What is the impervious surface ratio (ISR)?

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The Impervious Surface Ratio (ISR) is the portion of a lot that is covered by impenitrable materials, such as concrete. The ISR is dictated by the Future Land Use designation of a property. The table below shows the permitted ISR for each Future Land Use designation: 

 

Future Land Use

Maximum Density/Intensity

Office

Less than or Equal to 65% ISR

Restricted Commercial

Less than or Equal to 65% ISR

Commercial

Less than or Equal to 65% ISR

Industrial

Less than or Equal to 65% ISR

Downtown Development District

Less than or Equal to 90% ISR 

Public/Semi-Public

Less than or Equal to 65% ISR

Recreation

Less than or Equal to 65% ISR

High Intensity Planned Development -Target Industry

18 DU/1 Acre, Maximum 65% ISR and 35% Minimum Open Space

High-tech / Industrial

Corridor Protection Area  

Less than or Equal to  65% ISR

Transit Oriented Development Overlay   

Less than or Equal to 90% ISR 

Downtown Economic Policy Initiative Overlay   

Less than or Equal to 90 %ISR