Concrete Patios & Stairs in Vashon Island, WA

Patios & stairs in Vashon Island: what to know

A patio set flat to grade and lacking any retained edge carries no wall, so the county’s wall rule does not reach it. The exemption in code section 16.02.240 covers decks that stand no more than 30 inches above grade and sit over no basement or story, so anything taller, or built over one, falls outside it, and we ask King County whether a permit applies before layout. A deck no taller than 30 inches with no roof needs no permit under the county’s permit guidance when no critical area is involved.

Bluff-edge lots are read against the 2026 steep slope guidance from King County. Ground steeper than about 21 degrees that climbs 10 feet or more is treated as hazard ground, and work set more than 65 feet back from it avoids a geological critical areas report. Shore lots also get a designation check first, so the patio’s outer edge is laid out with the shoreline rules in view. Stairs down a bank are checked rise by rise, and the top landing is fixed before the footing is cut.

Permits and rules in Vashon Island

Before layout, every slab and step is run through the wall and deck lines, and we verify whether steep ground or any other critical area lies behind the work. A raised edge close to hazard ground is referred to King County by letter, and its reply is filed with the scope. A patio with no held-back edge stays outside the wall review, so it can be formed once the grade is set.

Rules change and vary by parcel, so we confirm the current requirements with the city before we start.

How we approach it

Survey each corner and fix the finished grade before forms go in
Route every patio exit away from the bluff face
Record footing depth and loads for each raised edge
Hold any raised stair until the county answers in writing

For the full process, see our Concrete Patios & Stairs page.

Building in the cold months? See our guide to winter concrete pours.

Our patios & stairs work, serving Vashon Island

Examples of our work. We build patios & stairs in Vashon Island and the cities around it. See all of our work

Questions from Vashon Island homeowners

Will a Vashon Island patio need a county review?

A patio at grade level, with nothing holding back soil along its edge, stays outside the county’s wall review. A raised edge near a bluff, or any structure inside a hazard setback, gets a county reading first, and we write to King County only where a load could reach that edge.

Are the stairs down a Vashon Island bank measured like walls?

Bank stairs are checked by rise, tread depth, and the landing at the top. A flight that meets retained ground is read through the wall review, while a freestanding flight is noted on the scope as open.

Can a Vashon Island patio go on a steep bluff?

Only after the bluff is surveyed. We measure the slope angle and vertical rise, keep the patio beyond the county’s 65-foot line from hazard ground where the layout allows, and send any remaining question to King County in writing.