Landscaping & Hardscaping on Mercer Island, WA

Mercer Island is one glacial ridge sitting in Lake Washington. It runs high along Island Crest Way at roughly three hundred and fifty feet and falls away to the water on every side. That shape gives you two completely different job sites within a half mile of each other. The interior is broad, gently rolling, heavily wooded and fairly easy to build on. The rim is steep and slide-prone, mapped for geologic hazard almost the whole way around. The island is put together the way most of this shoreline is. Permeable outwash sand lying on dense, impermeable till, groundwater coming out at the contact, and the bank above it moving after a wet winter. On a perimeter lot that is where every serious project starts.

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 is still standing around East Seattle and the north end. The real build-out came after. 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 came next. On top of all that there is a steady churn of teardowns. A 1958 rambler comes down and a much bigger house goes up on the same footprint. What is left is a narrower band of usable yard, a new grade, and construction fill where the original garden used to be.

Access is the thing people underestimate. Mercer Island has no alley system. Streets are narrow and winding. A lot of the private lanes are shared. Driveways are often steep and short, and there is frequently nowhere to legally park a dump trailer while a crew unloads. A big share of the work here moves by buggy, wheelbarrow or conveyor instead of by machine. An honest estimate accounts for that. Nobody is backing a truck up to your patio. That is also why we do not list paver driveways on the island. Plenty of island drives are steep enough that segmental pavers are the wrong product for the grade. The ones that are not are usually better off with a concrete contractor. We would rather tell you that than sell you 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. You need a permit to remove regulated trees, replacement or fee obligations come with it, and work inside a protected root zone gets real scrutiny. That is a hardscape problem as much as an arborist problem, because a wall footing is a root cut. The second rule is coverage. The city regulates hardscape as a share of lot area alongside building coverage. Patio plus walkway plus drive plus parking pad is one number, and it has to be checked against a cap before the layout is final. Out on the rim, geologic hazard review and a geotechnical report are routine. None of that makes a good project impossible. It does mean the design gets sized to the rules on day one. A contractor who has never worked here finds 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. On a tight island lot the layout gets drawn around the root plates of the retained firs, and around whatever the buggy or conveyor can actually reach. Those two decide the shape before taste gets a vote. Planting works with the island canopy. 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.