While accidental damage cover is given in addition to the fire and allied perils, the main difference is probably the difference in the way cover is described. Under a fire and allied perils policy, the wording defines exactly what perils are covered. Under an ISR policy everything is covered other than the exclusions, defined in the wording.
ISR Insurance was developed in the late 1980’s in Australia, and has undergone several revisions over the time, but in essence, the base level of coverage has remained the same. The coverage is designed for clients that have major assets at a single location, or clients with multiple locations with assets greater than $ 10M. Policies contain industry-agreed base wordings (Mark 4 & 5) that can be tailored to your specific business needs.
In tandem with an ISR insurance policy, you would consider having additional separate policies, where required, such as Liability, Directors and Officers, Professional Indemnity, Motor Vehicle, Cyber and Trade Credit.