How is it determined that the roof is unstable during the second method of inspection?

The determination of roof instability during the second method of inspection relies on auditory and tactile cues, particularly the drumming sound and vibrations. This method involves listening for specific sounds, as drumming indicates potential problems in the integrity of the roof structure. The vibrations felt in conjunction with these sounds suggest that the material may be shifting or settling, which could lead to imminent failure or collapse. This method is practical because it can reveal issues that may not be visible or apparent through visual inspection alone, thus allowing for timely interventions to ensure safety.

While visual cracks, the presence of water, and dust movement can certainly indicate issues related to roof stability, they do not provide the same immediate and nuanced feedback as the sounds and vibrations detected during inspection. Therefore, the reliance on drumming sounds and vibrations is a key aspect of identifying roof instability effectively.