Roaches Coming From the Fireplace

Which Roach You Are Probably Seeing

Two large outdoor roaches fit the description of a fireplace roach, and they behave differently. Tell them apart before deciding what to fix.

• American cockroach: the largest of the common house-associated roaches, about 1.5 inches long on average, according to UF/IFAS. Outdoors it lives in moist, shady places such as hollow trees, woodpiles and mulch, and occasionally under roof shingles and in attics.
• Florida woods cockroach, often called a palmetto bug: a large, slow-moving native roach without effective flight wings, which UF/IFAS describes as mostly living outdoors in tree cavities, under bark, in leaf litter, woodpiles and around the base of palms. It can spray a defensive secretion when disturbed.

Why They Come Through the Fireplace

UF/IFAS explains that American cockroaches live outside but wander indoors to look for food and water or to escape extreme weather, and that they move into houses from trees and shrubs beside the building or with branches hanging over the roof. A chimney is the tallest opening on the roof, often right under those branches. An unused flue is dark and, when uncapped, damp from rain, which suits a roach that seeks moist, shaded harborage.

The Florida woods cockroach arrives differently. UF/IFAS says it is an occasional invader of homes and that its presence indoors is usually the result of being carried in on something else, such as firewood. A palmetto bug on the hearth the morning after you brought in an armful of logs probably rode in with them.

Egg Cases Mean They Are Staying

A roach or two after a storm is a visitor. Egg cases mean a population is settling in. UF/IFAS describes the American cockroach's egg case as a hardened, purse-shaped capsule about a third of an inch long that is brown when laid and turns black within a day or two, and says the female deposits it near food, sometimes gluing it to a surface. The Florida woods cockroach also glues its egg case to a surface, often somewhere like a decaying log.

Look with a flashlight along the back of the fire box, under the grate, along the damper frame you can reach and in the corners of the hearth. Egg cases there point to roaches living in the chimney or the ash pit, which makes closing the damper and the cleanout more urgent.

How to Tell Which Route They Use

Watch when they show up. The answers point to different fixes.

• After rain or on hot nights, out of the fire box: the flue top, the damper, or both.
• Near the hearth edge or the wall beside the fireplace: gaps at the hearth, surround or a pipe passing through.
• From the floor of the fire box: an ash dump that opens into a chamber with a cleanout door outside.
• Only after firewood comes in, slow and large: hitchhikers from the woodpile.

Fixes That Close the Chimney

Start with the damper, because it is the barrier between the flue and the room. Florida Building Code section R1001.7.1 requires a ferrous metal damper on a masonry fireplace, and a damper that closes flat keeps whatever comes down the flue in the flue. Close it every time the fireplace is cold and get it repaired if it no longer seals.

Then the top. A screened cap keeps rain from wetting the flue and blocks the larger roaches; section R1003.9.2 sets spark arrestor openings at no more than 1/2 inch. Then the bottom: section R1003.17 requires a noncombustible cover on a masonry chimney cleanout, and an iron door that has rusted open is a ground-level doorway into the ash pit.

Fixes Around the House

UF/IFAS recommends caulking penetrations through walls at ground level, removing rotting leaves and limiting moist areas around a structure to make it less attractive to American cockroaches. For a fireplace that means caulking the joint between hearth and floor, clearing leaves and mulch away from the cleanout door and the chimney base, and trimming branches back from the roof and the chimney top.

Store firewood outside, off the ground and away from the wall, and bring in only what you will burn. Empty cold ash from the fire box regularly, since damp ash and debris are just the kind of organic matter roaches use. Keep glass doors or a tight screen closed when the fireplace is cold, too; they are a second barrier behind the damper, and they keep a roach that does reach the fire box from walking out into the room at night.

What Not to Do

Do not fill the fire box with insecticide or set off a fogger in it before a fire. Any treatment indoors is a job for a pest control company, which can also treat the outdoor harborage the roaches come from. And do not light a fire to drive them out; roaches that come down a flue have usually been living in the yard, not in the chimney, and will be back once the fire is out.

When to Call a Chimney Crew

If roaches keep appearing out of the fire box itself, the chimney is open at the top, the damper or the base. Our chimney cap replacement work fits a screened cap and checks the damper and cleanout on the same visit. For the broader picture of insects and how they get in, see how to keep bugs out of chimney.

Our experienced crew fits the screened cap and repairs the damper after a free inspection and a written estimate. The company is family-owned, local to Spring Hill and Proudly American. That practical, Proudly American help means your pest service is not fighting the same roaches every month.

Sources

• UF/IFAS Featured Creatures: American cockroach: Largest common peridomestic cockroach, about 1.5 in; outdoors in moist shady areas (hollow trees, wood piles, mulch), occasionally under roof shingles and in attics; wanders indoors for food, water or extreme weather; migrates from trees and shrubs with branches overhanging roofs; caulking, removing rotting leaves, limiting moist areas
• UF/IFAS Featured Creatures: Florida woods cockroach (palmetto bug): Florida woods cockroach called palmetto bug; native; lacks effective flight wings; slow; occasional invader carried in on firewood; tree cavities, bark, leaf litter, woodpiles, base of palms; defensive spray; name also used for other large cockroaches
• 2023 Florida Building Code, Residential, chapter 10: chimneys and fireplaces: R1001.7.1 ferrous metal damper; R1003.9.2 spark arrestor openings not larger than 1/2 inch; R1003.17 cleanout with noncombustible cover