House or building remodels or expansions

Steps for house or building remodel or expansions

• Download the application for approval of building permit (357 KB).
• You may apply for this review prior to or at the same time as the Building Department's review of your application.
• While preparing your application, it is important to accurately describe the location of all septic system components on your site plan. Search and download a drawing of your septic system (as-built drawing).
• Each application is reviewed by an inspector and receives a site visit. Examples the inspector are looking for includes:

  • Age of septic system
  • Condition of system
  • Type of system
  • Location of system as compared to area of remodel
  • Presence of a reserve drainfield area
  • Size of remodel
    • existing square footage vs. square footage being added
  • Use of addition
    • are bedrooms being added? If so, call the King County Septic Expert first! 206-477-8177
    • number of bedrooms equals occupancy equals size of septic system
  • Water source
    • a drinking water well requires certain setbacks to structures
    • structures must be served by an approved water source
  • As-built and past permit history
• Due to the scope of your remodel and condition, location and age of your septic system, you may be required to have the septic system evaluated by a licensed septic professional. The inspector will notify you in writing what this evaluation must include and what type of septic professional must be contacted.
• You may also be required to upgrade or replace your septic system. For example, a house with an older septic system and your proposal is to tear the house down to the foundation and rebuild, it would require a new septic system. Call the King County Septic Expert 206-477-8177 to ask about your potential project.