Chimney Chase Cover Installation in McMinnville, Oregon | Stop Rain from Entering the Chase

A chimney chase is the wood-framed, siding-covered enclosure that surrounds a prefabricated (factory-built) chimney pipe. Unlike a masonry chimney made of brick and mortar, a chase is essentially a tall box built around a metal flue pipe, with insulation between the pipe and the framing. The chase cover is the flat or slightly angled metal plate that caps the top of this box, with an opening for the chimney pipe and rain cap to pass through.

On most homes built from the 1980s onward in the McMinnville area, prefabricated chimneys with wood-framed chases are the standard. You’ll find them in subdivisions around Baker Creek, the Michelbook area, and newer developments throughout Yamhill County. The original chase covers installed by builders are almost always galvanized steel. Galvanized steel holds up for a while, but in Oregon’s persistent rain and coastal moisture, the galvanized coating breaks down. Once bare steel is exposed, rust starts. And once a chase cover starts rusting, it doesn’t stop.

The failure pattern is predictable. Rust forms in the low spots where water pools on the cover surface. Pinholes develop. The pinholes widen. Water drips through onto the chimney pipe, the insulation batting around it, and the wood framing of the chase. By the time you notice rust stains on the chase siding from the outside or water stains on a ceiling or wall near the chimney from the inside, the cover has been leaking for months. The insulation inside the chase may be saturated, and the framing may have started to rot.

We remove the failed cover, inspect the chase interior for water damage, and install a new stainless steel cover. Stainless steel doesn’t rust in this climate the way galvanized does. We measure the chase opening on site, because chase dimensions vary by builder, chimney brand, and home design. The replacement cover is fabricated to fit your specific chase with a slight pitch for water runoff, a storm collar around the chimney pipe opening, and a drip edge that overhangs the chase siding to direct water away from the wood framing below.

If the chase interior has water damage from a long-term leak, we document what we find and let you know the extent. Minor moisture in the insulation dries out once the new cover stops the water entry. Rotted framing or a corroded chimney pipe may need additional work before the new cover goes on. We’ll tell you the full picture before proceeding.

This is one of those repairs where the cost of waiting goes up every month. A chase cover replacement is straightforward and relatively affordable. Replacing rotted chase framing, water-damaged insulation, and a corroded chimney pipe because a galvanized cover was left to rust for years is not.

Signs your chase cover needs replacement

Rust stains running down the exterior siding of the chimney chase are the most visible indicator. The stains start at the top of the chase where the cover meets the siding and streak downward. If you can see orange or brown staining from ground level, the cover has been corroding for a while.

Water stains on the ceiling or walls near the chimney inside the house mean water is already getting past the cover and into the chase. In some cases, homeowners notice a musty smell near the fireplace that comes from wet insulation inside the chase. During heavy Willamette Valley rainstorms, you may hear dripping inside the chase wall.

If your home was built in the 1980s or 1990s and the chase cover has never been replaced, it’s worth an inspection even if you don’t see obvious signs. Galvanized covers from that era are at or past their expected life in this climate. A quick look from roof level tells us the condition and whether replacement is needed now or can wait.