Could it be covered by the insurance the renters are taking out on their contents. If it was you in the house, your contents in the shed should be covered so why not if its your friends in the house? Just a thought.
This brains trust recommends keep searching. Can't you just insure the whole property, including the shed, goods and chattels? Heck, if I can insure an on-site van in Broome with a photo of my cyclone tie-downs, surely a photo of your shed security would do it for you. Try National Seniors who are underwritten by Allianz may entertain your proposal. Good luck.
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20ft Roma caravan - Mercedes Benz Sprinter - SA-based at the moment. Transport has no borders.
Management makes the decisions, but is not affected by the decisions it makes.