Attached ADU Build in Mercer Island, WA

Attached ADU Build in Mercer Island, WA

Xion Build provides expert attached ADU build in Mercer Island. As a trusted Mercer Island adus & conversions contractor, we manage design, materials, permits, and every trade in-house so your project stays on schedule and on budget. Attached accessory dwelling units within the home's footprint.

Mercer Island projects often involve sloped lots, shoreline rules, and mid-century homes that benefit from thoughtful structural and design planning.

We write scope in plain terms: what we'll do, the materials, the sequence, and how any surprises are handled if something is uncovered.

What's included in your attached ADU build

A typical attached ADU build in Mercer Island can involve foundation, utilities, finishes, the kitchen and bath — and we put the full scope in writing so you know exactly what's covered before work starts.

You get a single point of contact, licensed and insured trades, and clear communication from the first sketch to the final walkthrough.

How much does an attached ADU build cost in Mercer Island?

Most attached ADU build projects in Mercer Island fall between $197,000 – $591,000, depending on the size of the space, the finishes you choose, and the condition of what's already there.

Because every home is different, we don't quote final numbers sight unseen. After a free in-home consultation you get a detailed, itemized estimate tied to your actual adus & conversions project — so there are no surprises later.

Why Mercer Island homeowners choose Xion Build

Meticulous job sites and clear daily communication, with respect for your home, your time, and your neighbors.

Local crews who know Eastside permitting, inspections, and the way Pacific Northwest weather tests a home.

Transparent, written estimates with no hidden fees — you know what you're paying for before work begins.

Our Mercer Island adus & conversions process

It starts with a free, no-obligation consultation: what you want, the constraints, and a realistic budget range before you commit to anything.

We pull the permits, schedule every trade in the right order, and protect your home, landscaping, and daily routine throughout the build.

Design and material selections come next, so finishes, fixtures, and pricing are locked in before demolition — no surprises mid-project.

Frequently asked questions

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