ADU & DADU Contractor — King County, WA

Add a Legal Dwelling Unit
to Your King County Property

From permit application to final walkthrough — Prolific handles design-build ADU and DADU projects across Federal Way, Issaquah, Renton, Kent, and greater King County.

$180KAverage ADU Cost (King County)
6–12moTypical Timeline Permit to Move-In
$1,800+Monthly Rental Income Potential
3–5yrAverage ROI Payback Period

What We Build

Every ADU project is custom-designed for your lot, your goals, and King County code.

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Detached ADU (DADU)

A standalone dwelling in your backyard. Most flexible for rental or multigenerational living. Requires setback compliance and separate utility connections.

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Attached ADU

Connected to the primary home via a shared wall. Lower cost than detached, faster permitting. Ideal for in-law suites or long-term rental income.

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Junior ADU (JADU)

Converted from existing interior space — garage, basement, or bonus room. Lowest cost entry point. Limited to 500 sq ft per King County code.

The King County Permitting Process

Prolific handles every step. Most homeowners have never pulled a permit — we've done hundreds.

1

Site & Zoning Review

We verify your parcel's zoning, setbacks, lot coverage, and utility capacity before design starts. Catches 80% of project-killers on day one.

2

Design & Engineering

Architectural plans drawn to King County standards. Structural engineering included where required. Typical design phase: 3–6 weeks.

3

Permit Submission

We submit to King County DPER or the applicable city (Federal Way, Renton, Issaquah, Kent). Electronic submission with full plan set.

4

Review & Corrections

County review typically takes 6–12 weeks. We respond to all correction requests and manage the back-and-forth until permit issuance.

5

Build & Final Inspection

Construction with milestone inspections. Final inspection and certificate of occupancy required before the unit can be rented or occupied.

Cost Ranges for King County ADUs

Rough estimates — every project varies by site, size, and finish level. Free estimate available after a site visit.

ADU TypeSize RangeTypical Cost Range
Junior ADU (JADU)Up to 500 sq ft$60,000 – $120,000
Attached ADU400–800 sq ft$120,000 – $200,000
Detached ADU (DADU)400–1,200 sq ft$160,000 – $320,000

Ready to Add a Unit to Your Property?

Free site consultation. We'll tell you what's possible on your lot before you spend a dollar.

Get Your Free ADU Estimate

Prolific's Differentiator

While We're Restoring Your Home, Let's Make It Better Than Before

Most contractors patch the damage and leave. We use the restoration as a launchpad — pairing insurance coverage with a remodel that upgrades what you had.

Storm + Remodel

Federal Way — Hail Damage + Kitchen Upgrade

Insurance covered the roof and siding. While we had the crew on-site, the homeowners financed a kitchen remodel they'd been putting off for years. One mobilization, two wins.

Water + Addition

Renton — Burst Pipe + Primary Bath Expansion

A burst pipe triggered an insurance claim for the subfloor and drywall. We rebuilt the bathroom larger than it was — same timeline, carrier paid the base, owner paid the delta.

Fire + Rebuild

Issaquah — Garage Fire + ADU Conversion

Garage total loss became a permitted two-car garage with a studio ADU above. Insurance rebuilt what burned. The ADU now generates rental income to offset the mortgage.

Insurance Claim? We Handle Everything.

Your Insurance Company Has Adjusters.
Now You Have Us.

STORM DAMAGE RESPONSEthousands more for homeowners just like you.

Bathroom Remodel Timeline: How Long Does It Really Take in the Seattle Eastside?

One of the first questions homeowners ask us about a bathroom remodel is “how long will this take?” It’s a fair question — nobody wants to be without a functional bathroom longer than necessary. Here’s what a realistic timeline looks like based on our experience remodeling bathrooms across Issaquah, Bellevue, Redmond, Kirkland, and the rest of King County.

The Short Answer

A standard bathroom remodel takes 3 to 6 weeks of active construction, depending on scope. But the total timeline from “I want to remodel my bathroom” to “I’m showering in my new bathroom” is typically 8 to 14 weeks when you include the planning, design, and permitting phases that happen before anyone picks up a hammer.

Phase 1: Design and Planning (2-4 Weeks)

This is where the foundation of a successful remodel is built. During this phase, we assess your existing bathroom, discuss your goals and budget, select materials, and create a detailed scope of work. If you’re changing the layout — moving the toilet, adding a shower where a tub was, or expanding the footprint — this phase also includes engineering drawings.

Material selection is a big part of this phase, and it’s where many homeowners underestimate the time involved. Tile, vanities, fixtures, and hardware all have lead times. Some specialty items can take 4 to 8 weeks to arrive. We always recommend making material selections early to avoid construction delays.

Phase 2: Permitting (1-3 Weeks)

Not every bathroom remodel requires a permit, but many do — especially if you’re moving plumbing, changing electrical, or altering the layout. Permit timelines vary significantly across King County. Issaquah and Sammamish tend to process residential permits relatively quickly, while Bellevue can take longer for more complex projects.

At Prolific, we handle all permit applications, plan reviews, and inspections as part of our project management. This is one area where having an experienced local contractor makes a real difference — we know the requirements and the reviewers in each jurisdiction.

Phase 3: Construction (3-6 Weeks)

Active construction follows a predictable sequence. Week one is typically demolition and rough inspection of the existing conditions. This is when we discover whether there are any hidden issues — water damage behind walls, outdated plumbing that needs replacing, or subfloor problems.

Weeks two and three are for rough plumbing, electrical, and any framing changes. This work needs to pass inspection before we can close up walls. Weeks three through five are for tile installation, vanity and fixture installation, and finish work. The final days involve final plumbing connections, painting, hardware installation, and cleanup.

What Can Extend the Timeline

The most common delays we see are material back-orders, hidden water damage requiring remediation, and permit inspection scheduling in busy jurisdictions. We mitigate these by ordering materials early in the design phase, building contingency time into every schedule, and maintaining strong relationships with local building departments.

Weather typically doesn’t affect bathroom remodels since it’s interior work, but if your project involves exterior venting or window changes, winter conditions can occasionally cause minor delays.

Tips for a Smooth Bathroom Remodel

Start material selection as early as possible — don’t wait until construction begins. Have a clear budget conversation upfront so there are no surprises mid-project. If you have a second bathroom, plan to use it exclusively during construction. If this is your only bathroom, discuss temporary arrangements with your contractor before work begins.

The most important factor in keeping a bathroom remodel on schedule is choosing a contractor who manages the entire process. When your designer, builder, plumber, electrician, and tile installer are all coordinated under one roof, scheduling conflicts and communication gaps are minimized.

Ready to start planning your bathroom remodel? Contact Prolific Design-Build and Restoration for a free consultation. We serve homeowners throughout King County including Issaquah, Bellevue, Sammamish, Redmond, Kirkland, Woodinville, Renton, Kent, Auburn, Maple Valley, Covington, and Newcastle.

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We Got Your Request

We respond within 2 business hours — same day for emergencies.

A member of our team will reach out shortly to schedule your free estimate or inspection. Here's what to have ready when we call:

What to Have Ready

  • Photos of the damage or area of concern (phone photos are fine)
  • Your insurance carrier name and claim number (if applicable)
  • Best time and number to reach you
  • A rough idea of when the damage occurred or project timeline
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Prolific Design-Build & Restoration — Federal Way, WA

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