Portland's Premier ADU Specialists
Turn your property into an income-generating asset with a beautiful, functional Accessory Dwelling Unit. From permits to construction, we handle every aspect of your Portland ADU project.
Comprehensive ADU Services
Everything you need to build your Portland ADU, all in one place.
Design & Planning
Personalized ADU designs that maximize space and functionality while adhering to Portland's zoning requirements.
Permitting
Navigate Portland's complex ADU permitting process with our expertise. We handle all paperwork and inspections.
Construction
Quality ADU construction from foundation to finish with our skilled Portland-based builders and contractors.
Financing
Discover ADU financing options tailored to Portland homeowners, including loans, refinancing, and investment strategies.
Educational Resources
Learn about Portland ADU regulations, costs, timelines, and benefits with our comprehensive guides and workshops.
Property Management
Maximize your ADU investment with our optional property management services for Portland rental properties.
Portland ADU Requirements Factsheet
Key regulations and requirements for building an ADU in Portland
Size Requirements
- Maximum Size: 800 square feet or 75% of main dwelling's living area (whichever is less)
- Minimum Size: No official minimum, but must meet habitable space requirements
- Bedroom Size: Minimum 70 square feet with no dimension less than 7 feet
- Ceiling Height: Minimum 7 feet for habitable rooms
- Room Dimensions: Per Oregon Residential Specialty Code standards
Height & Setback Rules
- Maximum Height: 20 feet (or 15 feet if within 10 feet of property line)
- Setbacks: Typically 5 feet from side/rear property lines
- Street-facing Setbacks: Must match underlying zone requirements
- Entrance Placement: Main entrance cannot face the same street as main house (exceptions apply)
- Distance from Main Home: No minimum separation requirement
Permitting & Fees
- Required Permits: Building, mechanical, electrical, plumbing permits
- System Development Charges: Currently waived for ADUs with covenant against short-term rental use
- Permit Costs: Approximately $2,000-$5,000 depending on scope
- Review Timeline: Typically 2-4 months from submission to approval
- Design Review: Required in historic districts and conservation districts
General Requirements
- Parking: No additional parking spaces required
- Owner Occupancy: No requirement for owner to live on property
- Design: Must be compatible with main dwelling design
- Number of ADUs: One ADU allowed per residential lot
- Short-term Rentals: Allowed, but requires permit and owner occupancy for 270+ days/year
Requirements subject to change. Last updated: May 2025
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Frequently Asked Questions
Get answers to common questions about Portland ADUs.
An Accessory Dwelling Unit (ADU) is a secondary housing unit on a single-family residential lot. In Portland, ADUs can be detached new constructions, converted garages, basement conversions, or additions to existing homes. They typically include a kitchen, bathroom, living area, and separate entrance.
In Portland, ADUs cannot exceed 75% of the living area of the primary dwelling or 800 square feet, whichever is less. However, recent code changes have increased this limit to 800 square feet regardless of the primary dwelling size. The ADU must also comply with height, setback, and lot coverage requirements specific to your property's zoning.
The cost of building an ADU in Portland typically ranges from $200-$300 per square foot, meaning a 600 square foot ADU might cost between $120,000 and $180,000. Costs vary based on design complexity, site conditions, finishes, and whether it's detached or attached. Permits and System Development Charges (SDCs) add approximately $15,000-$25,000 to the budget.
No, Portland does not require additional parking spaces for ADUs. This is one of the favorable aspects of Portland's ADU regulations compared to other cities, making ADU development more feasible on smaller lots or properties with limited driveway space.
Yes, Portland allows ADUs to be used as short-term rentals (like Airbnb or VRBO), but specific regulations apply. If renting for less than 30 days at a time, you'll need to obtain a Short-Term Rental Permit and follow occupancy rules. The property owner must reside in the primary residence or the ADU for at least 270 days per year.
The timeline for an ADU project in Portland typically ranges from 8-12 months from initial planning to completion. This includes 2-3 months for design and planning, 2-4 months for permitting, and 4-6 months for construction. Timelines can vary based on project complexity, contractor availability, permit review times, and any unforeseen site conditions.
In Portland, you'll need a building permit for your ADU project. Depending on the scope, you may also need electrical, plumbing, and mechanical permits. If you're converting an existing structure or adding to your home, you might need a zoning permit. For detached ADUs, site development permits may be required for grading and stormwater management.
System Development Charges (SDCs) are fees charged by the City of Portland to offset impacts on city infrastructure. For ADUs, these can include charges for parks, transportation, water, and sewer systems. Currently, Portland has waived many SDCs for ADUs, saving homeowners approximately $15,000-$20,000. However, these waivers are periodically reviewed, so it's important to check current policies.
Most residential lots in Portland can accommodate an ADU, but there are some limitations. Your property must be zoned for residential use, and typically needs to have a single-family home already on it. Some factors that might affect eligibility include lot size, existing structural coverage, environmental overlays, or historic district regulations. A feasibility study can help determine if your property is suitable.
In Portland, ADUs can generate significant rental income. For long-term rentals, a well-designed ADU can bring in $1,500-$2,500 per month depending on size, location, and amenities. As short-term rentals, they can potentially generate $2,500-$4,000 monthly, though with more management requirements and seasonal fluctuations. The Portland rental market remains strong, particularly for smaller, efficient units in desirable neighborhoods.
While not legally required for all projects, working with an architect or design professional experienced in Portland ADUs is highly recommended. They'll ensure your ADU meets all building codes and zoning requirements while maximizing the space and functionality. Professional designs typically result in faster permit approvals, fewer construction issues, and a more valuable final product.
Yes, several financing options are available for Portland ADU projects. These include home equity loans, cash-out refinancing, construction loans, renovation loans like FHA 203k or Fannie Mae HomeStyle, and personal loans. Some Portland homeowners also utilize ADU-specific loans from local credit unions or Portland's ADU SDC waiver program to reduce costs. The best option depends on your financial situation, home equity, and intended use of the ADU.
Yes, your Portland ADU can have its own address, which is often important for mail delivery, emergency services, and utility setup. The process involves applying for address assignment through Portland's Bureau of Development Services. Having a separate address does not make the ADU a separate legal property—it remains part of the main property for tax and ownership purposes.
In Portland, attached ADUs are connected to the main house, like basement conversions or additions, while detached ADUs are separate structures. Attached ADUs typically cost less (leveraging existing walls, foundation, and roof) but offer less privacy. Detached ADUs cost more but provide maximum privacy and design flexibility. Portland regulations allow either type, with specific requirements for each regarding entrances, utilities, and fire separation.
Portland ADUs can have either separate or shared utilities with the main house. For detached ADUs, options include separate meters for electricity and water (preferred for rental situations) or connections to the main house's systems. Separate utilities give tenants control over their usage and simplify billing, while shared utilities may be more cost-effective during construction. Portland building codes require ADUs to have their own heating and cooling systems.
Currently, Portland regulations allow for one ADU per single-family residential lot. A tiny house on wheels is not considered an ADU unless it's permanently affixed to a foundation and meets building code requirements. You could have a tiny house on wheels as a temporary structure, but it couldn't be used as a permanent dwelling in addition to an ADU.
Portland requires ADUs to be compatible with the main house in terms of exterior finish materials, roof pitch, trim, window proportion, and other design elements. For detached ADUs visible from the street, design compatibility is especially important. In historic districts, additional design review may be required. These requirements ensure ADUs blend with existing neighborhood character while allowing for modern building techniques.
In Portland, a detached ADU can be up to 20 feet tall, or 15 feet if located within 10 feet of a property line. In some zones, ADUs may match the height of the primary dwelling up to 25 feet. These height limitations are measured from the average grade to the midpoint of the highest gable on a pitched roof.
Yes, all Portland ADUs must meet current Oregon Energy Efficiency Code requirements, which include standards for insulation, windows, heating/cooling systems, and appliances. Many ADU owners opt for additional efficiency measures like solar panels, heat pumps, and low-flow fixtures, which can reduce long-term operating costs and may qualify for energy incentives or tax credits through Energy Trust of Oregon or federal programs.
No, in Portland, an ADU cannot be sold separately from the primary residence. The ADU and main house must remain under the same ownership. ADUs are not eligible for condo conversion or separate tax lots. However, some homeowners use creative legal structures like limited liability companies to create arrangements similar to separate ownership.
Portland's zoning code doesn't specify a minimum lot size specifically for ADUs. However, your property must meet setback requirements and maximum lot coverage limits. Typically, detached ADUs need at least 3-5 feet of setback from property lines (more for taller structures), while attached ADUs follow the setback requirements of the main dwelling. A feasibility study can help determine if your specific lot can accommodate an ADU given these constraints.
In Portland, an ADU is a secondary dwelling unit subordinate to the main house, with size limitations (maximum 800 square feet or 75% of the main dwelling's living area). A duplex consists of two equal primary dwelling units, potentially with separate ownership. ADUs can be built on most single-family lots, while duplexes require specific zoning allowances. ADUs generally face fewer regulatory hurdles and lower development costs than duplex conversions or new duplex construction.
No, Portland does not require dedicated parking spaces for ADUs. This is one of Portland's most ADU-friendly policies, making it feasible to build ADUs on properties where adding parking would be difficult or impossible. While not required, some homeowners choose to add parking for practical reasons, particularly in neighborhoods with limited street parking or to make the ADU more attractive to potential renters.
The permitting process for a Portland ADU typically takes 2-4 months from submission to approval. Simple projects with complete, well-prepared plans may be processed more quickly, while complex projects or those requiring special approvals can take longer. Working with experienced designers and builders familiar with Portland's requirements can significantly streamline the permitting process and help avoid costly revisions or delays.
Yes, Portland allows pre-fabricated and modular ADUs as long as they meet all building code requirements and design standards. These factory-built options can reduce construction time and sometimes cost, while still requiring proper foundations, utility connections, and finishes. Any prefab ADU must still go through the same permitting process as a site-built ADU and meet Portland's design compatibility requirements.
Yes, you can build an ADU in Portland's historic districts, but you'll face additional requirements. Your ADU design will need to undergo Historic Resource Review to ensure compatibility with the historic character of the neighborhood. This review considers factors like materials, detailing, scale, and placement. While this adds complexity to the process, many successful ADUs have been built in Portland's historic districts with thoughtful design that respects historical context.
Adding an ADU to your property will require updating your homeowners insurance policy. Inform your insurance company about the new structure to ensure proper coverage for both the main house and ADU. If you rent out your ADU, you'll likely need landlord insurance. For short-term rentals, specialized insurance may be required. Some insurance companies offer discounts for newer construction with updated systems, potentially offsetting some of the increased premium.
In Portland's strong housing market, ADUs typically offer excellent return on investment. Most Portland ADUs recover their construction costs within 7-10 years through rental income. They also increase property values by approximately 20-30% of the ADU's construction cost. Beyond financial returns, ADUs provide flexibility for changing family needs, housing for aging parents or adult children, or work-from-home space. The exact ROI depends on location, design quality, and how the ADU is used.
The most common ADU types in Portland include: 1) Detached new construction ADUs (free-standing structures in backyards), 2) Garage conversions (transforming existing garages into living spaces), 3) Basement conversions (especially in Portland's many homes with daylight basements), 4) Additions to existing homes, and 5) Above-garage ADUs (adding living space above a new or existing garage). Detached ADUs are particularly popular due to the privacy they offer both the main house and ADU residents.
Portland has stringent tree preservation ordinances that can impact ADU construction. Trees of certain sizes (generally 12+ inches in diameter) are protected and require permits for removal. If tree removal is necessary for your ADU project, you may need to pay fees or plant replacement trees. Site planning should account for significant trees early in the design process, potentially adjusting the ADU's footprint or placement to preserve valuable trees while meeting setback requirements.
Portland ADUs must meet building code requirements for habitable spaces, which generally means a minimum ceiling height of 7 feet for living rooms, bedrooms, kitchens, and bathrooms. For sloped ceilings (like in attics), at least 50% of the room must have the 7-foot minimum height. Basement conversions can be particularly challenging due to these height requirements, sometimes necessitating floor lowering or other structural modifications to achieve compliant ceiling heights.
Yes, two-story ADUs are permitted in Portland, subject to height restrictions (typically 20-25 feet depending on zone) and setback requirements. Two-story designs can help maximize living space while minimizing the ADU's footprint on your property. However, they typically cost more to build, require stairs (reducing usable floor area), and may have greater impact on neighbors' privacy. Design considerations like window placement can help mitigate privacy concerns for both your neighbors and ADU occupants.
Portland follows Oregon Residential Specialty Code for minimum room sizes. Habitable rooms (excluding kitchens) must be at least 70 square feet with no dimension less than 7 feet. Kitchens have no minimum size but must include required fixtures and clearances. Bathrooms need sufficient space for fixtures with required clearances (typically 30 inches for toilets, 24 inches for sinks, etc.). Careful space planning is essential for smaller ADUs to meet these requirements while maintaining comfortable, functional living spaces.
Portland does not require a separate water meter for ADUs, but having one is an option. Using the main house's water meter is generally more cost-effective during construction, avoiding the expense of a new water service connection and meter installation (which can cost $5,000-$15,000). However, for rental situations, a separate meter allows tenants to pay for their own water usage and makes tracking utility expenses easier. Some homeowners install sub-meters to monitor ADU water usage without the full cost of a new service connection.
While building an ADU will increase your property taxes due to the increased property value, there are potential tax benefits. If you rent the ADU, you can deduct expenses like mortgage interest, property taxes, insurance, maintenance, and depreciation against rental income. For short-term rentals, additional business expense deductions may apply. Some energy-efficient components may qualify for federal or state tax credits. Consult with a tax professional familiar with rental properties to maximize potential tax advantages.
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