Name of the Metal in the Edge of the Roof Tile

Basics

• The uniform dimensionality of clay or concrete tiles allows them to overlap and protect the underlying roof deck in most cases. However, when two roof planes meet in a valley, their edges cannot overlap. When an edge also meets a vertical surface such as a chimney, it cannot overlap the surface. In both cases, the deck is exposed to moisture and the elements, which can cause damage and leaking. A sheet of metal in the joints under the tile covers the exposed areas. This metal is called flashing.

Types

• Roof flashing consists of four types. Perimeter edging protects edges of the roof during severe weather, such as rainfall followed by freeze-thaw cycling. Penetrations such as exhaust vents and pipes have flat flashing flanges that extend around the penetration under the shingles. Valley flashing is suited for points where two descending roof surfaces meet. And vertical surface flashing is what you install when the tiles abut a vertical surface such as a chimney. Several types of flashing are in use here, but the one that protects the decking is known as channel flashing because it forms a U-shaped channel through which rain or other precipitation can flow away from the roof.

Valley Standards

• Install valley flashing according to manufacturer’s instructions. Metal varieties must be at least 0.019 inch thick, which is equivalent to No. 26 galvanized sheet gauge. It also must be corrosion resistant. The flashing needs to extend at least 11 inches each way from the center of the valley and should contain a splash diverter rib that is at least 1 inch high as part of its form. If the slope of the roof rises three units or greater for every 12 units of forward movement, which is equal to 25 percent or more, then the flashing requires a 26-inch-wide underlayment running the length of the valley. This is in addition to any other underlayment required by the tile.

Sources

• The standards for roof flashing come from two sources. The first is the National Roofing Contractors of America, the trade association for the roofing industry. Its recommendations are practiced by professional roofers but are not legally binding unless a construction project is based on the International Residential Code. This is the second source of roofing standards; it forms the foundation for all local and state codes in the United States. The International Code Council manages this information. These standards are binding. Roofers who do not follow them will not have their roofs approved for use by municipal inspectors who adhere to International Residential Code.