Why Off-the-Shelf Chimney Caps Fail (And How Custom Sheet Metal Solves It)
What Rots Under an Off-the-Shelf Lid Hardware store caps look fine in cardboard packaging, but they are stamped from paper-thin sheet tin. You take one out of the box, and you can twist the lid with bare hands. Put that on top of an exposed chimney flue , and the weather goes to work on it immediately . Rust starts along the underside where acidic wood smoke condenses against bare metal. Within three or four seasons, the top pinholes and water pours directly down the flue pipe. That is why experienced masons refuse to install catalog lids. They order custom weather-resistant chimney caps brake-formed from 24-gauge structural steel. A heavy steel cap stands up to falling tree limbs and hail strikes without caving in. Thin tin creases if a racoon stands on it. Heavy steel stays flat. Once moisture gets past a failed cap, it pools directly on the flat concrete mortar crown. Concrete soaks up standing rainwater like a sponge. When a winter freeze blows through, that trapped moi...