The structural performance of cladding is typically assessed by comparing an equivalent panel with a non-cladded panel. A typical coating system is typically rated in terms of the specific resistance (Rf) of the coating to structural loads, usually by looking at the mean of the rated values for a building and the estimated physical maximum of that building.
However, a single coating system can have several components. For instance, if one coating system has a structural limit of Rf 10 and another has a structural limit of Rf 30, the current rating system will calculate the maximum temperature rise between Rf 10 and Rf 30. Therefore, the rated values are not a precise representation of the performance of a complete cladding system.
“If you are using different components in different applications or different systems in different buildings, these ratings are quite meaningless. You need to compare the total performance for the whole system, in other words how the components behave, given the requirements of the system,” Richard Fitzpatrick, technical manager for the structural products sector at the Building Research Establishment, told the EBS.
Cladding systems are assessed
“Cladding systems are assessed and rated in different ways. You can put the best CLADDING in a structure that has maximum performance for cladding and other systems, such as insulation or circulation, can be rated in a different way, which might be quite different.”
The draft version of the Brexit framework for trade has a completely different approach to cladding: “all materials or components needed for the construction of such structures and facilities shall be eligible for equal treatment with respect to registration under the EU” – see Brexit Britain proposes that materials or components used for the construction of such structures and facilities, or parts thereof, shall be eligible for equal treatment with respect to registration under the EU.
The EC has allowed the UK to treat cladding in a different way than these regulations, because a recent study of cladding materials in England and Wales found that certain cladding materials applied in buildings are not appropriate for their intended purposes and produce a non-structural material impact.
Meanwhile, the EU has produced a guidance note for members about the next steps on cladding standards. “Cladding systems are not suitable for all buildings,” the EC states.
