In 2023, Washington passed HB 1337 — the most significant ADU legislation in state history. Here’s what it means for your property in 2026.
The five rules that matter
- Two ADUs per lot. Cities must allow at least two accessory units (attached, detached, or both) on most residential lots.
- No owner-occupancy. You don’t have to live on the property. Rent both units if you want.
- 1,000 sq ft floor. Cities can’t cap detached ADUs below 1,000 sq ft.
- Parking is capped. No mandate within half a mile of major transit; at most one space elsewhere.
- Sale is possible. Cities may allow condo-style separate sale — Everett already does.
What still varies by city
Setbacks, height limits, design review and utility requirements still differ — Edmonds applies design standards in some zones; Seattle and Everett have streamlined most reviews. The binding constraint on most lots is no longer zoning — it’s geometry and utilities.
How to check your lot
Free option: call us. We do lot checks daily and can usually tell you in one conversation what your address allows. Or read our city-by-city rules table.