Do I need to worry about Tenants Improvements and Betterments as the building owner?

Both the tenant, and the building owner need to be concerned about improvements and betterments. In most cases, when an insured installs improvements and betterments at their own expense, they have an insurable "use" interest in that property, and this can be covered by insurance, but legally, once they become part of the real property, they become the property of the building owner. The biggest danger here is that the building owner could suffer a coinsurance penalty (see what is coinsurance) if they have not included them in their insured building value.