Do you need a permit for a deck?
Check the permitting authority for the property before you build. A deck permit is a jurisdiction-specific question, and local triggers are not interchangeable. Seattle requires a permit when a deck is more than 18 inches above the ground. (Seattle Department of Construction and Inspections) Fairfax County lists decks among new additions for which a permit is required. (Fairfax County Land Development Services)
Those two official examples show why a generic height or area cutoff cannot settle your project. Check the city or county that issues building permits for the address, and describe the deck height, footprint, attachment, stairs, roof use, and site conditions.
Why the permit review matters
A deck review covers more than whether the framing can carry people. It can also reach the deck location, connections, guards, stairs, and site constraints. Seattle says deck design must provide sufficient structural support and attachments to meet safety standards. (Seattle deck requirements)
In Seattle, a deck more than 18 inches above ground can face rear property-line limits tied to the number of units on the lot. (Seattle deck requirements) That is a useful warning for any project: confirm zoning and setbacks before committing to a footprint, even if the structure itself is simple.
Which permits may apply
The permit path depends on the project and site. Ask the permitting authority for the property which building or construction permit, if any, applies and whether other approvals are needed. Seattle says most decks require only a subject-to-field-inspection construction permit. (Seattle deck requirements) Seattle routes decks more than 8 feet above ground, decks with beams 14 feet or longer, roof decks, decks in environmentally critical areas, solid-surface decks, and decks over 750 square feet through its addition-or-alteration permit path. (Seattle deck requirements)
Fairfax County says additional permits or approvals may be required by other agencies even when a land-development permit is not. (Fairfax County permit guide) Ask your local office whether building, zoning, land-disturbance, floodplain, septic, electrical, or other approvals apply rather than assuming one approval covers everything.
Plan inspections before you build
Do not schedule the crew as if inspectors only arrive at the end. Seattle lists a foundation inspection before concrete, a framing inspection before framing is covered, and a final inspection after construction and related permit finals are complete. (Seattle construction inspections) Seattle also states that the permit holder is responsible for requesting each inspection. (Seattle construction inspections)
Your jurisdiction may use different names or combine visits. Put every required hold point on the schedule, keep approved plans on site, and do not pour footings or conceal connections until the relevant inspection is cleared.
When a deck might be exempt
Do not carry an exemption from one city into another. Seattle lists three basic permit triggers: a deck more than 18 inches above ground, a roof deck, or a deck in an environmentally critical area. (Seattle deck requirements) Fairfax County lists on-grade paver and concrete patios, including wood patios, among residential projects that do not require a permit, subject to notes about other approvals. (Fairfax County permit guide)
Classify the project correctly before relying on an exemption. An on-grade slab is not the same project as elevated deck framing; our guide to whether you need a permit for a concrete patio or slab covers that separate question. A shade structure can also follow different rules, so use the pergola and gazebo permit guide when that is what you are actually building.
Checklist scope note: In the fixed checklist below, ‘the local threshold in the rule above’ means the threshold in the controlling published rule for this property’s jurisdiction. Seattle’s more-than-18-inch permit example is not a portable threshold and applies only when Seattle is the authority. For a project elsewhere, use that jurisdiction’s written height, area, location, and site criteria when answering the checklist question.