Bellevue reformed its ADU code twice in quick succession: a 2023 ADU Reform (Ordinance 6746) removed owner-occupancy and legalized detached ADUs, and June 2025 middle-housing ordinances implemented WA HB 1110 and HB 1337. Up to two ADUs are now allowed on any lot that permits a single-family home, at up to 1,200 sq ft each, and ADUs may even be sold as condominiums separate from the main house. High Eastside rents make Bellevue one of the strongest ADU rental markets in the country despite high build costs.
Zoning & Size Requirements [1][2][3]
Yes — Bellevue allows ADUs. A detached ADU can typically be up to 1,200 sq ft under current Washington and Bellevue zoning rules.
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| Allowed Zones | Any lot in a land use district that allows a single-family dwelling (LUC 20.20.120) |
| Max Size (Detached) | 1,200 sq ft (Director may approve more for single-floor units in the primary structure or conversions/additions to existing accessory structures) |
| Max Size (Attached) | 1,200 sq ft, or 40% of the structure, whichever is greater |
| Max Size (JADU) | Not a category in Washington (no JADU designation) |
| Max Height | Detached ADUs: 24 ft to the highest point (28 ft when built as an addition over an existing accessory structure) |
| Max Units | 2 ADUs per lot (any combination of attached/detached); ADUs may be condominiumized and sold separately |
Setback Requirements [1][2][3]
Bellevue requires a rear setback of about 20 ft for a detached ADU, and parking requirements vary by unit size or location. Owner-occupancy is not required — you can rent it out without living on the property.
| Rear Setback | Subject to middle-housing dimensional standards (LUC 20.20.538) — Confirm with Bellevue Development Services |
| Side Setback | Subject to middle-housing dimensional standards (LUC 20.20.538) — Confirm with Bellevue Development Services |
| Front Setback | Per underlying district / middle-housing standards (LUC 20.20.538) — Confirm with Bellevue Development Services |
| Parking Required | None under 1,000 sq ft; 1 space for 1,000-2,000 sq ft; none required within a half mile of frequent transit (HB 1337 also caps ADU parking mandates) |
| Owner Occupancy | Not required (removed by Ordinance 6746 in 2023; prohibited by HB 1337) |
| Min Lot Size | No ADU-specific minimum — allowed wherever a single-family dwelling is permitted |
Permit Process & Fees [4][5]
An ADU permit in Bellevue typically costs Permit and plan review fees based on project valuation — Confirm with Bellevue Development Services and takes Several weeks to a few months depending on review queue — Confirm with Bellevue Development Services, through a ministerial, by-right review.
| Approval Process | By-right building permit through Development Services (registration and neighbor-notice requirements were removed in 2023) |
| Review Timeline | Several weeks to a few months depending on review queue — Confirm with Bellevue Development Services |
| Permit Fees | Permit and plan review fees based on project valuation — Confirm with Bellevue Development Services |
| Impact Fees | School/transportation impact fees may apply; HB 1337 caps ADU impact fees at 50% of those for the principal unit — Confirm with Bellevue Development Services |
| Plan Check | Standard plan review; timing varies with queue — Confirm with Bellevue Development Services |
| Pre-Approved Plans | No city pre-approved plan library — Confirm with Bellevue Development Services |
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Construction Costs [6]
Building an ADU in Bellevue typically costs $180,000-$380,000 ($200-$350 per sq ft); a garage conversion runs $90,000-$190,000.
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| Average Build Cost | $180,000-$380,000 |
| Cost per Sq Ft | $200-$350 |
| Garage Conversion | $90,000-$190,000 |
| Prefab ADU (Installed) | $120,000-$280,000 |
Finance Your ADU Project
Most ADU projects are funded through HELOCs, construction loans, or cash-out refinancing. Compare rates from top lenders.
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Rental Income Potential [7][8]
A 2-bedroom ADU in Bellevue rents for around $3,100-$3,900/mo, an estimated 6-8% annual return.
| Avg Rent (1 Bedroom) | $2,500-$2,900/mo |
| Avg Rent (2 Bedroom) | $3,100-$3,900/mo |
| Short-Term Rental | No citywide STR ban identified — Confirm current short-term rental licensing with the City of Bellevue |
| Est. Annual ROI | 6-8% annual return |
Explore Prefab ADU Options
Prefab ADUs can save 20-40% vs. traditional construction and cut build time in half.
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Recent Law Changes
What's Changed Recently
- Ordinance 6746 (July 17, 2023) ADU Reform: legalized detached ADUs (DADUs), removed owner-occupancy, removed design-matching controls, and allowed ADUs to be sold separately as condominiums
- Ordinances 6851/6852 (adopted June 24, 2025) implemented WA HB 1110 and HB 1337 middle-housing requirements, expanding units allowed per residential lot (up to 4, or 6 near major transit/with affordable units)
- WA HB 1337 (effective for Bellevue mid-2025): 2 ADUs per lot in urban growth areas, no owner-occupancy mandate, parking caps, and ADU impact fees limited to 50% of the principal unit's
- DADU height set at 24 ft (28 ft over an existing accessory structure) with size cap of 1,200 sq ft (LUC 20.20.120)
Tips for Building an ADU in Bellevue
- Bellevue's 1,200 sq ft cap is generous — but the Director can approve even larger units for conversions of existing accessory structures
- Keep the ADU under 1,000 sq ft or build within a half mile of frequent transit to avoid the parking requirement entirely
- The condo provision is rare nationally: a Bellevue DADU can be sold separately, which changes the investment math — talk to a real estate attorney
- Eastside rents are among the highest in the US; even at $300+/sq ft build costs, a 2BR DADU can pencil out
ADU Builders in Bellevue
Looking for an ADU builder in Bellevue? ADU projects need a contractor experienced with local zoning, the permit process, and utility connections — not every general contractor has built one. We match Bellevue homeowners with experienced local ADU contractors who provide free, no-obligation quotes. Getting at least three bids typically saves 20-40% on the same scope.
Sources & References
All data on this page is sourced from official government records and verified market data. View our full methodology.
- Accessory Dwelling Unit (ADU) Reform LUCA — City of Bellevue government — Accessed 2026-07-10
- LUC 20.20.125 Accessory structures in residential districts — Bellevue Land Use Code Municipal Code — Accessed 2026-07-10
- LUC 20.20.538 Middle housing — Bellevue Land Use Code Municipal Code — Accessed 2026-07-10
- Middle Housing Code Amendments — City of Bellevue government — Accessed 2026-07-10
- Accessory Dwelling Unit (ADU) Reform LUCA — City of Bellevue government — Accessed 2026-07-10
- Bellevue ADU Construction Law Changes 2025 — TrueTown industry — Accessed 2026-07-10
- Average Rent in Bellevue, WA — RentCafe Market Data — Accessed 2026-07-10
- Average Rent in Bellevue, WA — Zumper Market Data — Accessed 2026-07-10
Frequently Asked Questions
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