Do Cast Iron Stoves Need Fire Bricks? (Explained)

A friend bought a house with an old cast iron wood stove. When he looked inside, he was surprised that there were no fire bricks.

There also didn’t appear to be room to insert new bricks into the back or sides of the interior.

He asked me what he should do, so I did a lot of research on the topic. This is what I found.

Not All Modern Stoves Need Fire Bricks

Many modern stoves are designed to use fire bricks as an important part of how they work.

I explain the ins and outs in a separate article on why wood stoves use fire bricks.

In general, all modern steel stoves use bricks as part of their design. New units should come with them already installed.

Most modern cast iron stoves also need fire bricks. However, some modern models use steel or cast iron plates instead of fire bricks.

Steel Or Cast Iron Plates Instead Of Bricks

When plates are used, there will be three in the chamber: one at the back and two at each side.

Here is an example from a well-used unit.

These plates provide much of the same functionality as fire bricks. A thick cast iron stove doesn’t need the extra durability that fire bricks give to steel stoves.

However, the plates provide an extra insulating barrier that reflects the heat back into the fire chamber. This allows the stove to heat faster and more efficiently.

Some Older Cast Iron Stoves Do Not Need Fire Bricks

When you look inside an older cast iron wood stove from the 1960s or 1970s, you may not even see the obvious steel plates in the picture above.

The original Vermont Cases Defiant model is still a popular second-hand choice. Owners often describe them as being built like tanks!

They used a thicker casing. If there doesn’t seem room for plates or bricks inside, it’s because the body itself is thick enough to do the job.

However, you should always be careful to double-check the model. Companies use the same brand names for newer designs. Your model may need fire bricks.

You should use the model number as well as the brand name to find the correct instruction manual.

Some Models Need Ash Or Sand At The Base

Some older cast iron models were designed to operate best when the interior floor has a layer of ash and/or sand.

With some, you spread a layer of refractory sand as a base and allow a bed of ash to form on top of that.

An early Defiant model had ribs running along the interior bottom. You fill these with ash or sand.

If you’ve inherited or purchased one of these big old tanks, don’t guess what is needed. Find the appropriate manual.

If it’s hard to track down, contact the manufacturer with the model number.

Models That Depend On The Fuel

Buck Stove started manufacturing its brand out of Spruce Pine, North Carolina in the mid-1970s.

Their early cast iron models had an interesting design that didn’t need fire bricks when burning wood.

However, if the stove owner wanted to burn coal, then they had to add bricks.

Personally, I wouldn’t be wild about hauling bricks in or out of the stove from one fire to the next. I don’t believe that the company persisted with this design for very long.

Is It Okay To Use A Cast Iron Stove Without Fire Bricks?

Let me finish by coming back to my friend’s question.

When I investigated the model, I saw that the relevant manual from the manufacturer’s website stated that fire bricks came with this stove.

In other words, they were designed to be used with bricks.

This means that the previous owners must have removed them. My friend wanted to know if he could go ahead and fire up the stove without the bricks. After all, the nights were getting cold!

My advice was not to do so until he had purchased replacement bricks. These aren’t very expensive.

However, if the weather is poor and it will take a few days to get hold of new bricks, then there probably wouldn’t be much risk from a couple of fires.

I wouldn’t say the same for a steel stove, but a cast iron stove is less likely to be damaged.

Let’s look at this a bit closer.

Could the stove body be damaged?

One of the main functions of the bricks is to protect the stove casing from warping or cracking by getting too hot.

This is less likely to happen with a few fires in a cast iron body in good condition.

However, I’d worry that the previous owners may have spent months running high-temperature fires without bricks when the stove was designed to have them.

Each fire would put a little extra stress on the casing. My friend doesn’t want his first fire to be the straw that produced a big crack in the stove’s body.

I told him to shine a torch around the interior and look closely for any signs of damage. If there already was a crack, then my advice was not to go ahead.

Less effective fires are the main issue

A good quality old cast iron stove is less likely to be prone to cracks from fires. The main issue is that the model has been designed to use fire bricks to increase the efficiency of combustion.

This means that the stove won’t reach higher temperatures and retain heat as well as it should. They may also emit a lot of smoke.

If it’s the only option for heat on a cold night, then the worst outcome will be saying cold in a smoky room!