Fire Bricks’ Lifespan in Wood Stove

It’s not unusual to see cracks appear in the fire bricks that line the interior of a wood stove.

Hairline cracks are usually not a problem. However, if there is a large gap or the brick has started to crumble, then you should replace them.

There are ways you can ensure that your bricks last longer than average. Some stove owners haven’t had to replace a brick in over twenty years.

It isn’t luck! This article explains their secrets.

How Often Do Wood Stove Fire Bricks Need To Be Replaced?

We conducted a straw poll of sixteen people to ask when they replaced a fire brick for the first time after they purchased a new wood stove.

Three people said they replaced a cracked brick within two years.

Nine people gave answers that ranged from two to five years.

This was in contrast to three people who owned their stoves for over ten years and had yet to replace a brick.

One guy told me he’d replaced several bricks the previous year for the first time in twenty-seven years!

This is how the numbers broke down:

• 3 people: under 2 years
• 9 people: 2-5 years
• 1 person: 27 years
• 3 people: never replaced a brick (each stove was over ten years old)

Are some stove owners just lucky?

You may be wondering if the three people whose bricks have lasted over ten years are just lucky. But the big clue was in the response of one owner.

Let’s call him Joe.

Joe told me that when his two children were growing up and living under his roof, it was their job to fill and empty the stove.

If he was in the room and spotted them chucking logs in toward the back with force, he’d tell them off. But of course, he wasn’t always in the room.

Joe confirmed that he had to replace at least one brick every eighteen months.

Both adult children moved out of the house four years ago. Joe hasn’t had to replace a brick since.

The message here is that one factor in why bricks crack is how they are treated. Let’s look at this and other factors in more depth.

How To Make Fire Bricks Last Longer

There are several factors involved in how long different bricks last:

• amount of care taken when loading the stove
• quality of the material
• the kind of heat cycles that the stove operates on

Let’s look at these in turn.

Take care while loading

There are two common mistakes that people make when loading a stove that contribute to cracks in their fire bricks.

Firstly, they chuck logs into the burner so hard that they bounce off the back brick.

You wouldn’t hold out a brick and drop it onto a wooden floor. It stands to reason that you should carefully place logs or coal in such a way that they don’t hit off the interior casing.

Secondly, they ram as many logs as they can into the burner so that the edges of the logs are scraping the sides and back plate. They then have to push hard on the stove door in order to get it closed.

The advice here is not to overfill your stove. Stressing the bricks over time will lead to them cracking or crumbling.

Choose quality bricks

Some fire bricks are steel plates, particularly ones in cast iron stoves. But most are made up of dense ceramic material.

Depending on the manufacturer and brand, some tend to be more likely to crack. This is a question of quality.

If there are several brands available from a vendor, I advise that you chat with someone on the shop floor about which lasts longer.

If you are buying replacement bricks online, you probably shouldn’t default to the cheapest option without some research.

Take a look at the reviews. For one cheap brand, I saw several people mention that the bricks had broken when they arrived. That’s not a good sign!

Regulate your heat cycles

In general, you don’t want a stove to get to a very high temperature very fast or to cool down to a low temperature too quickly.

Normal usage of a stove should ensure that this doesn’t happen. However, some people take ill-advised actions to get their stoves to a high heat as rapidly as possible.

That can affect the durability of both your stove and the bricks inside.

Specifically, the heat cycle makes the brick expand and contract more rapidly than the manufacturers designed them for.  

This can cause them to crack or warp.

Do Cracked Fire Bricks Always Need To Be Replaced?

If you’ve never seen a cracked fire brick, here is an example at the back of a stove.

You may be wondering if this brick should be replaced immediately.

I personally wouldn’t be in a hurry with this specific example. The structure is still intact, and the brick is still doing its job. (Check out our article on why wood stoves have fire bricks).

The problem is when there is a large gap between two pieces. This means that a part of the interior casing of the stove is exposed.

It also means that the bricks aren’t doing the insulating job that they are designed to do.

You should replace bricks in these circumstances:

• When a significant gap has opened
• When pieces of the brick can no longer stay upright

Do Crumbling Fire Bricks Always Need To Be Replaced?

Unlike a cracked brick, I’d recommend replacing bricks as soon as they start to crumble.

Unlike hairline cracks which are relatively common, fire bricks shouldn’t crumble in the first place. It’s a sign that they are of poor quality.

Crumbling bricks won’t provide as much interior insulation as they are supposed to. They also tend to deteriorate very quickly.