Landscaping & Hardscaping on Mercer Island, WA

Mercer Island is a single glacial ridge sitting in Lake Washington, high along Island Crest Way at roughly three hundred and fifty feet and falling away to the water on every side. That shape produces two completely different working environments within a half mile of each other. The interior is broad, gently rolling, heavily wooded and comparatively easy to build on. The rim is steep, slide-prone and mapped for geologic hazard almost the whole way around, because the island is built the way most of this shoreline is built: permeable outwash sand lying on dense, impermeable till, with groundwater emerging at the contact and the bank above it moving after a wet winter. Every serious project on a perimeter lot starts with that fact and works outward.

The housing tracks the bridges. Before the first floating span opened in 1940 this was a ferry-served summer place, and a handful of that older stock still exists around East Seattle and the north end. The real build-out came afterward: First Hill, Mercerwood, Shorewood and the Island Crest corridor filled with ramblers, split levels and daylight basements through the 1950s and 60s. The Lakes and the later plats followed. On top of all that sits a steady churn of teardowns, where a 1958 rambler comes down and a substantially larger house goes up on the same footprint, leaving a narrower band of usable yard, a new grade, and construction fill where the original garden used to be.

Access is the constraint people underestimate. Mercer Island has no alley system. Streets are narrow and winding, many private lanes are shared, driveways are frequently steep and short, and there is often nowhere to legally park a dump trailer while a crew unloads. A large fraction of the work here moves by buggy, wheelbarrow or conveyor rather than by machine, and the honest version of an estimate accounts for that instead of pretending a truck can back to the patio. It is also why we do not list paver driveways on the island. Many island drives are steep enough that segmental pavers are simply the wrong product for the grade, and the ones that are not are usually better served by a concrete contractor. We would rather say that than sell something that does not fit the site.

Two Mercer Island rules shape almost every design we draw. The tree code is among the strictest in the region, with permits required to remove regulated trees, replacement or fee obligations attached, and real scrutiny of work inside a protected root zone, which is a hardscape issue as much as an arborist issue because a wall footing is a root cut. Separately, the city regulates hardscape as a share of lot area alongside building coverage, so patio plus walkway plus drive plus parking pad is a number that has to be checked against a cap before layout is finalized. On the rim, geologic hazard review and a geotechnical report are routine rather than exceptional. None of that makes a good project impossible. It does mean the design has to be sized to the rules on day one, and a contractor who has never worked here will find that out at the counter.

What we build most on the island is grade work and outdoor rooms: a level terrace cut into a slope behind a mid-century house, block or slab steps replacing a set of failing railroad ties, a low seating wall that frames a patio without eating the coverage allowance, a pondless basalt fountain where the yard is too shaded for a lawn. Design happens in our own office and our own crew self-performs the hardscape, which matters on tight island sites because the plan has to be built by people who understand why the base was drawn the way it was. Planting works with the island canopy rather than against it: sword fern, salal, evergreen huckleberry and rhododendron under mature Douglas fir and bigleaf maple, hydrangea and Japanese maple where there is filtered light, dwarf conifers for structure on a view lot where mature height is a liability, carex and red twig dogwood along the seep lines that show up on the lower slopes. Irrigation is city water with a backflow assembly and a test on every install, zoned separately for the deep shade and the few genuinely sunny exposures the island has.