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Vermiculite Spray vs Intumescent Coating

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A Comparison Of The 2 Major Fire Protective Coatings For Structural Steel And Other Materials

Intumescent materials and vermiculite coatings are effective and reliable passive fireproofing options commonly used in construction to protect the structural adequacy of the building when exposed to extreme fire temperatures.

What is Vermiculite Fireproofing

Vermiculite spray  is a lightweight fire retardant made of vermiculite or other lightweight aggregates mixed with heat absorbing materials such as Gypsum or Portland cement (for external use). It insulates the steel structure from effects of high temperatures and extends the time for structural steel to retain its integrity and stability during the rising temperatures.

It is applied directly on the structure that requires protection from fire and can be used to fireproof structural steel, concrete frames, metal floor and roof decks. The amount of time the material will be protected from the effects of fire depends on the product used, the size of the structural element and the fire resistance period required.

CAFCO® 300 from Promat is the most popular vermiculite spray product on the market and can provide fire resistance of up to 4 hours to Australian Standards.


What are the Properties of Vermiculite

Very similar to mica, Vermiculite is an aluminum-iron-magnesium silicate with the same thermal and chemical resistance mica is known for. Vermiculite is a very popular product in the construction industry, used as a fire-retardant surface coating for its low density and impressive insulation properties.
You can find vermiculite in a lot construction materials such as:

  • Building boards
  • Fire door cores
  • Encased ductwork
  • Steel building elements
  • Gypsum plasterboard
  • Cementitious spray


Benefits of Vermiculite Spray Cafco® 300

  • Very lightweight material so it doesn’t require the over-specification of structural steel
  • Very cost-effective option, it provides very efficient fire resistance with minimal thickness
  • Resistance to High Temperatures for up to 4 hours


How to apply Vermiculite Spray

The sprayed coating needs to be mixed with water and is layered continuously to achieve the required thickness based on the predetermined Fire Resistance Level (FRL). Each product and brand has specific application procedures and must be correctly specified to meet the current building codes and regulations.

Promat vermiculite premix:

The application of CAFCO®  300 consists of mixing the material with water in a paddle or ribbon type mixer. The mixed material is then put into a pump hopper from where it is conveyed through the hose to a spray nozzle, where the slurry is broken up into a fan pattern by air and directed at the surface to be covered in an even, uninterrupted pattern.

It can also be trowel applied, the application methods are detailed in the product manual, available in the downloads section of the CAFCO® 300 product page.


Where can you use Vermiculite Spray (Cafco® 300)

Vermiculite fireproofing is most commonly used in the construction industry to fireproof steel materials but can also be used on concrete frames, metal floor and roof decks, return air plenums and air handling ductwork. Prime for dry environments, it is best installed in areas that are going to be covered up by a suspended ceiling or within a cladding system.

CAFCO 300 has been used for over 30 years in a wide range of educational, leisure and entertainment centres, multi-storey buildings, hospitals, airports, office towers and large commercial projects throughout Australia.

Some examples of commercial projects in Western Australia that used CAFCO®  300:

Vermiculite applied to beams and columns as well as Ducts.


What is an Intumescent Coating

Intumescent coating, also called intumescent paint and sealants are made from materials which expand when they are exposed to a heat source.  Passive at low temperatures, the material expands and swells when exposed to high temperatures. The significant volume increase (up to 25 times its original thickness) combined with the subsequent decrease in density slows down the heating of the substrate and prevents the steel structure from collapsing.
Cafco® SPRAYFILM WB3 is a water based intumescent coating consisting of polyvinyl acetate resins and fillers for the protection of structural steel. In a fire, a chemical reaction takes place causing the coating to expand and form an insulating layer.


Benefits of Cafco Sprayfilm® WB3

  • Thin and seamless finish
  • Quick application and easy cleanup
  • Fast drying time
  • Provide fire resistance for up to 120 minutes


How it is applied?

Intumescent coatings can be either spray applied with airless paint equipment or with a brush or a roller. Before applying the product to structural steel, the substrate must be blast cleaned and primed.
It is applied directly to the contour of primed I and H section columns, angles, channels, beams and hollow sections to provide fire protection for up to 120 minutes depending on the product and environment.

Promat water-based intumescent coating:

Cafco SPRAYFILM®  WB3 is supplied ready for use in 25kg drums. It must be applied on a clean, dry and free from dust, oil and other conditions preventing good adhesion.

It is important to apply the product in full compliance with the manufacturer’s recommendations, especially for the primer thickness measurements. The application methods are detailed in the product manual, available in the downloads section of the Cafco SPRAYFILM®  WB3 product page.


Where to use Promat Intumescent Coating

Intumescent coating systems consist of a primer, intumescent and top coat. They provide both protection and high-quality finish with no further treatment requirements. They are ideal where the exposure of structural steel is required as a part of the architectural design of the building.   It shouldn’t be used or specified in areas that require secondary structures or elements to be fixed to the fire protected structural steel. Examples where intumescent paint should not be used include; where window or door frames are required to be fixed to the structural steel, inside walls or above ceilings.  As a general rule, any structural steel with an intumescent coating applied requires a minimum clearance zone from any object of 50mm to allow the product to expand under fire conditions.

Example of commercial projects in Western Australia that used Cafco SPRAYFILM®  WB3:

structural steel fire protection



Vermiculite spray is generally more cost-effective than intumescent coating and is often favoured for budget considerations. However for aesthetic requirements, it is common for both intumescent paint and cementitious vermiculite fireproofing to be provided together in the same project.



Do both need primer?

No, Vermiculite spray doesn’t require primer and can be applied directly on steel, concrete frames, metal floor and roof decks thus saving time in preparation. Note that vermiculite provides no corrosion protection- if this is required a suitable primer should be applied prior to the application of vermiculite spray.

However, for steelwork, intumescent paints must be applied on a primed element. Before being coated with a compatible primer, steelwork must be prepared according to SA 2.5. If that is already the case, it must be cleaned and free from grease, oil, rust, dirt or any other contaminant that may inhibit the bonding.

The list of compatible primers, tested with Promat products, are listed on the Cafco SPRAYFILM®  WB3 product page.

How much does it cost?

Vermiculite spray is usually the most affordable solution, however, depending on the project requirements the price may vary and fire-resistant paint for steel or vermiculite spray fire protection might not be the best option. Please contact our team of experts for advice on what system is recommended for your project and get a custom quote tailored to your specific requirements.

Can you paint over intumescent coatings? And vermiculite sprays?

Yes, in fact, intumescent paint systems require top coats for the following reasons

  • Aesthetics
  • Protection of the underlying intumescent coating
  • Warranty purposes

External use of top coats is required due to high ambient humidity application.  Applying a top coat on intumescent paint provides protection to the structural steel element against environmental degradation.  Top coats should be inspected and maintained regularly in line with the manufacturer’s requirements. Refer to the product manual and application guide for the list of compatible top coatings.

A top coat is not necessary for cementitious coating such as CAFCO® 300, however, it can be painted for aesthetic purposes. Please contact our team to discuss this process prior to application.

How long does it take to dry?

Depending on the product, brand used and environment conditions, the drying time may vary.

The Cafco® SPRAYFILM WB3 water-based intumescent coating has a drying time of 6 hours if applied within a temperature of 5 °C and a curing time of 7 days.

CAFCO® 300 will obtain an initial set in approximately 3 to 6 hours depending on temperature and humidity. CAFCO® Accelerator can be added to the vermiculite spray mix to reduce the set time.

Do you provide training for the specification of promat products?

Yes. We are the technical consultants for Promat products in Western Australia and are experts in passive fire protection.
Our technical consultants offer training sessions for Architects, Engineers, Certifiers, Contractors on how to correctly specify, install, inspect and maintain our wide range of systems (Promat’s range).

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