Company Blog

The Anatomy of Your Chimney

The Anatomy of Your Chimney Image - Poughkeepsie NY - All Seasons Chimney Inc.Knowing the names and functions of the different components of your chimney system can be very helpful when a problem arises. Our staff at All Seasons Chimney always appreciates having as many details as possible when you call us to tell us about a chimney problem, and sometimes we can even troubleshoot the problem over the phone if you are able to tell us exactly which part is malfunctioning. We do understand, however, if you are unfamiliar with the anatomy of your chimney, which is why we would like to share with you more information about the different components of your chimney.

Do you have a masonry or a prefabricated (prefab) chimney?

If you do not know the answer to this question, you can find out by looking at the firebox that surrounds your fireplace. A masonry chimney will have a firebox constructed from typically yellowish firebrick. A prefab chimney has a firebox made from cast refractory panels, according to the Chimney Safety Institute of America (CSIA).

Tell me about the anatomy of a masonry chimney.


At the top of a masonry chimney, you will find a chimney crown, which is made of mortar and keeps water out of the chimney. Typically, the flues in masonry chimney are lined with clay tiles, but these liners could also be stainless steel. Right above the firebox is the smoke chamber and smoke shelf. This is where the smoke and other byproducts of combustion begin to exit out of the chimney. Directly below the smoke shelf, you will find the damper, which is generally constructed from metal and should have a gasket around the edges to seal off the chimney when the damper is closed. Underneath the damper is the firebox, which takes the brunt of the heat from the fire. You should check out the condition of the mortar joints of the firebox every so often to be sure there are no cracks that could lead to carbon monoxide leaks. Between the firebox and the foundation of your home is the ash dump, which can be helpful when cleaning out the ashes from the firebox. However, you should also clean out the ash dump and not let it get to the point of overflowing.

How is the anatomy of a prefab chimney different?

The anatomy of a prefab chimney is much more simple than that of a masonry chimney. You basically have a chimney cap at the top, flashing around the chimney where it meets the roof, a fire-stop at the ceiling for clearance purposes, the chimney, and the firebox. Unlike a masonry chimney that is built brick by brick, a prefab chimney and fireplace are a complete system and are manufactured to work efficiently and safely with each other. You should never use a different type of fireplace with a prefab chimney, and it is equally important that a prefab chimney be installed by a certified chimney professional because of the standards and clearances involved with these types of chimneys. You should also always follow the instructions given in the owner’s manual to your prefab chimney and fireplace as there are certain safety precautions to consider.

Have questions about the anatomy of your chimney? Contact us at All Seasons Chimney to learn more about the different parts of your chimney system.

All About Chimney Crowns

From our years in experience of working in the chimney industry, All Seasons Chimney understands the problems that water can cause to a fireplace and chimney system. In fact, the Chimney Safety Institute of America (CSIA) named water as the biggest enemy of a masonry chimney. Except for stone, all masonry chimney construction materials suffer from accelerated deterioration when exposed to water for an extended period of time. Preventing water penetration of chimneys is one of our most important duties as chimney experts, and we know how to best keep the water out of your chimney. One of the most simple ways to stop water from entering your chimney in the first place is the installation of a chimney crown. We would like to tell you more about chimney crowns and how they can protect the masonry materials of your chimney.


What exactly is a chimney crown?

Also known as a chimney wash, a chimney crown is the top part of a masonry chimney. Constructed from mortar, the chimney crown covers and seals the top of a chimney from the flue liner to the chimney edge.

Why do I need a chimney crown installed on the top of my chimney?

Without a chimney crown, your chimney is open to rainwater and water from melted snow. This water will penetrate the bricks and mortar of your chimney. In the winter, this water repeatedly freezes and thaws, and this process causes problems. When water freezes, it expands as much as 10 percent. This can create cracks in the bricks and mortar, which worsen each time this water freezes. Even tiny amounts of water can cause this type of spalling damage. Eventually, if left unrepaired, the bricks and mortar can become so deteriorated that your chimney is no longer structurally sound.

If a chimney crown is made from mortar, how is it protected from spalling damage?

Since the chimney crown sits on the top of your chimney exposed to all of the elements of weather, it should be sealed with a durable waterproofing treatment to protect it from water penetration. A customized chimney crown from All Seasons Chimney is also constructed from a Portland cement-based mixture that is designed for years of weather abuse.

How can I tell if my chimney crown is properly constructed and installed?

A properly built chimney crown should have a slope to best protect your chimney from water damage. Your chimney crown should provide a downward slope to direct water from the flue to the edge of the crown. There should also be an overhanging drip edge to direct water from the crown away from the chimney to help prevent any erosion of the bricks and mortar in the vertical surfaces of the chimney. This overhang should project beyond all sides of the chimney by a minimum of two inches for best protection from water damage.

In need of a chimney crown? Contact All Seasons Chimney to schedule a custom installation of a crown for your chimney.