Plumbing Vent Boots
You see these on almost every roof. They are the vent pipes that let the sewer drain pipes “breathe”. Without vents, your drain pipes would not function properly. Much like holding your finger over the top of a straw and finding out the liquid will not drain out of the straw, your drainage system needs to allow air in to allow liquids out.
Most of our vent drains have a lead boot covering them. Something like this:
But if you have squirrels in your neighborhood, and they travel across your roof, they will often stop to gnaw on these lead vents. Evidently, chewing on the lead feels good to them. The down side is that once they chew through the top of the boot, moisture (rain) can get into the home via the gap now in the system. This water will drain down into a wall cavity where it and it’s associated damage are hidden from view.
Here we can see two examples of failed boots. They both are allowing water into the walls of the home.