February 2008
Practically stylish
Rainscreen cladding systems are a popular construction choice because they offer a practical build method that is both efficient and cost effective. In recent years there has been a sharp rise in rainscreen specification, a pattern that has emerged alongside advances in façade technology. These innovations have made increasingly stylish finishes available, resulting in rainscreens being specified as much for aesthetics as they are for practicality.
The primary function of a rainscreen is to protect the inner leaf of a building from wind driven rain and ultra violet light. While early façade products were selected based on achieving this primary objective, more modern systems enable the specifier to push the boundaries of the building exterior and at the same time fulfil the practical requirements of a development.
Natural materials such as stone and terracotta are particularly favoured, although historically remained the preserve of only the most premium of developments because of their high purchase cost and labour intensive installation.
Responding to market demand, innovative façade manufacturers have risen to the challenge and made these natural systems more affordable. Advances in material manufacture and system installation have created a new generation of terracotta and stone facings, which are set to further increase the popularity of rainscreens in modern construction.
Stone matters
To help make natural finishes such as stone more competitive, façade innovators have developed lighter weight systems which are durable and easier to install than conventional constructions. Where stone is concerned, this has been achieved by creating a facing that is reinforced with a high strength fibre, aluminium or aluminium honeycomb backing. Stone facings are then bonded to one of the backing systems, with the type of backing determined by the specification requirements of a project.
The intelligent engineering of the backing has afforded a significant reduction in the stone thickness required. While traditional natural façades demanded the stone to be approximately 40mm thick, in order to deliver the strength required and to withstand aggressive environmental conditions, modern systems now range between 6mm to 15mm, according to application.
Sandstone, slate, limestone, granite, basalt and marble can all be manufactured in this slimline way to achieve a durable, high performance finish, without the need for a stonemason. By making the products easier to manage onsite and quicker to install, site programmes are substantially reduced, delivering significant cost savings. Overall system cost is also brought down because less of the raw material is required per square metre.
Modern terracotta
At the same time as advances in stone facing technology, new terracotta systems are emerging which make the system a natural choice for all types of development. Historically, twin skin tiles have been necessary to deliver the required impact performance. However, new systems launched to market are removing the need to use a twin skin design because technological advances have made the lighter weight single skin tile a viable option.
Increased strength and durability is achieved through an innovative manufacturing process. A porcelain base baked at a high temperature significantly reduces the water absorbency of the system, making it more resistant to the freeze/thaw phenomenon that causes some silicon sprayed alternatives to fail.
The precision calculated carrier systems of these modern terracotta systems offer complete design versatility as well as fast installation. To accommodate the full range of design requirements, they are available in module sizes ranging from small, typically 150mm x 400mm, to very large at 300mm x 1,200mm.
Large format panels deliver the clean finish demanded by many premium developments, and remain easy to install owing to the sophisticated carrier system and minimal weight of the tile. At the same time, smaller tiles provide a cost effective solution for breaking up the monotony of a lower end finish, such as render. This is because the vertical carrier system will easily integrate with the primary frame of most alternative exterior finishes.
Emerging trends
Already a popular choice, the adoption of the rainscreen as a preferred build method is set to continue, now cost is not the barrier to its specification that it once was. Moreover, the increasingly stylish finishes, which include a wide variety of materials, surfaces, colours and panel sizes, make natural rainscreens a flexible specification. Whereas early façade systems were more commonly used in urban areas, the lightweight stone systems also make rainscreens a viable construction option for more rural developments, where the building material must be in keeping with the external environment.