Oregon ADU (accessory dwelling unit) rules in 2026: A practical guide for homeowners

Many single-family lots inside Oregon cities can have an accessory dwelling. Local siting, design, utility, and permit rules still apply. The state sets the baseline, and each city sets its own fees and details.

The statewide rules

Inside an urban growth boundary: an urban growth boundary is the line around a city that marks where urban growth is planned. ORS 197A.425 covers cities with more than 2,500 residents and counties with more than 15,000 residents. They have to allow at least one ADU for each detached single-unit dwelling in qualifying zones. Local siting and design requirements still apply.

For ADUs covered by that provision, local rules can’t require the owner to live in either home. They also can’t require construction of extra off-street parking. The law does let local governments set different rules for vacation occupancy. Those can include owner-occupancy or parking conditions. Check the local rules before you count on short-term rental income.

Outside an urban growth boundary: the urban allowance doesn’t apply automatically. ORS 215.495 lets counties adopt a rural residential ADU program with conditions, but it doesn’t require one. Check whether your county has adopted a program. Also look at resource-land (farm and forest) restrictions, water supply, wastewater, and fire access. Historic-home conversions have a separate path in state law.

More homes or separate ownership: middle-housing and land-division rules are separate from a basic ADU approval. Middle housing means types like duplexes, triplexes, townhomes, and cottage clusters. Before you plan multiple units or a separate sale, ask the city or county which housing type and approval path apply.

System development charges

System development charges (SDCs) are fees a city or service district may charge when you add a home. They help pay for public infrastructure. They’re separate from construction costs, and they can make a big difference in the budget.

SDCs vary by city, service provider, and project. A waiver in one city doesn’t tell you what the next city over charges. Ask for a current, itemized estimate that shows:

• The city and utility districts assessing the project.
• The water, wastewater, stormwater, park, and transportation charges that apply.
• Any available waiver, what it takes to apply, and the charges it doesn’t cover.

Get that estimate before you commit to a design. In your budget, keep agency fees separate from Wolf’s permitting service and the connection work on site.

Portland metro fees and waivers

Portland has a separate ADU SDC waiver. Qualifying residential ADUs can apply through the city’s Revenue Division. The recorded covenant bans short-term rentals throughout the property for 10 years from final inspection approval. That includes the main house and individual bedrooms. Review the ADU waiver instructions before you count on the savings.

The temporary housing exemption doesn’t cover ADUs. Ordinance 192082 set up a separate program for eligible housing permits issued August 15, 2025, through September 30, 2028. Portland Code 17.14.070 J expressly excludes accessory dwelling units. For an ADU, look at the waiver under subsection F, with its covenant.

Check each city and service district. Beaverton, Gresham, Hillsboro, Oregon City, Tigard, and Tualatin each set their own SDC schedules and design standards. A Portland rule usually doesn’t apply across a city line or across the river.

SW Oregon and the rest of the delivery range

South and west of the metro, check the property’s jurisdiction first. Is it inside an urban growth boundary? Answer that before you lean on the statewide rules. Salem, Corvallis, Eugene, and the coastal towns have their own fee schedules and siting rules. Their local review covers the dwelling, utilities, setbacks, height, and overlays, so know those before you pick a model.

Permitting steps, setbacks, and height

The typical path looks like this:

1. Zoning and feasibility check: confirm your lot is eligible. Find the setbacks, height limit, lot coverage, and maximum ADU size for your zone. Setbacks are how far the ADU has to sit from property lines. There’s no statewide set of ADU dimensions. They all come from the local code.
2. Land use review, if your city requires one for ADUs. Many cities treat them as a permitted use with no discretionary (case-by-case) review.
3. Building permit: structural, plumbing, mechanical, electrical, and the site work (foundation, utility connections).
4. SDC assessment: the fees get calculated here, and any waivers or exemptions get applied.
5. Inspections and final occupancy.

How modular approvals work

The Oregon Building Codes Division’s Prefabricated Structures Program reviews qualifying factory construction. Its approval and insignia cover the building itself. They don’t decide whether zoning allows the home on your lot. They also don’t give you permission to move in.

Local review covers site design, the foundation, accessibility where it applies, utility connections, installation, and any work finished on site. Final occupancy comes after the required inspections. The state insignia is not a certificate of occupancy.

An approval from another state isn’t automatically an Oregon approval. The program can also authorize the final inspection and the insignia at the installation site. So the tag isn’t always on the home when it leaves the factory.

How Wolf handles Oregon projects

Wolf builds in Battle Ground. We coordinate the home and site approvals for your property. Before we schedule delivery, we confirm the model, the state approval documents, the foundation design, utilities, and the local permit scope.

Our permit team also handles in-house permitting for Oregon and Washington projects. We pull the zoning, run the SDC numbers for your city, and file the paperwork. That includes the Portland SDC waiver documents when they apply. We check feasibility early. If the project can’t be permitted, your signed permitting agreement spells out the refund and what it excludes. Read those terms before you pay the permitting service fee.

SDCs and local design rules decide whether most backyard cottages pencil out. That’s why we pin them down first. To get started, request a free property evaluation. It’s our first look at the zoning, setbacks, and what’s generally allowed on your lot.