Most building materials are hygroscopic, which means they will absorb or lose moisture depending on the humidity of the surrounding air or the presence of excess water from broken pipes, leaky roofs or worst from floods.
High moisture levels should be avoided, and if they exist, remediation should be done without delay. When too much moisture has been absorbed, building materials will lose their structural integrity and strength. Another hazard of too much moisture is mold growth. It is only a question of time until mold will start to grow, if enough humidity is in the air and enough moisture in the material.