Reports of small-scale facing components failing from cladding systems have been recorded. These systems do not necessarily fall within the existing guidance provided by the CWCT, however, as with all components, the designer remains responsible for ensuring that the selected components and systems are fit for purpose. The reported failures highlight potential issues with some of these components and/or systems.
Exercising caution around the use of bonded connections is clearly requested in the CWCT guidance, often requiring safety factors far in excess of those for bolted or welded connections etc. Although the guidance was not specifically written with bonded brick slip systems in mind, the bonded connection of a system regardless, should also be given appropriate consideration.
A number of brick slips falling from height have been recorded by CROSS-UK, with ‘de-bonding’ being highlighted as the failure point. This type of failure may not present in general load testing, and consideration of other aspects is essential, for example, the impact of freeze/thaw cycles, wetting/drying of the system and cyclic wind loading could all be factors that affect the system (especially the bonded element).
It is also important to understand that Agremént certificates and similar are a record of tests undertaken, not suitability of a system for a specific use case. The content of these certificates needs to be assessed to ensure that all required tests are contained within the certificate(s) to suit the application. If they are not present, these additional requirements need to be addressed. Certificates of this type do not absolve any specifier from responsibility to ensure all requirements of the system are met, whether or not they are present in the certificate.
These types of system can be used, if all the relevant tests and investigations have been recorded and demonstrate suitability of the product for the intended project.
Finally, we would also urge those who are aware of these types of failures, to report them. If this needs to be done anonymously, CROSS-UK is set up to receive this information with full anonymity for the reporter.
At the time of writing, CROSS-UK has published the following reports on bonded brick slip failures:
Revision 1, 25 May 2023
Jim Rowley - October 29, 2024
This is a good thread and one that has been debated many times. There should be a risk assessment carried around the application, i.e. extent of the application, height of application, performance evidence etc. In most cases this would drive towards a mechanically fixed solution, but there are some cases whereby a bonded connection can be appropriate. Regards the bonding, it is the control of the environment and the substrate condition/quality which is most critical and often the most difficult to achieve, especially if undertaken at site. For systems bonded in controlled factory conditions (as is the case with structurally bonded insulating units), the risk is reduced and the resulting bond is usually stronger than the materials themselves. Regarding the reaction to fire of adhesives, there are suitable Class A products commercially available.
Dan Gleeson - October 25, 2024
Additionally to the points Robert makes, its also worth considering this application under a fire load for higher risk buildings and relevant buildings. If bonding brick slips you must consider if this is combustible? if so what classification does it achieve to 13501-1, and if A rated, is the adhesive thinner to get the required calorific value?, will this increase the risk of detachment? If the reaction under the fire load is that brick slips detach, there is a potential risk to people exiting the building or fire fighters entering the building so this should be considered…
Robert Simcock - October 25, 2024
This is a good point to discuss; For external facades, SRM will not consider bonded brick slip without any mechanical restraint. Its too much of a risk in terms of longevity (even if there is test data). If there is a detachment it would have serious ramifications in terms of making the area safe and undertaking corrective measures and/or verifying the other slips are secure. We do not believe this risk is worth it and specify mechanically fixed slip only