What is flashing?

We have had some comments about why there is flashing. Why cant they they simply put the vent pipe through the roof. Well, if you look at a roof deck when they build a house you will see that the roofing contractor will simply cut a square or round hole where the vent pipe is supposed to go through the roof. The plumbing contractor runs the vent pipe up, and the roofer comes back and has to have a way to seal the vent to the roof, after all a big square hole under a bunch of shingles will leak. So they use flashing to seal it. There are two types, rubber and lead. Rubber is used in most places as its inexpensive and holds up relatively well unless its exposed to high sunlight and high rain. In those places, mostly located in the South and along the coast, lead is used because it will last forever basically. However, the squirrels like to gnaw on it, and that’s where we come in.