Chase Covers for Stucco Chimneys

If the chimney on your house is stucco rather than brick, there is almost certainly no masonry inside it. It is a wood-framed box, the chase, wrapped around a metal factory-built flue or vent pipe, and the top of that box is a sheet of metal with an opening for the flue and a collar around it. That is how the newer half of the metro was built, and it is the standard in Surprise, Goodyear, Buckeye and Gilbert, where most homes date from 2000 or later.

The cover takes direct sun for months on end, and intense sun and heat age paint, sealant and gaskets faster. Then monsoon wind drives rain sideways across it. A cover that has dished in the middle holds water against its seams and the collar; one that has rusted lets water into the framing below, where it stays hidden until it stains the stucco, a ceiling, or the inside of the firebox.

Signs you need this

• Brown or orange streaks running down the stucco below the top
• Rust flakes or water marks inside the firebox
• A dip in the middle of the cover you can see from the yard
• The storm collar around the flue is loose or its sealant is gone
• Damp smell or a ceiling stain near the chimney after rain

How we do it

1. Look from the roofWe check the cover, collar, cap and seams, and photograph them so you see what we see.
2. Look from insideFirebox, the attic around the chase where it can be reached, and the stucco below the top for water signs.
3. Measure for a new coverChases are not standard sizes, so the new cover is made to the measured top, with a pitch that sends water off.
4. Install and sealOld cover off, top of the framing checked, new cover fastened at the sides, storm collar and cap refitted and sealed.

Chase cover vs chimney cap: what is the difference?

The chase cover is the metal sheet over the whole top of the chase. The chimney cap is the smaller hooded piece on the flue pipe that comes through it, and it keeps rain and animals out of the flue itself. On a factory-built chimney that cap is part of the listed system. You can have a good cap on a rotten cover, or the other way round, and either one will leak.

We look at both on every visit. HomeGuide puts a chimney cap on the chase at $200 to $850 installed, and we only quote one when the existing cap is damaged, missing or the wrong part.

What a better cover looks like

The covers that last have a slight pitch or cross-break so water can't stand on them, a skirt that wraps down over the stucco with a drip edge, and a raised collar around the flue opening. Galvanized steel is the usual builder cover; stainless and powder-coated options cost more and resist rust longer. We price each so you can choose.

Fixr's range for replacing a chase cover is $300 to $700. Bigger chases, more than one flue opening, or an odd shape put a job toward the top of that range.

What happens if you wait

Water that gets past the cover runs down the inside of the chase. It wets the framing and sheathing, and can reach the top of the firebox, where it rusts the metal. Repairing stucco and framing is a much bigger job than a new cover.

The best time to check is right after the monsoon, in October, before the fireplace goes back into use.