To the untrained observer, a chimney is simply a straight path that allows smoke to exit your home. However, this is not the case. The chimney system consists of many parts with a variety of purposes to safely and properly function. Read below to learn more about the anatomy of your chimney, then give SirVent Chimney & Venting Service of Lexington, KY a call to schedule an appointment!

What is Inside Your Chimney?

Learning your chimney's anatomy!Both on its interior and exterior, there are many intricate parts of your chimney that make it run properly and safely. Each part of your chimney works together to bring you a comfortable and cozy fire each time you use your fireplace. So what are the parts that make up your chimney?

On the very top of your chimney, there is a chimney cap, chimney crown, and flashing. As we enter the chimney, there is a flue, chimney liner, smoke chamber, and damper. Finally, there are the more visible parts of the system inside your home such as the firebox, mantel, cleanout door, and hearth. Let’s dive deeper and learn about each part and what they do for your chimney below.

Parts Of A Chimney System

Chimney Cap

The chimney cap sits at the very top of your chimney, to protect your chimney from invasions of all kinds such as weather, animals, back drafts, and more. It is usually made out of metal such as copper or stainless steel.

Some of them even include a wire mesh caging to prevent animals and debris from entering. Without a cap in place, water can enter your chimney to cause leaks and further deterioration. Without a cap, birds can invade your system and leave debris behind to cause a chimney fire or dangerous carbon monoxide leak. Invest in a cap to ensure your peace of mind!


The crown is the cement area above the masonry and below the cap. It is built with a gentle slope to divert water away from the chimney, and it is built into the masonry structure. Cement is used to construct it and give it more stability. It needs to be built at least 2 inches past the flue to properly protect water from entering.

A damaged or cracked chimney crown can cause water to enter into your chimney structure and if not dealt with, the water damage can produce some serious issues.

chimney technician repairing chimney crown

Flue & Flue Liner

Inside the chimney, there is a flue, a hollow and vertical pathway, for smoke to exit. With the close encounter of hot smoke and other substances, it is critical to have a liner in place to protect your flue and masonry surrounds. There are many different kinds of liners on the market such as stainless steel liners, copper liners, aluminum liners, clay liners, or cast-in-place liners.

Each liner has its pros and cons depending on the system you have. While metal liners are more durable and can be used with any fuel source, clay and cast-in-place liners are just as long lasting and give you the results you are looking for.

Smoke Chamber

Smoke chamber is located right above the firebox, and it is where the smoke accumulates before rising out of the flue. Many older chimneys were built with corbelling – jagged and tiered steps, this is harmful for the chimney and can trap smoke in. Parging the smoke chamber smoothly is the best method for repairing a damaged a corbelled smoke chamber.


The damper controls how much smoke and heat escapes through the chimney. It is usually adjusted by a latch or handle, and should be closed when the system is not in use. There are two types of dampers, the traditional throat damper or the lock-top dampers.

The traditional damper is the mechanism built-in the chimney and has a latch or pulley to open and close the system. The lock-top dampers are energy saving and sits at the top of the chimney like a chimney cap. They do the job of a chimney cap and the damper, as you can open or close it. They also offer an airtight seal to your chimney, which helps to save you energy and money.


The firebox is where the fire is built. This is where the wood or gas logs sit. It is what you see when you gaze into a fireplace. As you constantly use this place with each fire, it can suffer a lot of abuse. Overtime, repairs are needed to ensure your fireplace stays functional and beautiful.

Firebox repairs usually entails replacing damaged mortar joints with refractory mortar, which are more durable and has the ability to endure the intense heat of your fire. It also sometimes entails replacing cracked bricks with firebrick or paneling, to give it new life and a more durability.


chimney flashing


The flashing is sheets of metal laid out to protect the most vulnerable area of your chimney, where the chimney intersects with the roof. This is a very vulnerable area for water entry, if it is not protected with flashing. Since it’s on the roof, it is best to leave this job to the professionals. Proper flashing also need to be custom cut, bend, laid out tightly to ensure maximum protection from water.


The hearth extends from the firebox to the front of the fireplace. The hearth is a slab of material on the bottom of a fireplace, and it is usually made of stone, brick, marble, or cement. It works to protect any stray sparks from catching flames inside your home.

The hearth should extend at least 16 inches in the front of the fireplace that has an opening of 6 feet or smaller. The hearth should also extend at least 8 inches from each side of the fireplace opening (left and right).

Hearth thickness also matters as the thickness of the hearth should be at least 2 inches. The only exception to this rule is provided by the 2006 International Residential Code (IRC):

“When the bottom of the firebox opening is raised at least 8 inches (203 mm) above the top of the hearth extension, a hearth extension of not less than 3/8-inch thick (10 mm) brick, concrete, stone, tile, or other approved noncombustible material is permitted.”

fireplace hearth
fireplace mantel


Your mantel surrounds your fireplace, and it sits on top and around the firebox. it is a focal point for any decorator, a perfect ledge to place your dream home decor. Sometimes, mantels can extend all the way to the ceiling, and they can be made out of wood, concrete, or stones.

We can all get carried away with decorating our homes sometimes but it is important to practice safety when dealing with decorating around the fireplace and the mantel is no exception. 

The National Standard Building Code recommends that all combustible mantels and similar trim be kept at least 6 inches from the fireplace opening. We recommend the same for any decorative elements surrounding your fireplace.


Cleanout Door

The cleanout door is located at the base of your flue, and it is a metal, access door where chimney professionals use to clean the flue of soot and creosote. Fireplaces do not have a cleanout door, as you can directly clean out the soot from the fireplace opening.

What Chimney Services Do We Offer?

At SirVent Lexington, all of our technicians are professionally trained and certified by organizations such as the Chimney Safety Institute of America (CSIA) and National Fire Prevention Agency (NFPA). Therefore, we can perform any chimney maintenance. We want to keep homeowners safe and protected while operating their fireplace. Some services we offer include sweepings, inspections, construction, water damage repairs, and masonry repairs. Additionally, we also offer dryer vent services and carry products and appliances  such as stoves, fireplaces, and gas logs.

Schedule an Appointment Today!

Our staff has unparalleled knowledge of your chimney’s anatomy and we can handle any maintenance or services such as inspections, repairs, and more. If you need chimney services or appliances in the Lexington area, give us a call or schedule an appointment online today!