Chimney Flashing Leaks are very susceptible to leaks for many different reasons. The most common reason chimney leaks are:
• Chimney Flashing made of brick mortar or stucco, a specific size of flashing is required depending on the brick cut made with the grinder. If the flashing is too small, the flashing underneath the shingles will get loose and will leak. The chimney with stone instead of brick mortar, in older houses when very old or has very deep mortar requires a custom flashing. The standard flashing in the industry is 5” metal exposure with a ¼ inch lip and in these cases requires a larger lip depending on the size of the stone or the brick mortar because the exposure depends on the size needed. We have a partnership with a sheet metal shop that provides custom flashing in the moment according to our specifications.
• Chimney Cricket: Manufacturers recommended every chimney larger than 20”, (IRC only recommends 24”) have to have a chimney cricket built. The lack of a chimney cricket, especially when you have a tree close to your roof, accumulates of leaves and when you have a pile of leaves can rotten your metal flashing and cause leaks. The reason you need a chimney cricket.
• Step flashing is needed during the chimney flashing installation, it is required to have the chimney step flashing (Tin Shingles) installed on your chimney.
• Does the leak barrier around the chimney make a difference during the installation? Yes and no. Leak barrier really helps and works as a moisture barrier but if the chimney flashing is not properly installed or the roofer didn’t install the wings on the flashing, there will be leaks.
• The bottom flashing below the chimney is important. Most of these flashings have 3” exposure and the flashing has to be at least 4” exposure, and we always recommend doing this at the job site using the valley metal. Never buy the premade flashing already bent in a 90 degrees angle, no matter how good you open it the flashing will always lift up.
• Chimney Chase Covers in a lot of cases the rust penetrates the metal or the roofer who installs the chimney chase covers put nails on the flat area making it a source for leaks, so we always recommend to install a high temperature tape between the chimney chase cover and actual chimney tube, underneath the storm collar, when the tape is not installed this are becomes another source for leaks.
• At the time to perform a chimney repair, it is very important to remove the shingles, underlayment, flashings, leak barrier around the chimney to inspect the plywood. If the plywood is rotten or has moisture transferred, the plywood has to be removed! If it is not done this way, it will leak again!