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 lets a homeowner convert an existing garage into an accessory dwelling unit under Community Development Code § 12.40.100(C)(1). The unit must measure at least 250 and no more than 750 square feet, only one ADU is allowed per single detached dwelling or townhouse, and the city requires no off-street parking for the ADU itself. Zoning Review under Section 12.80.170 applies.
Hillsboro Garage Conversion to ADU Rules
Some RestrictionsHillsboro Community Development Code § 12.40.100(C)(1), (D)(5)
Converting existing floor area in an existing dwelling or accessory structure such as a garage; ... 5. Minimum and Maximum Floor Area. See Section 12.01.500 for information about how to measure floor area. Below are additional standards relative to floor area for ADUs. a. Except as provided in subparagraph c. below, an ADU shall be at least 250 square feet, but not more than 750 square feet in ...
Looking for Washington County county-wide rules?
County ordinances apply to unincorporated areas and may supplement Hillsboro city rules.
Accessory Structures in Washington County →