The Navien flat roof weather slate, also known as a flat roof weathering slate or flat roof flashing, is a component used to seal the penetration where a flue pipe passes through a flat roof. Its primary purpose is to provide a watertight seal to prevent rainwater and debris from entering the building at the point where the flue exits the roof.

The flat roof weather slate ensures that the area around the flue pipe is sealed against water ingress. The base plate is typically fixed to the roof surface using appropriate sealants and fasteners, while the collar provides a snug fit around the pipe to prevent leaks.

In summary, a flat roof weather slate is an essential component for any flue system passing through a flat roof, providing a reliable seal to protect the building from water ingress and ensuring the integrity of the roof and the flue system.