Impervious Surface Ratio (ISR) Worksheet

Building Department

February 9, 2023
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  • Method of Calculation

  • IMPERVIOUS SURFACE- "Any hard-surfaced, man-mad area that does not readily absorb or retain water, including but not limited to building roofs, parking and driveway areas, sidewalk and paved recreational facilities."
  • IMPERVIOUS SURFACE RATIO (ISR)- "The total area of impervious surfaces divided by the net area (excluding right-of-way) of the lot."
  • LOT AREA- "The total horizontal area included within the list lines of the lot. No public right-of-way or access easement for a public street or handle of panhandle lot shall be included in the calculation of the lot area, nor shall the public right-of-way cross the lost area."
  • Lot information:

  • sq.ft.
  • Permit application number, if applicable
  • sq.ft.
  • sq.ft.
  • sq.ft.
  • sq.ft.
  • sq.ft.
  • Total Impervious Surfaces:

  • Total Impervious Surfaces divided by Lot Area.
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