Roof Flashing Penetrations
Flashing is usually made of sheets of aluminum or steel. It is designed to expand and contract, which helps shed water away from the most vulnerable areas of the roof.
The termination points of the roof, like chimneys or other roof protrusions such as plumbing stacks, valleys and around dormers or skylights can be the weakest area of a roof.
They can also be the most neglected because they are the most time consuming part of the roof installation.
Consider using a trained professional to deal with damaged flashing, since these repairs can be complicated.
Even if roof flashing has been properly installed, it can still become rusty, or the sealant can dry up and crack.
Remember: working on a roof can be dangerous. The flashing may have come loose and allowed water to penetrate into the roof's surface or there may be other structural issues with the roof that you might not be aware of. It is always good practice to install a waterproofing membrane behind the flashing as a secondary defense to guard against a roof leak.
Either way, flashings have to be inspected regularly and replaced if damaged.