Which is a sign that a structure is susceptible to collapse?

A structure that has doors stuck in shifted frames indicates significant movement or settling of the building’s foundation or structural elements. When the alignment of door frames is altered, it suggests that there may have been a shift in the load-bearing components of the structure, which can often precede or accompany a potential collapse. This is particularly critical in firefighting operations, as it can signal to firefighters that the integrity of the building has been compromised, creating an immediate danger for anyone inside and for the firefighters responding to the emergency.

Signs such as discolored drywall, delaminated plywood, or inverted fire patterns can indicate other issues such as moisture damage, fire behavior, or materials breaking down but do not directly point to the imminent risk of collapse in the same way that shifted frames do. The presence of stuck doors is a clear indicator that something has changed structurally, which requires heightened caution and potentially a reevaluation of tactics when approaching the building.