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Metal firebox vs. Firebricks – what's the difference?

Metal firebox vs. Firebricks – what's the difference?

If you want to install an outdoor fireplace, choosing the most effective materials is crucial. Not only will this impact the heat output of the fire, but it will also affect durability, longevity, and visual appeal. 

In an outdoor fireplace, you will typically have the option of a firebox with a lining or a firebrick structure. In this article, we explain what each of these options includes and how to choose the right one for your needs. 

The structure of an outdoor fireplace

The basic structure of an outdoor fireplace can vary depending on the design and materials used but some components must be included for functionality and safety. These include the inner chamber, chimney, fire surround, and hearth. Optional features can also be added, such as a mantel, grate, and screen. 

The inner chamber, also known as a firebox, is where the fire burns. It is usually made of fire-resistant materials such as metal, firebricks, refractory concrete, or stone. 

What is a firebox?

A firebox is a compartment inside the fireplace surround that is designed to contain the fire. They are typically made from fire-resistant materials, such as refractory concrete or steel. This means they can withstand high temperatures and prevent the spread of flames to the surrounding area. 

What is firebrick?

Firebrick, also known as refractory brick or fireclay brick, is a specialised type of brick made from refractory clay or a blend of clay and other materials. They are designed to withstand extremely high temperatures and thermal stress without deforming or cracking. 

Metal fireboxes vs. firebricks

When comparing fireboxes and firebricks, the key factors to consider are:

Material composition 

Fireboxes can be made with fire-resistant materials like refractory concrete or metal. At Trendz, our fireboxes are made with 6mm black steel for maximum durability and sleek aesthetic appeal. 

Firebricks are made from refractory clay and sometimes blended with recycled clay. They typically contain additives to enhance the heat-resistance properties and maintain structural integrity. 

You can choose either material for your outdoor fireplace and both will perform the job of reducing heat transfer through the material of your fireplace and directing heat out through the opening. However, there are limitations to both which means one may be more suited to your project than another.


Firebricks are an appealing option to many as they are simple to acquire and lay when constructing a DIY outdoor fireplace. They can be cut into shapes to suit any construction method, meaning you can design and build the entire fireplace and lay the firebricks afterwards, if that suits your process.

Alternatively, a metal firebox is pre-constructed and has set dimensions. This is advantageous in that installation is quick and simple because you can simply slot it in and fix it in place. However, due to the fixed dimensions, there’s a need to build the fireplace around the metal firebox.

Temperature tolerance 

Depending on the material composition, the heat resistance of a metal firebox is generally higher than firebrick. Firebricks have equally effective heat tolerance until they are damaged. Once punctured or damaged, they are unable to deflect the heat and their primary function is reduced, requiring replacement. 

Our steel fireboxes are harder to puncture and are designed to withstand extreme heat for many years of use. This helps prevent heat loss and improves temperature tolerance over time. Like any fireplace, a steel firebox will require maintenance, however, they do not normally require items to be replaced as firebricks do.


The cost of an outdoor fireplace can range from a few thousand to tens of thousands. In terms of the inner chamber, firebricks tend to cost slightly less than a steel firebox. 

It is also worth considering the long-term value of your fireplace. It has been proven time and time again that a quality outdoor fireplace increases the sale price of a home and reduces the days it takes to sell. For this reason, we recommend investing in a durable steel firebox that is built to last.

If building a DIY fireplace, the dollar cost of the fireplace will be the lowest but the time investment will be high. People often make the mistake of placing no value on their time when evaluating the savings of doing something themselves.

When comparing a pre-made or ‘off-the-shelf’ outdoor fireplace, one made with a firebrick lining is likely to be cheaper than one with a metal firebox. This is due to the engineering and material cost of a metal firebox being higher but with the advantage of not only a longer lifespan and durability but also a firebox that is a lot more efficient due to the design of the back and top baffles.

This means that you don't have to burn as much wood to keep your friends and family warm when sitting down and enjoying those balmy nights around the fireplace.


As the internal chamber of the fireplace, there isn’t much need for design customisation. However, if you do want to incorporate an interesting design, firebricks may offer more options. Since they are laid individually, bricks can be installed in custom patterns or various colours. 

On the other hand, metal fireboxes are generally a standard shape and style because they are made of a single or double-lined steel structure. In saying that, the firebox is generally a functional component while the fire surround is your opportunity for aesthetic customisation. 

For example, with a Trendz fireplace, you can choose to custom-clad your fireplace in materials such as brick, stone, timber, plaster and paint, or precast concrete. The black steel firebox is designed to complement whichever design you choose.

Common applications 

Steel fireboxes are commonly used in residential settings to safeguard structures from direct exposure to flames and extreme heat. In comparison, firebricks are often used in kilns, ovens, and industrial furnaces. While firebricks can also be used in residential outdoor fireplaces, the high maintenance requirements mean this is less common. 

Should I choose an outdoor fireplace with a metal firebox or firebricks?

If you’re looking at two different outdoor fireplace options and one has a firebrick firebox and the other has a metal firebox, the answer will come down to which of the following priorities rank higher for you.

If you want a fireplace that requires minimal ongoing maintenance, increased durability, and higher efficiency, a steel firebox will be best. If you want a lower-cost fireplace that may require some maintenance over time, a firebrick construction may be your best option.

There is also an aesthetic element, which comes down to personal preference. When unlit, a fireplace with a metal firebox will have a black surround, which some people find more appealing as it hides the remnants of the last fire and the char/smoke from use. A firebrick fireplace will show the brick and smoke stains but could be laid in a nice pattern. 

A common myth is that a steel firebox will rust out which can be true if a thin grade of steel is used. However, at Trendz, we use a solid 6mm steel to ensure your firebox will stand the test of time and not be damaged when burning large, hot fires.

If you are in a marine environment, we recommend adding our solid stainless steel door to your fireplace. This will protect the firebox and keep it looking like new for many years if you give it a quick paint touch-up once a year.

Trendz outdoor fireplaces

At Trendz, all our outdoor fireplaces are made with a black steel firebox and a prefabricated surround. From our 17 years of experience with fireplaces, we've found that steel fireboxes have proven to be the most efficient, and long-lasting option. With a firebox option, you can choose your favourite cladding option to complement your landscaping design while still obtaining a durable, effective heat source. 

Cladding ideas include: 

  • Plaster and paint
  • Custom schist
  • Custom brick
  • Custom riverstone
  • Mixed materials

See our gallery for examples of fireplaces all around New Zealand. 

We also offer accessories: 

If you’re interested in an outdoor fireplace, contact our team for advice or browse our range. We also offer the option to purchase fireboxes by themselves, which is ideal if you plan to incorporate them into masonry. Explore our selection of fireboxes by clicking the button below.

Browse our fireboxes

Have a question? Contact us