Basement ADU Conversion in Mercer Island, WA

Basement ADU Conversion in Mercer Island, WA

When Mercer Island homeowners search for basement ADU conversion or a dependable adus & conversions contractor near them, they want craftsmanship that lasts and a crew that communicates. That's exactly what we do. Turn a basement into a separate-entry dwelling unit.

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

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

What's included in your basement ADU conversion

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

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

How much does a basement ADU conversion cost in Mercer Island?

Most basement ADU conversion projects in Mercer Island fall between $113,500 – $255,000, 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

Honest guidance on where to invest and where to save, so your budget goes toward what adds real, lasting value.

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

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

Each phase is inspected and documented, and we keep you updated so you always know what's happening and what's next.

Handoff includes a detailed walkthrough and a written warranty — not a crew that vanishes the moment the dust settles.

Frequently asked questions

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