Valley detailing on EPDM roofs is a crucial step to ensure proper water drainage and prevent leaks where two roof slopes meet. EPDM, a synthetic rubber membrane, can be installed over valleys using different methods depending on the roof design, such as woven valleys, closed-cut valleys, or open metal valleys. A woven valley involves overlapping EPDM sheets from both roof planes, carefully stretching and adhering them to create a continuous waterproof barrier. Closed-cut valleys require cutting the EPDM on one side of the valley and fully embedding it into the valley pan or metal flashing underneath, while the other side’s membrane laps over it. Open metal valleys involve installing a metal valley flashing first, usually galvanized or aluminum, with the EPDM membrane butted against the metal, secured by sealants and fasteners. Issues like improper adhesion, wrinkles, or sharp bends often cause leaks. Checking these valleys involves visually inspecting for cracks, debris, or pooled water. A simple safe check includes gently running water to see if it drains smoothly without backing up or leaking under the membrane edges.
As a homeowner or DIY roofer, approach valley detailing work with caution, as improper handling can void EPDM warranties or cause damage to the membrane. If you notice bubbling, peeling, or cracked seams within the valley areas, it’s time to call a professional roofer experienced in EPDM systems. When consulting a contractor, ask specifically if they have experience with your chosen valley type (woven, closed-cut, or open metal), and request details on how they ensure secure adhesion and seam integrity in valleys. Also, inquire about their warranty coverage on these critical areas, as valleys are high-stress points prone to premature failure without proper detailing. A knowledgeable roofer will explain how they prep the substrate, apply primer, and use manufacturer-approved bonding agents to maintain a lasting, watertight seal.