Tigard, OR Accessory Structures: Garage Conversions (2026)
Garage conversion rules in Tigard, OR, sometimes called garage-to-ADU or accessory living unit conversions, govern permits, ceiling height, egress, and parking replacement.
Key Facts
- Conversion allowed from
- Existing accessory structures such as detached garages
- Square footage cap
- 800 square feet for the entire structure
- Maximum height
- 25 feet, combined for a unit above a garage
- Rear setback option
- Five feet if 15 feet or less in height
- Extra parking
- No additional off-street parking
- Governing section
- § 18.220.040.G
Summary
In the City of Tigard, Oregon, a detached garage can be turned into a detached accessory dwelling unit, but the 800 square foot cap applies to the entire structure, including any part that stays a garage. A unit built above a garage must keep the combined height within the ADU maximum.
C. They may be newly constructed or converted from existing dwelling spaces or accessory structures; ... E. The units require no additional off-street parking. ... G. Accessory structure additions and conversions. Detached accessory dwelling units may be added to or created from existing accessory structures such as detached garages. The maximum square footage requirements for the accessory dwelling unit apply to the entire structure, including any portion that remains in use as an accessory structure.
Full Breakdown
The City of Tigard, Washington County, Oregon, handles garage conversion to living space through its accessory dwelling unit chapter. Section 18.220.010.C says detached ADUs can be newly constructed or converted from existing dwelling spaces or accessory structures. Section 18.220.040.G is the operative rule: detached accessory dwelling units can be added to or created from existing accessory structures such as detached garages, and the maximum square footage requirements for the ADU apply to the entire structure, including any portion that remains in use as an accessory structure. Because Section 18.220.040.B sets the maximum size of a detached ADU at 800 square feet, a garage that stays partly in use as a garage still has the whole building measured against that limit.
Height gets a second check. Section 18.40.120.B provides that if an accessory dwelling unit is located above a detached accessory structure, such as a garage, the combined height of the accessory structure and the accessory dwelling unit must not exceed the maximum height for a detached accessory dwelling unit, which Section 18.220.040.C sets at 25 feet. Section 18.40.120.A adds that the square footage of a garage attached to a detached ADU is included in the ADU's square footage.
The converted building still has to meet the rest of Section 18.220.040: the ADU must be located no closer to a front property line than the primary dwelling, and it can sit within five feet of the rear property line only if it is 15 feet or less in height. Lot coverage and window and street-facing facade standards come from Chapter 18.290, Small Form Residential. Section 18.220.010.E states that the units require no additional off-street parking. The one-per-lot limit in Section 18.220.040.A applies, and Section 18.220.020.B prohibits detached ADUs on lots with apartment, cottage cluster, courtyard unit, quad or rowhouse development. Table 18.110.3 allows ADUs in RES-A through RES-D and prohibits them in RES-E. The standard quoted here covers detached garages; attached ADUs fall under Chapter 18.290.
Violations & Fines
Section 18.220.030 requires each accessory dwelling unit to comply with Section 18.220.040 and all other applicable standards of the Community Development Code. In the City of Tigard, Section 6.01.030.B declares violations of other titles of the code to be public nuisances unless another title characterizes them differently, and Section 6.01.040 makes a Title 6 violation a Class 1 civil infraction with each day a separate infraction. Section 1.16.640.A.1 sets the Class 1 penalty at an amount not to exceed $250 per day.
Frequently Asked Questions
Can I convert a detached garage into an ADU in the City of Tigard?
Does a garage that stays in use count toward the size limit?
What if the ADU sits above the garage?
Does the conversion trigger a new parking requirement?
Sources & Official References
Other rules in Tigard
Compare Tigard to another location·View the Oregon accessory structures overview
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Garage Conversions in Nearby Cities
How other cities in Washington County handle garage conversions.