Pre-fabricated fireplaces have a flat metal covering (chase cover or chase top) to prevent water from entering the interior of the chimney structure.

The chase top is usually made of galvanized sheet metal with a life expectancy of 7 to 10 years. Over time, the metal coating wears off from exposure to sun, rain, snow, ice and other environmental factors. Most tops also develop a low spot around the flue pipe that holds water as well. With time, the metal starts to rust and when water runs off the top during a rain it carries the rust down the side of your chimney causing unsightly staining of the siding. The rust stains on the outside of the chimney are the first clue that there is a problem. Left untreated, eventually the corrosion will eat through the metal allowing water to seep through. You may hear water dripping on the inside of the chase after it rains. This is an indication that the rust has pitted the metal allowing water into the chimney where it can cause damage to the interior components of the chimney.

The time to act is when you first notice rust stains not after you hear water dripping.

To correct the problem, the existing chase cover can either be resurfaced and resealed or replaced with a new stainless steel chase cover that will last a lifetime.