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Many modern wood stoves are designed to use fire bricks that line the interior casing. The fire bricks are designed to:
- provide structural protection to the stove casing
- ensure stoves are more efficient at reaching high temperatures
- allow secondary combustion
- allow lower clearances around the stove
This article explains each of these benefits in plain English.
We also look at what happens if you use a stove that is missing the fire bricks it should contain. We strongly advise that you don’t do this! We explain why at the end of the article.
Protect The Stove Casing
Fire bricks project the body of the stove from cracking due to heat stress over time.
To understand why the casing could crack, remember that heat causes metal to expand.
Modern wood stoves are designed to heat up as rapidly and intensely as is safe. But the intense heat isn’t uniformly distributed across the body of the stove. That means that some parts of the casing expand faster than others.
Similarly, when the fire goes out and the metal cools, some parts will contract faster than others.
These differences in expansion and contracting cause stress to the metal. This could result in cracking. It could also cause the welded joints to fail.
How fire bricks provide protection
The fire bricks provide an absorption layer between the heat of your coal or wood and the outer casing of the stove.
You can consider them as a thermal buffer. They partially absorb the rising heat in a way that it is distributed more evenly around the firebox.
As the fire goes out, the fire bricks release the absorbed heat. This ensures that the cooling effect is also distributed.
Combustion Efficiency – A Hotter And More Efficient Stove
Fire bricks provide an insulation layer that both absorbs heat and reflects it back into the combustion zone.
Insulating the fire chamber means that the combustion temperature is increased. This design allows wood stoves to reach very high heat levels.
These effects are referred to as combustion efficiency. By making the combustion process more efficient, the stove owner uses less fuel (wood or coal) to get higher heating.
Benefits of combustion efficiency
The fire bricks don’t just give stove owners a lovely warm room. There are other benefits that arise from having a more efficient combustion process.
When you burn wood or coal, the burning process produces gasses like carbon monoxide, sulfur, and hydrocarbons.
If these emissions hang around, you will experience them in the form of foul-smelling smoke. They also cause creosote if they hang around.
However, these intermediate emissions get burned off as the temperature rises.
The efficiency provided by the fire bricks ensures that there is a more complete burning of these intermediate products.
This means that firebricks are protecting wood stove owners from smoke emissions and the build-up of creosote.
Fire Bricks Allow Secondary Combustion
Don’t worry if you’re not familiar with the term “secondary combustion”, I’ll explain it simply here.
When the fire gets going in your stove, the smoke would simply go up the chimney without secondary combustion.
The secondary burn uses air vents at the top of the stove to draw and circulate that smoke back into the chamber.
The stove system pushes oxygen towards this smoke, making it even hotter. Igniting these gases is what’s known as secondary combustion.
The inside of your stove must get hot enough to allow secondary combustion. Fire bricks enable those high temperatures to be reached.
Stoves With Fire Bricks Have Lower Clearances
We have several articles on how much clearance is needed when you install a wood stove.
Because fire bricks provide an insulating layer within the casing, your sofa doesn’t have to be across the other side of your living room.
You should always check clearances in the manufacturer’s manual for a specific model. When the stove comes with fire bricks, these measurements assume that you don’t take them out!
Not All Stoves Need Fire Bricks
Many modern stoves need bricks, but this doesn’t apply to all of them. In particular, some cast iron models may not need them.
If you want to know more, check out our article on whether cast iron wood stoves need fire bricks.
Some people seek out models that don’t take need them. That’s a personal choice.
Sometimes people buy or are donated a second-hand stove that doesn’t contain bricks. It’s important not to assume that you’ve found a model that was designed not to use them.
The prior owner may have removed cracked bricks and not bothered to replace them.
If you look inside an acquired stove and see there are only bricks on the sides, check out our article on whether fire bricks should be on the bottom of stoves.
If you do acquire a second-hand stove, you should always inspect the inside before lighting the first fire. Don’t just bung in a few logs and get going!
Why? Read on…
What Happens If You Use A Wood Stove Without Fire Bricks?
This section only applies to wood stoves that were designed to be used with fire bricks.
I’ve seen people speculate in forums that there may be a benefit from removing the bricks. They seem to assume that because the bricks are providing an insulation layer, removing them will release more heat into the room.
This is a fallacy! The truth is the complete opposite.
Without the bricks, the heating process will be far less efficient within the stove. You won’t get as high temperatures and the stove will cool far faster. So, you don’t get as much heat, and the heat won’t last as long as with the bricks.
Another reason I see for people removing firebricks is that they can pack more logs inside. Again, this is a big mistake.
Possible damage to the stove
The least of your worries would be having a less efficient heater.
We explained earlier that the bricks regulate the heating and cooling cycles.
The risk from running hot fires over time without the bricks is that you cause the casing to warp or crack.
Common Issues With Fire Bricks
Unfortunately, it’s not uncommon for cracks to appear in fire bricks over time. Depending on the quality of the material, you may also see deterioration through crumbling.
It’s important to replace bricks that are no longer structurally capable of providing the benefits that we describe above.
However, it’s relatively simple to take actions that make your bricks last longer. Check out the tips in our article on how long fire bricks last in wood stoves.
