Is HardieBacker Fireproof: Cement Board Fire Rating

For construction projects, HardieBacker is a go-to option for most floor and wall renovations. After all, this line of fiber cement boards has an excellent reputation in terms of durability.

But in terms of fire resistance, you may be wondering how resilient is HardieBacker cement board. Is HardieBacker fireproof? What is the fire rating? And, heat resistance?

This guide has the answer.

Is HardieBacker Fireproof?

Yes, HardieBacker cement board is fireproof and deemed non-combustible when tested to ASTM E 136 standards. It also meets the European standard for fiber cement, EN 12467, and its reaction to fire, in accordance with EN 13501-1.

HardieBacker Cement Board Fire Rating

HardieBacker cement board has an A1,S1-d0 fire rating, which means it is fully non-combustible, and emits little or no smoke or flaming droplets within the first 10 minutes of fire exposure.

Here’s a breakdown of the HardieBack fire resistance rating:

  • A1: Non-combustible
  • S1: Little or no smoke
  • d0: No droplets

You can view the official HardieBacker Material Safety Data Sheets (MSDS) here.

Fireproof HardieBacker cement board on floor

Factors that Affect HardieBacker’s Fire Resistance

Here are the factors that affect the fire resistance of HardieBacker cement board:


HardieBacker is a fiber cement product. It is made with cellulose fibers, portland cement, and sand. These inorganic materials are non-combustible, meaning they will not ignite or support combustion.


The thickness plays a role in the fire-resistance level of the Hardie boards. Thicker boards tend to have a higher capacity to withstand heat. This is because it takes longer for heat to penetrate through a thicker material. HardieBacker boards range from 1/4 inch to 5/8 inch (6 mm to 15 mm).


Proper installation is critical for HardieBacker’s fire resistance. The boards should be installed with the correct fasteners and spacing to ensure a tight fit and prevent flames from spreading behind the siding.

Fire Exposure Conditions

The severity of a fire will also affect HardieBacker’s performance. A minor fire may only cause the surface of the board to char, while a more intense fire could cause the board to crack or break.

Frequently Asked Questions

Does Hardie Board burn?

Hardie board will not ignite when exposed to a direct flame, nor will it contribute fuel to a fire. As a result, Hardie board will not burn, but it can char or crack from intense heat.

Can HardieBacker be used in a fireplace?

Yes, you can install HardieBacker in a fireplace because it is non-combustible. To ensure the most fire resistance, use HardieBack cement boards in conjunction with other non-combustible materials around a fireplace.

Does HardieBacker require special installation methods to maintain its fire resistance?

No, HardieBacker itself doesn’t require special installation for fire resistance. This is because HardieBacker is inherently fire-resistant due to its composition. As long as you install HardieBacker according to the manufacturer’s instructions, its inherent fire resistance will be maintained.

What about other types of cement boards? Are they


Most cement boards share similar fire resistance properties because of their non-combustible base. To find out how resistant other popular brands of cement boards are, check out these related guides: Is Durock Fireproof? and Is Wonderboard Fireproof?


In conclusion, while HardieBacker is fireproof with a fire rating of A1,S1-d0 (meaning it won’t burn and contributes minimally to fire spread), achieving a specific fire resistance for your floors and wall assembly requires considering the entire system. Consult a professional or James Hardie’s resources to ensure your construction project meets the necessary fire rating for safety.