| City | ADUs per Lot | Max Detached Size | Owner-Occupancy | Parking |
|---|---|---|---|---|
| Everett | 2 allowed | 1,000 sq ft | Not required | 0–1 space |
| Seattle | 2 allowed | 1,000 sq ft | Not required | None in most zones |
| Lynnwood | 2 allowed | 1,000 sq ft | Not required | 0–1 space |
| Edmonds | 1–2 | 800–1,000 sq ft | Not required | 1 space typical |
| Mill Creek | 1–2 | 800–1,000 sq ft | Not required | 1 space typical |
| Marysville | 2 allowed | 1,000 sq ft | Not required | 0–1 space |
The five rules that matter most
- Two units per lot. State law requires cities to allow two ADUs (attached and/or detached) on qualifying lots.
- No owner-occupancy mandate. Live where you want; rent both units if you like.
- Size up to 1,000 sq ft. Cities can’t force detached ADUs below 1,000 sq ft.
- Parking is capped. No mandate near transit; at most one space elsewhere.
- Sale possible. Cities may allow condo-style separate sale — Everett does.
This page is general information, not legal advice. Codes change — we verify current requirements for your address during the free lot check. Deep dive: our HB 1337 explainer →
Do I have to live on the property to build an ADU?
No. HB 1337 prohibits owner-occupancy requirements. You can rent both the main house and the ADU.
Can I sell my ADU separately?
Sometimes — HB 1337 allows cities to permit condo-style separate sale of ADUs. Everett has adopted provisions enabling this; it requires a condominium declaration. We can walk you through it.
Is there a minimum lot size?
State law restricts minimum-lot-size mandates for ADUs. In practice, most residential lots in our service cities qualify — the binding constraints are usually setbacks, height and utility capacity.
Do I need extra parking?
Usually no more than one space, and often none — HB 1337 prohibits parking mandates within half a mile of major transit stops and caps requirements elsewhere.