Attached ADU (AADU) Permits in City of Issaquah
An ADU built inside or attached to the primary residence — basement conversion, garage conversion, or bump-out addition. Lower cost; constrained by the primary footprint. Junior ADUs (JADUs, ≤500 sf) are a subset of this category.
Drops the placement canvas on your parcel for attached adu (aadu) scope. Live setback + coverage + easement checks; packet generation when you’re ready.
Permit fees in City of Issaquah
Fee schedule not yet aggregated — check the City of Issaquah fee schedule directly.
City of Issaquah fee scheduleBuilding permit fee is valuation-based (Issaquah adopts UBC Table 1-A bracket schedule). Plan review fee 65% of building fee. WA state BCC surcharge $4.50/unit. Application fees invoiced via https://mybuildingpermit.com; 3% credit-card service fee or pay by check / exact cash. Impact fees apply on top of permit fee: traffic concurrency, school, parks. HB 1337 caps ADU impact fees at 50% of single-family unit rate — confirm Issaquah's current adopted ADU schedule at fee schedule URL. King County sewer capacity charge (~$8k-$10k) applies separately if ADU is on the King County sewer system.
Review timeline
Typical: 45–120 business days
AADU-specific requirements
- Egress on every bedroom — IRC R310 net clear opening ≥5.7 sf; sill ≤44″ from floor.
- Smoke + CO alarms — interconnected throughout primary + AADU per IRC R314/R315.
- 1-hr separation — required between AADU and primary in some cases; otherwise a continuous draft stop.
- Independent kitchen + bath — full plumbing + cooking provision in the AADU.
- Separate address / unit number — required by USPS + 911 dispatch.