Chase Covers

What a chase cover is

Many homes have a factory-built fireplace with a metal chimney pipe running up inside a wood-framed enclosure, called a chase. The chase is finished on the outside like the rest of the house. A chase cover is the sheet-metal panel across the top of that enclosure. It has a collar where the chimney pipe passes through, and the chimney's own cap sits above it.

Not sure whether your chimney is masonry or factory-built? Our guide to masonry vs. factory-built chimneys shows how to tell.

Why chase covers rust

Many original chase covers are galvanized steel and flat. Water sits on a flat panel, works through the zinc coating, and starts rust. Rust streaks run down the siding. Eventually the panel rusts through, often around the collar, and water drops straight into the chase.

Once water gets inside, it can soak framing and insulation, rust the metal chimney pipe and firebox from the top, and stain ceilings near the chase. Because the chase is closed in, this can go on for a long time before anyone notices.

Signs of a failing chase cover

• Rust streaks on the siding or stucco below the top of the chase
• A chase cover that sags, holds a puddle, or looks patched
• Rust or water in the firebox of a factory-built fireplace
• Water stains on the ceiling or walls near the chase
• Soft or swollen siding or trim near the top of the chase

How we assess it

From the roof, when it's safe, we look at the chase cover: its material, shape, rust, how it's fastened, the seal around the collar, and whether it slopes to shed water. We measure the chase top for a replacement. We also look at the chimney cap and the pipe where it passes through.

Inside, we look at the firebox and the visible parts of the chimney pipe for rust or water damage, using a chimney camera where the flue allows. If the attic or chase can be safely accessed, we check for wet framing. You get photos and our findings, with options, before any work is scheduled.

Repair or replace

A chase cover that's still sound with only surface rust can sometimes be cleaned and coated, or have its collar resealed. That's a short-term measure on galvanized steel, and it only makes sense when the metal hasn't thinned or holed.

Replacement is the usual fix once rust has gone through, the panel is flat and holding water, or it's been patched before. The chase covers we install are aluminum and custom-made to measure. We measure your chase top, including the collar position and any extra flues, and the new cover is built to those dimensions rather than picked from stock sizes.

Shape matters as much as metal. A cover with a slight pitch or cross-break to shed water, a skirt that laps down over the siding, and a drip edge to throw water clear of the chase will stay drier than a flat panel.

When the cover is replaced, the collar seal and the storm collar on the chimney pipe are checked and redone as needed, since a new panel with an old, cracked seal at the collar will still leak.

Factory-built systems have rules

A factory-built fireplace and its chimney are tested and listed as a system. The manufacturer's installation instructions specify the parts that belong to it, including the termination cap and, in many systems, details of the chase top. When a chase cover is replaced, the chimney's own parts and clearances need to stay as the manufacturer intended. If we find damaged chimney pipe or parts that are no longer available, we'll explain what that means for the system. Our guide to factory-built fireplaces covers their care and limits.

Checking your chase cover yourself

You don't need to go on the roof to keep an eye on a chase cover. From the ground, with binoculars if you have them, look for:

• Orange or brown streaks running down from the top of the chase
• A cover that looks dished in the middle, or has a visible puddle after rain
• Patches, tar or sealant smeared around the collar
• A cap that's tilted or missing above the cover

Inside, look into the fireplace with a flashlight after a heavy rain. Rust spots or water on the firebox floor are a reason to have it checked.

Catching a rusting chase cover early usually means the job is just the cover. Leaving it until water has been running into the chase for several seasons can mean framing, insulation or chimney pipe repairs too.

Limits and what affects the scope

• Size and shape of the chase
• Number of flues passing through
• Whether the chimney cap or pipe also needs replacing
• Water damage to framing, siding or insulation, which is carpentry work outside the chase cover itself
• Roof pitch and access

Next step

If you see rust streaks below the top of your chase, or water in a factory-built firebox, request an assessment. A photo of the chase from outside helps. A team member will contact you to confirm a time.

Request a chase cover assessment

Questions homeowners ask