Caps, Chase Covers and Waterproofing in Orem

The chase cover is the leak

Factory-built fireplaces sit inside a framed, sided box called a chase, and the top of that box is closed with a sheet metal pan. That pan is the roof of the assembly, and on the housing stock this city built during its growth decades it was almost always galvanized steel, cut flat, with the flue pipe coming up through a collar in the middle.

Flat is the fatal detail. Water ponds in the middle of a flat pan instead of running off. Galvanized coating protects steel until it does not, and the point where it gives out is the low spot where the water sits. From there it goes to rust, from rust to a pinhole, and from a pinhole to a steady drip landing on the top of the firebox and the framing inside the chase. By the time a stain appears on a ceiling inside the house, water has usually been getting in for years.

Rust-colored streaks running down the siding below the chase top are the visible symptom and they are worth walking outside to check. The correct repair is a new cover in stainless steel, formed with a cross-break so the middle is higher than the edges, with a proper drip edge and a collar sealed to the pipe. It is a one-time fix rather than a recurring expense, and it is the single most cost-effective thing many owners of these systems can do.

Caps, screens and top-sealing dampers

The cap itself keeps rain and snow out of the flue and, with a stainless mesh screen, keeps birds out during nesting season and stops embers landing on a roof. A top-sealing damper is a different item that solves a different problem: it closes the flue at the top with a gasket, which stops the constant loss of heated house air that a leaky throat damper allows, and keeps the flue column warmer so the fireplace lights and drafts more readily. On a masonry chimney it is one of the few upgrades that pays for itself in a measurable way.

For masonry, waterproofing with a breathable siloxane repellent is worth doing once the brick and crown are sound. It has to be a product that lets water vapor out while keeping liquid water off the face. A film-forming sealant does the opposite and will accelerate the damage.