Update August 2025
Earlier this year, CROSS reported further cases of failing bonded brick slips. See here for details.
Evidence is needed to better understand the level of potential risk associated with bonded brick slip systems. If you have any experience of this, please share the information with CWCT, or submit a report to CROSS.
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
Alexis Harrison - September 03, 2025
I am a clay materials expert from the Materials team at Arup, and have investigated several brick slip system failures, as well as designing various ceramic-based cladding systems. I have previously provided evidence to CROSS, the Building Safety Regulator and CWCT on these issues.
The most frequent failure mode I have seen is fatigue of the key components of adhesively bonded brick slip systems. For example, many systems feature (fired clay) bricks slips adhesively bonded to a substrate board, where I have commonly seen adhesive and/or cohesive failures of the materials, typically after around 8-12 years of service. This is most likely caused by differential thermal and moisture expansion of the components, and/or deflection of substrate boards (such as fibre cement). In addition, as brick slips and pointing mortars are porous, the adhesives are subjected to frequent wetting, leading to hydrolysis of the adhesives.
Having reviewed the independent product certification schemes (e.g. Agrement Certificates) of the systems I have investigated, I have found the scope of testing to be wholly inadequate in many cases.
In general, my advice is to avoid adhesively bonded systems altogether, and there are now a wide range of mechanically fixed systems available as alternatives.
The advice given in the CWCT article above must be followed for mechanically fixed systems as well though – I have recently become aware of issues around broad size tolerances in the engagement slots cut into brick slips which engage into cladding rails being excessive in some cases, which may lead to brick slips falling from height, as well as lack of integrity in the systems prior to pointing.
I wrote the following LinkedIn article in 2018 on brick slip cladding and will be providing an update in the coming weeks so please do follow these to keep up to date: https://www.linkedin.com/pulse/brick-slip-cladding-systems-safe-alexis-harrison/
Claudia Farabegoli - January 22, 2025
in order for an existing fire certification to be relevant and applicable it needs to clearly identify the amount and type of bonding agent used in the fabrication of the prototype(s) tested, and the production must have a good QA/QC procedure to confirm that the final assembly meets the limits of the field of application. I’ve also seen fire certificates that did not quite say if the test was carried out from one side/which one….
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