In accordance with the CWCT standards and supporting documents, yes, redundancy should be provided. However, in accordance with the Building Regulations, the requirement is only to provide information about whether the fixing in question provides redundancy or not. It is therefore a legal requirement to confirm whether a fixing to structure is redundant or not for cladding.
Technical Note 90 states:
“The Approved Document to Part A of the Building regulations requires cladding fixings to be able to transmit loads on the cladding to the primary structure. In considering the safety of fixings account should be taken of whether the fixings are redundant or non-redundant but non-redundant fixings are not prohibited.”
However, Technical Note 90 continues:
“The CWCT Standard (2006) requires that fixings shall be designed such that failure of any one connection does not lead to progressive failure of adjacent fixings. Fixings are defined as components providing the attachment of the structural frame (of the cladding) or brackets to the primary structure or backing wall.
This may be achieved by:
Ensuring that any group of fixings is capable of carrying the load with one fixing failed.
Ensuring that the wall can transmit loads to brackets adjacent to a bracket that fails.”
If, against CWCT guidance, non-redundant fixings are employed, it is worth noting that meeting the minimum legal requirement of reporting the status of a non-redundant does not absolve a designer from their obligations towards providing a safe structure under either the Building Regulations or the Construction (Design and Management) Regulations.
Revision 1, 25 May 2023