FLASHING PRIMER Details for leak-free flashing with slate, wood, asphalt, and clay by Les Gove The copper valleys and other flashings, installed when the slate roof was completed in 1899, began to develop pinhole leaks around 1975, and was replaced 10 years later by the author of this article. flashing principles and techniques that The primary purpose of any roof is to protect the interior of a building from rain and snow. In addition, the roof should add to the character of the building. A proper flashing job is essential for both. In fact, how long a roof will serve you maintenance-free depends largely on the durability of the flashing materials, and how they are applied. In this article, we'll discuss basic apply to