The Importance of Counter Flashing
Proper installation of flashing materials at roof penetrations, is an extremley important facet of a properly functioning roof system. These roof penetrations are largely where troubles occour on a roof. One of the most common places that flashing is required on a residental roof is along walls, chimneys and skylights. These areas are also the most common places for leaks to show up, especially at the corners.What normally is installed along these walls and chimneys is called step flashing. Step flashing is an L shaped piece of very thin sheet metal (usually aluminum), normally 7 inches long by 3” by 4”. It is placed along a wall or chimney and then covered with a shingle and then another piece over laps this step just above the exposure of a shingle. .This process is repeated all along the wall and then either is covered by siding or counter flashing. On chimneys, at the top and bottom is placed what is called a front and back, also known as pans in some circles. Next the counter flashing is installed. Counter flashing involves cutting a riglet into the brick mortar or stone of an chimney or wall. Alot of roofers dont actually understand what counter flashing is. Most, especially in the North East do something I refer to as Philly flashing. this involves putting a 45 degree bend on a piece of coil stock and nailing it through the brick, and then caulking the top of the metal. Below are some pictures of some pretty decently installed counter flashing also some diagrams of counter flashing to give you a better idea of what the process looks like on paper. I also added a few pics of Philly flashing.Can you tell the difference ? Included here are diagrams for chimney flashing, also known as counter flashing. These diagrams should be enough to give you a pretty good idea of what is involved with counter and wall flashing systems. They may also give you a pretty good guide of things to look for, if you are having problems with your chimney flashing. These diagrams are valid for copper, lead and galvanized metals. If you are having trouble with a detail flashing a chimney these may help you as well.