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Accessory Structures

How Portland Handles Accessory Structures: A Practical Guide

By CityRuleLookup Editorial Team

Portland maintains 144 local ordinances across all categories, and 2 of those deal specifically with accessory structures. Here is a breakdown of what the city actually requires, what is prohibited, and where Portland falls on the strict-to-permissive spectrum compared to other cities.

ADU Rules

Portland caps accessory dwelling units at 800 square feet or 75% of the primary home's living area, whichever is smaller, and requires a 40-foot front setback or placement behind the main house's rear wall.

Key details: Max size: 75% of house or 800 sq ft. Front setback: 40 ft, or behind rear wall. Zones allowed: RF, R20-R2.5, multi-dwelling, C, EX. Permit: Building permit required, § 33.700.005.

Violating Title 33's ADU standards is unlawful under Portland City Code § 33.700.030. The Bureau of Planning and Sustainability issues a written notice of violation and can pursue enforcement under Chapter 3.30 and Title 22 of the City Code.

Shed & Carport Rules

Portland caps detached sheds and other covered accessory structures at 20 feet tall, holds them to standard building setbacks unless they qualify for a small-structure exception, and limits total accessory building coverage to 20 percent of the lot.

Key details: Max height: 20 feet. Max coverage: 20% of site. Per-structure cap: 900 sq ft or primary footprint. Setback exception zones: R7, R5, R2.5 only. Small-structure exception size: 24 by 24 feet max.

Portland Permitting & Development enforces Title 33 under § 33.700.030; violations can trigger a notice of violation and enforcement under Chapter 3.30 and Title 22 of the City Code, including required removal or reconstruction of a nonconforming structure.

The Bottom Line

Portland's accessory structures rules are a mixed bag. Some areas are strict, others are relaxed, and the details matter. The best approach is to check the specific rule that applies to your situation rather than assuming Portland is broadly strict or permissive.

All of the above reflects Portland's municipal code as of our last review. If you need specifics on fines, exemptions, or filing requirements, the detailed ordinance pages linked above have the full breakdown.