You may think of a valley as a geographical feature, but your roof may have some valleys too, depending on its design. Roof valleys are the seams where two slopes come together to create angled depressions that are particularly prone to leaking. When you've chosen an asphalt shingle roof, you must choose between open and closed valley styles during installation or re-roofing.
Open valleys expose a strip of metal flashing to the sky, while closed valleys are covered by a carefully woven layer of shingles. Before you choose closed valleys based on the look alone, consider these other differences between the two styles that are especially applicable to the challenges faced by a roof installed in Florida's wet and stormy climate.
Removal of Debris
First, leaving a layer of smooth metal flashing exposed in the bottom of each valley helps this part of the roof stay clean. Debris like palm fronds and pine needles gather in valleys, creating tiny dam-like obstructions that catch water and allow it to soak in under the shingles to either side of the valley.
Open valleys tend to clean themselves, while the shingles in a closed valley are more likely to trap debris and require extra maintenance. If a storm blows in both debris and rain, a closed valley has a chance of leaking before the storm is even over.
Indication of Damage
The open valley style does make the flashing visible to your neighbors, but a little visibility is often a good thing when it comes to spotting early signs of damage to your roof. When the metal flashing in the valley is getting old and breaking down due to corrosion, it's easy to spot even from the ground.
Closed valleys also require metal flashing, but since the metal is covered with woven or cut shingles, you'll have to rely on a professional roof inspection alone to know when it's time for a repair.
Wear of Shingles
A working valley carries water from both slopes down to the gutters as quickly as possible. Yet all that rushing water also creates a lot of wear and tear on asphalt shingles, resulting in granule loss that occurs faster in the valley than the rest of the roof.
Since an open valley directs the water over galvanized or coated metal flashing instead, none of the shingles take all the extra wear and tear. Since exposed flashing has no granules to lose, the valley will look new for longer.
Cost of Installation
Most roofing companies charge different prices for closed and open valleys because they require different amounts of effort. In general, closed valleys cost a few hundred dollars more than open ones because of the extra work required to carefully weave shingles together so moisture isn't funneled under a layer of shingles.
However, some roofing companies charge more for open valleys instead. Before picking a style based on price alone, consider the long-term maintenance costs, which are higher for closed valleys than open ones.
Slope of Roof
Finally, low-slope roofs that have a 4:12 slope or less should only have open valleys. Since low-slope roofs are a popular style in South Florida, open valleys are the best choice for most roofs in the area. Low slopes meeting in a valley dump water into the area at a slow speed, and slow water has a greater chance of penetrating under shingles. Open valleys can handle the slowest flow and lowest slope without increased risk for leaks.
Of course, we here at Eagle of the Keys Roofing Contractor can also make a closed valley work for your roof if it's important to you. Talk over your options today with our team.