Moisture accumulates without a chance to dry producing mold.

Check Your House for Mold to Avoid Rising Insurance Costs

Leaky foundations, roofs and plumbing are a few of the circumstances that lead to water and moisture buildup and consequent mold growth.  When it comes to mold removal, home insurance companies generally regard mold to be a home-maintenance problem, just like insect damage and rot as a result of oversight or neglect.  For these reasons, mold is specifically excluded from standard homeowners policies.  The exception is if the mold resulted from a “sudden and accidental” source such as a burst pipe, or other covered peril.

Be on the lookout for repeated water leaks and moisture, because while it is possible to add a mold rider to an existing policy, mold is usually not covered.  Keep bathrooms and dryers vented to the outside and use dehumidifiers in basements to keep the chances for mold to a minimum.