Normal wear and tear exclusion in an insurance policy asserts that damage done to the insured property will not be covered if it was caused by expected and normal deterioration. Insurance companies routinely include these exclusions in their policies since they are designed to keep the insurer from being liable when the policyholder fails to properly maintain, repair, and replace deteriorated and/or defective portions of the insured property.

How does this lead to denied insurance claims?

Poor maintenance, prior damage, manufacturing defects, or faulty installation. A prevalent example involves roof damage claims: