Fire Resistance in Construction Sealants

Approx read time: 5 minutes

Fire safety is critical in building construction, especially in high density residential and commercial/high rise buildings. 

Beyond the active systems – smoke detectors, sprinkler and suppression systems – passive systems must be factored into the building’s design to mitigate the potential for fire to spread. These include non-combustible materials such fire rated doors, plasterboard and cladding. 

It is crucial from both a legal and obligation stance that the correct materials are used in the project. 

If incorrect materials are utilised, the outcome can be dire as witnessed a few years ago in the Grenfell Tower in West London. Further, the legal and financial ramifications can be crippling. Ignorance and/or neglect is not tolerated by the courts.  

Therefore, it is critical to consult with fire consultants and engineers to ensure that the correct materials are specified and implemented. The product must meet or exceed the fire rating for the project and more importantly should be certified as having passed the relevant testing. 

In addition to these fire resistant building materials, the sealant used to fill the gaps between substrates is just as important. An intumescent sealant that swells when exposed to heat provides a better seal and protection for the building materials surrounding it.  

With that in mind we have two great offerings from HB Fuller in their fire rated sealant range: The newly developed (flagship) FulaFlex™ FR hybrid polymer sealant and Firesound, an acrylic based product suitable for a variety of applications including plasterboard and concrete walls. 

FulaFlex FR – Fire Rated Wall Joint Sealant 

FulaFlex FR is a high performance, elastomeric and intumescent hybrid polymer construction joint sealant. It has been tested with up to 4 hours rating in accordance with AS1530.4-2014 in joints from 10mm to 50mm wide. 

Its low modulus properties offer a very versatile flexibility (+/-25% joint movement capability); great for interior and exterior joint sealing applications where a high degree of movement may be present – typical with high thermal expansion. 

FulaFlex FR cures to form a durable, permanently flexible and highly weather resistant sealant with negligible shrinkage and excellent adhesion to a wide range of substrates. FulaFlex FR is a hybrid polymer sealant that carries a non-hazardous classification and is solvent and isocyanate free and low in VOC.  

You’ll find that it is very easy to apply, tool off and clean up. It also cures exceptionally well compared to other technologies such as polyurethane. 

Why choose a hybrid polymer sealant over polyurethane 

Hybrid polymers have many benefits over other technologies, such as polyurethane, include faster skinning, excellent cold weather gun-ability with bubble free curing in hot/humid climates. Also, being solvent free it’s safe to use in confined spaces as it is non-hazardous, non-toxic and virtually odourless. And best of all, hybrid polymers will not blacken hands. 

Easy to Apply and Tool Off 

With excellent UV stability and weather resistance this sealant can be applied to damp surfaces and where a sealant is required that is unaffected by rain exposure early in the cure phase. FulaFlex FR is ideal for sealing interior/exterior construction joints in concrete panels, block work, brickwork and fire-rated plasterboard and is paintable once cured. 

Remember to consult relevant fire test reports for specific FRL’s relating to installed minimum wall thicknesses and joint designs and always check certification requirements or consult a fire engineer before use in a fire rated application. 

Key Features 

  • Fire rating up to 4 hour for wall joints 10 – 50mm wide  
  • Excellent flexibility; ±25%, UV stability and weather resistance  
  • For interior/exterior use  
  • Paintable  
  • Can be applied to damp surfaces  
  • Solvent and isocyanate free  
  • Water and acrylic free 

Key Benefits 

  • Developed and made in Australia 
  • Tested in Australia (to meet Australian Standard AS1530.4-2014) 
  • Skins in 40-50 mins – nearly 2 ½ times faster than Polyurethane sealant 
  • Easy to gun out and tool off in all weather conditions especially very cold or hot and humid 
  • Will not shrink or sag during curing process 
  • Solvent and isocyanate free – virtually odourless, non hazardous and no toxic fumes 
  • Safe to use in confined spaces 
  • Will not stain hands like with PU (black hands) 
  • Bubble free curing in all conditions – unlike polyurethane which may bubble in hot and humid conditions 
  • Very low VOC (<30g/L) 

Firesound – Fire Rated Acoustic Sealant 

Your other option in fire rated sealants is Firesound: a premium quality, flexible, water-based construction sealant that acts as a barrier to the passage of both fire and sound through construction joints and service penetrations. It’s compatible with a variety of substrates including concrete, aerated concrete, block work, brickwork and fire-rated plasterboard. 

Firesound has been tried and proven in Australia and overseas for many years. It has been extensively tested to the current standard – AS1530.4-2014 offering up to 4 hours fire rating in myriad configurations in joints up to 50m wide. 

You’ll find working with Firesound a pleasure. As an acrylic sealant it is easy to apply, tool off and clean up.  

Key Features 

  • Fire rated for up to 4 hrs in joints up to 50 mm  
  • Good flexibility – accommodating up to ±20% joint movement 
  • Paintable 
  • UV Stable 
  • For interior/exterior use  

Key Benefits 

  • Developed and made in Australia 
  • Tested in Australia (to meet Australian Standard AS1530.4-2014) 
  • Intumescent; expands to compensate for deflection of building elements that result from exposure to extreme heat or fire 
  • Non-hazardous, free from solvents, isocyanates and asbestos 
  • Excellent acoustic performance; low shore A hardness and high density formula achieving up to Rw 65 (-2;-5) when tested in accordance with AS1276.1 
  • Low VOC Green star project compliant sealant, 31g/L (SCAQM Rule 1168.) 

So which one should you choose? 

Both sealant products are premium grade, high performance sealants that are almost equally capable in most situations. Both have been engineered and made in Australia and tested locally to meet Australian standards. And both offer 4 hours of fire rating in similar joint widths.  

Due to its longevity in the market Firesound has received more testing in a greater variety of situations, substrates and with service penetrations. 

As an elastomeric hybrid polymer sealant FulaFlex FR is more flexible and resilient to movement as well as environmental and climatic factors during curing – i.e. washout. 

While both sealants are suitable for both internal and external joints, if your project and budget allows you may find that FulaFlex FR performs slightly in external joints. 

Ultimately what is most important is that if the sealant you choose is intended to be used in a fire rated application that you check certification requirements or consult the relevant certifying authority before use. 

Shop online for Firesound

Shop online for Fulaflex FR