This was an inverted roof system also known as an IRMA system on one of our local schools.  This roof was leaking around the entire perimeter, many of the HVAC units and various penetrations in the field area.  The ballast, cloth and insulation had to be removed.  The exposed decking had to be power washed and primed.  All penetrations were inspected and treated with trowel grade silicone before applying 22 mils of silicone to the entire roof.