ADU Rules: Gresham vs Troutdale
How do adu rules rules compare between Gresham, OR and Troutdale, OR?
Gresham and Troutdale have similar restriction levels.
Gresham, OR
Multnomah County
Gresham allows accessory dwelling units (ADUs) in residential zones per Oregon state law (HB 2001). One ADU is permitted per lot. ADUs must meet development code standards for size, setbacks, and parking.
View full Gresham rules →Troutdale, OR
Multnomah County
TDC 8.170 allows up to two accessory dwelling units per legal primary single-family dwelling — one must be an interior conversion or attached, and the other detached. Each ADU is capped at 800 square feet or 50% of the primary dwelling, whichever is smaller.
View full Troutdale rules →Key Facts Comparison
| Fact | Gresham | Troutdale |
|---|---|---|
| Allowed | One per single-family lot | - |
| Size | Up to 800 sq ft typically | - |
| Types | Attached or detached | - |
| State Law | Oregon HB 2001 | - |
| Code Section | - | TDC 8.170 |
| Max ADUs Per Lot | - | 2 (1 attached, 1 detached) |
| Max Size | - | 800 sq ft or 50% |
| Setbacks | - | Per underlying zone |
| Review | - | Type I attached; Type II detached |
Highlighted rows indicate differences between cities.
Gresham FAQ
Can I build an ADU in Gresham?
Yes. Oregon law requires cities to allow one ADU per single-family lot. Building permits are required.
How big can an ADU be in Gresham?
Typically up to 800 square feet, subject to the Development Code standards for the zone.
Troutdale FAQ
How many ADUs can I build in Troutdale?
TDC 8.170(C) allows two: one attached or interior conversion, and one detached. Both ADUs on the same lot cannot be of the same type.
How big can my ADU be?
TDC 8.170(D)(2) caps each ADU at 800 square feet or 50% of the primary dwelling's floor area, whichever is smaller. Interior conversions may occupy a full floor.
Do I need to live on-site?
TDC 8.170 does not impose owner-occupancy, consistent with Oregon SB 1051. Standard land use approval and building permits still apply.
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