Which condition could lead to structural issues in the roof?

Rafter sag or spread is a condition that can significantly compromise the structural integrity of a roof. When rafters sag or spread, they may indicate that the roof is experiencing excess loads or insufficient support. This can result from factors such as overloading due to heavy snow, inadequate framing, or deteriorating materials. The sagging alters the roof's ability to bear loads correctly and can lead to further complications, such as leaks, cracking of interior walls, and in severe cases, potential collapse.

In contrast, adequate bracing, proper venting, and efficient drainage are all practices aimed at preventing structural issues and maintaining the roof's health. Adequate bracing helps stabilize the rafters, ensuring they can handle the weight they carry. Proper venting allows for air circulation, which can prevent moisture buildup that can weaken framing materials. Efficient drainage ensures that water is directed away from the structure, preventing pooling that could lead to added weight and stress on the roof. Thus, rafter sag or spread poses a much more immediate risk to the structural integrity compared to the other options.