Bond breakers – what are they?
All current Australian waterproofing standards including AS370 for Internal Wet Areas and AS4654.2 for External areas (above ground) reference the requirement of bond breakers for critical movement areas. These include wall/floor junctions and dedicated movement joints including expansion and control joints.
They play an important role in ensuring the success of the waterproofing system, but exactly what is a bond breaker and why is it required?
A bond breaker, as stated in Australian Standard 3740 is a “System that prevents the membrane bonding to the substrate, bedding or lining” But why wouldn’t you want the membrane to bond to the surface? Take a wall/floor junction for example, the most critical movement joint and source of most waterproofing failures. Having a membrane fully bonded at this point would put all of the associated movement stresses directly on the membrane. A bond breaker is therefore employed to minimise the stresses by providing bond relief and ensuring proper functionality of the membrane.
Types of bond breakers.
Bond breakers can be flexible sealants like silicone or polyurethane, bond breaker tapes, fabric mesh or foam rods.
The type of bond breaker required under the abovementioned standards is dependent on the elongation properties of the selected waterproof membrane. Basically the less flexible the membrane, the more bond relief or the bigger the bond breaker required. The classification of waterproof membranes based on their elongation properties are as follows:
Class 1 – Low extensibility – Elongation at break between 10% and 59%
Class 2 – Medium extensibility – Elongation at break between 60% and 299%
Class 3 – High extensibility – Elongation >300%
The specified minimum bond breaker tape/tape width for wall/floor junctions for each class of membrane has been designed to accommodate the joint opening up by 5mm
Class 1 – 75mm tape with backing rod
Class 2 – 35mm
Class 3 – 12mm
Gripset bond breaker systems:
Critical to the success of Gripset waterproofing systems is the Elastoproof Joint Band, a modern day advancement in bond breaker technology. It has revolutionised the waterproofing industry by enabling significant time efficiencies and providing a far more robust and durable system for critical movement areas. It has also removed compatibility issues and extended curing times associated with traditional sealant based bond breakers. Furthermore the Elastoproof Joint Band is compatible for use with all 3 membrane classes.
The success of the Elastoproof system lies in its simple design. It is constructed of a unique grade of rubber that has high elastic recovery, flexibility and high tensile strength, it is completely waterproof, vapour proof and durable. So while not only providing the function of a bond breaker, it further enhances the waterproofing system by providing an impermeable barrier at the most volatile areas.