SB 391 ADU Oregon 2026: What Eugene Homeowners Need to Know Now

I've been fielding calls about SB 391 ADU Oregon 2026 changes since the bill passed. Eugene homeowners are confused, and frankly, they should be. The state legislature dropped a significant regulatory bomb on local ADU rules, and the implications are still shaking out.

Let me cut through the noise and tell you exactly what SB 391 means for your property in Eugene and the greater Willamette Valley.

What Is SB 391 and Why Should You Care?

Senate Bill 391, passed in 2023, represents the most significant overhaul of Oregon's ADU regulations since we first allowed them statewide. The bill doesn't take full effect until 2026, but smart homeowners are already planning.

Here's the reality: SB 391 strips away many local government restrictions on ADUs. Cities like Eugene can no longer impose several common limitations that have frustrated homeowners for years.

I've watched Eugene's ADU regulations evolve since I started practicing here. Some rules made sense. Others felt arbitrary. SB 391 eliminates many of the arbitrary ones.

Key Changes Coming in 2026

Size Restrictions Are Getting Relaxed

Under current Eugene code, ADUs are capped at 800 square feet or 75% of the primary dwelling's floor area, whichever is smaller. SB 391 ADU Oregon 2026 rules bump this to 1,200 square feet or 100% of the primary dwelling.

That's a game-changer. I've designed plenty of 800-square-foot ADUs that felt cramped. An extra 400 square feet gives us room for proper storage, a real kitchen, and livable bedrooms.

For context, most of the Craftsman homes in the Whiteaker or Friendly neighborhoods hover around 1,000-1,200 square feet. Under the new rules, you could potentially build an ADU the same size as your main house.

Parking Requirements Are Mostly Gone

This one's huge for Eugene's inner neighborhoods. Currently, you need one off-street parking space for your ADU unless you're within a quarter-mile of frequent transit. That requirement killed projects on narrow lots along 13th Avenue or in the Blair Boulevard area.

SB 391 eliminates most parking requirements for ADUs. Cities can only require parking if the ADU is more than half a mile from frequent transit or a quarter-mile from any transit.

Given Eugene's bus system, most residential areas will qualify for the parking exemption. I'm already working with clients who shelved ADU projects because they couldn't squeeze in another parking space.

Setback Rules Are Getting Standardized

The new law caps residential setbacks at four feet for ADU walls under 16 feet tall. For context, Eugene currently requires five-foot side setbacks in most zones.

That extra foot matters more than you'd think. On a standard 50-foot-wide lot, gaining two feet (one on each side) can mean the difference between a cramped ADU and a functional one.

What Eugene Can Still Control

Don't assume SB 391 ADU Oregon 2026 changes mean anything goes. Eugene retains significant regulatory authority.

The city can still enforce:

I expect Eugene to lean heavily on design review and environmental regulations. The city has always been particular about fitting new construction into existing neighborhoods. That won't change.

Impact on Different Eugene Neighborhoods

South Eugene and Amazon

These areas have larger lots and fewer constraints. The size increases matter less here, but the relaxed setbacks could allow for better ADU placement. I'm seeing interest from empty-nesters who want rental income without sacrificing their garden space.

Whiteaker and Blair Boulevard

These dense, walkable neighborhoods will benefit most from eliminated parking requirements. Lots here are often too narrow for additional parking, but they're perfect for ADUs under the new rules.

West Eugene and Bethel

Suburban areas with good transit access will see new opportunities. The larger size allowances make sense here, where lot sizes can accommodate bigger ADUs.

River Road and Santa Clara

These areas might still face parking requirements due to limited transit access. But the size and setback changes still create new possibilities.

Preparing for 2026: What to Do Now

Start Planning Early

I'm already booked into early 2025 with ADU projects. The design and permitting process takes time, especially for complex sites. If you want an ADU ready for 2026, start planning now.

Understand Your Lot's Constraints

Not every property will benefit equally from SB 391. Steep slopes, poor soils, or utility conflicts can limit what's possible regardless of zoning changes.

I recommend getting a professional site evaluation before getting too excited about the new rules.

Consider Phased Development

Some clients are moving forward with ADU foundations and basic infrastructure now, planning to complete construction after 2026 under the more favorable rules.

This approach has risks, but it can make sense on constrained lots where the extra square footage or reduced setbacks are crucial.

The Design Implications

Better Functionality

Larger size limits mean I can design proper ADUs instead of oversized studio apartments. Real kitchens with full-size appliances. Separate bedrooms with actual closets. Storage that makes sense.

Improved Site Integration

Reduced setbacks let us position ADUs more thoughtfully. Instead of cramming a unit into the back corner of a lot, we can create better relationships between buildings and outdoor spaces.

Enhanced Rental Potential

Bigger, more functional ADUs command higher rents. The improved economics make ADU projects pencil out for more homeowners.

Potential Challenges Ahead

Infrastructure Strain

Eugene's sewer and stormwater systems aren't designed for the density increases SB 391 could enable. Expect the city to use infrastructure capacity as a limiting factor.

Neighborhood Resistance

Not everyone's thrilled about larger ADUs with reduced setbacks. I expect pushback in some neighborhoods, possibly leading to new design review requirements.

Construction Costs

Larger ADUs cost more to build. The improved economics need to overcome higher construction costs, especially given Eugene's labor shortage in the trades.

Timeline and Next Steps

SB 391 ADU Oregon 2026 implementation is still being worked out at the state level. Eugene has until July 2026 to update its ADU regulations to comply.

I expect the city to spend 2024 and early 2025 crafting new rules that comply with state requirements while addressing local concerns. Public hearings will happen. Neighborhood groups will weigh in.

Smart homeowners are using this transition period to plan. The regulatory uncertainty creates challenges, but it also creates opportunities for those willing to navigate the complexity.

My Recommendation

Start exploring your ADU options now. Even if you're not ready to build immediately, understanding your property's potential helps you make better decisions about timing and scope.

The SB 391 changes represent the biggest opportunity for ADU development in Oregon's history. Eugene homeowners who plan ahead will be positioned to take full advantage when the new rules take effect.

If you're considering an ADU in Eugene or the surrounding Willamette Valley, I'd be happy to discuss how SB 391 might affect your specific property. Contact my office to schedule a consultation and start planning for 2026's expanded possibilities.