In building and design, sealants are similar in criticality to waterproof walls on a tent- without this extra layer of protection keeping water and other elements out- your structure is somewhat useless.

Selecting a quality sealant that will last the 10 years (and more) that it is supposed to, requires all round knowledge of the sealant and substrate physical and chemical properties and also an understanding of joint design and the effect movement will have on your sealant.

Whilst most large construction projects will have standards for sealants clearly specified on plans, smaller projects aren’t always afforded this luxury.

So, if you should find yourself in the latter situation, here are four main points to consider when selecting your sealant:

Joint design

In construction, sealants are used to close gaps between adjacent building materials such as steel and glass or wood and concrete. Naturally, as the materials expand and contract in response to changes in temperature, humidity and other conditions, the sealants are regularly stretched, compressed and pulled in different directions.

Therefore when choosing a quality sealant designed and tested to cope with these movements, joint design must match up with a sealant's movement capabilities.

Physical and chemical properties

Properties of the sealant such as, modulus of elasticity, its stress/strain recovery characteristics, tear strength, and fatigue resistance are all factors that influence sealant performance in a joint.

However, when choosing a fire rated sealant, the stakes are higher. Choosing the wrong sealant in applications where a four hour fire rating is required, can in the worst case scenario result in loss of life. But even during the certification process, any product that cannot prove its certification with comprehensive test results will not be signed off by a certifier. The offset of this can be time-consuming and financially costly for everyone involved.

Durability properties

Degradation of the substrate due to ultra-violet radiation, humidity, and temperature and in turn - cyclic joint movements, all influences the service life, resistance and aging characteristics of any sealant.

Whilst you can’t control the environment, you can control how well your sealant will hold up against adverse conditions, by selecting a durable sealant product appropriate for its function and environmental exposure and ensuring that the application is carried out correctly.

Application/installation properties

Important considerations include the consistency of the sealant (pourable or gunnable), tooling time, tack free time, application temperature range, and low temperature "gunnability”.

Sealants used for interior applications, even in high-rise or light commercial structures, will have needs different from those used in other applications, such as structural sealant glazing or exterior building facade seals.

Often -when it is not necessary- a polyurethane sealant is used internally when really, an acrylic could have been used. Unfortunately, this also works in the opposite way, and acrylics (non-fire rated) will be used externally at great risk.

Fireban One from Bostik is a fire rated sealant, comprehensively tested to AS 1530.4-2005 for up to 4 hours fire protection.

It is a one-part polyurethane gun grade mastic with 50 per cent joint movement capability, designed for sealing joints and wall penetrations subject to high movement and high humidity.

Fire One sealant features excellent adhesion to metal, wood, plasterboard and all masonry, is paintable, non-staining and water and weather proof.

When in doubt as to what sealant to choose, it is always best to consult with someone who is knowledgeable on the standards in relation to the application.

For more information on Fireban One, its application uses and specifications fill out the form below.

Architecture & Design Team

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