Do You Need a Permit to Build a Deck in Seattle?

Any deck more than 18 inches above the ground, any roof deck and any deck in an environmentally critical area. According to the city, a deck needs a permit if it is:

• More than 18 inches above the ground
• A roof deck built on top of part of the building
• In an environmentally critical area (ECA), for example landslide-prone or flood-prone areas

The same goes for platforms and walks: no permit if they are less than 18 inches above grade and not over a basement or other building story.

Most decks only need a subject-to-field-inspection permit, and the city issues some simple building permits with minimal review within 48 hours of when you submit your application. You need an addition or alteration permit instead if any of these apply:

• It will be more than 8 feet above the ground
• It includes beams 14 feet or longer
• It will be a roof deck, or it sits in an ECA
• It has deck flooring that is a solid surface (no gaps between boards)
• It will be over 750 square feet in size

The quicker permit also costs less at review: it pays 40% of the plan review fee. See the deck cost guide.

Not within 10-15 feet of the front property line once the deck is more than 18 inches above the ground. Seattle's zoning code limits placement at that height: you can't build your deck within 10-15 feet of the front property line, or within three to five feet of either side property line in neighborhood residential zones. A deck more than 36 inches above the ground also counts toward lot coverage, and for neighborhood residential zones (NR1, NR2, and NR3), the total coverage is limited to 50 percent of the lot. In or near an ECA you need a pre-application site visit before applying for any construction permit.

A deck must carry at least 60 pounds per square foot, have a ledger tied to the house against earthquakes, and have guards once it is more than 30 inches up. The city sums up the main building code points:

• Load: a minimum live load design of 60 pounds per square foot
• Ledger: connected so the deck won't pull away from the house in an earthquake, using the standard connection the city's residential code sets out
• Guards: required on decks more than 30 inches above adjacent surfaces, at least 36 inches tall, with openings no more than 4 inches in diameter
• Stairs: a riser of no more than 7-3/4 inches, a tread that is at least 10 inches, and a width of at least 36 inches; a handrail for four or more risers
• Wood near the ground: treated or naturally decay-resistant wood where it contacts concrete close to earth

Deck drawings rarely require a professional's stamp. Check the composite and repair guides for how these show up in a quote.

Each city sets its own threshold, so check the town page before assuming Seattle's 18-inch rule applies:

• Bellevue puts new decks and repairs to deck framing under its single-family addition permit.
• Redmond exempts detached decks no more than 30 inches above grade.
• Bothell prices permits from project valuation.
• Renton measures its 30-inch rule including a 5 foot perimeter around the deck.
• Lynnwood exempts only small detached decks of up to 200 square feet.
• Edmonds requires a permit even to repair or replace a deck.

Normally the contractor you hire. In most instances, if you have hired a contractor, the contractor is required to take out the permits, and Washington lists a builder asking you to get the permit as a warning sign. See how to choose a deck builder.