Deck Permits in Seattle: Heights, Zoning and What SDCI Requires

Seattle Department of Construction and Inspections uses a lower height trigger than many cities. A deck needs a construction permit if it is more than 18 inches above the ground, if it is a roof deck, or if it sits in an environmentally critical area. Most decks qualify for a subject to field inspection permit, the simpler path.

When the full addition or alteration permit applies

• More than 8 feet above the ground.

• Beams 14 feet or longer.

• A roof deck.

• In an environmentally critical area.

• Solid surface flooring with no gaps between boards.

• Over 750 square feet.

Zoning limits

• Over 18 inches high: setbacks apply. In neighborhood residential zones, the deck must sit 3 to 5 feet from side property lines, plus front and rear setbacks.

• Over 36 inches high: the deck counts toward lot coverage. In NR1, NR2 and NR3 zones, total coverage is limited to 50 percent of the lot.

• Under 36 inches: SDCI does not limit deck size, unless the deck is in or near a critical area.

• Under 18 inches: placement is not limited, again unless near a critical area.

What SDCI checks

• Live load of at least 60 pounds per square foot.

• Ledger connection either prescriptive under Seattle Residential Code R507.9.1.3, or designed by an engineer.

• Guardrails where the deck is more than 30 inches above adjacent surfaces, at least 36 inches tall with openings no more than 4 inches.

• Stairs with risers no more than 7 3/4 inches, treads at least 10 inches and width at least 36 inches. Handrails are required at four or more risers.

• Glass guardrails carry special requirements and may need an engineer.

Critical area sites

On a site in an environmentally critical area, SDCI requires a pre-application site visit before applying for any construction permit, including a subject to field inspection permit. Steep slope lots are common in Seattle, so check this first.

Drawings

SDCI says stamped drawings are rarely required for decks, and someone with drafting skills can prepare them. The drawings still have to show the ledger, framing, footings, guards and stairs clearly enough to pass review and inspection.

Common questions

Do I need a permit for a deck in Seattle?

Yes, if it is more than 18 inches above the ground, a roof deck, or in an environmentally critical area. Most decks need only a subject to field inspection permit.

How big can my deck be?

SDCI does not limit decks under 36 inches high, unless near a critical area. Over 36 inches, the deck counts toward lot coverage, limited to 50 percent in NR1, NR2 and NR3 zones.

Do I need an engineer for a deck in Seattle?

Usually not. Stamped drawings are rarely required, but an engineer may be needed for a designed ledger connection, glass guardrails or larger decks.

What permit does a roof deck need?

A roof deck needs the full addition or alteration permit, not a subject to field inspection permit.

How SASHKOV handles it

• Confirms the permit type, setbacks, coverage and critical area status for the lot.

• Prepares deck drawings with ledger, framing, footing, guard and stair details.

• Brings in a structural engineer where the deck needs one.

• Submits through the Seattle Services Portal and tracks the permit to final.

Where a building requires a licensed architect or engineer of record, SASHKOV brings them into the contract.

Need deck drawings? See Permit and Construction Documents. For larger additions in Seattle, read Building a DADU or ADU in Seattle.

Planning a deck in Seattle? Send the address, size and height, and SASHKOV will confirm the permit type and timeline in business days.