Without chimney crowns chimneys would be penetrated by water from rain and melting snow that would run down the chimney. During chimney installation several precautions should be included in its construction that will prevent this water intrusion. Included among these precautions should be the installation of chimney crown flashings, including those that are built with metal.
At the top row of chimney bricks, prior to the chimney cap being built, the flashing should be put into place where it can lap onto the flu’s liner sides. If the flashing is installed correctly, the edge will project over the brick face and keep water from running down the brick face.