Steve Howard of Neaco gives his view on why there has been a revolution in balconies and decking, with the dominance of wood being usurped by aluminium
Decking design is undergoing something of quiet revolution. For many years, two materials – timber and wood-polymer composites – have been the dominant options for flooring applications in gardens, terraces, balconies and external walkways. That duopoly has been broken in recent years however, by the rapid growth of an aluminium alternative. This change is due in no small measure to the demands of housebuilding warranty providers seeking to improve safety and durability. While not yet enshrined in Building Regulations, their technical guidance and performance stipulations have driven an undercurrent of non-statutory regulation, which architects and developers need to follow with equal diligence to meet the approval of key stakeholders. In a post-Grenfell construction world, fire safety is under the spotlight and rightly so. In truth, even before Grenfell, housebuilding warranty providers were already showing increasing concern about fire safety on decking and balconies. Balconies can be a life-saving means of escape from a burning building, and timber’s vulnerability to the outbreak of fire is one of various reasons why it has seen a dramatic decline specification in these locations. Wood-polymer composite is slightly more fire resistant, but having timber elements it will never be totally fireproof. This is where aluminium performs extremely well – it is fully compliant with Class 0 of Approved Document B ‘Fire Safety.’ In the EU’s harmonised Euroclass system, aluminium has an A1 Fire Rating – the highest achievable score for non-combustibility.
Another important aspect of safety is slip resistance. Even with a grooved surface, timber decking becomes increasingly slippery underfoot with the build-up of dirt, moss and grime. It can become especially hazardous in wet conditions. In contrast, aluminium is a versatile metal that can be precision-engineered to provide a very finely grooved surface for outstanding anti-slip performance in the direction of travel.
Lifespan is also a vital stipulation for housebuilding warranty providers. In the NHBC’s technical guidance, Clause 7.1.4a states that structural elements of balconies should have a desired service life of at least 60 years. This is problematic for timber, which is vulnerable to woodworm, damp, mould and rot. The guidance states that timber can be used to form raised decks if it follows one of two routes to compliance: it must be designed and constructed in full accordance with relevant guidance documents published by TDCA, or designed by an engineer in accordance with Technical Requirement R5 with a desired service life of 60 years. Architects can avoid jumping through all of those hoops by avoiding wood-based materials altogether and opting instead for aluminium, which is corrosive-free and has a recognised design life of at least 60-100 years. One report has suggested that it has an infinite lifespan in internal installations, and a minimum lifespan of 120 years in external installations. It provides a maintenance-free decking solution that avoids all of the cost and labour of ongoing treatment that are necessary to prolong the lifespan of its more traditional rivals.
Another clear advantage of aluminium decking is its structural efficiency – in other words, it is lightweight (a third of the weight of steel) yet high in load-bearing strength. Aluminium decking panels are typically around 16 kg per m2 or lower, compared to over 25 kg per m2 for leading wood-polymer composite products. This difference is increasingly important for cost reasons: due to fire safety concerns, steel joists are now widely used instead of timber joists, but steelwork is expensive so substantial savings can be made by using decking that needs less structural support. Many balconies conventionally use ‘positive drainage’ – a catchment tray that is installed directly below the decking, encased within a soffit and fitted with a hopper and drainpipe. It is cumbersome, costly and laborious to construct, and vulnerable to blockages caused by the accumulation of dirt, sediment and waste substances. Aluminium grille decking can facilitate an alternative ‘eaves drop’ drainage method which is increasingly favoured by housebuilding warranty providers. The rainwater falls directly into a ‘French drain,’ a ground-level trench comprising a perforated pipe, which is installed below the ground and topped by a layer of pea gravel. Surface water seeps between the gravel and passes freely through the pipe. It’s an efficient way to divert water away from the building and avoid pooling. Compared with positive drainage, aluminium decking with a French drain is a lighter, more economical combination, which is faster and easier to install. All things considered, it’s easy to see why wood-based decking is in decline. By specifying aluminium instead, architects and developers have found a way to fast track the compliance of their projects and, more importantly, improve the safety and performance of their buildings.
Steve Howard is the sales office manager at Neaco