Bees in the Chimney: What to Do

Bees, wasps or something else?

Watch the chimney top from the yard or the sidewalk on a warm afternoon, when insects are busiest. What you see tells you who to call, and a few minutes of watching saves a wrong first call.

• Honeybees: fuzzy, golden-brown, a steady stream flying in and out of the flue all day
• Yellow jackets: smooth, shiny yellow and black, quick and aggressive near the opening
• Hornets: larger, often with a gray paper nest under the cap hood or the crown overhang
• Bees drilling into the mortar joints: solitary bees nesting in soft, crumbling mortar
• Buzzing inside the firebox: insects that came down the flue and are stuck behind the damper

Why a swarm picks a chimney

To a swarm looking for a home, an unused flue looks like a hollow tree: dry, dark, sheltered and high off the ground. Swarms move in spring and early summer, and an uncapped chimney or a flue that has not been used in years is an easy pick. Once a colony settles, it builds comb on the flue walls, on the smoke shelf, or in the space above a closed damper, and it can fill a surprising amount of the flue.

In this region the likely candidates are the sealed-off fireplaces of brownstones and rowhouses, a second flue in a stack that once served a coal stove, and chimneys on houses where the boiler was converted to a side-wall vent and the old flue was left open at the top. An active heating flue is a poor home for bees because of the heat and exhaust, which is why colonies tend to turn up in flues nobody uses.

Why a fire makes it worse

Lighting a fire sounds like a simple answer. It causes more trouble than it solves. The heat melts the wax and honey, which run down into the brick and mortar, stain the masonry and leave a sticky, flammable coating in the flue. Smoke drives the bees out, and many come down into the room or find gaps into the wall cavities beside the chimney breast.

A colony killed in place also leaves dead bees and rotting honey behind. That attracts ants, mice and wax moths, and brings a strong, sweet-sour smell into the house in warm weather. In a plaster-walled rowhouse, honey that has soaked into the chimney breast can show up later as dark, sticky stains on the wall.

Honeybees: live removal

For honeybees, call a beekeeper or a bee removal specialist who does live removals. Some local beekeeping groups keep a swarm list for exactly this. A swarm that has only just arrived and is hanging in a cluster can sometimes be collected quickly. An established colony with comb is a bigger job.

Getting comb out of a flue usually means working from the top of the chimney, from the firebox side through the damper opening, or in some cases by opening the masonry where the comb sits and rebuilding it afterward. Which route is used depends on how far down the comb runs and how the chimney is built. It is not a quick job, and it often takes a beekeeper and a chimney crew working in sequence.

Yellow jackets and hornets

Wasps are handled differently. Yellow jackets and hornets are not collected alive, and their paper nests are usually smaller and sit higher up, near the chimney top: under the cap hood, inside a gap in the crown, or tucked under the crown overhang. Pest control treats or removes the nest, ideally late in the day when the workers are back inside.

Spraying household insecticide up the flue from the fireplace rarely reaches the nest, fills the room with chemicals and stirs up a defensive response. A paper nest left in the cap mesh can also block draft on a fireplace you plan to use, so it needs to come out once the insects are dead.

While you wait for removal

Bees in the flue are rarely an immediate danger to the household as long as they stay in the flue. The aim is to keep it that way until the beekeeper or pest control arrives.

Anyone in the house with a known sting allergy should stay well away from the room, and a severe reaction to a sting is a reason to call 911.

• Keep the damper and the fireplace glass doors closed
• Stuff nothing up the flue and do not tape over the damper from below, which can trap bees in the firebox
• Keep children and pets out of the room
• Note where the bees enter at the top and whether there is more than one opening
• Do not run a fire in a neighbouring flue of the same stack to smoke them out

The cleanup nobody sees

Whoever removes the insects, the comb has to come out too. Leftover comb and honey carry the scent that draws the next swarm, feed ants and wax moths, and can drip in hot weather. Wax and honey in the flue also act as fuel, and they can ignite the next time the flue heats up.

After the comb is gone, the flue is swept, the smoke shelf is scraped clean, and the damper is checked, since honey and wax can glue the plate shut or stop it sealing. Only then is the fireplace ready to use again. On the inspection, the technician also lights the full length of the flue to look for wax still stuck to the tile walls and for cracked or missing tiles where comb was anchored, because a damaged liner has to be dealt with before the fireplace goes back into service.

Solitary bees in the mortar

Small bees drilling neat holes into the joints of a chimney are a different problem. They are not a colony in the flue. They are solitary bees choosing mortar that has gone soft and sandy, usually on the weather side where wind-driven rain and freeze-thaw cycles have broken it down.

The insects are a symptom; the mortar is the issue. Repointing the soft joints with a mortar suited to the brick takes away the nesting spots and closes the paths water uses to get into the masonry. Old lime-based mortar in pre-war brick needs a compatible repointing mortar, not a hard modern mix that can damage soft brick.

Keeping them out next season

A chimney cap with standard mesh keeps out birds and animals, but the openings are large enough for bees to pass through. What helps more is closing the flue below and above: a damper that shuts tightly, or a top-sealing damper on a flue that is not used, which shuts the flue opening at the top with a gasketed lid. For flues that that will not be used again, there are permanent ways to close the top, which a chimney technician can explain for your setup.

Sealing cracks in the crown and repointing soft mortar takes away the smaller openings. We look over the whole chimney top first and price the sealing plan item by item, in writing and at no charge.