Cities · King County

Can I build a backyard home in Bellevue?

Since 2023, Washington law lets most city lots hold up to two more homes. Bellevue writes its own rules on top. Here’s what the code says, in plain English — and a free report on what may fit on your lot.

Read from the Bellevue code on October 9, 2026 · confidence high · a summary, not legal advice. Rules change; the report re-reads them for your parcel.

The short version

What Bellevue allows.

The headline standards. Open any card for the full wording and the code section.

ADUs per lotUp to 2Full wording

Up to 2 ADUs per lot in single-family districts

Max size1,200 sq ft (+300 sq ft of parking or storage exempt)Full wording

1,200 sq ft; up to 300 sq ft of parking or unheated storage is exempt

Max height24 ft (28 ft over an existing structure)Full wording

24 ft; 28 ft when added over an existing structure

Front setbackThe middle-housing dimensional standardsFull wording

Detached units follow the middle-housing dimensional standards

Side setbackThe middle-housing dimensional standardsFull wording

Detached units follow the middle-housing dimensional standards

Rear setbackThe middle-housing dimensional standards; 0 ft at an alleyFull wording

Detached units follow the middle-housing dimensional standards; a unit may sit at an alley lot line

Lot coverage40–45% by structures (middle-housing table)Full wording

DADUs follow the middle-housing dimensional table (LUC 20.20.120.E.2 → Table 20.20.538.C.1): maximum lot coverage by structures 40% in LL-1, LL-2, SR-1–SR-3; 45% in SR-4, LDR-1–LDR-3, MDR-1, MDR-2; maximum impervious 50% (LL/SR-1–SR-3), 60% (SR-4, LDR-1), 65% (LDR-2+); height 32 ft flat / 35 ft pitched. The R-1–R-7.5 districts were renamed LL/SR/LDR/MDR by Ord. 6851 (June 2025)

ParkingNone under 1,000 sq ft or within 1/2 mile of a major transit stopFull wording

None under 1,000 sq ft or within 1/2 mile of a major transit stop; otherwise 1 space

Where a city figure reads stricter than the state floor (RCW 36.70A.681), the floor may control — the report flags it for your parcel.

The rest

Living there, selling it, plans, time and fees.

Each answer is the code’s own wording, with the section it comes from. “Not published yet” means the city hasn’t posted a figure — the report asks the city, not the internet.

Are backyard homes allowed?

Yes — since July 1, 2025 (Ord. 6851, adopted June 24, 2025). DADUs were previously prohibited.

Minimum lot size

None — LUC 20.20.120 sets no minimum lot size for a detached ADU; 'Up to two accessory dwelling units are permitted on each lot' (LUC 20.20.120.C.1); ADU floor area 'limited to a maximum of 1,200 square feet' (C.3); DADU height 24 ft, or 28 ft over an existing accessory structure (E.1)

Do you have to live there?

No — removed by Ord. 6746 (2023)

Can it be sold on its own?

Yes — the prohibition was removed by Ord. 6746 (2023)

Pre-approved plans

None found

How long the city takes

No target published; the city publishes actuals. Development Services 'Processing Days by Application Type' (Oct. 2025–Oct. 2026): single-family new structure median 164 days / average 240 (238 permits); single-family addition median 76 / average 143. No ADU category

Impact fees

No ADU-specific rule published. Transportation (BCC 22.16) exemptions do not mention ADUs and the 2026 rate schedule has no ADU row (single family $8,185; single-family attached $4,092); the city says a land use not in the table is decided by the transportation review engineer ([email protected], 425-452-4236). School (BCC 22.18.060) exemptions do not mention ADUs. The RCW 36.70A.681 50% cap applies as a floor — confirm the billed figure with Transportation Development Review

Your lot

The code is half the answer. Your parcel is the other half.

Lines and easements

Where the lot lines really are, which setbacks apply on each side, and whether a utility or access easement takes the corner you had in mind.

Critical areas and slope

Steep slopes, wetlands and streams come with buffers that no citywide number shows. The report reads the county’s maps for your parcel.

Sewer, septic, water, trees

Whether sewer reaches the lot or it’s on septic, where the water service is, and which trees a city protects — the things that decide where a unit can actually go.

Free, within a few hours, no obligation.
What Bellevue allows, what could fit on your lot, and a planning cost range. If something won’t fit, the report says so — and shows what might.

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Sources

Where this page comes from.

Read from the Bellevue municipal code and the city’s own pages on October 9, 2026. The same table feeds the HousUp report, so the report and this page never disagree. Cities amend their codes; before you design anything, confirm the current wording with the city.

Nearby

Other places in King County.

Kenmore Attached 1,000 sq ft Kirkland 1,200 sq ft gross floor area Redmond 1,000 sq ft Renton 1,000 sq ft Seattle 1,000 sq ft Shoreline 1,200 sq ft All cities →

Find out what your property could become.

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