Valley leaks in asphalt shingle roofs are a common problem area because valleys are where two roof slopes meet, directing water flow in high volumes. These leaks often happen because valleys experience more water flow, and any small gap, damaged shingle, or improper installation can let water seep through. Causes include improperly laid flashing, damaged or missing shingles along the valley, or debris build-up causing water to pool and eventually leak under shingles. During heavy rain or after snow melts, you might notice water stains or drips inside your attic or ceiling near valley lines. A simple diagnostic check is to safely inspect your roof valleys for curled, missing, or cracked shingles and to look for signs of exposed or damaged flashing along the valley. Cleaning out any debris is a helpful DIY task. However, avoid walking on wet shingles or using harsh tools that can cause damage.
If you spot problematic shingles or flashing issues, or if the leak source isn’t obvious after a visual check, it’s wise to call a professional roofer. They can perform a thorough inspection and fix flashing or shingle problems correctly, ensuring proper water drainage and seal integrity while preserving your roof warranty. When you consult a contractor, ask questions like: “How will you address flashing installation or repair in the valley to prevent future leaks?” and “Will the repair work maintain or impact my existing shingle warranty?” These questions help confirm that the fixes meet both industry standards and warranty guidelines, giving you peace of mind that the valley leak won’t return.