ADU Rules in Seattle, WA — 2026 Guide
Check if your Seattle property qualifies for an ADU in 20 seconds
Seattle ADU Rules at a Glance
Seattle is considered ADU-friendly. Here are the key regulations.
- Seattle allows two ADUs per lot (one attached DADU + one detached DADU).
- No owner-occupancy requirement since 2019.
- Detached ADUs can be up to 1,000 sqft and 23 ft tall.
- No off-street parking required for ADUs.
What ReadyPermit Checks for Seattle Properties
Enter any Seattle address and get an instant ADU feasibility analysis covering:
Zoning Compliance
Verify your Seattle lot is zoned for ADU construction under current WA and local rules.
Setbacks & Coverage
Check required setbacks, lot coverage limits, and height restrictions for your specific parcel.
ADU Size Limits
Calculate the maximum ADU square footage allowed based on your lot size and primary dwelling.
Permit Requirements
Understand what permits and approvals Seattle requires before you can break ground.
Flood & Hazard Zones
Identify if your property falls in a flood zone, fire zone, or other hazard overlay.
Lot & Parcel Data
Pull parcel boundaries, lot dimensions, and existing structures from county records.
Check Your Seattle Property Free
Enter your address below. In under 20 seconds you will know if your Seattle lot qualifies for an ADU — no phone calls, no waiting.
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