After publishing the original article about the ADU workshop on Vashon, I received the full presentation from Warren Clauss, Principal Planner at King County Permitting. The slide deck fills in many of the gaps that residents asked about after the meeting, especially around what steps come before, during, and after submitting an ADU permit application.
If you’re considering building an Accessory Dwelling Unit (ADU) on your Vashon property, here’s what the county presentation clarified:
An ADU is a self-contained living unit on the same lot as a primary residence. It can be attached, inside, or fully detached from the main home. Detached ADUs offer more flexibility but come with more restrictions, especially in shoreline or critical area buffers. For my own plans at Big Rock Ranch, I’m leaning toward a detached setup, given the layout of the land and road access. But I’m paying close attention to the permitting requirements, as detached units often require additional reviews for drainage, fire access, and environmental impacts.
What’s New in 2025
In January 2025, King County adopted new zoning code updates that affect ADUs. While most of the urban-focused updates don’t apply to Vashon, a few key points do:
- Detached ADUs are not allowed within critical area buffers.
- Attached ADUs may be allowed as additions within those buffers.
- The owner-occupancy requirement has been removed.
- No additional off-street parking is required.
If your lot is over 3,200 square feet and located in a designated rural town or meets the zoning size requirements, you may qualify for a detached ADU.
The biggest takeaway: the more prepared you are before submitting your permit, the smoother the process will be. County officials emphasized that complete applications with accurate site plans, utility confirmations, and environmental documents avoid the costly back-and-forth that slows down most projects.
Permit Process Overview
The permit process breaks into stages:
- Before You Apply: Critical Area Designation, Shoreline review, septic and water approval.
- At Application: Site plan, development plans, drainage documentation, and energy/fire checklists.
- Review and Inspection: Triage intake, zoning review, fire code compliance, and final site inspections.
The county now requires solar-ready zones for new roofs over 600 square feet and fire sprinklers for many projects on Vashon due to water access limitations. Fire inspections for Vashon-Maury occur on Thursdays only, and a pre-construction meeting is required once your permit is approved.
Community Questions & Concerns
Since sharing the original article, several residents raised thoughtful concerns across social media. Here’s a summary of what people are asking and how it fits into the bigger picture:
“The state passes ADU laws without understanding how restrictive local ordinances are.”
Yes, this is a real issue. Statewide ADU laws often don’t override King County’s rural zoning and shoreline protections, which can significantly limit what can actually be built here on Vashon.“King County is strict on new ADUs but won’t enforce code on unsafe existing ones.”
Enforcement wasn’t addressed at the meeting, but it’s a fair concern. Without consistent enforcement, residents who follow the rules can feel penalized while others bypass them.“How is KC approving a large development behind IGA while small ADUs take months?”
Larger developments often follow a different planning path, but the county is trying to make ADU permitting more efficient. Transparency and equity in processing timelines remain important issues.“TL;DR: Just build and forget the permit.”
It might be tempting, but skipping permits puts your investment at risk. The goal of workshops like this one is to make legal permitting more accessible for island residents.
What I’ll Share Next
I’ll continue posting updates as I move forward with planning a detached ADU at Big Rock Ranch. I’ll also add links to the site plan examples, permitting worksheets, and other resources from the presentation to help others navigate this process.
If you’re working on an ADU or even just exploring the idea, feel free to reach out or comment. The more we share, the more we can support each other in building thoughtful housing solutions that preserve what makes Vashon special.
