Insurance estimate for 2 buildings at one address

[Jairus Burpo]

My wife and I are considering the purchase of a 3 bed 2 bath with a detached 1 bed 1 bath on the same property. In my analysis, I estimated the annual insurance premium as if they were combined, then I learned that the 1 bed 1 bath must be insured separately. Both buildings are included under the same address.

Can I legally insure the 1 bed 1 bath as a shop even if I am renting it out, or does it have to be insured as a separate dwelling? I'm trying to get an accurate annual insurance premium estimate for my analysis.