Designing the exterior of a building has always been more complicated than it first appears to passers-by.
Cladding material, in particular, will play a large part in an architect’s vision, although it is only one aspect of the external envelope. There are a wide range of cladding materials, so architects need to be well-informed on products. Many existing buildings are also being considered for recladding as they don’t comply with fire regulations.
This doesn’t mean the death knell for design though, as manufacturers are coming out with more and more products that offer cost-effective alternatives to achieve that architectural flare.
The most important things to think about when cladding or recladding is the fire performance of products, as well as the aesthetic. Reducing fire risk is the number one consideration. While there is no limitation on colour choice, the cladding will have been tested for fire safety, but the exact colour the architect has specified might not have been.
Cladding considered
There are many elements to choosing the best cladding system to suit a building and its community. Offsite manufacture of façade materials means manual handling, overcrowding onsite and equipment needed are all reduced.
When we consider aluminium over other materials, for example, we take time to understand the cost, the speed
of installation and tolerance available. A flat sheet aluminium panel system is quick to manufacture and install, where the main saving is found in time saved onsite.
From a specifiers point of view, cladding system products need to be rated A2-s1, d0 or A1 to EN13501-1 under regulation 7.2 of the Approved Document B, but it’s important to look further into the testing systems. A manufacturer’s own fire report may not have sufficient rigour, so investigating for example, whether a test house is UKAS accredited, panel thickness is covered, colours are covered and cavity or substrates you will be using, is vital to ensuring safety all round.
Wind testing is not called for in Document B, but it would be prudent to test all cladding systems for wind, so it matches up to the project that is being designed.
When considering cladding it important to review applicable building regulations for the region, which may vary from the regulations in England. For example, Scotland’s regulations differ from the 18m in ADB to 11m height. The Scottish regulation also states A1 or A2 material can be used for cladding, with no reference to S or D.
Avoiding the pitfalls
The risk of choosing the wrong cladding system can mean higher costs onsite, as well as risking the safety of residents in the future. A recent project to reclad a building in London changed the façade and insulation layer in order to install fire barriers that were previously missing. When a fire broke out at the building there was no fire spread throughout the façade, because the new materials were all correctly installed and rated A2-s1, d0 or A1.
If correct products are used in the correct way, we can avoid problems throughout design, build and occupation. If we keep to the Document B mandate and in particular regulation 7.2 regarding fire ratings throughout, we can’t go wrong.
Architects can avoid pitfalls from design to delivery by avoiding these complications early in the design process. In choosing cladding, you need to consider costs as well the ability of the structure to take the weight of the design. At this early stage, getting involved with manufacturers and suppliers means architects and designers can check a product is a good option. Early collaboration saves on cost further down the line, especially in conjunction with checks that the architectural vision meets regulations and performance criteria.
So, it is vital that manufacturers provide architects with a range of choice within the boundaries of possibility and safety – this ensures a great result in meeting the vision and providing a safe home for residents.
“…cladding system products need to be correctly installed and rated A2s-s1, d0 or A1…”
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