In large scale multi-storey projects, steel-framed construction is favoured for its design flexibility, fast construction, durability and more recently often due to its recyclability. The downside of steel is its sensitivity to corrosion, and in the case of a fire, if not protected from heat and flames, it has a drastically reduced load-bearing capacity. This can quickly lead to deforming of the steel, heightening the risk of building damage or collapse.

The application of a fire protection product to structural steel aims to slow the heating of the steel and maintain its load-bearing capacity for the length of time, or Fire Resistance Level (FRL), indicated in the building’s fire engineering report.

To make sure the right fire resistance solution is selected for structural steel, the following points need to be considered:

  • The steel members size, profile and dimensions
  • The placement of the steel and number of exposed sides
  • The required Fire Resistance Level (FRL) in the fire engineers plans
  • The critical temperatures used by the structural engineer in the design

The three most common fire protection solutions are Vermiculite Fire Sprays, Intumescent Coatings (or Thin Coat Intumescent Paints), and Fire Retardant Boards.

In this post, we want to deep dive into everything you need to know about Vermiculite Fire Sprays.

Vermiculite

Vermiculite fire spray consists of cement fibres, vermiculite and plaster. It is very effective at retaining moisture, and in the event of a fire, this moisture turns to steam, which has a cooling effect on the steel member, substantially delaying an increase in temperature.

In addition to steel members, vermiculite can also be applied to ductwork which often needs to be fire rated as ducts can be responsible for allowing the spread of fire and smoke between building compartments. Duct access panels are commonly encased with Fire Retardant Board to allow for future access to the duct for maintenance.

Application 

Vermiculite is typically applied as a spray and thus can be rapidly applied to large areas where cost and speed are critical.

Typically, vermiculite can be applied to treated steel without the need for a primer, but it can be applied over primers if required. Depending on the thickness of vermiculite required, a layer of reinforcing steel mesh, such as expanded metal lath or ripple iron backing, is fixed to the steel to ensure the integrity of the vermiculite.

Site Requirements

Typically fire protection is applied to structural steel once it has been installed onsite. During the application of vermiculite, our team requires exclusion zones to be set up in the work areas for OHS reasons. Our team requires clear access to all structural steel as well as water and 3-phase 32 Amp power to operate our machinery.

The areas of application must be dry, so clear weather conditions are required. A minimum substrate and ambient temperature of 4°C must be maintained before, during and at least 24 hours after the application of vermiculite. If the required weather conditions are not met, the application may be delayed.

Fire Resistant Levels (FRLs)

Vermiculite can meet Fire Resistant Level (FRL) requirements up to 240/-/- when applied to steel. On ductwork generally, an FRL of up to 120minutes can be achieved. To find more information on FRLs click here.

Finishes

Vermiculite doesn’t have the aesthetically pleasing finish of the other fire protection products, such as intumescent paint or fire-retardant board offer, and its finish is bold and textured. A smoother finish can be achieved by lightly troweling during spraying, but not all fire protection companies offer this, and it does come at an increased cost, so it’s best to discuss this directly with your provider.

A surface coating can be applied to vermiculite to increase its aesthetic with dark colours generally being chosen as it can improve the visual aspect more so than lighter tones. It is important to note that due to the absorption characteristics of vermiculite, it is not always possible to guarantee a uniform appearance of finishing products.

Cost

What vermiculite lacks in its finish it makes up for in low product costs and speed of application. Depending on the size of the project, a rough cost of vermiculite per square metre is $50-$70, though very large projects, with larger steel members and clear access early in the project programme, can see costs as low as $34-$44 psm. On the other hand, very small jobs such as patch-ups and repairs will incur a minimum daily charge based on labour and product costs. Don’t hesitate to speak to our team if you require more specific pricing for your project budget.

Vermiculite Pros and Cons

With all fire protection solutions, there are benefits and limitations. The pro’s and con’s of vermiculite include:

Pros

  • Often the cheapest option
  • Very malleable, so can be used to fill tough to reach spots
  • Fast application

Cons

  • Can only be applied to internal members
  • It is brittle and can be chipped off
  • It is not possible to fix anything to members coated with vermiculite (e.g. walls/window frames etc.)
  • Its finish and appearance is not considered aesthetically pleasing
  • Messy application
  • Lengthy onsite cleanup*

*It is important to note that ProFinish has invested heavily in new technology that removes the need for onsite cleaning of the hopper – which typically causes a lot of mess on site. The only cleanup required, which is done by the PROFINISH team, is of overspray and droppings from the application.

Common mistakes we see

At PROFINISH Fire Protection, we work on many projects and often see mistakes when it comes to fire protection. Here are a couple of common mistakes we see when it comes to vermiculite:

  • The use of vermiculite on structural steel members that also need to be fixed to walls etc. In these instances, we would recommend the use of intumescent or fireboard. At a minimum, the designer must allow for heat transfer on any adjoining steel.
  • Delaying the application of vermiculite. This can slow the process down A LOT as it introduces a range of site access issues which result in extra time to complete the work and higher fees that could have been easily avoided. The best time for application is right after the steel frame has been erected. Any damage caused by others after application can easily be touched up.

Considering vermiculite for your project?

Vermiculite has many advantages over other types of fire protection products, and knowing how to correctly specify vermiculite in a project’s design can reduce project costs and help to avoid construction delays onsite.

PROFINISH Fire Protection is one of the few certified full-service applicators of passive fire protection solutions in Australia.

Discuss your project’s specifications with the expert team at PROFINISH Fire Protection who have intimate knowledge of passive fire protection products and can provide you with competitive quotes, helpful information and back it all up with exceptional service.

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