EXTERNAL ENVELOPE Pushing the envelope


John Nolan of Generix Facades looks at the importance of a robust approach to testing the structural integrity and capability of facade systems


H


aving a solid understanding of how a facade system will perform prior to construction is


crucial for architects, consultants and building specifiers. The Centre for Window and Cladding


Technology (CWCT) is one of the UK’s leading authorities in the field of glazing and building envelopes. Based in Bath, the centre helps to set and regulate industry standards in building envelope design and construction.


The centre offers a varied range of information which apply to different aspects of a building design. The CWCT Standard for systemised building envelopes was published in 2006 and is applicable to curtain walling, walls with ventilated rainscreens, and overhead glazing. Notably, both the National Building Specification (NBS) and the National House Building Council (NHBC) standards use the centre’s ‘Standard for curtain walling’ and ‘Standard for walls with ventilated rainscreen.'


What is rainscreen CWCT testing? A rainscreen test – or as it’s officially titled, a CWCT Sequence B Facade Test – is designed to test the serviceability and durability of a facade system in accordance with the appropriate standard (CWCT Standard for Walls with Ventilated Rainscreens).


A facade system is fixed to a full scale rig at a UKAS accredited testing site, and once the system has been installed it is put through a series of tests that determine serviceability. These tests focus on:  air leakage  dynamic pressure  water penetration  impact.


Test 1 –Water penetration – dynamic To measure water penetration, water is sprayed continuously at the facade for 15 minutes. An aircraft engine is used to provide direct wind force.


ADF APRIL 2021


73


Genbrix mechanically fixed brick slip system from Generix Facades undergoing water penetration, wind resistance and impact testing


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