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Planning and Sustainability

Innovation. Collaboration. Practical Solutions.

Phone: 503-823-7700

Curbside Hotline: 503-823-7202

1900 SW 4th Ave, Suite 7100, Portland, OR 97201

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About the Project

arborThis project addresses the City’s Zoning Code regulations for accessory structures. Accessory structures are of secondary importance on a site and include buildings such as garages, storage sheds, home offices and accessory dwelling units (ADUs). They also include residential decks, trellises, ADA ramps and mechanical equipment.

Portlanders are building and using accessory structures in new and innovative ways. Working at home has resulted in more backyard work spaces. Producing food at home necessitates the construction of greenhouses, chicken coops and animal shelters. And the increased popularity of ADUs has created new backyard living spaces and/or income-producing rental units.

Current rules for accessory structures have been amended over the years, resulting in complex regulations that treat similar structures differently. It is especially confusing for those wishing to convert one type of accessory structure to another, or build a structure that serves two purposes.

As the number of accessory structures has increased, concerns have also increased. Surrounding neighbors have focused on issues of noise, privacy and solar access. Architects, builders and property owners have been frustrated with the lack of flexibility and clarity of regulations.

Project Outcome

This project is exploring options to streamline the regulations for accessory structures, with an aim to create regulations that emphasize form (setbacks, height and bulk) over function (how the building is used). The focus of this project is on detached accessory structures associated with residential development. It will also address the special ADU regulations.


Jan – April 2015: Focus Group Meetings

May 2015: Publish Discussion Draft

May – June 2015: Public Review of Discussion Draft

Fall 2015: Planning and Sustainability Commission Public Hearing

Winter 2015: City Council Public Hearing

For more information

Accessory Structures

There are four categories of accessory structures being discussed during this project: 

detached garages1. Detached Garages
Garages are structures that provide shelter for a vehicle. Carports are also included in this category. Current standards for garages include exemptions to side and rear setbacks for small, single-story garages that are set back from the street. These setback exemptions create regulatory issues when garages are altered or expanded to incorporate other activities.

Detached ADU2. Detached Accessory Dwelling Units (ADUs)
Accessory dwelling units are secondary residential units built on a lot with a house or attached house. In addition to the standard regulations for accessory structures, ADUs have their own chapter of regulations. The special regulations that govern ADUs have been cited as a barrier to developing lower cost standardized plans, as well as restricting the use of innovative materials.

Other Covered Structures3. Other Covered Structures
Other covered accessory structures include storage sheds, offices, gazebos, water collection cisterns, greenhouses and chicken coops. These structures cannot be located within the setback unless their height is limited to six feet. There have been concerns with detached accessory structures that are built taller than the main house.

Mechanical Equipment4. Miscellaneous Accessory Structures
In addition to covered accessory structures, there are also miscellaneous uncovered accessory structures that the Zoning Code regulates to differing standards.

These structures are listed in the following categories:

  • Vertical Structures. Vertical structures include such outdoor elements as flag poles, trellises, arbors, play structures, antennas, satellite receiving dishes, and lamp posts.
  • Uncovered Horizontal Structures. Horizontal structures include such elements as decks, stairways, entry bridges, ADA ramps, pools, tennis courts and hot tubs that are not covered or enclosed. 
  • Mechanical Equipment. Mechanical equipment includes installations such as heating and air conditioning systems, radon filters and other equipment used in conjunction with the building. They are either mounted to the building or placed on the ground next to the building. Recent technological improvements have reduced the noise impacts of the equipment.