Hillsboro: City Floats Denser Apartment Zones, Two ADUs on Some Lots Before Thursday Open House
- Hillsboro planners are weighing code changes that could allow more homes on land already zoned for apartments.
- The ideas come from an Oct.
- The density idea covers six zones where apartments are allowed outright.
Hillsboro planners are weighing code changes that could allow more homes on land already zoned for apartments. Some homeowners could also build two accessory dwelling units, or ADUs, instead of one. Residents can ask questions Thursday, Oct. 22, from 6 to 7 p.m. in Room 113 of the Civic Center, 150 E Main St. Spanish translation will be available, says the city’s event listing.
The ideas come from an Oct. 7 memo by consultant DOWL. The Planning Commission discussed it at an Oct. 14 work session (pages 551 to 571 of the meeting packet). Nothing has been decided. The memo says each final density increase “needs to be determined,” and code drafting starts only after the city gives final direction.
More homes on apartment-zoned land
The density idea covers six zones where apartments are allowed outright. For each, the memo recommends a higher maximum density, measured in dwelling units per net acre (page 555).
| Zone | What the name means | Current max (units per net acre) | Recommended max | Increase (our calculation) |
|---|---|---|---|---|
| MR-1 | Multi-Dwelling Residential 1, lowest cap of the three MR zones | 16 | 25–30 | 56% to 88% |
| MR-2 | Multi-Dwelling Residential 2 | 21.25 | 30–35 | 41% to 65% |
| MR-3 | Multi-Dwelling Residential 3, highest cap of the three | 28.75 | 35–45 | 22% to 57% |
| SCR-DNC | Station Community Residential, Downtown Neighborhood Conservation, a zone for houses and plexes that also allows apartments | 14–23, depending on distance from light rail | 25 | 9% to 79% |
| SCR-MD | Station Community Residential, Medium Density | 23 | 30–35 | 30% to 52% |
| SCR-HD | Station Community Residential, High Density | 30 | 45–50 | 50% to 67% |
Our calculation: (recommended maximum minus current maximum) divided by current maximum, rounded to the nearest whole percent. For SCR-DNC, 9% compares 25 with the current top cap of 23, and 79% compares it with the lowest cap of 14.
Under the memo’s hybrid approach, developers could meet the cap by unit count or by floor area ratio. That ratio compares a building’s floor area with its lot size. The memo also suggests taller limits in three zones (page 557). MR-1 and SCR-DNC would go from 2½ stories to three, still capped at 35 feet. MR-3 could reach four stories without Planning Commission approval.
The memo raises open questions, too. Sewer, water and road capacity “may be insufficient” in some places where these zones sit, it says. It asks whether capacity studies should come first (page 556).
Room for a second ADU
House lots could change as well. The city’s online survey says the code now allows one ADU per property. Two, it says, might look like one unit in a basement or attic and one detached in the backyard.
The memo recommends allowing up to two ADUs on any lot with a single-detached house or townhouse (page 564). It would also let duplexes, triplexes and quadplexes be built as separate, detached buildings. Today an ADU cannot exceed 50 percent of the main home’s square footage, and the memo asks whether that should change.
The state law and the housing gap behind it
The memo names two goals: carry out the city’s housing plan and comply with recently adopted state laws. The project page says Phase 1 will carry out House Bill 2138 (2025). The page says that law requires cities to allow detached plexes.
The two-ADU idea traces to Hillsboro’s own Housing Production Strategy, the memo says. The city readopted that strategy on Dec. 2, 2025 (pages 551 and 552). The state Department of Land Conservation and Development (DLCD) had sent it back in 2024.
The strategy rests on the city’s 2023 Housing Needs Analysis. It found Hillsboro needs 14,046 new homes over 20 years, the memo says (page 552). That total includes 5,259 homes affordable to households earning less than 80 percent of median family income. The city hired DOWL with a DLCD Housing Planning Assistance Grant, according to the staff report.
Phase 1 also covers smaller changes. The memo suggests easing ground-floor commercial rules in some mixed-use, urban center and station-area commercial zones (page 559). It would also add single-room occupancy housing: at least four lockable units that share kitchens or bathrooms. State law requires residential zones to allow them, the memo says (page 567).
Two timelines, and how to weigh in
The city’s documents give different end dates. Its project page, last updated Oct. 13, lists a Planning Commission hearing in April 2027 and council adoption in May 2027. The DOWL memo lists a commission hearing on May 12, 2027, and final council adoption on June 15 (page 571). Neither document explains the gap.
Before the hearings, the memo lists a council work session on Dec. 1 and a second commission work session on Feb. 10, 2027. Work sessions do not take public testimony, the Oct. 14 agenda notes. A second phase, to streamline design standards and simplify the code, would run from 2027 to 2030, the project page says.
For now, the event listing points residents to the open house and an online survey. The Phase 1 survey asks four open questions. They cover density, apartments in commercial areas, ground-floor shops and two ADUs.
The project page lists three staff members under “Who’s Listening.” They are Rachel Marble, code and policy manager; Tamara Edwards, long-range planner; and Cindy Dauer, public information officer. The Planning Division’s phone number, on the staff report letterhead, is 503-681-6153.
As of the morning of Oct. 19, the survey showed 15 responses.
