National Home Inspector Practice Exam 2026 - Free Home Inspector Practice Questions and Study Guide

Staining on walls or flooring is a common sign of water intrusion in basements because it indicates the presence of moisture that has penetrated the building materials. This moisture can lead to discoloration and staining, often manifesting as dark spots or streaks on walls and floors. Identifying these stains is critical for identifying potential water damage, as they suggest that water is coming into contact with the structural elements of the basement.

In contrast, while crumbling walls can indicate deterioration often related to moisture, they may not always be a direct indicator of current water intrusion. Excessive insulation does not typically signal water intrusion directly and could lead to other concerns, such as mold growth if moisture is trapped but not visible. High humidity levels can be a sign of potential moisture issues, but they do not directly indicate water intrusion like visible stains do. Staining therefore serves as a clearer and more immediate sign of water intrusion problems that need to be addressed.