Do You Need a Chimney Cap? Rain, Birds and What the Law Says

Most people never look at the top of their chimney, so most people don't know whether theirs has a cap. It matters more than it sounds. A flue with nothing over it is an open pipe from the sky into your living room.

What a chimney cap does

The Chimney Safety Institute of America lists four ways to protect a chimney from water damage, and a cap is the first: "A well-designed cap will keep out rainwater and will also prevent birds and animals from entering and nesting in the chimney. Caps also function as spark arrestors, preventing sparks from landing on the roof or other nearby combustible material."

• Rain. Water running down an open flue rusts the damper and the firebox and soaks the masonry from the inside.
• Animals. A flue that sits unused all summer is a ready-made nest site, and a nest can block the flue completely.
• Sparks. The mesh around a cap stops embers from landing on the roof.

Birds in the chimney: what the law says

The bird most likely to be in a North Carolina chimney is the chimney swift, and it is protected. The U.S. Fish & Wildlife Service says the chimney swift is "protected by the Migratory Bird Treaty Act. Thus, harassing, injuring, or killing swifts, their eggs and their nests is illegal."

The N.C. Wildlife Resources Commission spells out what that means for a cap: "A chimney cap cannot be placed if there is an active nest, as excluding the adults will cause the young to die." An active nest, one with eggs or nestlings, cannot be removed without a federal permit. But "outside of the nesting season, a chimney cap can be placed over the top of the chimney to prevent birds from having future access."

Swifts arrive in March or April and leave in August or September, according to the Fish & Wildlife Service. So if you hear chittering in the flue in June, the answer is to keep the damper closed and wait. Once they have gone, the chimney can be swept and capped.

The other side: leaving it open for swifts

It is worth knowing that the Fish & Wildlife Service would rather you didn't cap a masonry chimney that swifts can use. Its advice to willing homeowners is to leave the chimney open in nesting season, keep the damper closed, and have the chimney cleaned every year after the birds leave. That is a real choice, and it is yours to make. If you take it, the yearly sweep matters more, not less. If you would rather keep birds and rain out, a cap installed between fall and early spring does it legally.

Squirrels and raccoons

These are a different matter. If an animal is living in the chimney right now, a wildlife removal professional should get it out first. Once the flue is empty and clean, a cap with a screen keeps the next one from moving in.

If you don't have a brick chimney

Factory-built fireplaces in newer Triangle homes vent through a framed chase with a metal chase cover on top, plus the manufacturer's own cap on the vent pipe. The part that fails there is the chase cover, which rusts through. Our chimney cap installation page explains the difference.

How we handle it

Caps are not one-size-fits-all, so we start with a $69 inspection, measure the flue, check the crown the cap will sit on, and give you a written price. Old nests and debris come out before the cap goes on. If there is an active nest, we wait.

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