By Daniel Watkins, Noble Chimney Sweepers.
By the middle of August most birds that took up residence in a chimney this spring have finished raising young and moved on. That makes the next several weeks the practical window for dealing with what they left behind, and for making sure next spring does not repeat it.
An uncapped flue is an appealing place to nest
From a bird’s point of view a chimney is close to ideal: vertical, sheltered from wind and rain, warm from the sun on the masonry, and out of reach of most predators. Chimney swifts in particular are built for it, clinging to vertical surfaces rather than perching. Starlings and sparrows will use a flue or a stove pipe just as readily.
The material is the problem. A nest is dry twigs, grass and shed feathers packed into the smoke chamber or wedged partway up the flue. It is highly combustible and it sits directly in the path of anything you burn. It also blocks the flue, which means combustion gases have nowhere to go but back into the house.
How to tell there is something up there
Sound
Scratching, rustling or chirping from behind the firebox is the obvious version. Sound that moves up and down the flue usually means a live animal rather than an abandoned nest.
Debris in the firebox
Twigs, straw, droppings or feathers on the smoke shelf or hearth mean material is above and some of it has fallen. What lands is a fraction of what remains.
Smell
Nesting material holds moisture and organic matter, and in humid weather it produces a sour, distinctly non-smoky odor. It is different in character from a creosote smell and most people can tell them apart once they have noticed both.
Smoke that will not draw
If the last fire you lit backed up into the room, and you have not had the chimney looked at since, assume an obstruction until proven otherwise. Do not light another one to test the theory.
Why timing this for late summer matters
There is a straightforward reason not to do this in May or June. Nests in active use may contain young birds, and chimney swifts in particular are a protected migratory species, so removing an occupied nest is not something to undertake casually. Waiting until the young have fledged avoids that entirely. It also means the work is finished well before you want a fire.
Homes in New Lenox back onto a good deal of open and wooded ground, and older chimneys there frequently turn out to be uncapped or to have a cap with rusted-through mesh that is no longer doing anything.
The cap is the permanent fix
Removing a nest solves this year. A properly fitted cap solves it structurally. A good chimney cap does four jobs at once: it keeps birds and animals out, it keeps rain off the flue and out of the masonry, it stops downdrafts from blowing smoke and odor back inside, and its spark arrestor mesh catches embers that would otherwise land on the roof.
The details matter. A cap has to be sized to the flue, secured so wind cannot lift it, and built from stainless steel rather than galvanized, which rusts through in a few winters and leaves you with the gap you paid to close. Mesh has to be the right gauge to exclude animals without choking the draft.
Nest removal is done as part of a chimney sweeping, since the material has to come out and the flue needs inspecting afterward to confirm nothing was left behind and nothing was damaged. Our rates are on the pricing page and you get the price up front before any work starts.
We are certified, bonded and insured, and in fourteen years I have pulled a remarkable variety of things out of chimneys that a fifty dollar cap would have kept out. Call (708) 432-5747, seven days a week, 7 AM to 7 PM.
Frequently asked questions
Can I just light a fire to drive the animals out?
No. It is dangerous and inhumane, the nesting material itself can ignite inside the flue, and a blocked chimney will push smoke and carbon monoxide into the house. The obstruction has to be removed physically.
Are chimney swifts protected?
Chimney swifts are a migratory bird species with legal protections, so an active nest should not be disturbed. Waiting until the young have fledged in late summer resolves the issue without that concern.
What if the animal is a raccoon rather than a bird?
Raccoons commonly den in smoke chambers and a mother with young will defend the space. That situation calls for a wildlife removal professional first, after which the chimney can be cleaned and capped.
How much does an uncapped chimney really matter?
Considerably. Beyond animals, an open flue admits rain directly onto the liner and smoke chamber, and water is the single largest cause of chimney deterioration in this climate.
Will a cap hurt my draft?
A correctly sized cap will not. Draft problems arise when a cap is undersized for the flue or the mesh is finer than it needs to be, both of which are avoidable with proper measurement.
How long does a stainless cap last?
Stainless steel caps typically last many years and are often sold with long warranties. Galvanized caps are cheaper initially and tend to rust through comparatively quickly in our freeze-thaw cycles.
I have a metal chimney, not masonry. Does this apply?
Yes. Factory-built metal chimneys need an appropriate termination cap as well, and birds will nest in them just as readily. The cap has to be one designed for that specific system.
Can I install a cap myself?
It involves roof work at the highest point of the house and correct sizing to the flue. If you are not equipped to work safely at that height, it is not a reasonable do-it-yourself project.
Published August 11, 2026