Leaking valleys are some of the most common type of roofing leaks a home can have. They can also be some of the most difficult leaks to track down and repair. This is one type of leak where experience can give a big advantage in locating and fixing the problem. A roof valley can be formed when two opposing sloped roof planes meet. There are many different types of valley leaks. Trying to decide if your roofs valley is leaking or some other part of your roofing is causing a leak can be tricky.
Since leaking valleys are one of the more common causes of leaking into homes have your roofing professional give a thorough valley inspection to any leak that is even remotely close to a valley on your roof. One of the more frequent winter time causes of valley leaks are ice dams. Valleys tend to have a funnel effect on snow and ice which makes the problem even more likely in a valley. Roofing valleys above dormer windows are especially susceptible to this since we have found they tend to have poorer attic ventilation and less insulation due to the smaller area. Once this type of leak starts you either have to have your professional roofer remove the ice blockage or wait until the ice dam melts sufficiently to allow the trapped water off the roof. See our article on ice dams for more information on this subject.
Another cause of leaks in valleys is water running between the shingles and the valley flashing system. As water runs down your roof it picks up speed. This speeding water can hit your valley and run up under your shingles. We have also found valley metal that had been dented by hail on open valley applications (valleys that consist of a metal center with shingles on both sides). Although these dents looked cosmetic they actually had formed small tears in the valley metal causing a valley leak. On a side note we recommend and prefer a closed valley where shingles are run from one slope up onto the other slope then overlapped by the shingles from the adjacent slope for a water tight valley.
Many homeowners will try and fix valley leaks by covering the valley in tar and or roofing cement. This method of trying to stop a valley leak is in our opinion a very poor choice. Even if you happen to temporarily stop the valley leak you may in fact create many more problems than you fix. Sealing and entire area with tar can trap any subsequent water that may penetrate this same area leaving no where for the trapped water to escape except into your home. Sealing roofing leaks in this way is also very unattractive.
When you re-roof your home we recommend that you install snow and ice shield in all valleys and on all eaves under your new shingles. This snow and ice shield acts as a back up to protect your interior living space should any water leak past your roofing shingles. Not only is this protection for winter months but it can give added protection when need during heavy rain and when your shingle roofing becomes overwhelmed. If you have this type of leak recurring in the same valley and you are unsure if the old valley was done properly you may want to replace the valley. In our opinion sometimes it easier and more effective to remove the entire old valley and start from scratch with snow and ice shield followed by installing a closed valley.
Bottom line on valley leaks weather you decide to attempt a repair or opt for complete replacement it helps to find a roofing professional who is experienced with diagnosing and repairing valley leaks. Leaking valleys can be some of the most common and frustrating leaks a homeowner will encounter.