Tigard, OR Accessory Structures: ADU Rules (2026)
ADU rules in Tigard, OR, also called accessory dwelling unit regulations or granny flat ordinances, cover setbacks, owner-occupancy, parking, and permit requirements.
Key Facts
- Detached ADUs per lot
- One maximum (§ 18.220.040.A)
- Maximum size
- 800 square feet
- Maximum height
- 25 feet
- Total units on lot
- Three maximum, including small form units
- Rear setback option
- Five feet if ADU is 15 feet or less in height
- Allowed zones
- RES-A through RES-D; not RES-E
- Added parking
- No additional off-street parking
Summary
In the City of Tigard, Oregon, a lot with small form residential development can add one detached accessory dwelling unit of up to 800 square feet and 25 feet in height. The unit cannot sit closer to the front property line than the primary dwelling, and the code adds no off-street parking requirement for it.
A. Unit count. A maximum of one detached accessory dwelling unit is allowed per lot. The total maximum number of dwelling units on a small form residential lot is three, including the units in the small form residential development. Detached accessory dwelling units are prohibited on lots with three small form residential dwelling units. B. Size. The maximum size of a detached accessory dwelling unit is 800 square feet. C. Height. The maximum height of a detached accessory dwelling unit is 25 feet. D. Setbacks. Detached accessory dwelling units must meet the setback standards for small form residential development in the applicable base zone, with the following exceptions: 1. Detached accessory dwelling units must be located no closer to a front property line than the primary dwelling, and 2. Detached accessory dwelling units may be located within five feet of the rear property line if the accessory dwelling unit is 15 feet or less in height.
Full Breakdown
Chapter 18.220 of the Tigard Municipal Code (Community Development Code) governs detached accessory dwelling units in the City of Tigard, Washington County, Oregon. Section 18.220.040 sets the standards as clear and objective numbers rather than a discretionary review. Section 18.220.040.A caps the count at one detached ADU per lot, and the total maximum number of dwelling units on a small form residential lot is three, including the units in the small form residential development. A lot that already has three small form residential dwelling units cannot add a detached ADU. Section 18.220.040.B limits size to 800 square feet, and Section 18.220.040.C limits height to 25 feet. Under Section 18.40.120.A, the square footage of a garage attached to a detached ADU counts toward the ADU's square footage, and under Section 18.40.120.B height is measured with the Section 18.40.040 method.
Setbacks follow the small form residential setbacks in the applicable base zone, with two exceptions in Section 18.220.040.D: 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 if it is 15 feet or less in height. Section 18.220.040.E sends lot coverage to Chapter 18.290, and Section 18.220.040.F applies the same window and street-facing facade standards that Chapter 18.290 sets for small form residential development, which include a 12 percent window or door minimum on street-facing facades in Section 18.290.040.D.
Where the housing type is allowed matters. Table 18.110.3 shows accessory dwelling units as allowed in RES-A, RES-B, RES-C and RES-D and prohibited in RES-E. Section 18.220.020.B prohibits detached ADUs as an accessory housing type to apartment, cottage cluster, courtyard unit, quad and rowhouse development. Section 18.220.010 describes these units as subordinate to the primary use, able to share utilities where the service provider allows, and requiring no additional off-street parking. Attached ADUs are treated as small form residential development under Chapter 18.290, not under this chapter.
Violations & Fines
Section 18.220.030 requires every ADU 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 of the nuisance title declares violations of other titles of the code to be public nuisances unless another title characterizes them differently. Section 6.01.040 makes a violation of Title 6 a Class 1 civil infraction under Chapter 1.16, with each day a separate infraction, and Section 1.16.640.A.1 caps a Class 1 penalty at an amount not to exceed $250 per day.
Frequently Asked Questions
How big can a detached ADU be in the City of Tigard?
Can a Tigard lot have more than one detached ADU?
Where on the lot can the ADU sit?
Does an ADU in Tigard need extra parking?
Sources & Official References
Other rules in Tigard
How Tigard compares: Easiest Cities to Build an ADU·Compare Tigard to another location·View the Oregon accessory structures overview
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ADU Rules in Nearby Cities
How other cities in Washington County handle adu rules.