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.

Sammamish Home Restoration and Remodeling: Your Local Contractor Guide

Sammamish: A Unique Market With Unique Needs

Sammamish consistently ranks among the most desirable — and most expensive — places to live in Washington State. With a median home value well above the King County average, Sammamish homeowners have higher expectations for their contractors, and rightfully so. Whether you’re dealing with storm damage to a hillside home, restoring water damage in a finished basement, or remodeling a kitchen in a 20-year-old Sammamish Plateau home, you need a contractor who understands this market.

Prolific Design-Build and Restoration serves Sammamish homeowners with both insurance restoration and custom remodeling. We understand the specific challenges of building and restoring homes on the Plateau — from steep lot drainage issues to the premium materials and finishes that Sammamish homes demand.

Common Restoration Needs in Sammamish

Storm and wind damage. Sammamish’s elevated terrain and tree coverage make it especially vulnerable to wind events. Fallen trees, damaged roofs, and broken siding are common after major storms. Our storm damage restoration services cover everything from emergency tarping to full structural rebuilding.

Water damage from drainage failures. Many Sammamish homes sit on hillsides or at the base of slopes. When drainage systems fail — clogged French drains, overwhelmed catch basins, or grading shifts — water finds its way into crawl spaces, basements, and lower levels. We provide complete water damage restoration including source identification and drainage correction.

Mold in finished basements. Sammamish homes frequently feature finished lower levels with bedrooms, home offices, and media rooms. These spaces are particularly vulnerable to moisture intrusion and mold growth because they’re below grade and often have limited ventilation.

Roof deterioration. Moss growth, debris accumulation from surrounding trees, and the constant wet conditions on the Plateau accelerate roof aging. Many Sammamish homes built in the late 1990s and 2000s are now approaching or past their roof replacement window. See our roof repair and replacement guide for cost breakdowns.

Remodeling for Sammamish Homes

The Sammamish housing stock is predominantly 15-30 years old — old enough to need updates, but structurally sound. This makes it ideal for remodeling rather than rebuilding. Popular projects include:

Kitchen remodels are the top request from Sammamish homeowners. Many Plateau-era homes have dated kitchens with honey oak cabinets, tile countertops, and closed layouts that don’t match how families live today. Our kitchen remodeling guide covers costs and trends specific to the Eastside market.

Bathroom renovations with modern fixtures, walk-in showers, heated floors, and updated tile are extremely popular. Check our bathroom remodeling guide for what Sammamish homeowners are choosing in 2026.

ADU and DADU construction is surging as Sammamish updates its zoning to allow accessory dwelling units. Whether it’s a detached backyard cottage for rental income or a mother-in-law suite for aging parents, we handle the entire process from permits through completion. Our ADU construction guide covers Sammamish-specific requirements.

Whole-home updates including flooring, lighting, paint, trim, and fixture upgrades to modernize homes without doing a full remodel.

Working With Insurance in Sammamish

Sammamish homes carry higher insurance values, which means claims involve larger dollar amounts and more scrutiny from adjusters. Having a contractor who understands how to document damage properly, communicate with adjusters effectively, and negotiate fair settlements is critical. We’ve handled restoration projects on high-value homes throughout the Plateau and know how to protect our clients’ interests.

Read our complete guide to navigating insurance claims before filing.

Why Sammamish Homeowners Choose Prolific

We’re not a franchise operation sending different crews to every job. We’re a local, owner-operated design-build and restoration company that handles every project personally. We understand the Sammamish market, we know the local building codes, and we deliver the quality that Plateau homeowners expect.

Call (425) 800-4775 or request a free consultation. Black-owned and Latino-owned — serving Sammamish with pride.

Related: Storm Season Prep Checklist | Fire Damage Restoration | Kitchen Remodeling Guide

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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.

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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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