You should know that one of the most vulnerable areas of any roof is the valley, where the roof’s panels intersect. If not properly protected and sealed, a valley can channel water directly into the home with potentially disastrous consequences. There are two very popular types of valley installation methods used among roofing contractors today, each with their own advantages and disadvantages.
Closed valleys have become popular among roofing contractors for their aesthetic qualities. For a closed valley, shingles are installed across the joint where panels intersect. With each new course, roofing shingles continue up the valley.
According to the president of Advanced Roofing Ltd. Justin Fall “Residential roofs still tend to favor closed valley systems because they’re more aesthetically pleasing” Fall says.
However, Fall points out that in a closed valley system, ice and water aren’t shed as quickly and the continuous build-up and channelling of water during storms may result in granule loss. And, while some homeowners may prefer the aesthetics of a closed valley, they will wear quicker.
For an open valley, a 36” roll of ice and water membrane is installed in the valley then a sheet of metal (usually steel, sometimes copper) is fastened to the roof deck. The metal is usually pre-painted to best complement the shingles’ color blend. Roofing shingles are installed then cut and sealed where they overlap the metal channel.
“Provided the rest of the roofing shingles were properly installed and are performing properly, my experience has been that an open valley system holds up better over time,” Fall says. He notes that due to the metal construction of an open valley, it may shed ice and water more quickly, which could help minimize granule loss. Installed correctly, it provides a unique aesthetic, especially when using painted or copper coil stock.
Fall says, “Homeowners understand the importance of choosing the right shingles. Color, performance, value and limited warranty are factors they consider, but very few know about open versus closed valley applications.”