Detached ADU (DADU) Build in Mercer Island, WA

Detached ADU (DADU) Build in Mercer Island, WA

When Mercer Island homeowners search for detached ADU (DADU) build or a dependable adus & conversions contractor near them, they want craftsmanship that lasts and a crew that communicates. That's exactly what we do. Stand-alone backyard cottages from foundation to finish.

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 detached ADU (DADU) build

A typical detached ADU (DADU) build in Mercer Island can involve utilities, foundation, permits, finishes — 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 detached ADU (DADU) build cost in Mercer Island?

Most detached ADU (DADU) build projects in Mercer Island fall between $234,000 – $585,000, 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

Licensed, bonded, and insured in Washington — every project is built to meet or exceed code and backed by a written warranty.

One dedicated point of contact coordinates the entire job, so you're never chasing subcontractors or wondering who's responsible.

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

Our Mercer Island adus & conversions process

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

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

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

Frequently asked questions

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