1. What is middle housing? What are the "nine types" of middle housing?
“Middle housing” or “middle-scale housing” is a term used to refer to residential developments that are more dense than single-family housing and less dense than a typical midrise apartment building, but similar in scale to single-family homes.
State law defines nine “types” of middle housing. These nine types are defined by either the number of units included in the structure or the form of the building structure.
The middle housing types defined by number of units are:
- Duplexes
- Triplexes
- Fourplexes
- Fiveplexes
- Sixplexes
The middle housing types defined by building structure form are:
- Townhomes
- Stacked flats
- Cottages
- Courtyard/garden style apartments
These definitions are complicated as a middle housing development can fit within the definitions of multiple middle housing types. All housing types in the first group refer to an attached structure with multiple units. Stacked flats, courtyard buildings, and townhome structures are included in the second group, but are all also examples of attached housing and can also be categorized as part of the first group. For example, a fourplex can also be four townhome units attached in a row, or four attached units on one story arranged around a central courtyard.
2. Why are we updating the city's codes for middle housing?
In 2023 the Washington State Legislature passed House Bill (HB) 1110, which requires many cities in the state to update their codes to permit middle housing in all residential areas. These changes are intended to increase the variety of housing options and overall housing capacity in Bellevue and throughout the state.
3. How many middle housing units can be built per lot?
State law requires cities to allow up to 4-6 middle housing units per lot, depending on the location and whether units are affordable. Bellevue’s regulations establish minimum sizes and dimensions for lots, which will be retained. These dimensions respond to Bellevue’s individual land use districts.
It will not always be possible for every lot to achieve 4-6 middle housing units. There are additional development regulations and circumstances which can limit the extent of development. In addition, property owners can always choose to build fewer units, or to build a single-family home instead of middle housing.
4. Why does the LUCA include a fee-in-lieu option for developers to build six units, instead of relying solely on the state's affordable housing incentive that permits six units when two are affordable?
State law requires cities to permit up to six units on any residential lot if at least two of those units are affordable. However, based on stakeholder input and staff analysis, the requirement for two affordable units out of six (a 33% set-aside) exceeds the typical threshold found in most inclusionary zoning programs, which often require only around 10%-15%. This higher standard may unintentionally discourage affordable housing production when middle housing projects are proposed.
To address this concern, the Planning Commission recommended an alternative approach: allow six units per lot if the developer pays a fee of $150,000 per unit instead of constructing affordable units. In-lieu fees will be used to develop affordable housing projects elsewhere in the city.
5. Which middle housing types will be allowed in Bellevue?
Bellevue is required to allow at least six of the nine middle housing types defined by state law. Under the current proposal, all nine middle housing types would be allowed.
Staff recommend this approach because the nine middle housing types are not all distinct from each other and have significant overlap which limits the benefits and practicality of limiting the list. For example, a fourplex can also be four townhome units attached in a row, or four attached units on one story arranged around a central courtyard. Ultimately, the scale of these housing types is still determined by development regulations. Under the proposed LUCA, all middle housing types may be allowed, but must be accommodated within a similar lot coverage, building height, setback dimensions and so on. Providing flexibility within this “building envelope” keeps projects within a desirable scale while allowing flexibility for design to respond to the characteristics of a site and neighborhood.
6. Is the city proposing to go beyond the minimum requirements of HB 1110?
Yes. The city is proposing a few components that go beyond the minimum requirements of HB 1110, which include:
- Permit all of the nine types of middle housing, subject to any applicable development regulations.
- Allowing up to six units by-right within one-half mile walking distance of a major transit stop, rather than a one-quarter mile walking distance as required. (Light Rail and RapidRide stops)
- Allowing up to six units by-right within one-quarter mile walking distance of Regional and Candidate Countywide Growth Centers. (Downtown, BelRed, Wilburton, Crossroads, Eastgate and Factoria.)
- HB 1110 requires that we allow up to six units when two are affordable citywide. The recommendation would also allow market rate development to build up to six units citywide when providing a fee in lieu for the two additional units. This fee will go toward affordable housing development in Bellevue.
- Exempting attached Accessory Dwelling Units (ADUs) from the maximum allowable density and square footage allowed on a lot. The recommended LUCA would allow up to two attached ADUs per lot, which is required under state law.
- Allowing for limited flexibility in development standards such as setbacks and lot coverage, which is encouraged by the state’s guidance.
- Adopt a parking standard of one space per unit for all middle housing rather than for only smaller lots as required.
- Limited flexibility for tree retention for cottage style developments, to accommodate additional circulation requirements.
7. Does middle housing include Accessory Dwelling Units and will the city allow them?
The state also approved HB 1337 in 2023, which requires that jurisdictions adopt regulations permitting up to two accessory dwelling units (ADUs) per lot, which can be any combination of an attached and/or detached ADU. Bellevue’s code does not currently allow detached ADUs. However, the Comprehensive Plan was recently amended to permit them. We are updating regulations to align with the new Comprehensive Plan policies related to detached ADUs and the HB 1337 requirements. Attached ADUs, such as an ADU in a converted basement space, are already allowed. The current recommendation from Planning Commission allows attached ADUs in addition to the allowable middle housing density, with detached ADUs counting towards the allowable middle housing density.
After the adoption of the middle housing code update, the city plans to develop a pre-approved ADU design program to help residents construct ADUs on their lots.
8. Why does the middle housing LUCA count detached ADUs toward the allowable middle housing density but not attached ADUs?
Detached ADUs are proposed to be counted toward middle housing density based on Planning Commission feedback. This is largely because they are standalone structures that appear as separate units, similar in form and impact to other middle housing types. Their visibility makes them functionally equivalent to additional units on a lot.
Attached ADUs, on the other hand, are integrated into a primary structure, limited in size, and often indistinguishable from a single dwelling. Bellevue has allowed attached ADUs since the 1990s without counting them toward density, and this approach has been effective.
Requiring attached ADUs to count toward density would reverse longstanding policy and likely discourage their development, especially when homeowners could instead build other middle housing types that use up their density allowance. Maintaining the current approach supports housing diversity and preserves flexibility for homeowners.
9. When will the new regulations go to into effect?
The city is required to adopt regulations consistent with HB 1110 and 1337 by June 30. If Bellevue fails to adopt its own regulations, the state’s model ordinance will go into effect.
10. What does this mean for my lot?
If you own a home in a single-family land use district (R-1 through R-7.5), once the regulations are in effect you may be able to have multiple units on your lot, if you wish. This could include the addition of one or two ADUs with your primary home, or any other combination of units and structure types that works with the space you have and your needs. If you prefer to keep your property as-is that is also allowed under the new regulations. There is nothing in the bill or the anticipated code changes that would require someone to change their property.
11. What if my lot has covenants?
The city does not enforce private covenants or homeowners association (HOA) requirements. Covenants are private legal agreements—typically recorded in county real property records—that impose restrictions on land use. Many covenants prohibit the construction of any type of dwelling unit besides a single-family dwelling. These covenants are contracts, and both the Washington State Constitution and the United States Constitution limit the extent to which government can interfere with previously executed contracts.
Residents whose homes are subject to HOA requirements should review and understand what HOA rules apply to their property that may restrict some of the development regulations that apply to their lot.
12. What does "walking distance" mean?
Walking distance is the term used when looking at whether or not a property may qualify for additional middle housing units adjacent to certain geographies, or parking exemptions near transit. Applicants will need to provide visual evidence that it is feasible to walk from a given property to the transit stop or other geography that provides the allowance for extra units or parking exemption.
13. Is middle housing affordable?
Middle housing is generally less expensive than single-family homes, but often doesn’t meet the affordability criteria used by many jurisdictions. Affordable housing is typically defined as non-market rate units affordable to individuals earning 80% or less of the area median income. However, encouraging middle housing adds valuable housing diversity, providing options for those who cannot afford single-family homes and prefer alternatives to a typical apartment.
14. Can middle housing be rented or purchased?
The city does not regulate whether housing is for sale or for rent regardless of the type of housing. The decision of whether to rent or sell housing units is up to the owner of the property.
15. What is a unit lot subdivision and how do they differ from standard subdivisions?
Unit lot subdivision is a land division process to create fee simple lots for multifamily projects like townhomes and other middle housing types. The intent is to allow each unit within a development to be placed on its own lot, even though the project was originally developed as a single site.
Under HB 1110, cities must allow any of the middle housing types to use unit lot subdivisions. For example, a cottage housing project could be subdivided so that each cottage sits on its own lot. Unlike standard subdivision processes, unit lot subdivisions do not have a required minimum lot size—instead, the design of the housing project drives the lot layout.
Importantly, unit lot subdivisions differ from standards subdivisions because the resulting lots are categorized as “unit lots,” and the original lot is categorized as a “parent lot,” meaning they are intrinsically tied to each other. This means “unit lots” are not independent buildable sites. Additional development beyond the project proposed through the original unit lot subdivision may be restricted. Within the context of middle housing, this ensures the unit lot subdivision process cannot be used to circumvent minimum lot size standards to create new lots that could then be redeveloped at higher middle housing densities. New middle housing densities apply to the “parent lot” only, not individual “unit lots.”
16. How will middle housing impact critical areas and trees?
All development in the city must comply with critical areas and tree code requirements. The city recently updated its tree code requirements in anticipation of middle housing code changes. To ensure these recent code changes are effective, staff plan to evaluate the tree code and make adjustments to support middle housing and minimize impacts of tree code and landscaping requirements.
The current Planning Commission recommendation includes an allowance that cottage housing developments may utilize the tree credit system for commercial development rather than for residential. Cottage housing has to set aside a minimum of 20% in open space and also has minimum landscaping requirements, so the reduced credit requirements will help with infill feasibility.
Additional clean-up items are included in the update, such as refining definitions, clarifying how to treat trees located on property lines, and providing an alternative planting path when a certified tree professional has determined that full planting compliance could lead to planted trees not surviving.
17. What are the proposed requirements for detached accessory dwelling units (DADUs)?
DADUs would be subject to the following:
- Maximum size of 1,200 square feet
- Additional 300 square feet for a garage or unheated storage space
- Maximum height of 24 feet, or 28 feet when built above an existing detached structure
18. What are the proposed requirements for cottage housing?
Cottages would be subject to the following:
- Maximum size of 1,750 square feet
- Additional 300 square feet for a garage or unheated storage space
- Maximum height of 38 feet, restricted to up to three stories.
- Lot coverage increase of 5% over other middle housing types, and where covered porches are provided up to 25%.
- Open space is required at 20% of the site in total, with some of that space dedicated common open space. Common open space is required at 100 square feet per cottage. Smaller cottage developments may utilize driveway access for common open space.
- Minimum landscaping and maximum hard surface requirements for open space
Cottages would not be subject to density limits, instead, floor area ratio (FAR) would control. This means that how many cottages you can build on a property is not restricted by the 4- or 6-unit maximum. Instead, the total amount of building floor area you can construct is governed by FAR -- a zoning tool that regulates the total square footage of buildings relative to the size of the lot.
With a FAR of 0.9: 5 cottages (at 1,750 sq ft each) can be built on a 10,000 sq ft lot. This offers greater flexibility for cottage development, allowing a property owner to maximize housing units while keeping building bulk in check.
19. What are the proposed parking requirements and how do those differ from the minimum required by state law?
State law sets a minimum parking requirement based on lot size. For lots 6,000 square feet or smaller, the parking requirement is 1 stall per unit. For lots larger than 6,000 square feet the minimum parking required is 2 stalls per unit. The middle housing code update proposes 1 stall per unit, regardless of the lot size.
20. What are the proposed requirements for courtyard apartments?
Courtyard buildings would be subject to the following:
- Building shall be in an L- or U-shaped configuration
- There shall be a central courtyard area accessible by all units
- Minimum landscaping and maximum hard surface requirements for courtyard
21. What is the maximum number of stories for middle housing?
The maximum height limit for middle housing is 38 feet or three stories.
22. What is the impact on infrastructure?
Any time a new development application is received by the city, an applicant must show that either the existing infrastructure can support the proposal or show how they are improving infrastructure in order to be able to support the proposal. In the event that existing infrastructure – such as water, sewer, or transportation – cannot support a proposed middle housing development on a site, the developer is responsible for funding the necessary improvements to support the project. These improvements made at the time of development can include upgrades to water and sewer mains, frontage improvements that include sidewalks and street trees, undergrounding of any existing overhead utilities like power lines, and others.
While the city does work to upgrade utilities over time, the timing and projects for city-funded infrastructure improvements are developed through the utilities planning team. However, this process takes time and occurs in the areas that have been planned for in specific planning windows. Infrastructure improvements are often very costly, meaning it is likely that many smaller infill projects may not be feasible if extensive infrastructure requirements would be needed in order for the project to be built. These required infrastructure improvements are one of the very likely feasibility limitations on middle housing development that will be seen in the city.
23. Has middle housing been considered in planning for infrastructure?
Yes, middle housing has been considered in infrastructure planning as part of Bellevue’s Comprehensive Plan update. Under the Washington State Growth Management Act, the city is required to periodically update its Comprehensive Plan to reflect 20-year housing and job growth targets. For this update, adopted by the city council in October 2024, this included identifying where new housing types—such as middle housing—could be located.
As part of the Comprehensive Plan update, the Transportation, Utilities and Capital Facilities elements were revised. More detailed functional plans—which translate broad Comprehensive Plan goals and policies into specific capital projects, design standards, and funding strategies—will be updated in alignment with the latest Comprehensive Plan to support the planned growth.
Additionally, middle housing was specifically analyzed through the Final Environmental Impact Statement (FEIS) completed as part of the Comprehensive Plan update. The FEIS examined several growth scenarios. The preferred growth alternative included middle housing in residential areas and analyzed a potential housing capacity of 152,000 units—well above the anticipated housing target of 35,000 new units by 2044 and well beyond what we expect this LUCA to enable in the next 20 years. Importantly, the FEIS concluded that this level of growth would not cause significant adverse impacts to key infrastructure systems like utilities, schools, police, or fire services. Some unavoidable impacts were identified for transportation, but these occurred under all scenarios — including no change to current policy.
In short, middle housing has been thoughtfully incorporated into both land use and infrastructure planning to ensure Bellevue grows responsibly.
24. How is Bellevue's planned housing growth distributed across the city, and what role does middle housing paly in accommodating growth in areas outside of the mixed-use centers, particularly in single-family neighborhoods?
Bellevue’s planned housing growth is strategically distributed across the city to support both urban density and neighborhood livability. A significant portion of this growth is focused in mixed-use centers, such as Downtown, BelRed and Eastgate, which are well-served by transit and infrastructure. These areas are designed to absorb much of the city’s new development with high-density housing, jobs, and amenities.
In addition to these areas, approximately 2,400 housing units are planned for neighborhoods outside of the mixed-use centers. This growth will primarily be accommodated through middle housing, such as duplexes, triplexes, fourplexes, townhomes and cottage housing, within neighborhoods that have traditionally consisted of single-family homes.
Figure LU-2 of the recently adopted Comprehensive Plan illustrates how this planned growth is distributed by neighborhood for the period of 2019 to 2044, providing a clear picture of how both mixed-use centers and residential neighborhoods will evolve over time.
25. What is co-living housing? How does it relate to middle housing?
Under state law, adopted under HB 1998, co-living housing is defined as a residential development consisting of individually rented, lockable sleeping units that include living and sleeping space.
State law requires that we adopt regulations to allow co-living housing as a permitted use on any lot that allows at least six units, including lots zoned for mixed-use development. Any lot that permits six units by-right (as in not as a bonus for providing affordable housing or additional units allowed with a fee), must also allow co-living housing. The current middle housing proposal does not include provisions for co-living housing. Co-living housing regulations must be adopted by the end of 2025.
The project to adopt code to comply with HB 1998 will be initiated later this year and reviewed through a separate process.
26. What is lot splitting? How does it relate to middle housing?
HB 1096, passed in April 2025, requires cities to provide a streamlined administrative process to allow a single residential lot to be split into two residential lots. The two lots resulting from the split must still conform to cities’ minimum size and development standards in order to be eligible for this process. If the resulting two lots are still large, they cannot be split again through the same process, even if dimensional standards are met. As a result, this process only serves to provide a simpler process for uncomplicated lot splits. The process is not intended to provide a “loophole” to provide more housing density than would otherwise be possible.
To comply with this state legislation, the Development Services Department will draft a land use code amendment (LUCA) in 2026 to allow lot splitting in accordance with HB 1096. This LUCA will ensure that lot splitting does not increase the number of allowable dwelling units.
27. What is a Planned Unit Development (PUD), how does it relate to middle housing under the current code update?
A Planned Unit Development (PUD) is a zoning tool that allows denser housing by clustering homes to preserve open space and natural features. This process is most often used in areas with environmental constraints. Historically, the PUD process was one of the few ways that properties zoned for single-family housing could be redeveloped into multifamily housing.
Under the current middle housing code update, the PUD process remains unchanged and would be available for middle housing projects like duplexes, triplexes, and cottage clusters.
28. What are the potential property tax impacts of allowing up to four housing units per lot in Bellevue, and how can I learn more about King County's property tax assessment process?
Under Washington State law, Bellevue can increase total property tax revenue from existing properties by only 1 percent annually without voter approval. Property taxes are generally calculated for each of the levies as:
Tax = (Assessed Value / 1,000) × Tax Rate
In each case, the jurisdiction levies an amount per their legal authority, which is a dollar amount (example: $5,000,000). The Assessor then looks at the total assessed value of the properties in the legal area of that levy and calculates the rate per $1,000 as a relative share of the total assessed value.
In practical sense what that means is that while allowing four units per lot may increase assessed values due to greater redevelopment potential or new construction, if all of the properties in an area are increasing in value – then the rate per $1,000 goes down. So, this shift does not automatically lead to higher taxes for existing homeowners. While counter-intuitive, as neighborhood assessed values rises, the tax rate frequently decreases.
For more information on assessments and tax calculations, contact the King County Assessor’s Office at levyadmin@kingcounty.gov.
29. What public engagement has the city done to-date on middle housing?
Outreach for this project included a variety of formats and events, beginning with engagement efforts tied to the recently adopted update of the Comprehensive Plan. These efforts reached over 7,000 individuals through 78 events.
Key engagement work is summarized in publicly available documents, including a middle housing questionnaire from November 2022, a June 2023 engagement report compiled by Eastside Housing for All in collaboration with partner cities and A Regional Coalition for Housing (ARCH), and a statistically valid survey conducted as a part of the June 2023 engagement report.
Building on outreach for the Comprehensive Plan, LUCA engagement aimed to inform the public and gather feedback on proposed increases in housing density in key areas. Staff hosted six public information sessions—two in person and four online. The first round drew approximately 250 attendees, while the second round engaged about 175 participants.
Additional online engagement took place during the winter through an interactive StoryMap. This tool featured web maps highlighting potential density areas along with images illustrating various types of middle housing. The StoryMap also included a detailed questionnaire, which was available both online and in paper format at the first in-person event. The questionnaire received around 60 online responses and 12 paper submissions. While most participants supported increasing middle housing density in many areas, perspectives varied across respondents.
These materials are available on the Middle Housing Code Amendments project webpage.
30. How can I provide input on middle housing code updates in Bellevue?
Public input is always welcome. The middle housing code amendments are currently under discussion with the city council. If you would like to provide feedback or share any comments, please submit them directly to the council for consideration. Council can be reached by email at Council@BellevueWA.gov.