Valleys catch water rushing down from where the two roof planes meet and, thus, are the most likely areas for roof leaks. The leaks can be caused by:
• Water rushing up from the valley’s opposite side;
• Wear and tear from the friction of the channeled water on the roof material; buildup of snow and ice, and traffic (i.e., birds, rats and animals) on the roof.
In fact, leaking valleys are one of the most common types of roofing problems and also one of the most difficult to identify as to exact location. Yes, repairs of leaking valleys should be performed by roofing professionals because of the wide range of issues that can arise from even the smallest leak, not to mention that the valleys may not even be the root cause of the roofing problem.
The best solution to avoiding – or at least, lessening the frequency of roof valley leaks – is to ensure that the valleys are leak-proof in the first place. This is usually achieved by providing for a leak-proof underlayment system, which will back up the metal or shingle valley detail. Again, this is a job best left to the roofing professionals but it still pays to know a few details of the leak-proofing job.
• Remove loose nails, among other debris, before the valley underlayment is placed for asphalt shingle roofs.
• Install a 36-inch wide strip of bituminous membrane up the valley. Keep it as tight as possible to the valley center’s sheathing because hollow sections can be easily punctured.
• Install the felt underlayment across the roof, which should overlap the valley flashing by a minimum of 6 inches.
Roofing professionals should conduct thorough roof inspections when leaks appear to be close to the valleys. Keep in mind that determining where the leaks are coming from is not as easy as it sounds especially when valleys are involved so an experienced eye, so to speak, is necessary.
When the leaks are identified, roofing professionals should also be hired to solve the issues. Do-it-yourself efforts in patching up valley leaks are most likely to be failures because of the complexity of the problem.