ADUs & conversions · Mercer Island, WA
ADU Design & Permitting in Mercer Island, WA
Plans and permits navigating local ADU rules.
ADU Design & Permitting in Mercer Island, WA
Xion Build provides expert ADU design & permitting 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. Plans and permits navigating local ADU rules.
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 ADU design & permitting
A typical ADU design & permitting in Mercer Island can involve framing, permits, finishes, utilities — 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 an ADU design & permitting cost in Mercer Island?
Most ADU design & permitting projects in Mercer Island fall between $108,000 – $243,500, 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
Transparent, written estimates with no hidden fees — you know what you're paying for before work begins.
Meticulous job sites and clear daily communication, with respect for your home, your time, and your neighbors.
One dedicated point of contact coordinates the entire job, so you're never chasing subcontractors or wondering who's responsible.
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.
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.
Frequently asked questions
Do you offer an ADU design & permitting in Mercer Island, WA?
Yes. Plans and permits navigating local ADU rules. Xion Build is a licensed, bonded, and insured adus & conversions contractor serving Mercer Island and the surrounding WA communities.
Do you offer free estimates for ADU design & permitting near Mercer Island?
Absolutely. We provide free, no-obligation in-home estimates throughout Mercer Island and the greater Eastside, with transparent, itemized pricing.
Do you handle permits and inspections?
Yes. We manage permit applications, schedule inspections, and coordinate any required engineering so the work passes cleanly in Mercer Island.
What should we decide before starting an ADU design & permitting?
Your budget range, must-haves, timeline, and any finishes you already love. For adus & conversions work we also review access, existing conditions, and whether permits are required in Mercer Island.
How long does an ADU design & permitting take?
Timelines depend on scope and permitting. Once the plan is confirmed we give you a realistic schedule and keep you updated as the adus & conversions work progresses.
Related services in Mercer Island
Garage to living space
Convert a garage into a gym, office, or studio.
View detailsADU utility & meter separation
Separate utilities and metering for rentals.
View detailsBasement ADU conversion
Turn a basement into a separate-entry dwelling unit.
View detailsDetached ADU (DADU) build
Stand-alone backyard cottages from foundation to finish.
View detailsWe also serve these areas