ADU Construction

in the Greater Sno-King Area

Expert accessory dwelling unit builders — from detached ADU design and permitting to complete ADU construction.
One team. Every trade managed. Zero shortcuts.

WA Licensed General Contractor | ARKCOC*81207 | Licensed Home Inspector on Staff

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What Most ADU Builders Get Wrong — and What ARK Contractors Does Differently

Building an accessory dwelling unit is one of the most complex residential construction projects a homeowner can take on. It involves zoning compliance, permitting, site engineering, framing, plumbing, electrical, roofing, and finish work — all of which must be coordinated precisely and executed to code. When any one of those pieces breaks down, the entire project stalls.

Most homeowners who call us for ADU construction have already run into one of these problems:

The contractor who had no idea what the permit process actually required.

ADU permitting in Washington State is not a standard building permit. It involves zoning verification, setback review, utility connection requirements, and sometimes variance applications. Contractors who treat ADU projects like a standard addition routinely get projects rejected — costing clients months of delay before construction even begins.

The “estimate” that fell apart the moment real costs were calculated.

ADU construction cost ranges are wide — and contractors who quote low to win the project rely on change orders to make their margin. By the time the foundation is poured, the number you agreed to looks nothing like the number you’re being asked to pay. A detailed, fixed-price estimate from the start changes that dynamic entirely.

Trades working independently with no one managing the sequence.

ADU builds require plumbing, electrical, framing, insulation, roofing, and finish trades to work in a specific, coordinated sequence. When each trade is sourced separately and managed by a homeowner with no construction background, sequencing breaks down. Work gets redone. Timelines collapse. Costs escalate.

A finished structure that doesn’t hold up to Washington State winters.

An ADU is a permanent addition to your property. It needs to be built with the same structural integrity, waterproofing, and energy performance as your primary residence. Builders who cut corners on insulation, moisture barriers, or roofing details create problems that show up 18 months after the project closes — and long after any warranty conversation is useful.

These aren’t worst-case scenarios. They’re the most common complaints we hear from homeowners across Kirkland, Bothell, Redmond, and Snohomish County who came to us after a failed ADU experience with another contractor.

At ARK Contractors, our entire ADU construction process is built around preventing each one of these failure points — before the first shovel breaks ground.

What We Build: Complete ADU Construction from Site Assessment to Move-In Ready

Whether you’re adding a detached ADU in your backyard, converting an existing garage, or building an attached in-law suite, ARK Contractors manages the entire project under one coordinated plan — permitting, site work, framing, mechanical rough-ins, insulation, roofing, and finish work. You get one team, one timeline, and one point of contact throughout.

Detached ADU Construction

A detached accessory dwelling unit is a fully independent structure built on the same lot as your primary residence. ARK Contractors handles the complete detached ADU build — from site layout and foundation through framing, mechanical systems, roofing, exterior finish, and interior completion. Our detached ADUs are designed to integrate with your property, meet all local zoning setback requirements, and perform as permanent, high-quality housing — whether for rental income, a family member, or a private workspace.

Garage Conversion ADU

Converting an existing garage into a livable accessory dwelling unit is one of the most cost-efficient ADU options available. We assess the existing structure, engineer the required modifications, and manage all work — insulation, framing, plumbing, electrical, HVAC, drywall, and finish — to bring the space to residential code. Garage conversions allow homeowners to create additional living space or rental income without the site work and foundation costs of a new build.

Attached ADU / In-Law Suite

An attached ADU shares one or more walls with the primary residence but functions as a completely separate living unit with its own entrance, kitchen, bathroom, and living space. ARK Contractors designs and builds attached ADUs that integrate seamlessly with the existing structure — matching exterior finish, rooflines, and interior quality while meeting all state and local code requirements for separate dwelling units.

Junior ADU (JADU) Conversion

A Junior ADU converts existing interior space within the primary home — typically a bedroom, basement, or bonus room — into a self-contained unit with its own entrance and efficiency kitchen. JADUs offer a lower-cost entry point into ADU housing and are subject to different permitting requirements than full ADUs. ARK Contractors manages the full scope of JADU conversions, including all permit coordination and code compliance.

ADU Design, Planning & Permitting

ADU plans and permit applications require coordination with local planning departments, utility providers, and in some cases structural engineers. ARK Contractors manages the front end of every ADU project — site assessment, design coordination, permit application, and utility connection planning — so you aren’t navigating a complex regulatory process without professional guidance. We know what reviewers look for across Kirkland, Bothell, Woodinville, and Snohomish County jurisdictions.

Full-Service ADU Construction Management

Every ARK Contractors ADU project is managed as a complete, trade-coordinated build. We don’t hand you a list of subcontractors and step back. We manage framing crews, mechanical trades, insulation, roofing, exterior finish, and interior completion under a single contract, a single schedule, and a single standard of quality. This is what separates a well-built ADU from one that looks done but isn’t built to last.

The ARK Contractors Standard:
What Every ADU Build Includes

Permit-Ready from Day One

ADU permitting is the step where most projects stall. Incorrect applications, missing documentation, non-compliant plans, and unfamiliarity with local zoning requirements can delay a project by months before construction begins. ARK Contractors is fluent in ADU permit requirements across the Greater Sno-King area. We prepare complete, accurate permit packages — and we have the relationships and process knowledge to move through review efficiently.

Every Trade on One Coordinated Schedule

An ADU construction project touches more trades than most homeowners expect: site prep, foundation, framing, plumbing, electrical, HVAC, insulation, roofing, exterior siding, drywall, flooring, and finish carpentry. ARK Contractors manages every one of these trades directly. One schedule. One point of contact. Every subcontractor held to our standard. You focus on the result — we manage the execution.

Transparent, Fixed-Price ADU Construction Cost Estimates

ADU construction cost varies significantly based on size, site conditions, utility connections, and finish level. Rather than quoting a range that gives us room to move, ARK Contractors provides detailed, line-item estimates after a thorough site assessment. You’ll know exactly what your ADU build will cost before a single permit is filed. No surprises. No change orders engineered into the process.

A Licensed Home Inspector on Every Project

ARK Contractors is one of the only ADU construction companies in the Greater Sno-King area with a licensed home inspector on staff. Before framing begins, we assess site drainage, utility access, soil conditions, and any existing structural considerations on the property. Issues that blindside other contractors are caught and addressed in the planning phase — not discovered mid-build at your expense.

Built to Perform. Not Just to Pass Inspection.

An ADU is a long-term investment in your property. ARK Contractors builds to a standard that goes beyond minimum code — because a structure that “passes” isn’t the same as a structure that performs flawlessly for 30 years. We don’t cut corners on moisture barriers, insulation, roofing details, or structural connections. We build the way we’d want our own home built.

From Site Visit to Move-In Ready: How ARK Contractors Manages Your ADU Build

A successful ADU construction project requires more than skilled tradespeople. It requires meticulous front-end planning, disciplined project management, and clear communication at every phase. Here is exactly how ARK Contractors manages your ADU from first conversation to final walkthrough.

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Step 1 — Free On-Site Assessment & Consultation

We visit your property, assess the site for ADU feasibility, review local zoning and setback requirements, and have a detailed conversation about your goals, timeline, and budget. You leave the meeting with a clear sense of what’s possible — and we leave with what we need to produce an accurate, detailed estimate.

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Step 2 — Design Coordination & Permit Application

We coordinate ADU plans, finalize the design scope, prepare the complete permit package, and submit to the appropriate jurisdiction. We manage all back-and-forth with the permitting office so you don’t have to. Once permits are approved, we lock the project schedule and begin ordering materials and coordinating trades.

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Step 3 — Site Preparation & Foundation

Site clearing, grading, utility connections, and foundation work are completed in coordination with our licensed inspector review. All work is performed to code, documented, and ready for inspection before the next phase begins.

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Step 4 — Framing, Roofing & Exterior

Our framing crews build to engineered specifications. Once framing is complete and inspected, roofing and exterior finish work begin. We don’t rush this phase — the structural envelope of your ADU is what protects every interior system for decades to come.

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Step 5 — Mechanical Rough-In: Plumbing, Electrical & HVAC

All plumbing, electrical, and HVAC rough-in work is completed and inspected before insulation or drywall begins. Every system is installed to code by licensed trades, reviewed for compliance, and built to support the finished unit without rework.

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Step 6 — Insulation, Drywall & Interior Finish

Insulation is installed to Washington State energy code requirements before drywall goes up. Interior finish work — flooring, cabinetry, fixtures, lighting, trim, and hardware — is completed in proper sequence, reviewed against the original scope, and held to the same finish standard as our full interior remodeling projects.

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Step 7 — Final Inspections & Homeowner Walkthrough

We manage all final inspections with the jurisdiction, walk the completed ADU with you, confirm every detail meets our standard and yours, and deliver a clean, move-in-ready unit. We consider the project complete when you do.

More Ways ARK Contractors Can Serve Your Property

ADU construction is often one part of a larger property improvement plan. ARK Contractors brings the same trade-managed, preparation-first approach to every project we take on across the Greater Sno-King area.

Every ADU we build includes a properly engineered, fully installed roof — but our roofing services extend to your primary residence as well. Whether you’re replacing an aging roof on your main home, addressing storm damage, or upgrading materials ahead of an ADU project, our roofing services are performed by the same team that holds every other ARK trade to our quality standard. One contractor. Consistent results across your entire property.

Need more than ADU construction? As a licensed general contractor serving the Greater Sno-King area, ARK Contractors manages whole-home renovations, room additions, kitchen and bathroom remodeling, and commercial projects with the same meticulous planning and coordinated project management that defines everything we do. If your property needs more than a single trade, we’re the team built to handle it.

Many homeowners pair ADU construction with outdoor living improvements — and for good reason. A well-designed deck adjacent to a new ADU adds functional outdoor space, increases property appeal, and can be completed on the same project timeline. Our deck building services deliver custom, code-compliant outdoor structures that integrate naturally with both new and existing architecture.

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ADU Construction — Questions Homeowners Ask Before They Build

How much does ADU construction cost in the Seattle area?

ADU construction cost in the Greater Sno-King area varies considerably based on the type of ADU (detached, attached, garage conversion, or JADU), square footage, site conditions, utility connection requirements, and finish level. A garage conversion ADU and a new detached ADU build are fundamentally different investments. Rather than quoting ranges that don’t reflect your specific property and goals, ARK Contractors provides detailed, fixed-price estimates after a thorough on-site assessment. Contact us for a no-obligation estimate tailored to your project.

Do I need a permit to build an ADU in Washington State?

Yes — all ADU construction in Washington State requires permits, and the process involves more than a standard building permit. Zoning verification, site plan review, utility connection approvals, and in some cases variance applications are part of the process. ARK Contractors manages the complete ADU permitting process for every project we take on. We are thoroughly familiar with requirements across Kirkland, Bothell, Redmond, Woodinville, Snohomish, and surrounding jurisdictions. You don’t navigate that process alone. We handle it.

How long does it take to build an ADU?

ADU construction timelines depend heavily on project type, permitting jurisdiction, and scope. A garage conversion can often be completed in 8 to 14 weeks once permits are approved. A new detached ADU build typically runs 4 to 6 months from permit approval to final inspection, depending on size and site conditions. Because ARK Contractors manages all trades directly — eliminating the scheduling delays of coordinating independent subcontractors — we consistently deliver within the timelines we set at the outset. We provide a realistic, detailed schedule before work begins and keep you informed throughout every phase.

Can I rent out my ADU once it’s built?

In most jurisdictions across the Greater Sno-King area, yes — ADUs built to residential code and properly permitted can be rented as independent dwelling units. The specific rules around ADU rentals, owner-occupancy requirements, and short-term rental restrictions vary by city and county. ARK Contractors will walk you through the regulatory context for your specific property during the initial consultation so you can make fully informed decisions about your ADU’s intended use before the design is finalized.

What’s the difference between a detached ADU and a Junior ADU (JADU)?

A detached ADU is a fully separate structure on the same lot as the primary residence — built new or converted from an existing accessory structure like a garage. A Junior ADU (JADU) is created by converting interior space within the primary home into a self-contained unit with its own entrance and efficiency kitchen. JADUs are subject to different permit requirements, size limitations, and in some cases owner-occupancy rules. ARK Contractors builds both, and we’ll help you determine which ADU type makes the most sense for your property, budget, and goals during the initial assessment.

How do I find a reliable ADU contractor near me?

Look for an ADU contractor who is a licensed general contractor in Washington State, can demonstrate direct experience with ADU permitting in your specific jurisdiction, manages all trades under one contract (rather than handing you a list of subs), and provides detailed fixed-price estimates before the project begins. ARK Contractors meets all of those criteria — and we back every project with a licensed home inspector on staff, transparent project management, and a track record of completed ADU builds across the Greater Sno-King area. Schedule a free on-site assessment to get started.

Ready to Build Your ADU? Let’s Start with a Free On-Site Assessment.

Schedule a free, no-obligation estimate with ARK Contractors. We’ll visit your property, assess your site, walk through your ADU goals and budget, and provide a transparent, line-item quote — so you can move forward with confidence.