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.

Storm Damage Insurance Claims in King County: What Every Homeowner Should Know

A Step-by-Step Guide for King County Homeowners

Pacific Northwest storms can strike with little warning, bringing high winds, heavy rain, falling trees, and power outages that leave King County homeowners dealing with significant property damage. Whether your roof has been compromised by wind, a tree has fallen on your home, or floodwaters have entered your living space, the actions you take in the first 24 hours dramatically affect both the extent of damage and the success of your insurance claim.

Step 1: Ensure Safety First

Before assessing any damage, make sure everyone in the household is safe. If you smell gas, leave immediately and call 911. Do not enter rooms where ceilings are sagging from water weight. Avoid any contact with downed power lines or standing water near electrical sources. If the structure appears compromised, stay out until a professional can assess it.

Step 2: Document Everything Before Touching Anything

Your insurance claim depends on thorough documentation. Before moving any belongings or beginning cleanup, take extensive photographs and video of all damage from multiple angles. Capture wide shots of each affected room, close-ups of specific damage, and any external damage to the roof, siding, or foundation. Document the date and time. This evidence is critical for your adjuster.

Step 3: Prevent Further Damage

Most insurance policies require homeowners to take reasonable steps to prevent additional damage. This is called your duty to mitigate. If your roof is compromised, covering the opening with a tarp prevents further water intrusion. If pipes have burst, shut off the main water supply. Remove standing water if you can do so safely. Move undamaged belongings away from affected areas. Keep receipts for any emergency supplies you purchase.

Important: Do not make permanent repairs before your insurance adjuster inspects the property. Emergency mitigation like tarping and water extraction is expected, but full repairs should wait for adjuster approval to ensure coverage.

Step 4: Contact Your Insurance Company

File your claim as soon as possible. Most policies have time limits for reporting damage. When you call, have your policy number ready and provide a brief description of the damage. Ask for your claim number and the name of your assigned adjuster. Request a timeline for inspection. Do not accept a settlement offer before getting a professional damage assessment from your restoration contractor.

Step 5: Call a Professional Restoration Company

A qualified restoration company does more than just clean up. They provide professional moisture mapping that reveals hidden water damage behind walls and under floors. They use industrial dehumidifiers and air movers to properly dry the structure. They document everything in a format that insurance adjusters require. And they manage the entire rebuild process from demolition through final finishes.

For King County homes, look for a contractor who is IICRC certified, has experience with your insurance carrier, and can handle both the mitigation and reconstruction phases. Having one company manage the entire process prevents the gaps and miscommunication that happen when you hire separate mitigation and rebuild contractors.

Step 6: Understanding Your Coverage

Standard homeowners insurance in Washington State typically covers sudden and accidental damage from storms, including wind damage, falling trees, and water intrusion through roof damage. However, flood damage from rising water requires a separate flood insurance policy, either through the NFIP or a private insurer. If you live near the Green River, Cedar River, Sammamish River, or Lake Washington shoreline, review whether you carry flood coverage.

Common Storm Damage Scenarios in King County

Wind-Driven Rain Intrusion: High winds push rain through gaps around windows, doors, and roof penetrations. Damage may not be visible immediately but can cause mold growth within 48-72 hours if not dried properly.

Tree Impact Damage: The Pacific Northwest tree canopy is both beautiful and dangerous during storms. A fallen tree can compromise roof structure, break through walls, and create openings for water intrusion.

Power Outage Flooding: Extended power outages disable sump pumps and HVAC systems. Homes with below-grade living spaces can flood when groundwater pumps stop running during the storm that is generating the most water.

Storm damage in King County? Prolific Design-Build and Restoration provides 24/7 emergency response with complete insurance claim support.

Call (425) 800-4775Request Free Estimate

See what is happening now: Live King County Incident Tracker | Areas We Serve

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Dealing with storm damage? We're here — call now or submit your info and we'll call you within the hour.

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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