Detailing valleys on a polyurethane roof coating requires careful attention to ensure proper waterproofing and durability. Valleys are where two roof planes meet, naturally channeling water, so they are prone to leaks and wear. When working on a polyurethane coating, the goal is to create a seamless, reinforced, and weather-resistant surface that handles water flow efficiently. For woven valleys, use a compatible fabric embedded into the coating, applying it tightly along the valley line before adding a topcoat. Closed-cut valleys (metal lined but covered with coating) should have metal flashing securely fastened under shingles on one side, with the coating systems layered to overlap and seal above the metal edge. Open metal valleys, where the metal flashing remains fully exposed, need the coating applied up to—but not covering—the metal edge while ensuring waterproof sealants at seams and overlaps prevent water infiltration. Diagnosing issues in valleys involves checking for cracks, peeling, or gathered moisture, especially after rains or snowmelt, and running a thorough visual inspection for damaged or lifting coating.
Safe DIY checks include gently looking for any soft spots, bubbling, or discolored areas that may signal trapped moisture or deteriorated coating. Using a hose to simulate rainfall while watching closely for leaks underneath can help identify weaknesses. Avoid heavy walking on coating in these areas to prevent damage. When in doubt or if you find damage to flashing or complex fabric layers, it’s best to call a professional roofer experienced with polyurethane systems. Ask, “How do you ensure proper adhesion and sealing when detailing valleys with polyurethane coating?” and “What measures do you take to prevent warranty issues related to valley waterproofing?” This ensures the contractor understands the compatibility of materials and the importance of thorough detailing, which is critical for the longevity of your roof’s waterproofing.