Oregon's HB 2001: Eliminating Single-Family-Only Zoning
Oregon made national headlines in 2019 when it became the first state to eliminate single-family-only zoning statewide. House Bill 2001, signed into law on August 8, 2019, requires all Oregon cities with a population of 10,000 or more to allow middle housing — duplexes, triplexes, fourplexes, cottage clusters, and townhomes — by-right in all residential zones. For ADU purposes, the significance of HB 2001 is twofold. First, by eliminating single-family-only zoning, it made the regulatory environment for ADUs far more permissive across the entire state. Second, it specifically prohibits owner-occupancy requirements for ADUs in cities with populations of 10,000 or more — one of the primary barriers that had prevented ADU development in many Oregon cities. Oregon's approach differs from California's in an important way. California's ADU law directly governs ADU-specific rules — setbacks, size limits, fees, parking. Oregon's HB 2001 operates at the land use level, eliminating single-family zoning categories altogether. The result is similar in practice — ADUs and other secondary units are permitted in residential zones statewide — but the legal mechanism is different. HB 2001 required all Oregon cities with population 10,000 or more to update their development codes to allow middle housing by June 30, 2021. Cities that failed to comply became subject to a state model code administered by the Oregon Land Conservation and Development Commission (LCDC), which has enforcement authority. Most Oregon cities updated their codes on time or close to it. HB 2001 applies within Urban Growth Boundaries (UGBs) — the planning boundary Oregon requires each city to maintain separating urban from rural land. It does not apply in unincorporated rural areas below the 10,000-person threshold. Oregon SB 458 (2021) further expanded housing options by requiring cities that must allow middle housing under HB 2001 to also allow lot divisions for middle housing — enabling individual unit ownership of duplexes, triplexes, and cottage clusters.
Portland ADU Rules: Oregon's Most Permissive City
Portland was already one of the most ADU-permissive cities in the United States before HB 2001 passed. The city eliminated off-street parking requirements for ADUs in 2013 — years before the rest of Oregon or California took similar steps. Portland had no owner-occupancy requirement for ADUs since 2016. Portland's Residential Infill Project (RIP), implemented in 2021 to comply with HB 2001, went even further than state law requires, allowing triplexes, fourplexes, and cottage clusters on single-family lots citywide. Portland regulates ADUs under City Code Title 33, Section 33.205. The maximum size for a detached ADU is 800 square feet — somewhat smaller than California's 1,200-square-foot state limit, reflecting Portland's own local standard. Attached ADUs are limited to 75 percent of the primary dwelling floor area, up to a maximum of 800 square feet. Portland does not use the California JADU concept. Portland allows one ADU per single-family dwelling — either one attached or one detached ADU in standard single-family zones (R20 through R2.5). Under middle housing rules, a single-family lot can have up to 4 total units. Setbacks for detached ADUs are 5 feet from side and rear property lines per Portland Zoning Code 33.205.040.D — slightly more than California's 4-foot minimum. Portland's Bureau of Development Services (BDS) processes ADU permits ministerially. Standard ADU permits take 4-8 weeks for plan review. Portland offers pre-approved standard plan sets that reduce review time. The exterior design of a detached ADU must be compatible with the primary dwelling's exterior per 33.205.040.F — one of Portland's local design standards that goes beyond California's more permissive approach.
What You Can Build in Oregon
Oregon homeowners in cities subject to HB 2001 have multiple options for adding housing to their lots. Understanding the types and constraints helps match the right ADU type to your property. In Portland, detached ADUs (called 'backyard cottages' in Portland parlance) may be up to 800 square feet. This is the most independent form — a separate structure in the backyard with its own entrance, kitchen, bathroom, and utility connections. Detached ADUs work best on lots with usable rear yard space, typically 5,000 square feet or larger. Attached ADUs in Portland may be up to 75 percent of the primary dwelling's floor area, maximum 800 square feet. These are additions or conversions attached to the existing home — a side addition, a rear addition, or a basement conversion with a separate entrance. Garage conversions to ADU are permitted in Portland under the detached or attached ADU rules depending on the garage configuration. Converting a detached garage is a cost-effective option — you gain living space without the cost of foundation and framing. Interior conversions — finishing an unused basement or attic as a separate unit — are permitted and often the lowest-cost option. Portland's middle housing rules under HB 2001 also allow entirely new housing types on single-family lots: duplexes (2 units), triplexes (3 units), fourplexes (4 units), and cottage clusters (4 units of 900 sqft or smaller organized around shared space). These are not technically ADUs — they are the primary units — but they represent expanded options for lot owners who want to maximize housing on their property. In smaller Oregon cities (between 10,000 and 25,000 population), HB 2001 requires that duplexes be allowed by-right in all residential zones. Middle housing (triplex, fourplex, cottage cluster) is required only in cities over 25,000 population. ADUs remain a local decision in these smaller cities, though most have adopted permissive frameworks to comply with HB 2001's broader intent.
Permit Process and Costs in Portland
Portland's ADU permit process is administered by the Bureau of Development Services (BDS). The process follows a similar sequence to California cities, though Portland has its own fee structure and one notable significant cost item: System Development Charges (SDCs). Plan check fees in Portland typically run $1,500 to $4,000 depending on project value. Building permit fees run $1,200 to $3,500. These base permit fees are comparable to California cities. However, Portland's System Development Charges (SDCs) can significantly increase the total cost for new construction ADUs. SDCs cover transportation, parks, and water/sewer infrastructure — Portland charges SDCs for new residential units including new detached ADUs. SDCs typically add $10,000 to $25,000 to the cost of a new detached ADU in Portland. SDC deferrals are available for affordable housing ADUs — if you commit to renting the ADU at below-market rates for a qualifying period, SDCs may be deferred or waived. Garage conversions and attached additions may have lower or no SDCs because they do not add new plumbing or street connections. Always confirm current SDC rates with Portland BDS before finalizing your ADU budget. Total permit fees for a new detached ADU in Portland typically run $3,000 to $8,000 in base permit fees, plus $10,000 to $25,000 in SDCs — meaning total city-required fees can reach $35,000 before you break ground. This makes Portland's effective cost of permitting significantly higher than LA or Sacramento for new detached ADUs. For garage conversions or attached ADUs with no new utilities required, total fees may be considerably lower. Portland also requires that detached ADUs' exterior design be compatible with the primary dwelling, which may add design complexity and cost if your home has distinctive architectural features. Construction timelines in Portland follow general Pacific Northwest patterns: 3-9 months for construction after permits are issued.
How Oregon Compares to Washington
Oregon and Washington share a border, a progressive policy environment, and two major cities — Portland and Seattle — that are national leaders in ADU policy. How do the two states' ADU frameworks compare? Oregon's HB 2001 (2019) and Washington's HB 1337 (2023) both represent landmark state-level ADU reform, but they take different approaches. Oregon's HB 2001 is primarily a zoning reform bill — it eliminates single-family-only zoning categories and requires middle housing, which creates the conditions for ADUs but doesn't directly set ADU size limits or fee caps. Washington's HB 1337 is more directly focused on ADUs: it requires all Washington cities to allow at least 2 ADUs per single-family lot, sets a minimum ADU size allowance (1,000 sqft or 60% of the primary dwelling), and explicitly removes owner-occupancy requirements. Washington's HB 1337 allows 2 ADUs per lot by right — Portland's Zoning Code still limits single-family lots to 1 ADU (plus middle housing options). Seattle, under HB 1337, now allows 1 attached plus 1 detached ADU on the same single-family lot — a rule Portland does not have for standard single-family zones. Seattle's maximum ADU size is 1,000 square feet, larger than Portland's 800-square-foot cap. Seattle's permit fees ($4,000 to $12,000 in permit fees plus school impact fees) are somewhat higher than Portland's base permit fees but without the SDC component for all project types. Portland's SDCs make new detached ADU total fees comparable to or higher than Seattle's in many cases. Both Portland and Seattle have eliminated parking requirements for ADUs — Portland did it first in 2013, Seattle followed. Both cities require ministerial ADU approval. For homeowners deciding between the two markets, Seattle's larger ADU size allowance (1,000 vs. 800 sqft) and explicit two-ADU-per-lot policy may offer more flexibility, while Portland's earlier and more comprehensive middle housing framework offers more options for lot-level density overall.
Recent Changes and Upcoming Legislation
Oregon's housing law landscape continues to evolve rapidly. HB 2001 (2019) was the foundational reform, but subsequent bills have continued to expand housing options and refine compliance requirements. SB 458 (2021, effective July 1, 2022) was an important follow-on to HB 2001. It requires Oregon cities that must allow middle housing under HB 2001 to also allow lot divisions for those middle housing developments. When you build a duplex or cottage cluster on a single-family lot under HB 2001, you can now split that lot to create separate parcels for individual unit ownership — enabling condo-like or fee-simple ownership of middle housing units. This makes middle housing more financeable (individual units can be mortgaged separately) and more marketable. HB 3414 (2023) clarified HB 2001 compliance requirements and reinforced LCDC enforcement authority over non-compliant jurisdictions. Some Oregon cities had found technical workarounds to avoid fully implementing middle housing — HB 3414 tightened these requirements. Portland's Residential Infill Project, completed in phases from 2020 to 2021, is the most comprehensive local implementation of HB 2001. The RIP went beyond state requirements by allowing fourplexes on any residential lot citywide and establishing cottage cluster standards. The Oregon Legislature has signaled continued interest in housing reform. Advocates are pushing for additional ADU-specific legislation to directly address size limits, setback standards, and fee caps for ADUs — areas where Oregon's existing law (operating at the land use level) is less explicit than California's ADU-specific statutes. Watch for Oregon legislative developments each session. PropertyZoned updates state guide data when significant new laws pass.
Getting Started with an Oregon ADU
Planning an ADU in Oregon follows a logical sequence. Here is how to approach the process efficiently. Step 1: Confirm your city's HB 2001 compliance. All Oregon cities with population over 10,000 are required to allow ADUs and middle housing. The Oregon Department of Land Conservation and Development (DLCD) maintains a database of local code compliance. If your city has not updated its code, it is subject to the state model code, which is permissive. Step 2: Research your specific city's ADU rules. In Portland, consult the Bureau of Planning and Sustainability (BPS) and Bureau of Development Services (BDS). Portland's Title 33 Section 33.205 governs ADU development. Other Oregon cities have their own local codes — use PropertyZoned's city pages as a starting point. Step 3: Understand System Development Charges. If you are in Portland and considering a new detached ADU, get a current SDC estimate before you commit to the project. SDCs can add $10,000 to $25,000 and should be factored into feasibility analysis. Garage conversions and attached ADUs often have lower or no SDCs. Step 4: Use PropertyZoned's ADU Feasibility Checker. The tool incorporates Portland's local rules including size limits (800 sqft max detached), setback requirements (5 ft side/rear), and lot coverage constraints. Step 5: Hire a local architect. Portland has a strong ecosystem of ADU-specialized architects and designers. Portland's BDS offers pre-approved standard plan sets for some common ADU configurations — ask your architect or check BDS directly. Step 6: Apply for permits and track your application. Portland BDS processes standard ADUs in 4-8 weeks. If you use a pre-approved standard plan, review time may be shorter. Monitor your application through Portland's permit tracking portal. Oregon's progressive housing law environment means most homeowners in cities over 10,000 population have a clear path to ADU approval. Start with research, confirm your city's specific rules, and connect with local professionals familiar with your jurisdiction.
Frequently Asked Questions
Does HB 2001 require every Oregon city to allow ADUs?
HB 2001 requires all Oregon cities with population 10,000 or more (within Urban Growth Boundaries) to allow middle housing — duplexes, triplexes, fourplexes, cottage clusters, and townhomes — by-right. It also prohibits owner-occupancy requirements for ADUs in these cities. It does not apply to cities under 10,000 population or unincorporated rural areas.
What is the maximum ADU size in Portland?
In Portland, detached ADUs may be up to 800 square feet. Attached ADUs may be up to 75% of the primary dwelling's floor area, maximum 800 square feet. Portland's limit is smaller than California's 1,200 sqft state cap but larger than many older local standards.
What are System Development Charges (SDCs) in Portland?
System Development Charges are Portland's fee for new connections to transportation, parks, and water/sewer infrastructure. For new detached ADUs in Portland, SDCs typically add $10,000 to $25,000 to total project fees — significantly more than California cities' permit fees. SDC deferrals are available for affordable housing ADUs. Garage conversions and attached ADUs without new utility connections may have lower SDCs.
Can I build 2 ADUs on my Portland lot?
Standard single-family zones in Portland allow 1 ADU per lot (either attached or detached). However, Portland's middle housing rules under HB 2001 allow up to 4 total units on single-family lots via duplex, triplex, fourplex, or cottage cluster development. In multifamily RM zones, additional ADUs may be allowed based on zone standards.