Press Information
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| Issued: October 2008 |
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Advanced Façades
In an economic climate that is putting construction projects under increasing pressure, developers are being forced to find ways of minimising site programmes and reducing project costs. However, where building design is concerned, this must be achieved while maintaining both standards and performance. Rainscreen innovators have offered a solution to this challenge, by delivering new and advanced systems that are designed to bring down the cost of traditionally premium finishes, such as stone and terracotta. William Harwood, director, T.I. Dynamic Facades, discusses the drivers behind the development of these rainscreen systems and explains how they are already making a positive contribution to UK construction.
The nature of façade systems makes them a practical and cost effective choice, with early products selected almost exclusively on these factors. However, with architects increasingly pushing the boundaries of exterior envelope design, modern systems are now specified as much for aesthetics as they are for practicality. As such, façade innovators have responded by engineering systems that offer a high quality finish while retaining the affordability that has made rainscreen façades a preferred construction choice.
A Functional Choice
The primary function of a rainscreen is to protect the inner leaf of a building from wind driven rain and ultra violet light. While this is a major practical advantage, rainscreen cladding also helps to keep budgets down by making the speed of build more efficient and reducing the number of trades required for installation.
For example, the construction of a rainscreen enables one contractor to install the full building envelope. There is no need for a break in the site programme as the contractor can continue straight from the sub-wall to the outer-wall.
Natural materials such as stone and terracotta can be used with a range of building constructions, including metal stud, steel frame, timber frame and structural insulated panels (SIPs). Where metal stud or SIPs are used, these are generally fixed from floor slab to floor slab. The carrier system can then be directly attached to the wall and the rainscreen finish mounted on top.
Of all the structural walls, SIPs represent the most economical as they create a ‘through-wall’ construction that removes the need for additional cavity insulation, as it is an inherent component of the panels. As such, it further increases the efficiency of site programmes and offers superior acoustic and thermal insulation compared with standard frame constructions.
Designer Façades
While it is the sub-construction that provides a building with support strength, it is the façade that delivers the high quality finish for which a development will be recognised. For this reason, modern façade systems have been specifically developed to accommodate flexibility in design. As an exterior finish, rainscreen façades provide complete versatility and enable some of the most striking and unusual designs to become a reality.
There are many different types of façade systems on the market, offering a range of colours, textures, shapes and sizes. Although product innovation and local environmental factors have a strong influence on the popularity of these different systems, architectural trends suggest that natural materials such as stone and terracotta are the facings of choice.
The natural look and feel of stone and terracotta make these finishes a favourite at the specification stage, however, the inherent characteristics of traditional systems made them difficult to handle on-site. In response to the increased demand for natural finishes, façade innovators have engineered a new generation of rainscreen, helping to overcome barriers to use by making them more durable, lighter in weight and easier to install. Doing so culminates in a significant cost saving that puts a natural specification within reach of all development types.
Terracotta Choices
Terracotta has long been a favourite natural façade finish, owing to its ability to blend in with surrounding brick and mortar constructions. While early terracotta rainscreen systems used a twin skin tile, recent advancements have seen the launch of a single skin product.
As the single skin terracotta rainscreen is much thinner and lighter, there is a misconception amongst some specifiers that performance levels in terms of strength and durability will be compromised.
In fact the opposite is true, as the only complete terracotta rainscreen to be fully BBA (British Board of Agrement) certified, is a single skin system. This means it is proven to require little or no maintenance and its overall performance has been tested up to a height of 100 metres. Most twin skin terracotta rainscreens have only achieved elemental accreditation from the Centre for Window and Cladding Technology (CWCT), with the exception of just one, which is certified by the BRE (British Research Establishment).
The most advanced single skin systems weigh an average of 10kg per square metre less than traditional offerings. As well as ensuring health and safety legislative requirements are met, this also helps to significantly increase speed of installation. Moreover, because the tiles are a lot thinner, cutting is easier, which reduces the amount of wastage through breakages.
Compared to a twin skin tile that relies on thickness for strength, sophisticated single skin tiles achieve durability 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.
Stylish Stone
In the same way that terracotta rainscreens have been engineered to reduce the cost of purchase and increase the efficiency of installation, advanced stone systems have been developed to make a traditionally premium finish more accessible.
Although stone is naturally a durable material, to deliver the required performance levels and provide a viable exterior finish, stone façades have traditionally had to be approximately 40mm thick. The consequence of this is that the system generally takes longer to install, resulting in increased labour costs.
To help make stone more competitive, façade innovators have developed lighter weight systems that 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 fibreglass, aluminium or aluminium honeycomb backing. Stone facings are manufactured 6mm to 15mm thick and bonded to one of the backing systems, with the type of backing determined by the specification requirements of a project.
Sandstone, limestone, granite, slate, basalt and marble can all be manufactured in this way to achieve a durable, high performance finish, without the need for a stonemason. While this offers an on-site cost saving because it substantially reduces site programmes, it also brings the overall system cost down because less of the raw material is required per square metre. Importantly, this is achieved while delivering a finish that is indistinguishable from solid stone.
Intelligent Engineering
Whether a stone or terracotta finish is specified, key to maximising performance and preserving the aesthetics of the façade system, is the carrier rail.
There are two types of carrier system on the market – vertical and horizontal. While horizontal carriers have been in use for some time, vertical hangings are a more recent development, but offer a number of on-site benefits.
Compared with standard horizontal subframes, vertical systems significantly reduce the number of fixings required, and the fixings used are designed to be virtually invisible. As well as reducing the complexity of the installation, this preserves the aesthetics of the exterior finish. Ease of interface with other subframes accommodates flexibility in design, as a number of different materials such as render and glazing, can be used on the same elevation.
Engineered with ease of use in mind, some vertical carriers make it impossible for a tile to be fitted incorrectly. As well as offering peace of mind to the developer in terms of site safety, this also contributes to increasing the speed of installation, because it is much simpler to find the correct place for the tile.
Once installed, a vertical carrier gives greater flexibility in terms of tile replacement and removal. Individual tile access makes the installation of service lines at the end of a site programme straightforward, as the tiles are easily removed and then replaced, until the most appropriate point of entry is identified.
Urban Trends
As well as bringing down the cost of using natural materials, façade innovators have recently developed stylish urban glass systems, which are already proving as popular as more traditional finishes.
These high performance systems are available in high gloss or honed finishes to create a silk or matte look, which is extremely durable and impervious to staining. These systems are very versatile and, as well as being available in various panel sizes, they can be shaped and curved to clad pillars and create rounded corners.
As the façade industry continues to drive forward innovations that make systems as stylish as they are practical, the popularity of rainscreens as a preferred construction choice is look set to rise. Moreover, as these systems are developed with affordability in mind, rainscreen façades remain accessible to all types of development, across the full breadth of sectors.
