An insurance dwelling extension is an additional amount of coverage that can be added to a standard homeowner’s policy. It provides protection for structures on the property that are not attached to the home, such as detached garages, sheds, and gazebos. Dwelling extension coverage is typically 10% of the policy limit for the dwelling itself. So, if you have a $250,000 homeowners policy, your dwelling extension would provide $25,000 in coverage for detached structures.