Short answer: in Oregon, a deck needs a building permit when its walking surface is more than 30 inches above the ground. Chapter 1 of the 2026 Oregon Residential Specialty Code (ORSC), effective and mandatory since October 1, 2026, exempts:
“Porches and decks attached to or directly serving a regulated building where the walking surface is not more than 30 inches (762 mm) above adjacent grade measured at any point within 3 feet (914 mm) horizontally of the walking surface.”
A freestanding deck gets the same height test through a separate exception: “Detached platforms and decks that are located not more than 30 inches (762 mm) above adjacent grade measured to any point within 3 feet (914 mm) horizontally of the walking surface may be of any size.” Either way, height is what decides it, not size.
Portland’s own deck pages put it the same way: “If the walking surface is over 30 inches from the ground, you’ll need a building permit,” and they say to take the measurement 36 inches from the edge of the deck. Because the height counts at any point near the deck, on a sloping yard it is the low side that matters.
A low deck can still need other approvals. Roofs over decks, zoning setbacks, trees and, in a few cities, engineering rules all apply on their own terms. This guide covers each, for Portland and for the suburbs around it.
Deck covers have their own limit
A roof over a deck is a separate item in the code. The 2026 ORSC exempts “Deck, patio or porch covers” only when they are “not more than 200 square feet (18.58 m2) in floor area and not closer than 3 feet (914 mm) to lot lines.” A larger cover, or one near a property line, needs a permit even over a deck that does not. In Portland, covered decks also have zoning requirements “regardless of height”, and Oregon City requires planning and building permits for decks covered over 200 square feet or more. Our page on covered decks and deck roofs goes through the options.
Portland: what the City checks
Portland Permitting & Development (PP&D), at 1900 SW Fourth Avenue (503-823-7300), reviews residential decks. Its deck pages list the codes a deck is reviewed against: the ORSC, the Title 33 zoning code and the Title 11 tree code.
- Setbacks (Title 33). In Portland’s single-dwelling zones, decks, stairs and ramps “no more than 2-1/2 feet above the ground” may extend into the entire required building setback. Higher decks may extend into a setback by up to 20 percent of its depth and must be at least 3 feet from a lot line. Deck setbacks may also be reduced to the average of the setbacks on the abutting lots.
- Trees (Title 11). Detailed deck plans must show trees near the work and their root protection zone, with a “root protection zone radius (one foot per inch tree diameter)”. A 20-inch tree, for instance, has a 20-foot root protection radius.
- Overlay zones. PP&D says you may need a zoning permit if the deck is in an environmental, greenway or river overlay zone, even when it is low enough not to need a building permit.
- Two ways to design it. A deck can follow the code’s prescriptive path, using the standard construction rules and details, or be engineered. The plans have to show how the ledger board attaches to the house.
Permit fees in Portland are calculated from the project’s valuation rather than charged as a flat amount; our page on what a deck costs explains what else goes into a deck’s price.
How the suburbs differ
Every city below applies the same 30-inch state rule. What changes is who issues the permit and what each city adds to it.
| City | Permit office | What is different |
|---|---|---|
| Lake Oswego | Building Department, 380 A Avenue, 503-635-0290 | Decks over 10 feet tall need an engineered design; tree permits must be approved before the building permit |
| Tigard | Tigard Permit Center, 13125 SW Hall Blvd., 503-718-2439 | Unroofed decks 3 feet or lower may project into side and rear setbacks; own deck submittal guide |
| Happy Valley | Building Division, 16000 SE Misty Drive, 503-783-3800 | City policy requires engineering for any deck 10 feet or taller |
| Oregon City | Building Division, 625 Center Street, 503-722-3789 | Planning and Building permits for decks over 30 inches or covered over 200 sq ft or more; zone setback table |
| Beaverton | Building Division, 12725 SW Millikan Way, 503-526-2403 | Accepts the state permit-ready deck plan with a 12-inch frost line and a site plan showing setbacks |
| West Linn | Building Division, 22500 Salamo Rd., 503-742-6055 | States that rebuilding an existing deck over 30 inches needs a permit, as a new one does |
| Unincorporated Clackamas County | Building Codes Division, 150 Beavercreek Road, Oregon City, 503-742-4240 | County issues the permits; publishes a ready-to-build prescriptive deck plan |
| Unincorporated Washington County | Building Services, 155 N. First Ave., Suite 350, Hillsboro, 503-846-3470 | No permit for a ground-level deck, but check setbacks with Current Planning |
Oregon’s Building Codes Division also publishes a statewide permit-ready plan for an exterior deck under the 2023 ORSC. It is 28 sheets of standard details; the city fills in local values such as frost depth, and it requires the ledger to be flashed “to prevent water from contacting the house band joist.” Ask your city whether it accepts the plan and on what conditions before relying on it.
Railing height
A deck high enough to need a permit is also high enough to need guards. The ORSC requires them where a walking surface is more than 30 inches above the floor or grade below, within 36 inches horizontally, and sets their minimum height at 36 inches. Openings, stairs and handrails have rules of their own; our guide to deck railing height and stair code quotes each one.
The 2026 code change
Oregon adopted a 2026 edition of the ORSC, effective October 1, 2026. Its Chapter 1, which holds the permit exemptions quoted above, became mandatory that day. For the rest of the code there is a six-month phase-in: according to the Building Codes Division, during the phase-in period, except for Chapter 1, use of the 2023 ORSC or the 2026 ORSC is permitted, and the 2026 code becomes mandatory on April 1, 2027. The construction sections quoted on this site, such as the guard and stair rules, are from the 2023 edition, because the integrated 2026 book had not been published when we checked on October 9, 2026.
Before you build
Confirm the rules with the permit office for your address before work starts; these are summaries of the codes and city pages as published, not legal advice. A contractor who quotes your deck should say whether it needs a permit and who will apply for it. For the deck itself, see deck repair and replacement, composite deck builders, or start with our Portland deck builders page.
This page is general information, not professional advice about your specific situation. Have it assessed by a qualified professional before making decisions. Last reviewed October 9, 2026.