Basement Waterproofing in Vashon Island, WA

Basement waterproofing in Vashon Island: what to know

On a bluff lot, an exterior drain set at footing depth carries seepage to a discharge point on the lot, away from the bluff face and neighboring ground. Where the floor sits below every available outlet, a sump and pump lift the water, and the pump discharge is routed the same way. We do not send sump water over the bluff, because concentrated runoff at the edge can start erosion on a steep bank.

The island includes a Marine Recovery Area, where owners must inspect and, when needed, fix or replace their on-site sewage systems. Before any digging near the house, we look up the parcel’s on-site sewage records and mark the drain field on the plan, so the new run stays clear of it.

Permits and rules in Vashon Island

A bluff-side waterproofing job is screened first against the county’s four-foot wall line and its grading lines, and we confirm whether any digging sits beside a retaining element before cutting begins. Work that changes a load-bearing element goes to King County in writing first. Each outlet is checked against the parcel lines, the shoreline designation, and the septic record before a pump is connected.

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

How we approach it

Trace the seep path at the footing before choosing a fix
Run an exterior drain at footing depth on the bluff side
Add a sump only where the floor sits below every outlet
Vent the sump lid so vapor stays out of living space

For the full process, see our Basement Waterproofing page.

Our basement waterproofing work, serving Vashon Island

Examples of our work. We build basement waterproofing in Vashon Island and the cities around it. See all of our work

Questions from Vashon Island homeowners

Is a permit needed for a drain run outside a Vashon Island footing?

A drain run outside the footing, with the wall itself left as built, is screened against the county’s wall and grading lines. Any change to a bearing wall goes to King County for written review first, and that answer is kept with the scope.

Where does sump water leave a Vashon Island basement?

Into a discharge point on the parcel that stays off the shoreline, neighboring yards, and any bluff face. Each route is walked end to end before the pump is switched on, and the discharge point gets a second look once the first wet season has passed.

Does a bluff-side crawlspace on Vashon Island need a pump?

Sometimes not. If seepage can run by gravity past the footing to an outlet that works, no pump is required. When the low point sits beneath every outlet, a sump and pump go in, and the discharge route goes to King County first.