Quicker Permitting Option for Single-Family Substantial Alterations

We currently require plan review for all substantial alteration projects.  We consider a single-family project to be a substantial alteration if it does one of the following:

  • Repairs a building with a damage ratio of 60 percent or more
  • Extends the physical or economic life of the building
  • Changes use to one within the scope of Seattle Residential Code from a use not from within the scope of Seattle Residential Code
  • Changes use of an accessory structure to another use
  • Changes use from single family or duplex to townhouse
  • Changes use to an adult family home or family home child care


On October 1, 2017, we will begin issuing some single family substantial alteration projects as a Subject-to-Field-Inspection (STFI) permit.  We often issue STFI permits on the same day you apply. To qualify for this new permit type, your project must meet both of the following criteria.

  • Your work must meet the limitations described in Tip 316 Subject-to-Field-Inspection Permits for structural or non-structural alterations, ground level one-story additions and/or dormer additions
  • The project must be considered a substantial alteration because the physical or economic life of the building is extended (Seattle Residential Code section R107.9)

You will also need to show seismic upgrades to the foundations and cripple walls throughout your house unless it was built new per the 1985 Uniform Building Code or a more recent code.  You may provide a design by a licensed engineer or you may use our prescriptive Earthquake Home Retrofit Plan Set, also known as Project Impact.  If you use an engineered design, your application must include structural plans prepared and stamped by a licensed engineer showing the required upgrades.  If you use Project Impact, you will need a separate permit for that work.  Your Project Impact permit must be issued before we issue your STFI, and the work must be completed before the final STFI inspection.

Substantial alteration projects require certain upgrades throughout the structure, including in areas where alterations are not planned.  You may need to upgrade:

  • Egress windows
  • Stairs
  • Smoke and carbon monoxide alarms
  • Foundations and cripple walls
  • Unreinforced masonry chimneys


See the Seattle Residential Code section R107.9 for complete requirements.  Your building inspector will check to make sure that you have made all required upgrades to the house.

Questions may be directed to:

Jamie Anderson
(206) 615-0715