Concrete Driveways & Sidewalks in Mercer Island, WA

Driveways & sidewalks in Mercer Island: what to know

A driveway on Mercer Island uses part of a fixed share of the lot, and the share shrinks as the lot steepens. The city counts buildings plus vehicle surfaces as lot coverage: 40 percent on a lot under 15 percent slope, 35 percent from 15 to under 30, 30 percent from 30 to 50, and 20 percent above 50.

Height is the second limit. The code, as quoted in city permit files, lets hardscape and driveways in required yards stand no more than 30 inches above existing or finished grade, though a driveway can exceed that when the applicant shows the height is the minimum feasible. On a sloped lot the profile decides the design, so we take grades at each yard line before drawing the pour.

Permits and rules in Mercer Island

Community Planning and Development lists driveways and sidewalks as exempt from a building permit when built to the residential code and no more than 30 inches above grade, but an exemption does not lift land use rules, and it does not apply inside a critical area. The apron is public right-of-way, which takes its own permit, and anything left there needs an approved, recorded encroachment agreement. Before pricing, we look up the right-of-way and hazard-map requirements for your address.

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

How we approach it

Total buildings and driving surfaces against the slope-based coverage limit before widening anything
Take grades at each yard line, where driveway height is capped at 30 inches
Treat the apron as right-of-way work and ask the Development Engineer first
Check the hazard map, since October to April grading limits can apply

For the full process, see our Concrete Driveways & Sidewalks page.

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

Our driveways & sidewalks work, serving Mercer Island

Examples of our work. We build driveways & sidewalks in Mercer Island and the cities around it. See all of our work

Questions from Mercer Island homeowners

How much of my Mercer Island lot can be driveway?

Driveways count toward lot coverage with the house, and the cap depends on slope: 40 percent under 15 percent grade, 35 percent to 30, 30 percent to 50, and 20 percent above. We total your lot’s surfaces first.

Do I need a permit to replace a driveway on Mercer Island?

The city’s list exempts driveways and sidewalks built to the residential code and no more than 30 inches above grade, but not in a critical area, and the street apron needs a right-of-way permit. We confirm with Community Planning and Development where each part of your project falls.

Can a Mercer Island driveway be torn out between October and April?

On a lot mapped as an erosion, potential slide, or steep slope hazard, grading, filling, and foundation work are barred from October 1 to April 1 unless the city grants a waiver. We check your lot’s mapping before choosing a start date.