Attached ADU (AADU) Permits in City of Sammamish
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 Sammamish
Fee schedule not yet aggregated — check the City of Sammamish fee schedule directly.
City of Sammamish fee scheduleFull Construction Permit (Addition/Alteration) fees. Sewer capacity charges may apply (King County: ~$8k-$10k). Apply via https://mybuildingpermit.com. Apply via MyBuildingPermit.com.
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.