What can cause an overlying asphalt shingle to split at joints?

The splitting of asphalt shingles at the joints is primarily attributed to temperature-related shingle contraction. Asphalt shingles are made from materials that expand when heated and contract when cooled. During significant temperature fluctuations, such as from hot days to cool nights, the contraction can cause stress at the joints where the shingles overlap. If this stress exceeds the material's tolerance, it can lead to splitting.

Temperature changes are a natural occurrence that affects roofing materials, which makes this phenomenon particularly common in regions that experience a wide range of temperatures throughout the year. While other factors like moisture, installation techniques, and maintenance practices can impact the overall integrity and longevity of a roof, it is the thermal movement of the shingles that specifically leads to the visible splitting at the joints. Understanding this helps in diagnosing shingle damage and taking appropriate preventive measures in roof maintenance.