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 Repair in King County: What Every Homeowner Needs to Know

When a Pacific Northwest storm tears through King County — ripping shingles, toppling trees, and sending water cascading into attics — the decisions you make in the first 24 hours determine how smoothly your recovery goes. As a locally owned restoration contractor that has rebuilt hundreds of storm-damaged homes from Bellevue to Federal Way, we’ve seen what works and what leads to months of frustration.

The First 24 Hours After Storm Damage

Your immediate priorities after storm damage are safety and documentation. Before entering any room with ceiling damage, check for sagging drywall that indicates trapped water — a saturated sheet of drywall can weigh over 100 pounds and collapse without warning. If you see standing water near electrical outlets or your breaker panel, do not enter until power has been shut off at the meter.

Once you’re safely able to assess, photograph everything. Take wide shots of each affected room and close-ups of specific damage points. Photograph the exterior from multiple angles. Document the date and time on each photo. This becomes the foundation of your insurance claim.

Common Storm Damage in King County Homes

King County experiences distinct storm damage patterns shaped by our geography and building stock. The most frequent types we restore include wind damage to roofing — particularly on homes built before current wind-load codes were adopted in the 2000s. Homes in exposed areas like Sammamish Plateau and the Kent Valley face the highest wind exposure.

Fallen tree damage is extremely common in established neighborhoods throughout Kirkland, Redmond, and Issaquah where mature Douglas fir and Western red cedar tower over residential structures. A single falling limb can punch through roofing, rafters, and ceiling in seconds.

Water intrusion following wind damage accounts for the majority of storm repair costs in our experience. Wind compromises the building envelope and then King County’s persistent rain does the real damage over hours and days following the initial storm.

Filing Your Storm Damage Insurance Claim

Contact your insurance company as soon as it’s safe to do so — most policies require prompt notification. Request your claim number and the name of your assigned adjuster. Washington State law requires insurers to acknowledge your claim within 15 days and make a coverage decision within 30 days of receiving proof of loss.

Here’s something most homeowners don’t realize: you don’t have to accept the insurance company’s first estimate. If their adjuster’s scope of repair doesn’t match the actual damage, you have the right to dispute it. Having a restoration contractor who writes estimates in the same Xactimate software the insurance company uses creates a level negotiation.

Choosing a Storm Damage Contractor in King County

After every major storm, out-of-state contractors descend on King County offering quick repairs at low prices. These storm chasers create a real risk for homeowners. Check that any contractor you hire holds a valid Washington State contractor license (verify at lni.wa.gov), carries general liability and workers’ compensation insurance, has a permanent local business address, and can provide references from local projects.

At Prolific Design-Build and Restoration, we’re not going anywhere — we’ve been serving King County homeowners with storm damage restoration, remodeling, and design-build construction from our permanent local operation. When the next storm hits, we’re still here.

Get Your Storm Damage Assessed

If your King County home has sustained storm damage, call Prolific at (425) 800-4775 for a professional damage assessment. We respond 24/7 during storm events and provide emergency board-up and tarping to prevent further damage while your claim is processed.

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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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