Middle Housing: What Does It Mean for Trees?

More duplexes, triplexes, cottage clusters, and townhomes will be appearing in our established neighborhoods as Oregon's middle housing reforms take effect. A single house may be replaced by a duplex. A large lot may become a cluster of cottages. Townhomes will be built where one home once stood.

These changes are part of Oregon's middle housing reforms, intended to address the state's housing shortage by allowing more homes in neighborhoods that were once reserved primarily for single-family houses.

More housing options can help our communities grow and become more affordable. But as redevelopment accelerates across Washington County, many

residents are also raising important questions. What happens to trees, neighborhood involvement, and environmental equity?

What Is Middle Housing?

In 2019, Oregon became the first state in the nation to require many cities to allow "middle housing" in areas previously zoned primarily for single-family homes. House Bill 2001 opened the door for duplexes, triplexes, fourplexes, cottage clusters, and townhomes in many residential neighborhoods.

The goal was straightforward: create more housing options without relying solely on large apartment buildings or suburban expansion.

Why Trees Are Often the First Casualty

Many middle housing projects are built on relatively small parcels where every square foot matters. Mature trees require space—both above and below ground. When a lot that once held a single home is redeveloped to accommodate multiple units, space becomes scarce. New homes need foundations, driveways, parking areas, utility connections, sidewalks, patios, and stormwater facilities. Large existing trees can quickly become obstacles.

Developers often face a choice between preserving mature trees and maximizing the number or size of housing units. Because land costs are high, economic pressures frequently favor construction over retaining trees that took decades to grow. The result can be neighborhoods with less room for large canopy trees, fewer opportunities for future tree planting, and a gradual decline in overall tree cover.

How Much Input Do Neighbors Have?

One of the biggest surprises for many residents is how little public process is involved. Unlike major developments that often involve public hearings or neighborhood meetings, many middle housing projects are approved through an administrative process if they meet objective development standards. That means neighbors may not learn about a project until demolition or construction begins.

Middle housing supporters argue that streamlined approval reduces delays, lowers housing costs, and prevents projects from being blocked by neighborhood opposition. Critics counter that the lack of public notice can leave residents feeling excluded from decisions that affect neighborhood character, stormwater management, parking, and tree canopy.

For homeowners accustomed to participating in land-use decisions, this can feel like a significant shift. The concern is not necessarily opposition to new housing. Many residents support creating more housing choices for young families, older adults, and people who want to live closer to jobs and services. Instead, the concern is whether current regulations adequately protect the community benefits that mature trees provide.

Keep in mind that Oregon's housing laws were designed to prevent local regulations from becoming barriers to housing construction. As a result, local governments often have very little flexibility. As a result, even communities that value their urban forests can find themselves struggling to preserve mature trees during redevelopment.

Can We Have More Housing and More Trees?

Yes—but only if trees are treated as essential infrastructure rather than decorative landscaping. To be effective, we need to begin regarding mature trees as high-value elements, not as obstacles.

Requiring early communication and guidance, before building plans become firm or permits have been issued could be key to saving trees. Effective tree preservation should begin at the conceptual stage of building design, at a moment when the developers and architects have a vision, but are not locked into specifics.

Developers are key influencers of tree canopy, and development is complex as developers balance investor goals, regulations in different jurisdictions, and multi-year timelines.

The Urban Forester with the City of Hillsboro, Lisa Renee Wilson, shared with Treekeepers that she is pondering how to offer incentives to developers for retaining existing trees. Incentives might include allowing developers to increase the number of units or total building volume in exchange for preserving significant trees or enhancing the overall landscape. Another possibility would be to cluster buildings or decrease the required distance between structures and property lines to provide more flexibility in site design, saving buildable area.

Financial incentives could offer mitigation credits, allowing preserved trees to count toward local landscaping or tree-replacement requirements. Instead of paying hefty mitigation fees for removing trees, developers save money by maintaining what is already there.

And of course, championing the development and implementation of tree codes that prioritize trees has always been our Treekeepers vision.

None of these strategies are simple. Housing affordability, climate resilience, and tree preservation all compete for limited space and resources.

What Can You Do?

Become informed about what nearby middle-housing (or other) projects are in the works. Washington County tracks all active land use applications on its public portal. Visit the Washington County Development Applications Under Review page, then type the term "middle" or "cottage cluster" into the search bar to filter for related projects.

Because middle housing projects are just working their way through the permitting process, current projects are still under construction, not finished products. Two projects in the works are:

●  McDaniel Village: This 17-lot middle housing development on NW McDaniel Road (just east of NW 119th) was officially approved with required conditions like street widening and new sidewalks in early 2026.

●  Taylor Street Middle Housing: A newly proposed land division specifically targeting middle housing lots is moving through its initial review phases as of mid-2026.

Help us advocate for tree ordinance changes. Sign our petition [link] join with like-minded tree advocates in a monthly meeting [link, rewrite], and [what else?]

Looking Ahead

Washington County is expected to continue growing, and middle housing will remain an important part of that growth. The challenge is ensuring that growth does not come at the expense of the urban forest that makes our communities healthier, cooler, and more livable.

Residents, planners, and elected officials are grappling with housing shortages and climate challenges simultaneously. Mature trees take decades to grow but can disappear in a single day. Once lost, the cooling shade, habitat, and environmental benefits they provide may take generations to replace.

Now is the time to ask whether current policies are creating neighborhoods that will remain shaded, healthy, and resilient for future generations. The choices made today will determine not only how many homes Washington County builds, but also how much tree canopy remains for those who call these neighborhoods home.

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Further Reading:

● Greening development: Reducing urban tree canopy loss through incentives, Elise M. Willis et al, Urban Forestry & Urban Greening 9, 2024.

●  Developer Perspectives on Incentives to Save Trees, Vibrant Cities Lab, 2025.

●  Working proactively with developers to preserve urban trees, Bill Ames and Shane Dewald, Science Direct, April 2003.

●  Early Community Outreach for Design Review, Seattle Office of Planning & Community Development

Washington County Resources:

●  Search Development Applications Under Review

●  Visit the county's official Middle Housing / HB 2001 page.

●  If you want to know about proposed housing types or specific development processes for a particular neighborhood, contact Washington County Current Planning staff. Email lutdev@washingtoncountyor.gov or phone 503-846-8761