Vent Flashing FAQ
House plumbing vent flashing is required around the pipe at its roof surface penetration. Without it, or if improperly installed, rain water or melting snow will seep around the vent and damage the roof decking material, sometimes making its way down to the wall / ceiling surfaces inside the property.
Q: Why roofing cement should not be used as a permanent plumbing vent flashing:
A1: Because every roof structure contracts and expands independently from the plumbing vent stack
A2: Because every building settles differently from the plumbing vent stack
Both of the conditions (A1 & A2) will cause roofing cement applied around the plumbing vent stack to crack, separate from the pipe, and eventually leak water.