ADU Permit in Portland, OR
Permit Summary
ADU Types & Property Eligibility
ADU Type Rules
Portland allows ADUs within or added to a primary structure, conversions of existing accessory structures, and new detached ADUs. One ADU is allowed with a house, attached house, or manufactured home. In R20 through R2.5 and in multi-dwelling, commercial, and EX zones, up to two ADUs may be allowed with a house, attached house, or manufactured home under the applicable site conditions; only one of the two may be attached. A duplex may have one detached ADU where the applicable standards are met. ADUs are not allowed with floating homes, triplexes, fourplexes, cottage clusters, or multi-dwelling structures.
Lot / Zoning Eligibility Rules
Detached ADUs are allowed in Portland's single-dwelling residential zones RF, R20, R10, R7, R5, and R2.5, as well as applicable multi-dwelling, commercial, and Central Employment (EX) zones. The ADU must be accessory to an eligible primary dwelling. In R20 through R2.5, a detached ADU with a duplex and the two-ADU option have added minimum-lot-area, City-maintained-street-frontage, and Constrained Sites overlay conditions. ADUs are not allowed with floating homes, triplexes, fourplexes, cottage clusters, or multi-dwelling structures.
Size, Height & Placement
Setback Rules
A detached ADU must generally be at least 40 feet from the front lot line or be located behind the rear wall of the primary structure. Detached and connected accessory-structure standards govern side and rear setbacks. In qualifying R7, R5, and R2.5 situations, an accessory structure may extend into required side or rear setbacks only when the dimensional, height, screening, opening, and rooftop-deck conditions of Section 33.110.245 are met; the maximum height in that setback allowance is 15 feet.
Lot Coverage / FAR Rules
A detached ADU's building coverage may not exceed the building coverage of the primary structure, and all detached accessory structures together may not cover more than 20% of the site. Floor-area limits apply in all zones except RF. In R10 and R20, the cited floor-area limits apply only on sites smaller than 10,000 square feet; in R7 through R2.5, additional floor area is allowed for each proposed ADU.
Attached ADU Rules
An ADU may be created within or as an addition to an eligible primary dwelling. Where two ADUs are allowed with a house, attached house, or manufactured home, no more than one ADU may be attached to the house or another ADU. Residential-code ADUs must comply with the Oregon Residential Specialty Code requirements for two-family dwellings as modified by Portland's ADU Code Guide.
Detached ADU Rules
A detached ADU is a separate structure and must comply with the applicable base-zone and detached-accessory-structure standards. A duplex may have an ADU only as a detached unit. Detached ADUs are subject to the applicable location, height, coverage, exterior-design, utility, and site-eligibility rules; projects in R20 through R2.5 using the duplex-plus-ADU or two-ADU options also have street-frontage, minimum-lot-area, and Constrained Sites conditions.
Conversion ADU Rules
Portland allows conversion of part of an existing house and conversion of an existing garage or other accessory structure to an ADU. A building permit and trade permits are required. Portland's ADU Code Guide provides alternative standards for qualifying existing conditions, while new work must meet current code. For an existing unpermitted ADU, the owner must obtain a permit, and inspectors may require finishes or concealed work to be opened so code compliance can be verified.
Design, Occupancy & Parking
Design Standards
Detached ADUs taller than 15 feet must meet exterior standards for finish materials, roof pitch, trim, eaves, and window orientation; the City allows specified alternatives when they do not match the primary structure. Historic designations may add Community Design Standards or require Historic Resource Review. Where two ADUs are proposed with a house or one ADU with a duplex, at least one dwelling must meet Portland's visitability standards for zero-step access, bathroom, living area, and doors.
Owner Occupancy Rules
Oregon law does not allow ordinary ADU siting and design regulations to impose owner-occupancy requirements on the primary or accessory dwelling. Short-term or vacation occupancy is regulated separately, and Portland requires the applicable accessory short-term rental approvals. An ADU that uses Portland's SDC waiver is subject to a recorded 10-year covenant prohibiting accessory short-term rental use on the property.
Parking Rules
Portland states that no additional on-site parking is required because an ADU is created.
Rental / Short-Term Rental Rules
ADUs may be used for residential rental. Portland allows ADUs to be used as Type A or Type B accessory short-term rentals only with the applicable short-term-rental permitting and rules. If the property received the ADU system development charge waiver, the recorded covenant prohibits accessory short-term rental use of the ADU or any other structure on the property for 10 years from the ADU permit's final inspection.
Separate Sale Rules
Portland states that Middle Housing Land Divisions are not allowed on sites with ADUs. The current official sources reviewed did not establish whether a Portland ADU may otherwise be separately conveyed under a condominium or other ownership structure, so separate-sale eligibility could not be reliably established.
Address, Utilities & Trade Permits
Address Rules
Portland ADUs do not receive a separate unique street number. The primary residence uses the site's street number as Unit A and ADUs are assigned Unit B, C, D, and so on. The ADU's number and unit letter must be permanently displayed at its main entrance and, when not visible from the street used to access the primary residence, duplicated at the property's primary access point.
Utility Connection Rules
The ADU and primary dwelling must generally have separate independent water-supply and sanitary-drainage systems, subject to Portland's allowed shared-system exceptions. A City-approved common water supply may serve both units with the required accessible shutoff or control valves, and the line may need upsizing. An ADU in the same building may share sanitary drainage; a detached ADU may share a common sewer with the primary dwelling when no more than five toilets are on one 3-inch line. Backwater valves are required for new ADU fixtures when the ADU floor is below the next uphill manhole cover. Electrical circuits must be independent of the primary dwelling's loads.
Trade Permit Rules
Portland states that ADU projects require electrical, plumbing, and mechanical permits. They may be submitted with the building permit as a combination package or obtained separately. Portland's ADU Code Guide requires all new electrical work for creation or alteration of an ADU to be performed by a licensed electrical contractor; the homeowner electrical-work exemption does not apply to ADU work.
Fire, Energy & Special Requirements
Fire / Life Safety Rules
Residential-code ADUs must meet Oregon Residential Specialty Code two-family-dwelling requirements as modified by Portland's ADU Code Guide. New separation walls and floor/ceiling assemblies between dwellings or common space generally require at least a one-hour fire-resistance rating plus 45 STC and 45 IIC for floor/ceiling assemblies, with alternative allowances for qualifying existing construction. Egress, ceiling height, stairs, light, ventilation, and door requirements also apply. Sprinklers are configuration-dependent; for example, an ADU in a four-story structure using Portland's Four-Story Code Guide requires an NFPA 13-R sprinkler system throughout under a separate Fire Marshal permit.
Energy / Solar Rules
As of September 26, 2026, the adopted residential code is the 2023 Oregon Residential Specialty Code. New ADU buildings or additions, and new elements in existing buildings, must comply with its energy-conservation requirements; qualifying existing elements may use the allowances in Portland's Habitable Space Standards Code Guide. Portland's pre-approved detached ADU process also requires selection of an applicable energy-conservation measure. The 2026 ORSC is not treated as current because Oregon lists its effective date as October 1, 2026.
Special Area / Overlay Rules
Special site conditions can add requirements. In R20 through R2.5, the Constrained Sites 'z' overlay prevents use of the two-ADU option and the duplex-plus-ADU option. Historic-designated properties may need Community Design Standards compliance or Historic Resource Review. Portland also identifies additional review or documentation for floodplain sites and for sites with slopes of 20% or more or mapped landslide hazards, where a geotechnical report may be required.
Development / Impact Fee Rules
Portland City Code exempts an ADU from all system development charges when the ADU building-permit application has an intake date of August 1, 2018 or later and, before permit issuance, the applicant records the City's covenant prohibiting accessory short-term rental use of the ADU or any other structure on the property for 10 years from final inspection. If the covenant is violated or terminated, the exemption ends and previously exempt SDCs become due under the code. ADUs that do not use this exemption may be subject to otherwise applicable SDCs.
Preapproved Plans
Preapproved Plan Rules
Portland offers four optional pre-approved plan designs for detached ADUs. The plans are provided without a plan-design fee and can reduce project-specific design work and help speed review, but they are not suitable for every lot. Applicants still submit a building-permit application and site-specific materials, must satisfy zoning, utility, site, and other review requirements, and may need project-specific items such as an engineer-stamped truss package.
Permit & Review Path
Permit / Review Path
Apply through Development Hub PDX for the ADU building permit and required trade permits. Conversions follow the ADU conversion path; new detached ADUs follow the new detached ADU/new residential submittal path, with optional pre-approved detached plans. City reviewers issue checksheets when corrections or more information are needed, followed by pre-issuance and fee payment. If zoning development standards cannot be met, an Adjustment Review under Chapter 33.805 is required before the project can rely on the requested adjustment.
Inspections
Inspection Stages
The issued permit's inspection card identifies the project-specific building and trade inspections. Before ground-disturbing work, required tree-protection or erosion-control measures must be installed and approved; Portland identifies inspection 507 for required tree preservation and inspection 200 for pre-construction erosion control. Work then receives the required construction and trade inspections. All permits require final approval, including the 999 Final inspection; erosion-control projects also require the final 210 erosion-control inspection.
What You Need Before Applying
Requirements
An ADU must be established on an eligible site with a house, attached house, manufactured home, or qualifying duplex configuration and must meet Portland zoning plus the applicable Oregon building code. A building permit is required for a new ADU or conversion to habitable ADU space, and electrical, plumbing, and mechanical permits are also required. Applicants must verify site zoning, development standards, utilities, hazard conditions, and permit history before applying.
Exemptions
There is no general building-permit exemption for creating or legalizing an ADU. Converting existing space or an accessory structure to an ADU, constructing a new ADU, and legalizing an unpermitted ADU require the applicable permit process.
Required Documents
All ADU applications need a site plan. Conversion projects typically require the building-permit application, site plan, architectural or floor plans, and structural plans when structural work is proposed. New detached ADUs require complete plans and any project-specific forms; electrical, plumbing, and mechanical applications are required for the trade permits. Conditional submittals can include erosion-control or tree-protection information, a geotechnical report for qualifying slope or landslide-hazard sites, and the recorded covenant when requesting the ADU system development charge waiver.