Building an ADU in Eugene, Oregon
City code and Oregon law · Last reviewed October 9, 2026
Eugene allows one accessory dwelling unit (ADU) for each detached single-unit home in its R-1 through R-4 residential zones. Under the city's ADU standards, an ADU can be up to 800 square feet or 10 percent of the lot area, whichever is smaller, with 5-foot interior setbacks and, in most cases, a 25-foot height cap. The city runs a Pre-Approved ADU Program with one free plan and twelve plans for $500 each. [1][2][3]
| ADUs per lot | One for each detached single-unit home on the lot, in the R-1, R-2, R-3 and R-4 zones [1] |
|---|---|
| Max size | 800 sq ft or 10% of the lot area, whichever is smaller (measured at the exterior walls) [2][4] |
| Extra unheated space (detached ADU) | Up to 300 sq ft of unheated garage or storage not counted; up to 800 sq ft if the ADU is above a garage [2] |
| Interior setbacks | 5 ft, with a sloped setback starting 15 ft above grade [2][4] |
| Max height | 25 ft (or the zone's limit for attached ADUs within 60 ft of the front lot line) [2] |
| Parking | Cities can't require additional off-street parking (state law) [5] |
| Owner occupancy | Can't be required (state law) [5] |
| System development charges | Charged on a new ADU; pay at permit pickup or by contract over up to 10 years [4] |
| Pre-approved plans | One free city plan (The Joel, 576 sq ft) and twelve plans at $500 each; no plan review fee [3][6][7] |
| Special areas | Amazon, Fairmount and South University neighborhoods: 600 sq ft on lots under 9,000 sq ft and bedroom limits [2][4] |
On this page
What you can build in Eugene
Eugene's code says "One accessory dwelling is allowed for each detached single-unit dwelling on the same lot," and the R-1, R-2, R-3 and R-4 zones all permit ADUs. An ADU may be attached to or detached from the main home and includes space for living, sleeping, cooking and a bathroom. To count as attached, the ADU and the house must share at least 8 feet of common wall or ceiling.
The detailed standards are in Eugene Code 9.2751(17). Oregon law requires Eugene to allow at least one ADU for each detached single-unit dwelling, subject to "reasonable local regulations relating to siting and design." See our Oregon ADU law page for the state rules. [1][2][4][5]
Size, height and setbacks
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." Square footage is measured at the exterior walls and includes hallways, closets, stairs and bathrooms. A detached ADU can also have up to 300 square feet of attached unheated garage or storage space that doesn't count, or up to 800 square feet if the ADU sits above a garage.
Setbacks and height. Interior yard setbacks are at least 5 feet. For a detached ADU, and for any part of an attached ADU more than 60 feet back from the front lot line, the setback slopes inward starting 15 feet above grade, at a rate of 10 inches of height for every 12 inches away from the property line, to a maximum height of 25 feet. The slope doesn't apply along a lot line that abuts a public right-of-way or private street. An attached ADU within 60 feet of the front lot line can be as tall as the main house allows in that zone. ADUs above a garage or on sloped lots follow slightly different rules. Eaves and chimneys may project up to 2 feet into the setback.
Detached ADU extras. You need a hard-surface walkway at least 3 feet wide from the street or alley to the ADU's main entrance, and a covered entry at least 3 feet deep and wide. ADUs must also meet lot coverage, solar setback and utility undergrounding rules.
Amazon, Fairmount and South University neighborhoods. In the R-1 zone in these areas, an ADU can be 600 square feet on lots under 9,000 square feet and 800 square feet on larger lots. All roofed areas count toward lot coverage, and the ADU is limited to 2 bedrooms (1 bedroom if the main house has 4 or more). [2][4]
Parking and owner occupancy
Oregon law says reasonable siting and design rules for ADUs don't include "owner-occupancy requirements of either the primary or accessory structure or requirements to construct additional off-street parking." So you don't have to live on the property or add parking. Cities may still require owner occupancy or parking for ADUs used as vacation rentals. [5]
Fees and system development charges
"A new ADU will generate Systems Development Charges (SDCs)." They pay for roads, stormwater, wastewater and parks, and are due when you pick up your building permit. You can also put them on a contract and pay in installments over up to 10 years, at the prime rate plus 2 percent. Ask Public Works Engineering at 541-682-8400 for current SDC rates.
The Eugene Water & Electric Board (EWEB) charges its own water SDC; call EWEB at 541-484-2411. With a pre-approved plan, you skip plan review fees but still pay SDCs and building permit fees. For budgeting help, see our ADU cost guide. [3][4]
Pre-approved ADU plans
Eugene's Pre-Approved ADU Program offers detached ADU designs that have already been reviewed for the building code. The city lists twelve plans in its plans library for purchase at $500 each, bought directly from the designer, and one free plan from the city.
The free plan, The Joel, is a 576 square foot studio with a downloadable plan set that includes porch and roof options. You'll still need a site plan, and steep slopes, certain soils, two-story designs or tall walls may need extra engineering. When you apply, note in the project description that the plan is part of the pre-approved ADU program. [3][6][7]
Building code basics
The house and ADU must be separated for fire, either by 6 feet of open space between detached buildings or by 1-hour fire-rated walls or floors. Walls and floors between units need a sound rating of STC 45, and floors also IIC 45. Each unit's occupants need access to their own heating equipment and electrical panel. Depending on size, location and water supply, an ADU may need fire sprinklers; call Fire Prevention at 541-682-5411. [4]
Garage and other conversions
If an existing building can't meet the ADU size, height or setback standards, the city code lets you ask for an adjustment to convert it into an ADU. The code says those are the only ADU standards that can be adjusted, and that they can't be adjusted in the Amazon, Fairmount and South University neighborhoods.
Separately, a 2024 state law (SB 1537) requires cities to grant certain limited adjustments for new housing, including ADUs, such as side or rear setbacks reduced by up to 10 percent. See our Oregon ADU law page and ask Land Use staff whether it applies to your project. See our garage conversion guide for general steps. [2][8]
Check for code changes
Eugene's ADU handout is dated December 2021, and the code has been amended since. For example, the handout says the sloped setback doesn't apply along a lot line next to an alley, while the current code says it doesn't apply along a lot line abutting a public right-of-way or private street. Where they differ, follow the current code, and confirm the standards for your lot with Land Use staff at 541-682-8336 before you design. [2][3][4]
Permit steps in Eugene
Research your property
Use the city's Pre-Approved ADU Due Diligence Checklist to check your lot and costs. Ask Land Use staff at 541-682-8336 about setbacks, height and ADU standards. [3]
Choose a design
Pick a plan from the Pre-Approved ADU Plans Library, use the free Joel plan, or have a custom design drawn. [3][6]
Develop a site plan
Work with your designer on a site plan showing the ADU on your lot, so the city can review zoning, drainage and other site factors. [3]
Apply on eBuild
Submit a building permit application through eBuild. If you use a pre-approved plan, say so in the project description. [3]
Pay SDCs and pick up your permit
SDCs are due when you pick up the building permit, or you can sign an SDC contract to pay over up to 10 years. EWEB collects its water SDC separately. [4]
Build and get inspections
Build to the approved plans. For building code questions, call a residential plan reviewer at 541-682-5611. [3][4]
Pre-approved and sample plans
Eugene Pre-Approved ADU Program
Twelve pre-approved detached ADU plans sold by their designers for $500 each, plus the city's free 576 sq ft Joel plan; no plan review fee. [3][6][7]
Who to call
-
General permit process questions
Planning & Development, 99 W. 10th Avenue, Eugene, OR 97401
-
Zoning, setbacks, heights and ADU development standards
-
Systems development charges, sewer, stormwater, flood hazard areas
-
Residential building code questions
-
Eugene Water & Electric Board (EWEB)
Water SDC and water service
Questions people ask
How big can an ADU be in Eugene?
The ADU standards cap total building square footage at 10 percent of the lot area or 800 square feet, whichever is smaller. A detached ADU may add up to 300 square feet of unheated garage or storage (800 if above a garage) that doesn't count. Smaller limits apply in the Amazon, Fairmount and South University neighborhoods. [2]
How tall can a backyard ADU be in Eugene?
Up to 25 feet. Above 15 feet, the interior setback slopes inward at 10 inches of height for every 12 inches away from the property line, so the tallest part must sit farther from the lot line. Different rules apply above a garage or on sloped lots, and the slope doesn't apply along a street. [2]
Are there free ADU plans in Eugene?
Yes. The city's Joel plan, a 576 square foot design, is free to download. Twelve other pre-approved plans cost $500 each from their designers, and pre-approved plans skip plan review fees. [3][6][7]
Do I need parking or to live on site for an ADU in Eugene?
No. Oregon law bars cities from requiring owner occupancy or additional off-street parking for ADUs, except for ADUs used as vacation rentals. [5]
Sources (8)
- Eugene Code 9.2740 and 9.2741(3) Residential zone uses; Accessory Dwellings (code current through Ordinance 20742, passed July 13, 2026), City of Eugene. Accessed October 9, 2026.
- Eugene Code 9.2751(17) Accessory Dwellings (code current through Ordinance 20742, passed July 13, 2026), City of Eugene. Accessed October 9, 2026.
- Build An ADU, City of Eugene. Accessed October 9, 2026.
- Accessory Dwellings in the City (Form LU-230, updated December 2021), City of Eugene, Planning & Development. Accessed October 9, 2026.
- ORS 197A.425 Accessory dwelling units, Oregon State Legislature. Accessed October 9, 2026.
- The Joel by City of Eugene (free plan set), City of Eugene. Accessed October 9, 2026.
- Select an ADU Design (Pre-Approved ADU Plans Library), City of Eugene. Accessed October 9, 2026.
- Sections 38-43, chapter 110, Oregon Laws 2024 (mandatory adjustments to housing development standards), noted in ORS chapter 197A, Oregon State Legislature. Accessed October 9, 2026.