# King County, WA Site Plans — Two Plans Required and Critical Area Review
Most homeowners expect to submit one site plan with a permit application. In King County, for new construction, you typically submit two.
The Building, Drainage & Critical Areas plan shows where everything will be built and how it relates to the environment. The TESC plan shows how you will control erosion and sediment runoff during construction. Both must be submitted to the MyBuildingPermit.com portal, both must be at minimum 11" × 17", and both must be at a minimum scale of 1:20.
Do You Need a Site Plan for a Small Permit in King County?
Yes. If your project in unincorporated King County requires a building permit, you must submit site plans.
Building, Drainage & Critical Areas Plan must include:
- Address, parcel number, and owner information.
- Scale (minimum 1:20) and North arrow.
- Property lines with dimensions and total lot size.
- All easements and deed restrictions.
- Existing vs. new structures, clearly differentiated.
- Parking areas and driveways.
- Sewer connection or septic system location.
- Water connection or well location (with well radius if applicable).
- Existing and proposed grade elevations and contour lines.
- Survey benchmark location and datum.
- All impervious surface areas (existing and proposed).
- Location of drainage features and proposed drainage facilities.
- Critical area designations (wetlands, streams, steep slopes, floodplains).
- TESC measures.
The TESC Plan includes construction access, proposed drainage facilities, and erosion control measures in addition to the base site information.
Who Runs Into This in King County
- Redmond and Renton homeowners who apply to the King County permitting portal, only to be redirected because they live inside an incorporated city.
- Rural homeowners who are surprised to learn their 3-acre property in the foothills is within 300 feet of a mapped wetland, triggering a critical area review that adds weeks to the permit timeline.
- DIYers who submit a single site plan, unaware that the county requires two separate documents for most new construction.
- Pool Contractors who submit a site plan without any contour lines, failing the minimum engineering information requirement.
What Needs a Site Plan in King County
- Fence permit site plan — Fences over 6 feet require a permit. (Fences 6 feet or under are generally exempt from building permits).
- Shed permit site plan — Required for sheds over 200 sq ft. (Sheds 200 sq ft or less are exempt from building permits).
- Deck permit site plan — Required for decks over 30 inches above grade or attached decks. (Uncovered decks 30 inches or less above grade are exempt).
- Pool permit site plan — Required. Must show pool, equipment, barriers, grading contours, and critical area proximity.
- Addition permit site plan — Required. Must show expanded footprint, drainage, and critical area information.
- Retaining Walls — Walls over 4 feet require a permit (and typically engineered plans).
Why This Trips People Up in King County
The Two-Plan Requirement. Most homeowners, contractors, and even experienced drafters are accustomed to submitting one site plan. King County's requirement for a separate TESC plan catches many applicants off guard. If you submit only one plan for a project that requires two, your application will be marked incomplete.
Critical Areas. King County is defined by its rivers, lakes, wetlands, and steep slopes. The county's critical area regulations require that the Building/Drainage site plan identify any critical areas within 300 feet of the construction site. If critical areas are present, additional studies and setback buffers may be required before a permit is issued.
Impervious Surface Calculations. Every site plan must explicitly calculate existing and proposed impervious surface. King County uses this to manage stormwater, and land use permits may be required if you are creating more than 2,000 square feet of new impervious surface.
Hand-Drawn Plans Are Accepted for Small Projects. For small and simple projects, King County does accept hand-drawn site plans, provided they are properly scaled, contain all required elements, and meet the minimum 11" × 17" sheet size.
Zoning and Setbacks in King County
Setbacks are governed by KCC Title 21A. The county's Property Research Guide and Worksheet tool allows you to look up setbacks for your specific zone.
Typical Residential Zone Ranges:
- Street setback: Typically 15–25 feet.
- Interior side setback: Typically 5–10 feet.
- Rear setback: Typically 15–25 feet.
Special Notes:
- Garages often require a greater front setback than the residence itself.
- Fences exceeding 8 feet must comply with street and interior setbacks.
- Fall City Rural Town zone: 10,000 sq ft minimum lot, 10-foot interior setbacks, 20-foot street setback.
How the Tool Handles This — 5 Steps
SitePlans.ai loads King County parcel data so you can generate the properly scaled site plan required by MyBuildingPermit.com:
- Enter your address — Lot lines load from King County GIS records.
- Place your project — Add your deck, shed, or addition to the lot.
- Calculate impervious surface — Use the tool to total up existing and proposed hard surfaces.
- Annotate critical areas — Mark any known wetlands, streams, or steep slopes within 300 feet.
- Export a clean PDF — Download your Building/Drainage plan (and TESC annotations) ready for MyBuildingPermit.com.
Where This Tool Fits — and Where It Doesn't
| Situation | Best path |
|---|---|
| Shed, deck, or addition in unincorporated King County | SitePlans.ai for the required scaled site plans |
| Critical area on or near property | SitePlans.ai for layout + consult county for critical area setbacks |
| New home construction | Licensed WA Architect/Engineer required |
| Retaining wall over 4 feet | Licensed WA Structural Engineer required |
| Disputed property lines | Licensed WA Land Surveyor required |
What This Doesn't Replace
Our site Plan maker online webtool helps create preliminary, conceptual site plans for residential projects in unincorporated King County. It is not a licensed land survey, a critical area study, or a full TESC engineering document. For properties in critical areas, a licensed Washington State professional may be required to prepare the formal critical area study.
Comparison: Your Options for a King County Site Plan
| Method | Cost | Time | Stamp | Notes |
|---|---|---|---|---|
| Hand sketch | Free | 1–2 hrs | ✗ | Accepted for small/simple projects; must be minimum 11"×17" at 1:20 scale |
| SitePlans.ai | Free first plan | Minutes | ✗ | Generates correctly sized, properly scaled PDFs for MBP upload |
| CAD drafter | $300–$800+ | 1–2 weeks | Sometimes | Useful for larger projects or complex grading |
| Licensed WA Engineer/Architect | $800–$3,000+ | 2–5 weeks | ✅ | Required for critical area studies and new homes |
| SitePlans.us (done-for-you) | Custom | 1–3 days | ✗ | Best if your MBP submittal was rejected by the Permitting Division |
Common Mistakes That Delay King County Permits
- Applying in the wrong jurisdiction — Submitting to the county portal when the property is inside Seattle, Bellevue, or Renton.
- Submitting only one site plan — Forgetting the separate TESC plan for new construction or significant additions.
- Missing contour lines — Submitting a site plan without existing and proposed grade contours, failing the drainage review.
- No impervious surface calculation — Omitting the existing and proposed impervious surface totals.
- Missing critical area information — Not checking for wetlands or streams within 300 feet of the project area.
Support and Local Resources
- King County Permitting Division — 35030 SE Douglas St, Suite 210, Snoqualmie, WA 98065 | (206) 296-6600.
- MyBuildingPermit.com — mybuildingpermit.com — the online permit portal.
- King County GIS / Parcel Viewer — gismaps.kingcounty.gov/parcelviewer2/
- FEMA Flood Maps — msc.fema.gov
Nearby Counties
- Washington permit site plan requirements
- Snohomish County site plan guide
- Spokane County site plan guide
Frequently Asked Questions
1. How many site plans does King County require?
For most new construction applications, King County requires two: one for Building, Drainage & Critical Areas, and a separate one for Temporary Erosion and Sediment Control (TESC).
2. Do I need a permit for a shed in King County?
Sheds 200 square feet or less are exempt from building permits. Sheds over 200 square feet require a permit and site plans.
3. What are "critical areas" in King County?
Critical areas include wetlands, streams, steep slopes, floodplains, and wildlife habitat areas. If your property is near any of these features, additional review and setback buffers are required.
4. What is MyBuildingPermit.com?
It is the online portal used by unincorporated King County (and many other Puget Sound jurisdictions) to submit, review, and track building permit applications. All site plan submissions for unincorporated King County go through this portal.
5. What is the minimum scale for a King County site plan?
Site plans must be at a minimum scale of 1:20 (meaning 1 inch on paper represents 20 feet on the ground), on a minimum sheet size of 11" × 17".
6. Can I use SitePlans.ai for a King County permit?
Yes. For residential projects in unincorporated King County, SitePlans.ai generates the properly sized and scaled PDF site plans—including impervious surface calculations and critical area annotations—ready for MyBuildingPermit.com.
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Verify your jurisdiction using the King County GIS Parcel Viewer first. Then enter your address below to pull your property lines, place your project, calculate your impervious surface, and download the two scaled PDFs you need for MyBuildingPermit.com.
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