The importance of bond breakers
What is a bond breaker and why would you use one?
A bond breaker, as stated in Australian Standard 3740 is a “system that prevents the membrane bonding to the substrate, bedding or lining”. It literally breaks the bond between the substrate and waterproofing membrane to create an elastic ‘bridge’ that can stretch as buildings flex and move.
Bond breakers are applied in joints where walls meet floors or two walls meet in a corner. They are also used over movement joints. These are points that are most likely to experience flex and movement, and the hardest to get a proper seal with the membrane without a bond breaker.
Normally a bond breaker would be either a silicone applied by caulking gun, tape – either applied by placement under the waterproofing membrane, or a self adhesive tape. If gaps are large then backing rods are available in a range of sizes. Once the bond breaker has been applied and allowed to cure, the waterproofing membrane can be added over top.
Choosing a bond breaker
It is important that the correct bond breaker is applied in each situation. The compatibility between bond breaker and the covering membrane needs to be considered depending on the elongation properties of the selected waterproofing membrane.
- Class I membrane requires a 75mm bond breaker
- Class II membranes require 35mm bond breaker
- Class III membrane will require a 12mm bond breaker
Keeping this in mind will help understand if a silicone or backing rod is more applicable for the required joint.
The other consideration is whether a neutral cure silicone is more suitable than a PU. Many installers like to us a PU but these take longer to dry and must be fully cured to ensure there is no gassing off that happens below any water-based membrane. Both PU and silicone must be suitably cured to ensure the membrane does not stick which negates the use of the bond breaker in the first place.
Bostik bond breakers
Depending on the waterproofing membrane that will be applied from our Dampfix® range, we offer a variety of bond breakers including:
- SILICONE: Bostik V70 or Bostik 6S
- TAPE: Dampfix Instant Seal or Bostik Bandage
- POLYURETHANE: Bostik Seal 'N' Flex® Façade
While they might seem like a small and insignificant part of the job, bond breakers are important to the overall integrity of a waterproofing job, and should not be overlooked.
Need help with choosing a bond breakers? Contact our technical team on 1800 BOSTIK (267 845) for assistance
