ADU Rules in Salem, Oregon

Salem, Oregon's state capital and seat of Marion County, sits along the Willamette River in the heart of the Willamette Valley. As the home of the Oregon Legislature, Salem has a front-row seat to Oregon's continuing housing reform efforts. ADU development in Salem is governed by both the Salem Development Code and Oregon's landmark statewide housing laws.

Oregon Statewide ADU Law — Critical Context

Oregon HB 2001 (2019) requires cities with populations over 25,000 — Salem qualifies with over 175,000 residents — to allow middle housing (duplexes, triplexes, fourplexes, townhouses, and cottage clusters) in all areas zoned for residential use within their Urban Growth Boundary. Cities over 10,000 must permit duplexes in those zones. The law eliminated single-family-only zoning in Salem and requires the city to permit a range of housing types where previously only one house per lot was allowed.

Oregon has also constrained municipal authority over ADUs through prior statutes (notably SB 1051, 2017, which required cities over 2,500 to allow at least one ADU on lots with a single-family dwelling). Verify the current statutory floor and Salem's local implementation directly with the Salem Community Development Department.

What Salem Allows

Under the Salem Development Code and statewide law, the following ADU types are permitted in residential zones:

• Detached ADU: A standalone structure built on the same lot as the primary dwelling, separate from the main house.
• Attached ADU: An addition to the primary dwelling with its own entrance, kitchen, and bathroom facilities.
• Interior Conversion: Converting existing habitable space (basement, attic, or bonus rooms) within the primary structure into a separate dwelling unit.
• Garage Conversion: Converting an existing detached or attached garage into a full ADU, subject to meeting building code requirements for habitable space.

One ADU per single-family lot is permitted by right. Salem's updated code following HB 2001 may allow additional units on some lots.

Size and Setback Standards

Salem's Unified Development Code sets size, setback, and height standards for ADUs. Typical setback standards for detached ADUs include:

• Rear setback: Typically 5 feet minimum
• Side setback: Typically 5 feet minimum
• Height: Generally limited to 15–18 feet for detached ADUs

Existing legal nonconforming structures may be converted with their existing setbacks intact, even if they do not meet current standards for new construction.

Urban Growth Boundary

Salem maintains an Urban Growth Boundary coordinated with Marion County and overseen by the Oregon Department of Land Conservation and Development (DLCD). ADU permits are only issued for properties within the Salem city limits and UGB. Properties in Marion County outside the UGB are subject to county rural land use regulations, which do not permit ADUs on most parcels.

Seismic and Natural Hazard Considerations

Salem faces significant natural hazard considerations that affect ADU construction:

Cascadia Subduction Zone: The offshore Cascadia fault could produce a magnitude 9.0 or greater earthquake. Salem, in the Willamette Valley, would experience strong ground shaking. Oregon DOGAMI maps moderate to high liquefaction potential in low-lying areas near the Willamette River. New ADU construction must meet Oregon's current seismic building code standards.

Willamette River flooding: Portions of Salem near the Willamette River are in FEMA-designated flood hazard zones. ADU construction in these areas requires flood-resistant design, elevated foundations, or other FEMA-compliant measures.

Permit Process

1. Check your property's zoning and overlays using Salem's online mapping portal
2. Contact Salem Community Development for pre-application guidance on complex projects
3. Prepare architectural plans per Oregon Residential Specialty Code (ORSC)
4. Submit a building permit application to the Salem Building Division
5. Pay applicable fees (SDCs and permit fees per Salem Community Development schedule)
6. Undergo plan review and address any corrections
7. Schedule inspections at required stages (foundation, framing, electrical, final)

Contact: City of Salem Community Development — (503) 588-6173 — cityofsalem.net

Disclaimer

ADU regulations in Salem are subject to change as Oregon continues to implement and refine housing reform legislation. Always verify current requirements directly with the City of Salem Community Development Department. This page is for informational purposes only and does not constitute legal or planning advice.