Which of the following is a positive indicator of footing failures in construction?

Vertical cracking in foundation walls serves as a positive indicator of footing failures in construction for a couple of reasons. When a foundation is subjected to uneven settling, often caused by inadequate or failing footings, it can lead to vertical cracks in the walls. These cracks typically appear as the foundation settles unevenly or as the earth beneath shifts, creating a situation where the materials can no longer flex and adapt, leading to the formation of cracks.

In contrast, sagging floors may indicate structural issues, but they are not as directly linked to footing failures as vertical cracks. Horizontal cracking above windows often signifies stress related to thermal expansion or contraction rather than footing issues. Bowing foundation walls can also be related to similar structural problems but may point more towards lateral soil pressure rather than directly to the footing's failure. So, while all of the options can suggest foundational issues, vertical cracks in the walls strongly correlate with problems specifically regarding footing integrity.