Deck Permit in Seattle, WA
Permit Summary
Do You Need a Deck Permit?
Exemptions
A deck 18 inches or less above the ground generally does not require a deck construction permit if it is not a roof deck and is not in an environmentally critical area. A roof deck and a deck in an environmentally critical area require a permit regardless of the 18-inch height threshold. Work that is permit-exempt must still comply with applicable code and development standards.
Attached / Detached Rules
A deck may be attached to the house or freestanding. If the house supports the deck through a ledger, the ledger must be positively connected so the deck will not pull away during an earthquake. SDCI points to the prescriptive ledger connection in Seattle Residential Code Section R507.9.1.3, or an engineer may design the connection.
Egress Rules
Decks, landings, and stairs must preserve required building egress. SDCI states that work reducing required egress requires a permit. Deck stairs must also meet the applicable stair and handrail dimensions.
Permit & Review Path
Permit / Review Path
Most permitted decks use a Construction Permit - Subject-to-Field-Inspection. An Addition or Alteration construction permit is required when the deck is more than 8 feet above the ground, includes beams 14 feet or longer, is a roof deck, is in an environmentally critical area, has a solid deck surface with no gaps, or is over 750 square feet. STFI screening checks eligibility and land-use compliance; the building inspector reviews building-code requirements in the field.
Zoning & Placement Rules
Zoning Rules
Seattle land-use zoning regulates deck size and placement. In Neighborhood Residential zones, decks more than 18 inches above the ground are subject to front, side, and rear setback requirements, while decks 18 inches or less above the ground are generally not subject to deck placement limits unless they are in or near an environmentally critical area. Additional land-use review may apply depending on the site and project.
Setback Rules
For decks more than 18 inches above the ground in Neighborhood Residential zones, SDCI states that the deck generally cannot be within 10-15 feet of the front property line or within 3-5 feet of either side property line. Rear setbacks are generally 5, 10, or 15 feet depending on the number of units and site configuration. Decks 18 inches or less above the ground are generally not limited by these deck placement rules outside environmentally critical areas.
Lot Coverage Rules
Deck portions more than 36 inches above existing grade count toward lot coverage. SDCI states that the current Neighborhood Residential lot-coverage limit is generally 50 percent; current code also provides a 60 percent limit for qualifying stacked-unit development. Deck portions 36 inches or less above existing grade are excluded from lot-coverage calculations. Environmentally critical areas can impose additional constraints.
Special Area Rules
A deck in an environmentally critical area requires a construction permit even if it is 18 inches or less above the ground. SDCI requires a pre-application site visit before applying for construction work in or near an ECA and determines the applicable permit path based on site conditions; topographic, geotechnical, or other ECA documentation may be required.
Structural Requirements
Structural / Load Rules
Deck design must provide sufficient structural support and attachments. SDCI requires a minimum deck live-load design of 60 pounds per square foot.
Foundation / Footing Rules
Deck foundations and footings must comply with the approved plans and applicable Seattle construction code. SDCI requires foundation inspection before concrete is placed when that inspection applies. Wood in contact with concrete close to earth must be preservative-treated or naturally decay resistant.
Ledger / House Connection Rules
When a deck is supported by a ledger at the house, the ledger must be connected so the deck cannot pull away during an earthquake. SDCI identifies Seattle Residential Code Section R507.9.1.3 as the prescriptive connection path and allows an engineer-designed connection as an alternative.
Guardrail Rules
A guard is required when the deck walking surface is more than 30 inches above adjacent surfaces such as grade or a lower roof. For residential decks, SDCI states that the guard must be at least 36 inches high and openings must not allow passage of a 4-inch-diameter object. Glass guards have additional code requirements and may require structural engineering.
Stair / Handrail Rules
Deck stairs must have risers no more than 7-3/4 inches high, treads at least 10 inches deep, and a width of at least 36 inches. A handrail is required for stairs with four or more risers; the handrail must be 34-38 inches above tread nosings and landings, with a hand-grip dimension of 1-1/4 to 2 inches.
Roof Deck Rules
A roof deck always requires a construction permit and does not qualify for the typical STFI deck path. SDCI requires an Addition or Alteration construction permit for roof decks, with full plan review for applicable structural, zoning, and other code requirements.
Heavy Load Rules
Seattle's deck guidance requires the deck to provide sufficient structural support for the proposed use and establishes a minimum live-load design of 60 pounds per square foot. SDCI does not publish a separate deck-specific prescriptive heavy-load rule on its current deck page, so loads beyond the ordinary deck design assumptions must be addressed in the project design.
Plans & Professional Design
Prescriptive Plan Rules
Seattle's current Residential Code contains prescriptive deck provisions and SDCI specifically identifies a prescriptive ledger-to-house connection in Section R507.9.1.3. These provisions may be used when the deck fits their assumptions; engineered design can be used for conditions not covered by the prescriptive provisions.
Professional Design Rules
SDCI states that deck drawings rarely require an architect's or engineer's stamp and may be prepared by anyone with drafting skills. A structural engineer may be needed for items such as glass guardrails or a non-prescriptive ledger connection, and projects in or near environmentally critical areas may require professional geotechnical or other site-specific documentation.
Inspections
Inspection Stages
For permitted decks, required inspections depend on the work. SDCI's construction inspection sequence can include site or first-ground-disturbance inspection, foundation inspection before concrete, framing or subfloor inspection before framing is covered, and a final inspection after construction is complete. STFI building-code compliance is reviewed primarily during field inspections.
What You Need Before Applying
Requirements
Determine the deck height, area, roof-deck status, beam spans, surface type, zoning, setbacks, lot coverage, and whether the site contains an environmentally critical area before applying. A deck that requires a permit must comply with applicable Seattle land-use and construction codes and be submitted through the Seattle Services Portal under the appropriate construction-permit path.
Required Documents
Typical application materials include a site plan, complete legal description, and scaled project plans showing existing conditions and the proposed deck. For sites with applicable environmentally critical areas, SDCI may require a topographic survey, geotechnical report, or other site-specific supporting documents.