Where is a roof most likely to leak?

A roof is most likely to leak at the valleys. Valleys are the areas where two slopes of the roof meet and direct water runoff. Since these points collect water from larger surface areas of the roof, they are particularly susceptible to leaks, especially during heavy rain or snowmelt.

The design of valleys often involves various materials and joint constructions that can become points of failure if not installed properly or if they deteriorate over time. For example, if shingles or flashing in a valley are improperly installed, water can seep through, leading to leaks into the structure below. Moreover, valleys can accumulate debris, like leaves or branches, which can impede proper drainage and exacerbate the risk of leaks.

In contrast, while eaves, ridges, and overhangs can also have issues, they are generally less prone to leaks compared to valleys. Eaves may leak due to improper drainage or blockage, and ridges can have issues primarily with ventilation or flashing. Overhangs, being purely architectural features, typically do not gather water in the same manner as valleys, making them less likely points for leaks.