A leak in a masonry wall could be caused by which of the following?

A leak in a masonry wall can occur due to various structural issues, and all the listed factors can contribute to water infiltration. Crumbling of the masonry can create weaknesses in the wall's integrity, allowing water to penetrate through. Gaps in the mortar are particularly significant because they can directly allow water to seep through; if the mortar joints are not properly sealed, they serve as entry points for moisture. Similarly, cracks in the masonry itself can lead to substantial leakage as they can provide a pathway for water to travel through the wall.

Therefore, recognizing that each of these conditions—crumbling, gaps in mortar, and cracks—can independently and collectively lead to a leak reinforces the importance of regular inspection and maintenance of masonry walls to prevent water damage. This understanding is crucial for a general contractor, as addressing these issues promptly can avert more extensive repairs in the future.