Detailing valleys on a green roof is crucial to manage water flow effectively while protecting the underlying roof structure. A green roof typically involves layers like waterproof membranes, root barriers, drainage, and growing medium, so valley detailing must ensure water does not pool or leak. With woven valleys, two roofing surfaces interlock, often under metal flashing, directing water efficiently. Closed-cut valleys involve one roof slope ending against another, with a metal flashing embedded under shingles on one side to prevent water intrusion. Open metal valleys feature exposed metal strips or pans running down the valley that effectively channel water away. Each method requires careful sealing and flashing to prevent leaks, especially with the added moisture and weight of plant materials. On green roofs, the presence of soil and plants around the valley means extra attention is needed to avoid clogging and ensure drainage is clear.
To check the valley condition on your green roof, start by inspecting after heavy rain, looking for any signs of pooling water, erosion of medium along the valley edges, or visible damage to flashing. Safely examining these areas can often be done from the ground with binoculars or a ladder, but walking on a green roof should be limited to prevent damage to plants and structure. Watch for plant dieback along the valley line, which may indicate water infiltration or drainage issues. If you notice persistent wet spots or damaged flashing, it’s wise to call a roofing professional experienced with green roof systems. When consulting a contractor, ask how they will maintain the integrity of both the waterproof membrane and the plant layers during valley repairs, and whether their solution complies with your roof’s warranty conditions. Proper detailing and upkeep of valleys ensure your green roof remains both beautiful and functional for years to come.