A standard policy has exclusions, including earth movements (landslides, earthquakes, sinkholes), power failure, war, nuclear hazard, government action, faulty zoning, bad repair or workmanship, defective maintenance and flooding. Windstorms are typically covered, including tornadoes, although insurance companies exclude tornadoes or hurricanes in some high-risk areas.
Water damage is tricky. As a rule of thumb, water from above (rainwater or a burst pipe in an upstairs apartment) is usually covered, but water from below (backed-up sewers or ground flooding) generally isn’t. If your region is prone to floods and earthquakes, you should consider supplemental coverage.