Effective Steel Fireproofing: Intumescent Coating or Cementitious Coating?

30thMarch 2021
Effective Steel Fireproofing: Intumescent Coating or Cementitious Coating?

Protecting structural steel from fire is essential because unlike other building materials, it can only retain around 50 percent of its strength when exposed to extreme temperatures. During a fire, as the temperature reaches around 600 degrees Celsius, structural failure becomes an inevitability and the collapse of the building much higher.
It is because of this that the Building Code requires builders to implement measures that will protect the building and its occupants for as long as possible. Whilst there are many options available – concrete encasement, active fire systems, fire board, cementitious coatings and intumescent coatings – choosing the right one is essential as it not only can help protect the aesthetics of the building, but also reduce or increase the costs of construction (depending on whether you get it “right” or wrong”). But for now, let’s concentrate on passive fire protection and look at two solutions: intumescent coating and cementitious coating. While both mitigate and control the spread of flames and limit damage to structural steel, one of these fire-resistant options simply reigns supreme over the other.

What is cementitious coating?

This type of material, also known as lightweight cementitious, is proven and has been one of the most trusted materials for more than a century. To make this, perlite, vermiculite, or other lightweight aggregates are combined in a heat-absorbing material such as Portland cement. To reinforce its strength, other additives like foaming agents are mixed together.
Cementitious coating can be classified as low, medium, or high, based on its density. When used for fireproofing, it is applied to the substrate directly; however, to be effective, it needs to be layered continuously to achieve the requisite FRL.


  • Affordable raw materials and a more economical solution
  • Perfect for dry environments
  • Highly resistant to high temperatures


  • More field work required and labour cost is higher since the coating needs to be applied in many layers successively
  • Not ideal for places with high moisture levels as it can cause gaps between the substrate and the cementitious coating
  • Prone to spalling, cracking, or disintegration when exposed to vibrations and heavy impacts
  • Adds significant weight to the overall structure which may increase costs due to increased need for more structural steel.

What is intumescent coating for steel?

A popular passive fire protection material, intumescent paints or intumescent sealant (as used for extrusions) is made of materials that swell as a result of heat exposure. This act of swelling (technically called charring) makes the paint expand in volume and decrease in density, slowing down the steel’s heating to prevent its collapse.

Steel With Intumescent Coating - Hybrid Intumescent - Permax

Application of intumescent paint is easy for a qualified applicator; as often as not, one simple pass is enough to protect your building from fire. However, as required to achieve a commercial or architectural finish, additional coats can be added.


  • Relatively Easy to apply for trained applicators; a single layer can provide your much-needed structural steel fire resistance
  • Low maintenance; comes with excellent bond strength even without a finish coat
  • Does not absorb moisture, thus preventing corrosion. Is even capable of resisting severe water flow
  • Low labour cost
  • Low overspray
  • Low application time and ease of application makes on-site savings much higher than initial estimates make apparent


  • May not be ideal for facilities where impact damage is high
  • People often only compare the cost of application against cementitious coatings and fail to take into account time and material savings

The Verdict

While cementitious coating is a reliable passive fire resistance technology, it is clear that in terms of cost-effectiveness, level of fire protection, ease and flexibility in application, low overhead costs, and wide availability, the choice of an intumescent coating is best when it comes to protecting structural steel from fire.
Permax offers both water-based and Hybrid intumescent paints. Learn more about these coatings and find out which works best for your facility by contacting our specialists now.


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Permax constantly update the documentations based on the new fire testing outcomes and change of standards and regulations. To ensure the documents you read are up-to-date, please contact the Permax technical team.