Deck permits in Mercer Island: fees, timeline & requirements (2026)
Everything you need to know about pulling a deck permit in Mercer Island, Washington — when one is required, what it costs, how long review takes, what documents are required, and which inspections you can expect. Cited to Mercer Island Community Planning & Development.
Free lookup, no account needed — your lot polygon, zoning, setbacks and overlays, cited to Mercer Island's source.
When does a deck need a permit in Mercer Island?
Permit NOT required for sidewalks, decks and driveways constructed under IRC, not more than 30in above grade and not over any basement or story below. Decking replacement on existing decks WITHOUT changing/adding structural members and WITHOUT removing guardrails is also exempt. Per the multi-jurisdiction tip sheet, the 30-inch measurement is taken vertically to the grade below at any point within 36 inches of the outer edge of the deck. Critical-area / flood-hazard exemption rule applies.
How Mercer Island adopted this rule
The threshold comes from the state code (WAC 51.51), which Mercer Island adopts by reference in the provision quoted below.
“The 2021 Edition of the International Building Code (IBC), including the adoption of ICC/ANSI A117.1-2017, Requirements for Accessible and Useable Buildings and Facilities, as adopted and amended by the State Building Code Council in WAC Chapter 51-50, as published by the International Code Council, excluding Chapter 1, Administration, is adopted by reference, together with the following amendments and additions. The Construction Administrative Code, as set forth in chapter 17.14 MICC, shall be used in place of IBC Chapter 1, Administration.”Source ↗verified 2026-04-29
Required submittals
- Site plan with setbacks
- Framing plan w/ ledger detail
- Footing detail
- Guard/handrail detail
Inspection sequence
- Footing
- Framing
- Final
Contractor specialties needed
General contractor
Who can do this work in Mercer Island?
Kolmo Construction is a licensed Washington general contractor — KOLMOL*753JS, active through April 10, 2027, bonded and insured — working throughout Mercer Island and King County. Kolmo prepares the drawings and submittals, files the deck permit with Mercer Island Community Planning & Development, carries the project through review and inspections, and performs the construction. Call (206) 410-5100 for a Mercer Island deck quote.
Notes & caveats
From MICC 17.14.010 §105.2: "Sidewalks, decks and driveways constructed under the provisions of the IRC, which are not more than 30 inches (762 mm) above grade and not over any basement or story below" are exempt. Also exempt: "Decking replacement on decks without changing or adding any other structural members or removing guardrails." Critical-area override (per MICC 17.14.010 §105.2): exemptions DO NOT apply in flood-hazard or city land-use critical areas unless work is entirely within or on the exterior envelope of a legally established existing building.
Deck permit fee estimate in Mercer Island
Worked example for an $18,000 deck project (building permit). Your actual fee scales with project valuation.
| Building permit fee | $490.67 |
| Plan review | $343.47 |
| WA state surcharge | $6.50 |
| Estimated total | $840.64 |
A deck over 30 inches above grade or over a story below needs a building permit on Mercer Island, priced on the value of the work: $40.06 up to $500, and $118.83 for the first $2,000 plus $23.24 for each $1,000 more up to $25,000; plan check adds 70% of that fee where plans are reviewed (2026 Fee Schedule). Computed from Mercer Island's adopted fee schedule · source ↗. Land use, fire and engineering review, intake, impact and utility fees, where they apply, are charged separately.
How to apply yourself
- 1. Confirm your parcel's zoning & overlays. Run an address lookup for your deck in Mercer Island — we'll pull your specific lot polygon, zoning, setbacks, and any shoreline, critical-area or historic overlays.
- 2. Assemble submittals: the 4 documents under Required submittals above.
- 3. Submit through the city portal: Mercer Island Community Planning & Development ↗
- 4. Track review. Respond to reviewer comments promptly.
- 5. Pay issuance fees (about $841 for an $18,000 project) and pick up the permit. Inspection card travels with the job.
Or have Kolmo do it
Kolmo prepares the drawings and submittals, files with Mercer Island Community Planning & Development, handles reviewer comments, and builds the project.
Licensed WA general contractor KOLMOL*753JS · bonded & insured
Deck permits in Mercer Island — FAQ
When does a deck need a permit in Mercer Island?
Permit NOT required for sidewalks, decks and driveways constructed under IRC, not more than 30in above grade and not over any basement or story below. Decking replacement on existing decks WITHOUT changing/adding structural members and WITHOUT removing guardrails is also exempt. Per the multi-jurisdiction tip sheet, the 30-inch measurement is taken vertically to the grade below at any point within 36 inches of the outer edge of the deck. Critical-area / flood-hazard exemption rule applies.
How much does a deck permit cost in Mercer Island?
For a $18,000 deck project, the estimated Mercer Island permit fee is about $840.64 (building fee $490.67 + plan review $343.47 + surcharges) from Mercer Island's adopted fee schedule. Land use, fire and engineering review, intake, impact and utility fees, where they apply, are charged separately.