ADU & DADU Contractor — King County, WA
From permit application to final walkthrough — Prolific handles design-build ADU and DADU projects across Federal Way, Issaquah, Renton, Kent, and greater King County.
Every ADU project is custom-designed for your lot, your goals, and King County code.
A standalone dwelling in your backyard. Most flexible for rental or multigenerational living. Requires setback compliance and separate utility connections.
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.
Converted from existing interior space — garage, basement, or bonus room. Lowest cost entry point. Limited to 500 sq ft per King County code.
Prolific handles every step. Most homeowners have never pulled a permit — we've done hundreds.
We verify your parcel's zoning, setbacks, lot coverage, and utility capacity before design starts. Catches 80% of project-killers on day one.
Architectural plans drawn to King County standards. Structural engineering included where required. Typical design phase: 3–6 weeks.
We submit to King County DPER or the applicable city (Federal Way, Renton, Issaquah, Kent). Electronic submission with full plan set.
County review typically takes 6–12 weeks. We respond to all correction requests and manage the back-and-forth until permit issuance.
Construction with milestone inspections. Final inspection and certificate of occupancy required before the unit can be rented or occupied.
Rough estimates — every project varies by site, size, and finish level. Free estimate available after a site visit.
| ADU Type | Size Range | Typical Cost Range |
|---|---|---|
| Junior ADU (JADU) | Up to 500 sq ft | $60,000 – $120,000 |
| Attached ADU | 400–800 sq ft | $120,000 – $200,000 |
| Detached ADU (DADU) | 400–1,200 sq ft | $160,000 – $320,000 |
Free site consultation. We'll tell you what's possible on your lot before you spend a dollar.
Get Your Free ADU EstimateProlific's Differentiator
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.
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.
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.
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.
7 questions to ask before hiring any contractor in King County — takes 2 minutes to read.
Check your inbox in the next few minutes.
STORM DAMAGE RESPONSEthousands more for homeowners just like you.
undefined More Resources for King County Homeowners Kitchen Remodeling in Issaquah, Sammamish & Bellevue: Costs, Trends & What to Expect Emergency Water Damage Restoration: What to Do in the First 24 Hours Mold Remediation After Water Damage: What Homeowners Need to Know
Storm Damage Restoration in Issaquah & the Eastside: What Homeowners Need to Know Read More »
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
Bathroom Remodel Timeline: How Long Does It Really Take in the Seattle Eastside? Read More »
Accessory dwelling units have become one of the hottest topics in King County real estate. Whether you call them ADUs, DADUs, backyard cottages, or in-law suites, these secondary living spaces are transforming how Eastside homeowners use their property. At Prolific Design-Build and Restoration, we’ve been building ADUs and DADUs across Issaquah, Bellevue, Sammamish, Redmond, and
ADU and DADU Construction in King County: Rules, Costs, and What to Expect in 2026 Read More »
If you’re a homeowner in Bellevue, Issaquah, Sammamish, or elsewhere on the Eastside, you’ve probably wondered what a kitchen remodel actually costs in this market. The short answer: it depends on scope. The real answer takes a bit more nuance. At Prolific Design-Build and Restoration, we handle kitchen remodels across King County every month. Here’s
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:
Prolific Design-Build & Restoration — Federal Way, WA