Accessory Structures in Hillsboro, OR (2026)
3 verified accessory structures rules for Hillsboro, Oregon, sourced directly from the municipal code and official government pages.
Verified from official government sources
ADU Rules
Hillsboro allows one accessory dwelling unit per single detached dwelling or townhouse, sized between 250 and 750 square feet, as a use permitted by right under the Community Development Code.
Hillsboro ADU Zoning Standards
Some RestrictionsHillsboro Community Development Code § 12.40.100.D.2, D.5.a
2.Eligibility and Number. A maximum of one ADU is allowed per legal, single detached dwelling or townhouse. If the proposed ADU is on a child lot which resulted from a Middle Housing Land Division, the housing on the lot must be at or above the minimum density for the zone.3.Location. An ADU shall be located on the same lot as the primary single detached dwelling or townhouse.4.Parking. No off-...
Shed & Carport Rules
Backyard sheds, detached garages and other accessory structures in Hillsboro follow Community Development Code § 12.40.104: they generally must meet the base zone's setback standards, but a reduced 3-foot side and rear setback is available for structures 450 square feet or smaller, one story tall, with eaves at least 2 feet from the property line, placed behind the home's front building plane, and separated from other buildings by 6 feet.
Hillsboro Shed & Garage Setback Rules
Some RestrictionsHillsboro Community Development Code § 12.40.104(A), (B)(1)-(4)
A.Characteristics. Accessory structures are defined in Section 12.01.500, and are used by the residents, customers, or employees of the primary structure(s) on the site. Examples of residential accessory structures include playhouses, storage sheds, detached garages or workshops, and greenhouses. ... B.Standards.1.Except as provided in paragraph 2., below, accessory structures must conform to t...
Garage Conversions
Hillsboro allows homeowners to convert an existing garage into an accessory dwelling unit (ADU) under Community Development Code § 12.40.100(C)(1), one of three recognized ways to create an ADU alongside adding new floor area or building a detached unit. The converted space must meet the same occupancy, floor-area, parking, height and setback standards in Subsection D that apply to every ADU, and needs approval under § 12.80.170 before construction.
Hillsboro Garage-to-ADU Conversion Rules
Some RestrictionsHillsboro Community Development Code § 12.40.100(C)(1), (D)(5)
C.Creation of an ADU. An ADU may be created as follows:1.Converting existing floor area in an existing dwelling or accessory structure such as a garage;2.Adding new floor area to an existing dwelling or accessory structure; or3.Constructing a separate unit on a lot with a new or existing primary dwelling. ... 5.a.Except as provided in subparagraph c. below, an ADU shall be at least 250 square f...
Looking for Washington County county-wide rules?
County ordinances apply to unincorporated areas and may supplement Hillsboro city rules.
Accessory Structures in Washington County →