What's Required in Seattle
- A permit is required for any deck more than 18 in above the ground, any roof deck, and any deck in an environmentally critical area; platforms 18 in or lower are exempt.
- Most decks qualify for a subject-to-field-inspection permit; decks over 8 ft high, with beams 14 ft or longer, over 750 sq ft, roof decks, ECA sites or solid-surface flooring need an addition or alteration permit with plan review.
- Fees are value-based: Table D-1 index on SDCI's $36.09 per square foot deck valuation, 40 percent STFI plan review, 5 percent technology fee and the $6.50 state surcharge.
- Design for a 60 pounds per square foot live load and connect any ledger per SRC R507.9.1.3 or an engineered detail.
- Guards at least 36 in tall with 4 in maximum openings where the deck is more than 30 in above adjacent surfaces; stair risers 7-3/4 in maximum, treads 10 in minimum, 36 in width, handrail at 34 to 38 in on four or more risers.
- Decks over 18 in must respect NR setbacks (10-15 ft front, 3-5 ft side, 5-15 ft rear); decks over 36 in count toward the 50 percent lot coverage cap.
- Use treated or naturally decay-resistant wood where it contacts concrete near earth.
- ECA sites need a pre-application site visit before any construction permit application.
Do You Need a Permit to Build a Deck in Seattle?
Yes if it is more than 18 in above the ground, a roof deck, or in an environmentally critical area (ECA); no if it is a platform 18 in or lower that is not over a basement or story below (SRC R105.2 item 7, repeated on SDCI's Decks page). Most decks that need a permit qualify for a subject-to-field-inspection (STFI) construction permit, which SDCI screens in a few days instead of putting through full plan review. A deck goes to a regular addition or alteration permit with plan review if it is more than 8 ft above the ground, has beams 14 ft or longer, is a roof deck, sits in an ECA, has solid-surface flooring with no gaps, or exceeds 750 sq ft. The fee is value-based: about $625 for a 12x16 deck and $735 for a 16x20, all fees included.
Seattle Deck Permit Rules by Scenario
| What you are doing | City filing | Rule |
|---|---|---|
| Platform deck 18 in or lower above grade, not over a basement, not in an ECA | None (zoning does not limit placement either) | SRC R105.2 item 7; SDCI Decks page |
| Deck over 18 in and up to 8 ft above ground, beams under 14 ft, gapped boards, 750 sq ft or less | STFI construction permit, value-based | SDCI Decks page; Tip 316 |
| Deck over 8 ft above ground, beams 14 ft or longer, over 750 sq ft, or solid-surface flooring | Addition or alteration permit with full plan review | SDCI Decks page |
| Roof deck on top of part of the house | Addition or alteration permit with plan review | SDCI Decks page |
| Deck in or near an ECA (steep slope, landslide, flood-prone) | Pre-application site visit first; SDCI decides the permit type | SDCI Decks page |
| Deck more than 30 in above adjacent surfaces | Guard at least 36 in tall with openings no more than 4 in | SDCI Decks page; Tip 303A |
| Deck more than 36 in above ground | Counts toward the 50 percent lot coverage limit in NR zones | SDCI Decks page; NR summary |
How Much Does a Deck Permit Cost in Seattle?
SDCI prices construction permits on value using Table D-1 of the 2026 Fee Subtitle, and it sets the value from its own building valuation data rather than your contractor's bid. Director's Rule 5-2025 values open decks associated with a house at $36.09 per square foot for Type VB (wood frame) construction. For an STFI permit the permit fee is 100 percent of the Development Fee Index and plan review is 40 percent (minimum $116.75), plus a 5 percent technology fee and the $6.50 state Building Code Council surcharge.
Worked example, 12x16 deck: 192 sq ft x $36.09 = $6,929.28 of value. Table D-1: $325 for the first $1,000 plus 60 x $1.60 = $96, so the DFI is $421. Permit $421 + plan review $168.40 = $589.40; add $29.47 technology fee and $6.50 = $625.37. A 16x20 deck (320 sq ft, $11,548.80 of value) has a $494.60 DFI and totals $733.56. If the same 320 sq ft deck is more than 8 ft off the ground and needs full plan review, plan review becomes 100 percent of the DFI and the total is about $1,045. SDCI raised construction permit fees 18 percent on January 1, 2026, so a 2025 estimate will be low.
Building Code Rules SDCI Checks in the Field
The Decks page lists what the inspector looks for. Design live load is 60 pounds per square foot. A ledger-supported deck must be attached so it cannot pull away in an earthquake, using the prescriptive connection in SRC Section R507.9.1.3 or an engineered detail. Guards are required when the walking surface is more than 30 in above the ground or a lower roof: at least 36 in tall with openings no larger than 4 in. Stairs need risers no taller than 7-3/4 in, treads at least 10 in deep and 36 in of width, with a handrail on stairs of four or more risers set 34 to 38 in above the nosings. Deck drawings rarely need a professional stamp, but glass guards may need a structural engineer.
Zoning Rules for Decks
Placement rules kick in above 18 in: in Neighborhood Residential zones you cannot build the deck within 10 to 15 ft of the front property line, within 3 to 5 ft of a side line, or within 5, 10 or 15 ft of the rear line depending on how many units are on the lot. Above 36 in the deck counts toward lot coverage, capped at 50 percent in NR zones. SMC 23.44 was rewritten in 2025, so confirm your setbacks through SDCI's free land use coaching.
How to Get a Deck Permit in Seattle
Measure height above grade
At 18 in or lower with no basement below, no building permit is needed. Above 18 in, note whether it will exceed 8 ft, use beams of 14 ft or more, or exceed 750 sq ft, since those push it out of STFI.
Check ECA and zoning maps
Use SDCI's GIS map to confirm the lot is outside steep-slope, landslide and flood-prone areas, then lay out the deck against the front, side and rear setbacks and the 50 percent lot coverage limit.
Draw the plans
Prepare a site plan to Tip 103, a framing plan with joist, beam and post sizes, footing details, the ledger connection per SRC R507.9.1.3, and guard and stair details; no professional stamp is normally needed.
Apply through the Seattle Services Portal
Start a Building and Land Use Pre-Application with the site plan and legal description, upload the drawings, answer yes to the STFI question, and pay the value-based fee when SDCI issues the permit after a few days of screening.
Build and call for inspections
Keep the permit and stamped plans on site and schedule footing, framing and final inspections online or at (206) 684-8900; the inspector checks loads, ledger, guards and stairs on site.