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Attached ADUs in Seattle
An addition that becomes its own home: separate entry, separate kitchen, connected to the main structure.
When does attached make sense?
On lots without room for a detached unit, or when owners want one roofline and shorter utility runs.
What is different from a detached ADU?
Fire separation, soundproofing and how the new roof meets the old one. We plan those first.
Can part of my house become the ADU?
Often. Converting space inside the existing structure can avoid setback limits that apply to new construction.
Basement and attached units
Seattle's 2025 changes removed limits on entrance locations and exterior stairs for ADUs, which makes basement units easier to lay out.
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Is your lot ready for an ADU?
Send your address and a sentence about what you want. We look up the zoning, setbacks and utility routes and reply with the ADU types that fit.
We build in Seattle, WA.