A musty smell can indicate the presence of mold or mildew, which can be caused by water damage. When moisture is present, mold and mildew can grow on a variety of surfaces, including walls, floors, and ceilings. A musty smell is often the first sign of a mold problem, and should be taken seriously.

However, it's worth noting that a musty smell can also be caused by other factors such as humidity, dampness, or poor ventilation, so it's important to investigate the source of the smell to determine if it is caused by water damage or not.

If you suspect water damage and mold in your home, it's important to address the problem as soon as possible to prevent it from getting worse. A professional inspector or mold remediation expert can help you assess the extent of the damage and provide recommendations for repairs or remediation.