Eugene, OR Accessory Structures: ADU Rules (2026)
ADU rules in Eugene, OR, also called accessory dwelling unit regulations or granny flat ordinances, cover setbacks, owner-occupancy, parking, and permit requirements.
Key Facts
- Max attached ADU size
- 10% of lot or 800 sq ft, smaller controls
- Interior setback (near front)
- 5 feet minimum
- Detached ADU storage exclusion
- 300-800 sq ft unheated space excluded
- Minimum pedestrian walkway
- 3 feet wide, hard-surfaced
- Governing section
- EC 9.2751(17)
- Violation penalty
- up to $1,000/day, EC 9.0275
Summary
Eugene allows one accessory dwelling per lot in every residential zone under EC 9.2751(17), capping an attached ADU at 10 percent of the lot area or 800 square feet, whichever is smaller. Within 60 feet of the front lot line it needs only a 5-foot interior setback; height then follows the main house's limit under Table 9.2750.
(17) Accessory Dwellings. (a) General Standards for Attached Accessory Dwellings. Except as provided in subsection (c) below, attached accessory dwellings shall comply with all of the following: 1. Building Size. The total building square footage of an accessory dwelling shall not exceed 10 percent of the total lot area or 800 square feet, whichever is smaller. Total building square footage is measured at the exterior perimeter walls and is defined as all square footage inside of the dwelling, including, but not limited to hallways, entries, closets, utility rooms, stairways and bathrooms. 2. Building Height/Interior Setback. Except for accessory dwellings on flag lots (see EC 9.2775), the following standards apply: a. For any portion of an attached accessory dwelling located within 60 feet of a front lot line, interior yard setbacks shall be at least 5 feet, and maximum building height shall be limited to that of the main building as per Table 9.2750... (e) Enforcement. Failure to adhere to the standards required under this section shall constitute a violation subject to the enforcement provisions of section 9.0010 through 9.0280 General Administration.
Full Breakdown
2751(17) sets Eugene's standards for both attached and detached accessory dwellings across the R-1 through R-4 zones. An attached ADU's total square footage, measured at the exterior walls and counting every interior space including hallways, closets and stairways, can't exceed 10 percent of the lot or 800 square feet, whichever is smaller. 2750; farther back, the setback slopes upward past 15 feet of wall height toward a 25-foot maximum. 2751(17)(b): up to 800 square feet of unheated garage or storage space attached to a garage-top unit, or 300 square feet for any other detached ADU, doesn't count toward the size cap.
Detached units also need a hard-surfaced pedestrian walkway at least 3 feet wide from the street or alley, and a covered or roofed primary entrance at least 3 feet deep and wide. 2751(17)(c), including a bedroom cap tied to the primary dwelling's bedroom count and size limits of 600 or 800 square feet depending on lot size. 8030(34) to convert an existing building instead of building new.
Violations & Fines
EC 9.2751(17)(e) is explicit: failing to meet any accessory dwelling standard is a violation enforced under EC 9.0010 through 9.0280, Eugene's general land use enforcement chapter. That chapter's penalty section, EC 9.0275, sets a fine of up to $1,000 for each day the violation continues, confinement in jail up to 100 days, or both, in addition to stop-work or stop-use orders and withheld permits under EC 9.0270.
Frequently Asked Questions
How big can an ADU be in Eugene?
What setback does an ADU need from the property line?
Does a detached ADU above a garage count the garage space?
What happens if an ADU doesn't meet these standards?
Sources & Official References
Other rules in Eugene
How Eugene compares: Easiest Cities to Build an ADU·Compare Eugene to another location·View the Oregon accessory structures overview
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