King County Capacity Charge

Frequently asked

• What does King County Capacity Charge mean in the context of an ADU?

  King County Capacity Charge is part of the regulatory and technical vocabulary you encounter when permitting and building an accessory dwelling unit in Washington. Knowing the term matters because reviewers, inspectors, and your lender will use it without explanation. We define King County Capacity Charge in plain English and connect it to the specific code citation, fee, or construction detail that affects your project. Use the related-terms section to navigate adjacent concepts you'll need on the same plan set.

  Go deeper: Read the ADU utility upgrades: sewer, water, and electrical service guide→

• Where does King County Capacity Charge apply in the WA ADU process?

  King County Capacity Charge typically shows up in either the design phase (when the architect or designer is laying out plans against zoning), the permit phase (when reviewers check the submittal against code), or the construction phase (when inspectors verify built conditions match the approved set). The same term can appear in your loan documents if it affects valuation or risk. Each glossary entry maps the term to the exact phase where it matters most.

  Go deeper: Read the ADU utility upgrades: sewer, water, and electrical service guide→

• Why should I care about King County Capacity Charge for my project?

  Misunderstanding King County Capacity Charge is one of the most common reasons ADU projects hit avoidable cost overruns or permit delays. A clear shared vocabulary between you, your designer, and your builder shortens decision time and reduces change orders. Bookmark this glossary and refer back as you progress from feasibility through final inspection.

  Go deeper: Glossary: King County Capacity Charge→

• How does King County Capacity Charge affect my ADU budget?

  Most glossary terms map to either a cost line, a review timeline, or a permit fee. Where King County Capacity Charge drives cost, the impact is itemized in our standard fee schedule and itemized at feasibility — so by contract time, King County Capacity Charge is a known number, not a discovered surprise. Click through to the related cost or permit page for the current King County Capacity Charge-specific dollar range and timeline.

  Go deeper: Read the King County side sewer permits for ADUs: cost & timeline (2026) guide→

• Is King County Capacity Charge regulated under RCW 36.70A.681?

  WA statewide ADU preemption (RCW 36.70A.681 / HB 1337) covers many ADU-adjacent topics: size caps, setbacks, owner-occupancy, parking, height, lot-size minimums. Whether King County Capacity Charge falls under preemption depends on its specific scope — design review, side-sewer permitting, drainage review, and tree-protection rules are generally NOT preempted, while size/setback/parking generally ARE. Each glossary entry flags the preemption status.

  Go deeper: Read the King County side sewer permits for ADUs: cost & timeline (2026) guide→