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.

Water Damage Restoration Cost in Seattle and King County: What to Expect

One of the first questions King County homeowners ask after a flooded basement or burst pipe is “how much is this going to cost me?” The answer depends on several factors — but understanding the variables helps you make better decisions and avoid overpaying or underinsuring your claim.

What Drives Water Damage Restoration Costs

Water damage restoration pricing in the Seattle and King County area is influenced by three primary factors: the category of water involved, the extent of affected area, and the materials that need replacement.

Category 1 water (clean water from supply lines) is the least expensive to remediate because the water itself doesn’t pose a health hazard. Category 2 (gray water from appliances or overflows) requires additional sanitation steps. Category 3 (black water from sewage backups or floodwater) demands the most extensive remediation including removal of all porous materials that contacted the water.

Typical Cost Ranges for King County

Based on our experience restoring hundreds of water-damaged properties across King County, here are general ranges homeowners can expect. A single-room water extraction and dry-out from a clean water source — like a supply line break under a sink — typically falls in the range of several thousand dollars for mitigation alone. A multi-room event affecting flooring, baseboards, and lower drywall sections throughout a floor of the home increases costs significantly due to the scale of demolition, drying equipment, and reconstruction needed.

Full-floor flooding events — especially those involving Category 2 or 3 water — can require extensive reconstruction including subfloor replacement, lower cabinet removal, drywall replacement to 2-4 feet, baseboard and trim replacement, and potential mold remediation if drying wasn’t initiated within 48 hours.

These estimates reflect King County market rates, which trend higher than national averages due to local labor costs and material pricing in the Puget Sound market.

What Your Insurance Typically Covers

Most HO-3 homeowner policies in Washington State cover sudden and accidental water damage — a burst pipe, a failed washing machine hose, an ice dam backup. They generally do not cover gradual leaks, maintenance-related moisture, or flood damage (which requires separate NFIP or private flood coverage).

Your policy likely has two relevant coverage components: the dwelling coverage (Coverage A) for structural repairs, and the contents coverage (Coverage C) for personal property damaged by water. Many King County homeowners are surprised to find their policy also includes Additional Living Expenses (Coverage D) if the water damage renders your home uninhabitable during restoration.

How to Minimize Your Out-of-Pocket Costs

Speed is the single biggest cost-saving factor in water damage restoration. Every hour that water sits in your home, the damage scope expands. Materials that could have been saved with prompt drying become unsalvageable after 48-72 hours. Mold begins colonizing within 24-48 hours in King County’s humidity levels.

Working with a restoration contractor who also handles the rebuild eliminates the markup and coordination costs of hiring separate mitigation and construction companies. At Prolific Design-Build and Restoration, we handle water extraction, structural drying, demolition, and complete reconstruction under one contract — saving you both money and time.

Get a Free Water Damage Assessment

If you’re dealing with water damage in your Seattle or King County home, call Prolific at (425) 800-4775 for a professional assessment. We’ll identify the full scope of damage, explain your options, and if you’re filing an insurance claim, prepare documentation that maximizes your coverage.

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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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