Home additions · Mercer Island, WA
In-Law Suite Addition in Mercer Island, WA
Self-contained suite with bedroom, bath, and kitchenette.
In-Law Suite Addition in Mercer Island, WA
Xion Build provides expert in-law suite addition in Mercer Island. As a trusted Mercer Island home additions contractor, we manage design, materials, permits, and every trade in-house so your project stays on schedule and on budget. Self-contained suite with bedroom, bath, and kitchenette.
Mercer Island projects often involve sloped lots, shoreline rules, and mid-century homes that benefit from thoughtful structural and design planning.
From room additions and bump-outs to second stories and full primary suites, we handle structural engineering and permits up front so there are no surprises.
What's included in your in-law suite addition
A typical in-law suite addition in Mercer Island can involve roofline tie-in, framing, finishes, insulation — and we put the full scope in writing so you know exactly what's covered before work starts.
A home addition lives or dies on the connection to the existing house — foundation, framing, and rooflines have to marry seamlessly so the new space feels original.
How much does an in-law suite addition cost in Mercer Island?
Most in-law suite addition projects in Mercer Island fall between $151,500 – $441,500, 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 home additions project — so there are no surprises later.
Why Mercer Island homeowners choose Xion Build
One dedicated point of contact coordinates the entire job, so you're never chasing subcontractors or wondering who's responsible.
Local crews who know Eastside permitting, inspections, and the way Pacific Northwest weather tests a home.
Meticulous job sites and clear daily communication, with respect for your home, your time, and your neighbors.
Our Mercer Island home additions 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.
Handoff includes a detailed walkthrough and a written warranty — not a crew that vanishes the moment the dust settles.
Frequently asked questions
How much does an in-law suite addition cost in Mercer Island?
Most in-law suite addition projects in Mercer Island run $151,500 – $441,500, depending on scope, finishes, and existing conditions. After a free in-home consultation we provide a detailed written estimate so your Mercer Island price reflects the actual project — not a guess.
How long does an in-law suite addition take?
Timelines depend on scope and permitting. Once the plan is confirmed we give you a realistic schedule and keep you updated as the home additions work progresses.
What should we decide before starting an in-law suite addition?
Your budget range, must-haves, timeline, and any finishes you already love. For home additions work we also review access, existing conditions, and whether permits are required in Mercer Island.
Are you a licensed home additions contractor?
Yes — Xion Build is licensed, bonded, and insured in WA. Every project is built to meet or exceed code and is backed by a written warranty.
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.
Related services in Mercer Island
Sunroom & four-season room
Insulated, conditioned sunrooms usable year-round.
View detailsMudroom & entry addition
Drop-zone mudrooms with lockers, benches, and storage.
View detailsFoundation & footings for additions
Engineered footings and foundations for new square footage.
View detailsHome office addition
A quiet, code-built dedicated workspace with proper electrical.
View detailsWe also serve these areas