Everything To Know About Chimney Caps

When residential architecture in Europe evolved to include two-story houses, indoor fireplaces became the norm. Before this, central, open hearths were used for heating and cooking in single-story homes.

With the advent of fireplaces set into walls and corners, masonry chimneys came along, and subsequently chimney caps. Chimney caps might not be the first thing anyone thinks of, but they’re one of the most important elements of a properly-functioning fireplace.

What Is a Chimney Cap?

A chimney cap is the fixture — usually metal — that covers the top of a chimney. It rests atop the masonry that’s known as the crown or crown cap.

The chimney flue is the metal or masonry tube inserted inside the body of the chimney. It typically extends two to six inches past the top of the crown. The chimney cap often looks like a miniature roof — it’s flat, round or peaked.

Why Does a Chimney Need a Chimney Cap?

Chimney caps are multitaskers, says Russ Dimmitt, director of education for the Chimney Safety Institute of America. A chimney cap fulfills several needs:

• A spark arrester. “A chimney cap typically has a screen that will catch any sparks that could go out and catch leaves, roofing or areas of the yard on fire,” he says.
• A water barrier. “As we know, water is the biggest enemy of masonry,” says Dimmitt. A chimney cap is all that stands between rain and your chimney. “When you have water coming down your chimney, you can have issues with freeze/thaw damage,” Dimmitt says. “You can also have situations where that water mixes with soot and creates acidic residue that damages the chimney. In some cases, that water can actually come down the chimney and damage the surrounding areas of the home as well — like walls, ceilings and wood framing.”
• A debris blocker. All it takes is one good storm to blow tree branches and other debris into your chimney, potentially blocking it and causing smoke to back up into the house. A screened chimney cap prevents this.
• A critter deterrent. Your chimney is an inviting shelter for birds, squirrels and other animals, especially when not in use. Wildlife can often become stuck and die. A chimney cap with an intact screen keeps animals out.

Types of Chimney Caps

There are several styles of chimney caps. Which one you choose is often a matter of aesthetics (flat or peaked roof), but may also depend on how windy or exposed your chimney is.

• Inner- or outer-mounting chimney caps attach to the flue, with clamps, a pressurized spring or self-driving screws. For a single round flue, they’re usually the simplest solution.
• Top-mount chimney caps attach to the masonry of the chimney crown. They’re especially suited for chimneys with more than one flue; a single cap covers them all.
• Wind-directional chimney caps are for chimneys exposed to a lot of wind, or need help creating an updraft.
• Air-cooled chimney caps fit those with an inner flue surrounded by an air chamber that assists with the updraft.

How To Maintain a Chimney Cap

“Chimney caps typically require very little maintenance,” says Dimmitt, “especially if you have a stainless steel or copper chimney cap, which will not deteriorate with weather.”

With most chimney caps, Dimmitt says maintenance mostly involves making sure leaves and other debris haven’t accumulated around the cap. If your chimney cap has moving parts, such as a wind directional cap, make sure these function as they should. Also check for holes in the screen, where small animals might crawl.

Routine maintenance and cleaning are best scheduled for spring or early summer when you maintain your fireplace. Dimmitt says that’s when chimney sweeps are more available. “Plus,” he adds, “if your chimney needs any repairs, this gives them time to make those repairs before the colder months hit.”

This timing is also good if you’re climbing on the roof to do a maintenance check. You might discover you need to call a professional for repairs.

When To Replace a Chimney Cap

Stainless steel or copper chimney caps should last a long time, Dimmitt says. Many come with lifetime warranties. “But if you happen to have a galvanized or painted cap,” he says, “you’ll see rust stains coming down the chimney, which is a sign the cap needs to be replaced.”

Sometimes wind or felled trees can damage chimney caps, he says, adding you should be able to tell from the ground if something is wrong.

Chimney Cap Installation

Assuming you’re comfortable climbing a ladder and walking across your roof, chimney cap installation is a basic DIY task.

• Chimney caps that attach to the inside or outside of a metal flue usually come with a simple, built-in mechanism for installing. A screwdriver should be the only tool you need.
• Chimney caps that attach to the chimney crown are screwed into the crown masonry. For this, you’ll need a drill with a masonry bit, masonry screws and silicone caulk to seal the space between the cap and the crown.

However, Dimmitt recommends professional installation. A chimney and fireplace specialist will know which cap is best suited to your chimney.