Tigard, OR Accessory Structures: Garage Conversions (2026)

Tigard Community Development Code Chapter 18.220 expressly contemplates the conversion of existing accessory structures, including detached garages, into accessory dwelling units. Under CDC 18.220, a detached ADU created from an existing accessory structure must comply with the same 800-square-foot maximum size, 25-foot maximum height, and one-detached-ADU-per-lot limit as a new-construction ADU. The 800-square-foot cap applies to the entire structure, including any portion that remains in non-ADU accessory use such as continued garage parking. Setbacks, lot coverage, window standards, and street-facing facade standards under CDC Chapter 18.290 (Small Form Residential) apply to the converted structure. Tigard does not impose an owner-occupancy requirement and does not require additional off-street parking when an ADU is created, consistent with Oregon SB 1051 (2017) and HB 2001 (2019). Where an attached garage is converted into ADU or habitable space, the project is treated as small form residential development under CDC Chapter 18.290 and must meet the principal-structure setbacks of the underlying residential zone under CDC Chapter 18.110 (Residential Zones). All garage-to-habitable-space conversions, whether attached or detached, require building, electrical, plumbing, and mechanical permits from the Tigard Building Division and must comply with the Oregon Residential Specialty Code adopted under ORS 455.020, including egress, ceiling-height, light-and-ventilation, and energy-code requirements. System Development Charges (SDCs) apply to new dwelling units; Tigard has adopted reduced SDCs for ADUs as part of its 2018 housing-options reforms.