Bellevue has opened more of its residential land to accessory homes in recent years. Still, every lot has its own limits, and Seattle rules do not apply across the lake. Bellevue DADU zoning rules come from the city’s own Land Use Code, permit process and site standards. This guide explains what to check before you plan a backyard home in Bellevue.

It covers eligibility, size and height, parking, site constraints, the permit path and the status of the city’s pre-approved plan effort. The details below reflect official city pages checked in October 2026. Because codes change, confirm every point with the City of Bellevue before you design.

Where Bellevue DADU Zoning Rules Come From

Bellevue regulates accessory dwelling units in section 20.20.120 of its Land Use Code. When we checked, the online code noted a recent amending ordinance that was still pending codification. So the posted text may not show every current change, and the city’s planning staff remains the final word.

The city also notes that its council adopted middle housing code changes in 2025. According to the city, those changes allow ADUs on all residentially zoned lots. Meanwhile, state law under RCW 36.70A.681 sets minimum standards that apply in Bellevue and other cities.

How Many Units a Lot May Hold

The Land Use Code allows up to two ADUs on each lot in a district that allows a single family dwelling. A lot might combine an attached unit and a detached unit, or follow another allowed setup. However, other code limits such as setbacks and lot coverage still shape what fits.

The code also includes a notable limit. It does not allow an ADU on the same property as a business that operates under a home occupation permit. If you run a home business, ask the city how that rule affects your plans. Our article on whether a property can have two accessory dwellings explains how Seattle handles the same question.

Size and Height Under Bellevue DADU Zoning

The Land Use Code sets a maximum ADU size of 1,200 square feet, with some exceptions the Director may approve. It also excludes up to 300 square feet of parking or unheated storage from that total. As a result, a garage below or beside a unit may not count fully against the limit.

The city’s pre-approved plans page lists a maximum height of 24 feet for DADUs. That page also notes that code allows 28 feet when a DADU sits above an existing garage. In addition, the code allows conversions of existing structures regardless of setback and lot coverage limits, which can help with an older garage.

Parking Rules to Confirm

Parking can shape a site plan. Under the Land Use Code, Bellevue requires no parking for an ADU under 1,000 square feet or for one within one-half mile of a major transit stop. Otherwise, the code calls for one parking space for the unit.

Because transit service and maps can change, ask the city to confirm how these rules apply to your address. Also check whether street parking near your lot is already tight, since that can shape how tenants or family members will live with the new unit.

Site Constraints Worth Checking Early

Many Bellevue lots have slopes, mature trees, streams or wetlands nearby. These features can trigger extra review and can limit where a unit goes. Therefore, gather a survey, aerial photos and any past permit records before you sketch a plan.

A licensed surveyor can map boundaries, grades and utilities. Our article on why a property survey matters explains what a survey shows. If your lot slopes, our guide on building a DADU on a sloped lot covers common design and foundation questions.

The Bellevue Permit Path

Bellevue’s new house construction page says the city treats ADUs as regular dwelling units for permitting. According to that page, a detached ADU uses the New One or Two Family structure permit. That building permit also includes items such as clearing and grading, plumbing, mechanical and most electrical work.

The page also says that a project with more than one new structure on the site needs a separate clearing and grading permit. For water and sewer service, the city directs applicants to its Utilities staff. Ask about utility capacity early, since it can affect both design and timing. A long sewer run or a small water line may change where the unit sits on the lot.

Status of Bellevue Preapproved Plans

Bellevue is developing a pre-approved plans program for cottage housing and DADUs. The city describes three phases, ending with department approval of up to ten selected plans for purchase. When we checked, the program was still in development rather than open to applicants.

So for now, most Bellevue owners will work with their own designer. For site questions about land use, zoning and feasibility, the city points people to its Land Use division. Seattle runs a separate program, which our article on how Seattle preapproved DADU plans work describes.

Next Steps for Bellevue DADU Zoning Research

First, confirm that your parcel lies inside Bellevue city limits and note its zoning district. Next, read the current code section and the city’s ADU and middle housing pages. Then list your site features and questions. Include anything unusual, such as a shared driveway, an easement or an older structure you hope to convert.

Finally, contact the city before you commit to a design. A short conversation can confirm size, height, parking and permit needs for your exact lot. With that groundwork, Bellevue DADU zoning becomes a clear starting point rather than a guess.