ADU Rental Income in Seattle: Rates, Costs, and ROI (2026)
What Seattle homeowners actually earn renting an ADU — 2026 rent ranges by unit type, what a Seattle ADU costs to build, cap rates, and the HB 1337 zoning rules that make it possible.
How Much Does an ADU Rent for in Seattle?
Seattle is one of the strongest ADU rental markets in the country. High-wage tech employment (Amazon, Microsoft, Boeing), low single-family vacancy, and a state law that bars owner-occupancy requirements combine to make Seattle ADUs viable as pure investment rentals — not just a unit for a family member.
Seattle ADU rental rates (2026):
| ADU Type | Monthly Rent | Annual Gross Income |
|---|---|---|
| Studio / Junior ADU | $1,400–$1,900/mo | $16,800–$22,800 |
| 1 Bedroom ADU | $1,600–$2,600/mo | $19,200–$31,200 |
| 2 Bedroom ADU | $2,200–$3,400/mo | $26,400–$40,800 |
These figures track with what we publish in the full ADU rental income guide and power the Seattle defaults in our ADU ROI Calculator.
What an ADU Costs to Build in Seattle
Washington ADUs run $132,000–$320,000 statewide depending on scope, per our ADU cost report and 2026 cost guide. Seattle sits at the top of that range:
- Garage conversion: $150,000–$210,000 — reuses the existing structure and foundation
- New detached ADU (DADU): $230,000–$340,000 — full new construction; premium finishes and difficult lot access push toward the top
- Junior ADU (interior conversion): $35,000–$60,000 — the cheapest way into the Seattle rental market, since there's no new structure at all
Run your own numbers with the ADU cost calculator.
Seattle ADU Cap Rates and Break-Even
Example: Seattle 1BR detached ADU ROI
- Project cost: $220,000 (detached, 550 sq ft)
- Monthly rent: $2,000
- Annual net income (after 10% expenses): $21,600
- Cap rate: 9.8% — break-even: roughly 10.2 years
Example: Seattle JADU ROI
- Project cost: $38,000 (interior conversion, no new structure)
- Monthly rent: $1,100
- Annual net income (after 10% expenses): $11,880
- Cap rate: 31.3% — break-even: roughly 3.2 years
The gap between these two examples is the core tradeoff in Seattle: a detached ADU generates more total monthly income, but a JADU generates a dramatically better return on the dollar invested because there's no new foundation, framing, or roof to pay for. See our full ROI guide for more worked examples, or model your specific address and financing with the Washington ROI Calculator.
Seattle ADU Zoning and Permitting
Seattle ADUs operate under Washington's statewide ADU law, with local permitting layered on top:
- Two ADUs per lot: House Bill 1337 (2023) requires cities planning under the Growth Management Act — Seattle included — to allow at least two ADUs per single-family lot (typically one attached/JADU plus one detached).
- No owner-occupancy requirement: HB 1337 also eliminated the requirement to live on the property, so you can rent the main house and the ADU simultaneously.
- Size limit: up to 1,000 sq ft as a statewide baseline; confirm Seattle's current DADU (detached ADU) size limits with the Seattle Department of Construction & Inspections before finalizing plans, since city rules can be more generous than the state floor.
- Impact fees: capped at 50% of the single-family rate under state law.
- Permit timeline: 90–180 days statewide is typical; ask SDCI about pre-approved ADU plan sets, which can shorten this.
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Full detail on Washington's statewide law, including sources, is in our Washington ADU laws guide.
How Seattle Compares to Other Washington Markets
| Market | 1BR Rent | 2BR Rent |
|---|---|---|
| Seattle | $1,600–$2,600/mo | $2,200–$3,400/mo |
| Tacoma | $1,100–$1,700/mo | $1,500–$2,200/mo |
Bellevue commands rents in a similar range to Seattle thanks to its own concentration of tech employers, though at generally higher construction costs given land and permitting pressure on the Eastside. Tacoma is the value play — meaningfully lower rents, but also lower build costs, so cap rates land in a comparable range.
Find a Seattle ADU Builder
Our contractor directory lists licensed ADU builders, designers, and architects working in the Seattle metro — filter by service type to find garage-conversion specialists versus new-construction (DADU) builders.
Frequently Asked Questions
How much can I earn renting an ADU in Seattle?
Most Seattle ADU owners see $1,400–$3,400/month depending on size and unit type, or roughly $16,800–$40,800/year in gross rental income. Net income after typical expenses (vacancy, maintenance, property management) runs about 85–90% of gross.
Is building an ADU in Seattle worth it?
For most owners, yes — Seattle ADUs typically achieve high single-digit to low double-digit cap rates, and JADU conversions in particular can break even in as little as 3–4 years. HB 1337's removal of the owner-occupancy requirement makes Seattle one of the few major West Coast markets where you can buy a property specifically to rent both units.
Do I need a permit to build an ADU in Seattle?
Yes. Seattle requires a building permit through SDCI, and Washington's statewide law means most lots are entitled to at least one ADU by right rather than through a discretionary rezoning. Ask about pre-approved plan sets to shorten the process.
What's the cheapest way to add rental income with an ADU in Seattle?
A Junior ADU (interior conversion), typically $35,000–$60,000 in Seattle — it uses existing space within the home, so there's no foundation, framing, or roof cost. See our Junior ADU guide for the full breakdown, including how it compares to a garage conversion or new detached unit.
Plan Your Seattle ADU Build
Rental income potential is one side of the equation — build cost is the other. Use our ADU cost calculator to see cost ranges for Washington projects by ADU type and size. For Seattle-specific permit requirements, setback rules, and statewide law details, see the Washington ADU laws guide.