Detached ADU (DADU) Permits in City of Issaquah
A standalone backyard cottage with its own foundation, roof, and exterior. Maximum flexibility on layout; highest construction cost. HB 1337 floor: 1,000 sf gross allowed everywhere.
Drops the placement canvas on your parcel for detached adu (dadu) 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
What a DADU permit packet contains
- A1.1 — Site plan with rotated footprint, setbacks, coverage
- A2.1 — Floor plan with rooms, openings, egress
- A3.1 — Elevations (all four faces, dim strings)
- A4.1 / A4.2 — Foundation + framing plans
- A5.1 — Wall section with WSEC R-values
- A6.0 — Glazing schedule (NFRC U-factor + SHGC)
- Filled application forms (city-specific)
- Manual J energy compliance report