspection, final occupancy, or the eighteen-month deadline. 130.

Violations & Fines

No building permit for an ADU is issued until the capped or exempted fee is paid in full, per KMC 27.04.030(h); permits placed on the deferred-payment track must have the outstanding fee, less credits, paid before final inspection, final occupancy, or eighteen months after issuance, whichever is first. Missing the deferred deadline stops final inspection and occupancy sign-off. Applicants using the deferral option owe a nonrefundable $240 administration fee regardless of when the underlying impact fee is ultimately paid.

Frequently Asked Questions

Does Kirkland cap transportation impact fees for ADUs?
Yes. Under KMC 27.04.030(m), the transportation impact fee charged on an accessory dwelling unit regulated by KZC Chapter 115 cannot be more than fifty percent of the impact fee that would apply to the principal dwelling unit on the same lot. The city adopted this cap to comply with RCW 36.70A.681(1)(a).
Is my small backyard ADU exempt from impact fees entirely?
It can be. KMC 27.04.050(a)(1) exempts any legal ADU of 800 square feet or fewer from transportation impact fees, treating it as part of the existing single-family use. Larger ADUs are not exempt but still get the fifty percent cap under 27.04.030(m).
Can I delay paying the ADU impact fee?
Yes. KMC 27.04.030(g) lets applicants for single-family building permits, including ADUs, defer payment until the permit is completed or eighteen months after issuance, whichever is first, for a $240 administration fee paid at issuance. The deferred fee is due before final inspection or occupancy if that comes sooner.
What if I think the standard fee overstates my ADU's traffic impact?
You can request an independent fee calculation under KMC 27.04.040, prepared by a traffic engineer and paid for by you, plus a $100 administrative processing fee. The director may set an alternative fee based on that study, and director decisions can be appealed to the hearing examiner under 27.04.130.

Sources & Official References

Other rules in Kirkland

Noise Ordinances: Construction HoursSome RestrictionsADU RulesSome RestrictionsShed & Carport RulesSome RestrictionsParking Rules: RV & Boat ParkingSignificant RestrictionsGarage ConversionsSome RestrictionsNoise Ordinances: Leaf Blower RulesSome RestrictionsParking Rules: EV ChargingSome RestrictionsParking Rules: Driveway RulesSome RestrictionsParking Rules: Preferential Parking DistrictsLight Restrictions

All Kirkland rules

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ADU Impact Fees in Nearby Cities

How other cities in King County handle adu impact fees.

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