It depends on your insurance policy. Review it carefully. If the insurer traces it back to some type of flooding or flood-related, they may not cover it. This could also include flooding due to windstorms like hurricanes or tropical storms. Without that kind of coverage (flood & windstorm), you may be SOL. However, if it has just rotted due to water accumulation over time as a result of a defective roof, hole, or standing water in a low spot, the insurance company may be more accommodating.
Again, it depends on your specific policies.