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.

How to Read an Xactimate Estimate: A Homeowner’s Guide

After you file an insurance claim for storm damage, water damage, or fire damage, your insurance adjuster will produce an estimate using a software program called Xactimate. This estimate determines how much your insurance company will pay for repairs — and understanding it is one of the most important things you can do to protect your claim.

Most homeowners receive this document, glance at the total, and move on. That’s a mistake. The Xactimate estimate is a detailed, line-by-line breakdown of every repair your insurer has approved. Knowing how to read it helps you catch missing items, understand your payout, and work with your contractor to ensure nothing falls through the cracks.

What Is Xactimate?

Xactimate is estimating software made by Verisk that’s used by virtually every major insurance company in the United States. When your adjuster inspects your property and writes an estimate for repairs, they’re entering line items into Xactimate — selecting specific materials, labor tasks, and measurements from a database of over 10,000 standardized entries.

The software uses localized pricing — it pulls labor and material costs specific to your zip code, updated monthly. This means an Xactimate estimate for the same repair in Bellevue, WA will have different pricing than one in Phoenix, AZ. This localized pricing is one reason the software is considered the industry standard: both insurers and contractors can reference the same pricing database.

The Parts of an Xactimate Estimate

Header Information

The top of the estimate includes your claim number, policy number, date of loss, adjuster name, and property address. Verify all of this is correct — errors in the date of loss or property information can cause problems down the line.

Line Items

This is the core of the estimate. Each repair task appears as a separate line item with a category code, description, quantity, unit of measurement, and price. For example, a line item for roof shingle replacement might read: RFG SHIN28 — Remove and replace composition shingles, 30-year — 24 SQ — $XXX.XX

The code (RFG SHIN28) is the Xactimate category and item number. RFG means Roofing. The description tells you exactly what work is approved. The quantity (24 SQ) means 24 “squares” — a roofing measurement equal to 100 square feet. The price reflects local labor and material costs for that specific task.

Categories You’ll Commonly See

RFG — Roofing (shingles, underlayment, flashing, ridge caps, pipe boots, ice and water shield)

SDG — Siding (vinyl, fiber cement, wood siding removal and installation)

GUT — Gutters (gutter and downspout removal and replacement)

DRY — Drywall (drywall removal, hanging, taping, texturing)

PNT — Painting (interior and exterior painting, priming, caulking)

FLR — Flooring (carpet, hardwood, laminate, tile removal and installation)

PLM — Plumbing

ELC — Electrical

WTR — Water mitigation (extraction, drying equipment, moisture monitoring)

GEN — General items (debris removal, temporary protection, permits)

Overhead and Profit (O&P)

This is one of the most misunderstood — and most important — parts of an Xactimate estimate. Overhead and Profit (usually 10% overhead + 10% profit = 20% total) is a standard industry charge that covers the contractor’s business costs and reasonable profit margin. It’s standard on multi-trade projects — jobs that require coordination of two or more trades (like roofing + siding + painting + gutters).

Some insurance adjusters leave O&P off the initial estimate. If your project involves multiple trades, your contractor should request it. O&P is recognized as a legitimate cost by virtually every insurance carrier, and most will add it when properly requested with documentation showing multi-trade involvement.

Depreciation

If you have a Replacement Cost Value (RCV) policy — which most homeowners do — you’ll see two totals: the Replacement Cost Value (the full cost of repairs with new materials) and the Actual Cash Value (ACV) (the replacement cost minus depreciation based on the age and condition of the damaged materials).

Your insurance company initially pays the ACV amount. After repairs are completed and your contractor submits documentation, the insurer releases the recoverable depreciation — the difference between RCV and ACV. This is why completing repairs promptly matters: you don’t get that depreciation back until the work is done.

What to Look for When Reviewing Your Estimate

Missing items. Compare the estimate against your contractor’s assessment. Are all damaged areas included? Common items that get missed: underlayment replacement beneath damaged shingles, code-required upgrades (ventilation, ice and water shield, drip edge), interior damage from water intrusion, pipe boots and flashing, and matching for partial repairs.

Incorrect measurements. If your roof is 30 squares but the estimate only shows 24, that’s a significant shortfall. Your contractor should verify all measurements against the estimate.

Missing O&P. If your project involves multiple trades and the estimate doesn’t include Overhead and Profit, your contractor should file a supplement requesting it.

Incorrect pricing. Xactimate prices are localized, but occasionally line items use incorrect specifications. For example, the estimate might spec 25-year shingles when your existing roof has 30-year architectural shingles — the replacement should match or exceed what was there.

No code upgrade coverage. If your policy includes “ordinance or law” coverage, code-required upgrades during repair should be included. Washington State building codes often require upgrades when re-roofing, including enhanced ventilation and ice and water shield in valleys and eaves.

What to Do If the Estimate Seems Low

If your contractor’s assessment shows more damage than the Xactimate estimate covers, don’t panic — this is common. Your contractor can file a supplement, which is a formal request for additional line items with supporting documentation (photos, measurements, code references). Supplements are a normal, expected part of the insurance claims process.

At Prolific Design-Build and Restoration, we review every Xactimate estimate line by line against our own damage assessment. If items are missing or underestimated, we file supplements with detailed documentation. This is one of the most valuable things an experienced insurance restoration contractor does — ensuring the estimate reflects the true scope of repairs.

Why Your Contractor Should Know Xactimate

Not every contractor understands Xactimate — and that matters. A contractor who can read and write Xactimate estimates speaks the same language as your insurance adjuster. They can identify missing line items, verify pricing accuracy, calculate correct quantities, and file supplements in a format the adjuster’s own system recognizes. This alignment between your contractor and your insurer speeds up approvals and reduces disputes.

At Prolific Design-Build and Restoration, Xactimate proficiency is core to how we manage insurance claims. We review, verify, and supplement every estimate to ensure your claim covers the full scope of restoration. You pay only your deductible — we make sure the insurance payout covers everything else.

Have questions about your Xactimate estimate? Call (425) 800-4775 for a free estimate review and damage inspection. We’ll compare the insurance estimate against the actual damage and file supplements for anything that’s missing. Serving all of King County, WA.

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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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