What is a common cause for roofing leaks?

A common cause for roofing leaks is indeed damaged shingles or defective flashings. Shingles serve as the primary barrier against water intrusion, and if they are cracked, missing, or otherwise compromised, water can seep through the roof. Flashings, which are the metal elements that seal areas where the roof meets a vertical surface or around roof penetrations like vents and chimneys, are crucial for directing water away from these vulnerable spots. If flashings are improperly installed or have become damaged due to weathering or old age, they can allow water to enter the roofing system, leading to leaks.

While excessive rain can exacerbate leaking problems, it is not a direct cause of leaks; instead, it highlights issues that already exist with the roofing system. The installation of new roofing is typically intended to prevent leaks, assuming it is done correctly. Lastly, the use of incorrect roofing materials can lead to failures in specific conditions, but it does not inherently cause leaks unless the materials are inappropriate for the roof design and environment, leading to potential problems later on. Thus, the direct connection between damaged shingles or defective flashings and the occurrence of leaks makes it the most common cause.