Tech Update: Overview of Site Testing for Water-Tightness of Facades


Site water testing can be used both during the construction phase to test the performance of a façade element or after handover to identify a water ingress route in a failed system or interface.

Many components involved in cladding are tested for water-tightness in the laboratory or on a large scale off-site mockup to ensure the system elements can attain the performance levels required for the buildings site exposure, topography, scale and height. However, the cladding system installer is reliant upon the system fabricator to manufacture the product correctly, and are themselves responsible for correctly and robustly preparing and applying tapes and sealants to the system interfaces in a manner that can accommodate any site tolerances and movements.

To check the fabrication and installation have produced a robust solution it is important to site test a percentage of a completed cladding system to check both the system and the interfaces. On site testing can also be used to check interfaces that may not have been included in the projects large scale mock up.

An industry standard is for 5% of all fixed joints (non-opening) to be tested. Testing should be commenced in the earliest stages, to identify issues as early as possible, but should continue throughout the construction of the envelope to ensure that quality is consistent.

As with any testing, it is important that the correct test is selected, and that it is applied in accordance with the test standard. Inappropriate testing could lead to misleading results which in turn could mean that system or interface failures remain undetected, leading to costs for both remediation measures and consequential damage. This blog aims to provide some key points on site testing for water-tightness.

Frame of Reference

A frame of reference is only applicable to projects where a large scale mock-up of the project has been created offsite and has undergone some form of water testing regime, such as the ones included in the CWCT sequence B test sequence for facades.

Once a site test procedure(s) has been selected for the project it is beneficial, if at all possible, to carry out the same test on the offsite project mock up. By doing this you can ensure that the system, as designed, is capable of passing the test and that time and money is not wasted on site testing a system using a procedure that it is impossible for it to pass. This provides you with a frame of reference.

Where a system has passed the appropriate British / European test standard for that system in the laboratory or an off site mockup, but then fails to pass the proposed site test on the same mock up specimen it is possible to adjust the on-site test parameters until these adjusted parameters facilitate a pass.

Specifying and Witnessing Site Tests

Non-specialist specifiers should always seek advice from UKAS accredited test laboratories or cladding consultants on how to specify and witness tests.

For details of the different types for water-tightness tests for facades, click here
For more information on facades and cladding visit the CWCT website. 


Please Note: Every care was taken to ensure the information in this article was correct at the time of publication. Any written guidance provided does not replace the reader’s professional judgement and any construction project should comply with the relevant Building Regulations or applicable technical standards. However, for the most up to date LABC Warranty technical guidance please refer to your Risk Management Surveyor and the latest version of the LABC Warranty technical manual.


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