Since a fireplace chimney deals with fire and smoke, a damaged or broken chimney part can cause problems or even prove to be dangerous.
Most American homeowners have a fireplace that not only provides sweet warmth in the living room, but really ties the whole place together. A fireplace is considered the heart of any home yet most people are unaware of the inner workings or even the basic parts of a fireplace chimney.
The following article discusses the basic parts of a chimney and fireplace and their role in the functionality of a fireplace chimney. We’ll also share with you certain signs that let you know that a part might need repairing, or in certain situations, a replacement.
But, first: why is it important to know about your chimney? Let’s find out.
Why Should You Know About the Basic Parts of a Fireplace Chimney?
Having an idea about the basic parts of a chimney and their functionality can not only help you diagnose problems earlier but can also save you and your family from dangerous situations. It also helps to know a thing or two about chimneys when you’re out in the market looking for one.
Issues and faulty parts, if left unaddressed, have a tendency to become harder to repair. It increases the cost of the repair and the sheer hassle of having it fixed. Sometimes, a part is in such a condition that repairing is not an option, and you’ll have to get it replaced. So, it’s better to avoid such situations by learning about the anatomy of a chimney and its basic parts.
Before we go on to break down your fireplace chimney into its basic constituents, let’s talk about the different chimney types.
Types of Chimneys
Essentially, there are two types of chimneys that people have in their homes these days:
- Masonry Chimneys (Traditional)
- Prefabricated Chimneys (Factory-made)
Masonry chimneys are those old age-old chimneys made from brick and mortar. The factory-made chimney, unlike the traditional setting where the fireplace and chimney are separate, is a one-piece entity with the chimney attached to the fireplace.
Our focus today would be on the anatomy of a masonry chimney and the basic parts that award it such high functionality and durability (We’ll only consider parts that are paramount to the efficient working and safety of the fireplace chimney).
The Anatomy of a Chimney
Here is a detailed description of all the masonry chimney parts that’ll help you understand your chimney better and help you diagnose potential issues in your chimney before it’s too late:
Bricks are the foundation of a masonry chimney. Most masonry chimneys are made up of clay bricks (red bricks). And if they’re not in good condition, the structural integrity of your chimney is at stake.
If left without care and maintenance, cracks can start to form on bricks and in the masonry joints between them. These cracks enlarge over time and cause serious problems if not properly patched early on.
Moisture from rain, snow, and the outside atmosphere can seep in through the cracks of the outer brick layer. And if there’s one thing you should know about chimneys, it’s that moisture is its worst enemy.
Patching these cracks early on can literally save you thousands of dollars and ensure your safety and that of your family. Thankfully, it’s fairly easy to spot cracks and patch them up. Here’s an easy-to-follow guide on how to patch a chimney. However, you can also get professional assistance.
A flue is essentially a vertical duct that starts from the firebox (where the fire is ignited) and ends at the top. The purpose of a chimney flue is to take exhaust combustion gasses from the fireplace out of your home.
Without a flue, the smoke will have nowhere to go, and combined with heat, it can cause a house fire. Fire can also break loose if there are any cracks inside your flue allowing it to get to combustible materials inside your home e.g. drywall.
How to Know if Your Chimney Flue Requires Maintenance?
Before starting a fire, make sure that the chimney flue does not have any white buildup (residue), cracks, or loose bricks. You can do this by flashing a light up from the inside of a firebox to see if anything’s out of order.
Regular maintenance and annual inspection are mandatory to ensure your safety and that of your loved ones.
A wythe is a vertical, single-brick masonry wall used to separate chimney flues.
Often, houses have a single chimney for various appliances such as furnaces, water heaters, fireplaces, etc. However, all these appliances should have designated flues. A single flue for various appliances is dangerous as harmful gasses from one appliance can be conducted to another via the shared flue.
While multiple flues in a single chimney are allowed, they should be divided by a wythe wall. Also, the partitions should be bonded or tied securely to the chimney, according to NFPA 211-2019.
Chimney flues and liners go hand in hand. While a flue is tasked to take the exhaust gasses out of the house, it is still close to a drywall and other materials that can catch fire. A chimney liner is, therefore, placed inside the flue to limit the heat transfer and prevent fires.
The liner also keeps the flue bricks safe from harmful byproducts of combustion that would otherwise disintegrate the mortar in between the bricks, creating cracks. These cracks are dangerous because of two main reasons:
- Heat can pass through them and the nearby combustibles can catch fire.
- CO gas can leak into your home.
Types of Chimney Liners
Chimney liners are of three main types:
Metal Liners are used to repair an already existing chimney and are known for their durability.
Clay Tile Liners are common, especially in older homes, and are quite cheap.
Cast-in-place Liners are permanent liners that improve the structural strength of the chimney flue.
Found at the base of a chimney stack (a portion of the chimney above the roof), a chimney flashing is essentially there to water-proof your chimney. Depending upon the structure of your roof and your environment, a chimney flashing can be made up of vinyl, copper, steel, or aluminum.
While there are various types and methods used for flashing, it all comes down to the kind of chimney and roof you’ve got.
Some of the more common flashing types, used together with caulk, are:
Step flashing—present under the roofing shingles and along with the chimney bricks, is a piece of L-shaped metal.
Counter flashing—also called cap flashing, is fixed parallel to the chimney and covers the step flashing.
Base flashing—used at the chimney base, to keep moisture from entering.
A leaking flashing can prove to be disastrous to your chimney and even your rooms. A leak in the chimney flashing lets the moisture in which penetrate into the mortar joints that become brittle and break down.
But, how do you know if your chimney flashing needs repairing?
Some of the most obvious signs of a damaged chimney flashing include dripping sounds or puddles, water stains, discolored bricks, rust, and gaps in the caulking.
However, often we don’t notice water damage until it has entered your attic or ceiling and seriously damaged your drywall and roof. So, it’s better (and a lot cheaper) to opt for regular inspection and maintenance of your chimney flashing, than to wait for serious damage to occur.
You can call professional help but if you’d like to take it upon yourself, here’s a simple guide on how to repair a leaking chimney flashing.
The top of a chimney is called a chimney crown and is usually slanted so that rainwater can be directed away from the chimney. The chimney crown is covered with cement or mortar to insulate the chimney from water and environmental elements that may corrode the chimney.
Since the chimney crown is placed at the top, it’s common sense that it takes a lot of damage which, over time, results in cracks. These cracks are harmful since they allow water to seep in and damage the chimney. Thus, regular checkups and maintenance of a chimney crown is essential for its durability.
While a chimney crown protects the better part of the chimney, the flue is still exposed. Open chimneys are exposed to outside debris and small animals (that can get inside for shelter) and clog the chimney flue. A clogged chimney flue is dangerous as it traps hazardous gasses and exposes you and your family to smoke and CO.
So, a chimney cap, which is a mesh of stainless steel, is installed. The cage-like structure allows the smoke to escape while keeping rainwater, birds, and small animals from getting inside.
Chimney Chase Covers
Commonly known as chase tops or chase pans, chimney chase covers are rectangular covers that seal the chimney tops. Chase covers are only used for factory-built fireplaces.
A chimney top is open, which means anything from water and dust to small animals and birds can get inside and corrode or clog the chimney. A chase cover ensures that your chimney is free of moisture, dust, and anything harmful.
When to replace your chimney chase covers?
If you notice reddish-brown stains on your chase cover top, that means that rust and corrosion has gotten the best of it. Rust and corrosion can eventually cause the chase cover to leak, thus, defeating its purpose.
Finding water in your fireplace is another sign of a damaged or leaking chase cover.
If you notice any of these signs, call professional help to get your chase cover replaced before moisture and other environmental elements damage too much of your chimney.
A damper is a mechanism inside the flue that lets you control ventilation. By controlling the airflow inside the flue you can control the intensity of the fire. But when the chimney is not in use, the damper is closed to keep the outside cold air from entering.
There are various ways to open or close your chimney damper depending upon the type of damper installed. The most common fireplace chimney damper types are:
- Throat Damper ((located just above the fireplace)
- Top-Sealing Damper (creates a tighter seal)
If your damper is not functioning properly, there’s a high chance that it has been clogged due to debris. You might want to call a certified professional to clean it up.
Shaped like a reverse funnel, a smoke chamber sits just above the damper and connects the firebox to the chimney flue.
The smoke chamber is designed such that the smoke escapes quickly and efficiently, through the flue. However, most smoke chambers are made from corbeled masonry that has gaps and steps that trap smoke and soot, creating a buildup.
It is important to parge your smoke chambers so that they are smooth, and smoke-tight allowing for an efficient exhaust of smoke.
Sitting right between the smoke chamber and the firebox is a smoke shelf that is designed to prevent downward drafts to keep the smoke and other toxins from entering your living space.
Parts of a Fireplace
Often a square or a rectangular box, a firebox is the main part of a fireplace. It’s the place where the fire is ignited.
Fireboxes are made from non-combustible materials (e.g., cement or bricks) to withstand the heat coming from open fires, etc.
Over time, your firebox can form cracks or gaps between the bricks or cement due to various reasons such as poor quality construction materials, moisture, frequent expansion (thermal) and contraction.
Before igniting a fire, make sure there aren’t any spaces or gaps. Excessive heat can get concentrated in such areas, which can seriously damage your firebox.
A fireplace hearth is the flooring on which the fire is ignited. It is essentially the base of a fireplace and is made from non-combustible materials such as granite, stone, ceramic tiles, marble, etc.
The hearth ensures that the floor is safe from the heat from the fireplace and that’s why it also extends into the room. Hearth’s also serving aesthetic purposes which is why you’ll find them in electric fireplaces, even though they’re not mandatory.
But you can’t do without a hearth if you’ve got a wood burning fireplace or stove.
A fireplace mantel is a shelf on top of a fireplace used, basically for aesthetic purposes. Traditionally, fireplace mantels were used to catch smoke from the fire before it entered the room. But, now, the only need for a mantel is to tie the room together with a visually pleasing design and to place various items on top of it.
Fireplace mantels are installed in either of the following two ways:
- As a standalone floating mantel, like a shelf on top of a fireplace.
- As a part of a fireplace surround.
A fireplace lintel is a bar that lends structural support to the chimney and protects it from the intense heat and from successive fires. Traditionally, wood was the material choice, but nowadays, stone, concrete, steel, or brick lintels are common.
Since bricks and mortar joints become weaker over time, there’s a risk of the chimney falling into the firebox. A fireplace lintel keeps it from happening while also increasing the chimney’s life by protecting it from excess heat.
Don’t remove your fireplace lintel
Some homeowners or contractors detach the lintel to lengthen the firebox. While it might look better, it’s a recipe for disaster. Not only will you see the structural integrity of your chimney deteriorate over time, but the more immediate effect would be smoke flowing into your room.
A fireplace face, made of non-combustible materials, surrounds the outer front of a fireplace. While a fireplace face is there to protect the surrounding walls and materials from the heat coming from the fireplace, it also serves aesthetic purposes.
Often confused with a fireplace face is a fireplace surround. A fireplace surround doesn’t serve any purpose apart from being an aesthetic bridge between the fireplace and the room. Fireplace surrounds can be attached to both traditional masonry fireplaces as well as prefabricated ones.
When we’re thinking of fireplace dangers, we often think of the ‘worst-case scenarios’ like burning houses or chimney fires. However, we often disregard scenarios that might not be as dangerous as chimney fires but are much more common. Fireplace glass doors help keep you and your family safe from such dangers.
From burning logs tumbling to red hot coals jumping out of the fireplace, glass doors keep us safe.
Apart from protection, glass doors also keep the ash and other fireplace residue contained, allowing for a cleaner room. These doors are also great for conserving energy as they keep the cold air out (in winters) and the cool air within the room (in summers).
Fireplaces are not as efficient as one might think. That’s because a traditional fireplace drafts the hot air up the chimney while cooler air from outside is dragged into the room. Due to this, a lot of heat is wasted.
To improve the efficiency of a fireplace, fireplace inserts are used. Covered by cast iron or steel, fireplace inserts are essentially fireproof boxes that create a closed combustion system. Some of them even come with blowers to pump in the hot air.
While there are three main types of inserts: wood, gas, and electric; gas and electric inserts are much more efficient and easier to operate.
The ash dump is located directly below the ash door (usually made out of cast iron or aluminum, and vented). It is the space where the ash falls whenever the ash dump door is opened as per need. A typical ash dump has an opening area of about 4 inches by 8 inches.
This opening provides the space for the ash to fall directly onto the ash pit from where the ash can later be cleaned out.
Under the ash dump is an ash pit, surrounded by concrete or blocks of cinder. Accessed through the clean out door, the ash pit collects all the ash from the fireplace. You should clean the ash pit frequently as it may clog the clean out door. Ash pits range from having small to large areas usually based on the type of fireplace installed in the house.
The clean out door is often located in the basement of the house and is usually made up of cast iron (for minimal warping). The purpose of a clean out door is to access the ash pit. Old ash collected in the ash pit is shoveled out through the clean out door. The door opening is about 8 by 8 inches.
The footing is a horizontal surface that lies directly under the ashpit and the foundation of the chimney. The footer of a fireplace chimney is a 1-foot thick concrete layer that also provides support to the chimney. It is usually located in the basement.
The foundation of a chimney, made out of reinforced concrete, would be around 12 to 24 inches thick and this is often connected to a small number of grade beams. The foundation is located below the ash pit section of the chimney and its sole purpose is to provide stability from the ground to the chimney by distributing the weight of its whole structure over a large area of ground.
Fireplace mortar is the type of mortar usually used in chimneys. Firebrick joints should be around a quarter-inch thick. And the best mortar for this purpose is the ASTM refractory mortar. This type of mortar should be protected from water (which may cause it to deteriorate).
A fireplace chimney is at the heart of your home and like the heart, is quite critical. Understanding the various fireplace chimney parts such as the chimney flue, liner, smoke chamber, glass doors, fireplace inserts, etc. is crucial to a safe and efficient fireplace.
Therefore, not only have we discussed the various fireplace chimney parts in detail, but also how they operate and what purpose they serve for you to understand their importance. And, finally, we talked about various warning signs to look out for before lighting that fire.
Hopefully, you are in a better position to diagnose any issues and call professionals before it’s too late. But, if you’ve still got unanswered questions regarding fireplace chimneys, let us know and we’ll be glad to help.