The NFPA issued a technical paper in 2018, Fire resistance of concrete for electrical conductors which concluded with the recommendation “electrical feeders are to be encased in 5 inches of concrete when this is the method of fire protection” to achieve two hours of protection from fire.
Historically, many buildings and building codes have allowed concrete construction methods as a way to protect wiring to critical circuits. This process of encasing standard building wires supplying power to critical life-saving equipment with up to two inches of concrete was the norm.
While this approach has historically been accepted, this practice is specifically not approved in the newly released 2026 National Electric Code!
Article 700.10 Note 6 states “The cable or raceway is encased in a minimum thickness of 127 mm (5”) of concrete measured from each point on the surface of the cable or raceway”
Let’s explore the fire resistance of concrete, and how it compares to fire-rated wiring solutions. This code change was made since 2” of concrete only provides 1 hour of fire protection – Let’s go deeper.
Why is Concrete an Option for Buildings?
Concrete as a structure and a material is inherently fire resistant. It’s a non-combustible material with a slow rate of heat transfer, making it a natural choice for building fire protection. All critical wires and circuitry could be encased in the concrete for a relatively low cost.
The Evolution of Building Codes
As buildings have grown larger and the time required to safely evacuate and respond to fire has grown, a number of NEC building standards have upgraded from one hour of fire protection to two hours over the last twenty years. These include:
- Article 695 “Fire Pumps” requires 2 hour protection per 2008 NEC
- Article 700 “Emergency Systems” requires 2 hour of Protection per 2011 NEC
- Article 708 “Critical Operating Power Systems requires 2 hour Protection per 2011 NEC
- New Article 728 “Fire-Resistive Cable Systems” in 2014
- Article 760 “Fire Alarm Systems” requires
- 2 hour Protection per 2005 NEC
- NFPA 72 “Fire Alarms” requires 2 hour “Survivable Circuit” and cables must be installed per Article 760
These updates fell in line with NFPA codes requiring two hours of fire protection applied to emergency power supply generators, elevator circuits, fire pump circuits, smoke venting fans and more. Many states require a minimum two-hour fire rating. This means critical circuits should remain operational in temperatures from 1000°F (537°C) at 5 minutes to 1850°F (1010°C) at 120 minutes.
How Do Concrete Methods and MI Cable Compare for Fire Protection?
The main problem with concrete and fire protection, is that you need more than the historically accepted 2 inches of thickness for two hours of protection. Buildings using 2” or less of concrete to protect wiring will not meet the new 2026 NEC code.
Downside of Using 5” of Concrete for Fire Protection in Buildings:
- Buildings with one or two inches of concrete do not provide 2 hours of fire protection
- Using 5” of concrete to achieve two hours of protection increases costs significantly and leads to less usable space, a critical aspect for modern building design
- Lack of approval or testing once installed can lead to inadequate protection
- Concrete is prone to damage which reduces protection
- Concrete is not ideal for building retrofits or remodels
Upside of using Pyrotenax SYSTEM 1850 MI cable for Fire Protection in Buildings:
- Pyrotenax MI cable is UL/ULC fire rated for two hours of protection
- Pyrotenax MI cable is Free air rated so you can deliver more amps while consuming less usable space
- Pyrotenax MI cable can be installed in tight, or hard to maneuver spaces
- Pyrotenax MI cable can withstand the impact of a blow, or falling concrete, etc.
- Pyrotenax MI cable can be spliced and rerouted as buildings evolve over time
- Pyrotenax MI cables have a Lifetime warranty
For well over one hundred years, fire safety codes have evolved to save lives and property by codifying best practices in building design. With the availability of UL/ULC Approved fire-rated products, building professionals are better equipped to specify the safest systems and meet NFPA 70/NEC 2026 requirements. To learn more, please visit us here.
To download our specifications please visit Deltek: Pyrotenax Product Listing