Press Information
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| Issued: February 2008 |
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The Great Rainscreen Debate: Twin Skin Versus Single Skin
Advances in rainscreen cladding technology have enabled designers to push the boundaries of what can be achieved with the building envelope, bringing increasingly innovative finishes to market that are as stylish as they are practical. While natural rainscreens made from terracotta and stone and have risen generally in popularity, it is the terracotta systems that have experienced the most rapid rate of adoption. William Harwood, T.I. Dynamic Facades, discusses why this is the case, and debates the relative benefits of using a modern terracotta single skin product over the more traditional twin skin tile.
The launch of the original terracotta rainscreen brought a system to market that seemed to meet the demands of every stakeholder in the construction chain. At the same time as satisfying the architect’s desire to create striking and unusual finishes, it remained relatively cost effective, because the system is quick and easy to install and does not require specialist trades. Moreover, for both residential and commercial developers, the terracotta rainscreen represented a practical and sustainable alternative to using metallic façades.
While all of these factors contributed to the initial popularity of the terracotta rainscreen, ongoing product development by façade innovators is expected to be the driver behind continued enthusiasm to specify this type of cladding. The most major innovation to date is a new generation of terracotta rainscreen, which delivers performance equal to that of the traditional twin skin tile, except it is a lighter, single skin version.
Twin skin versus single skin
The twin skin tile was the original terracotta rainscreen, and over time has built up market confidence in its reliability. Launched to market more recently, the single skin terracotta rainscreen is much thinner and lighter, leading to the misconception amongst some specifiers that performance levels in terms of strength and durability will be compromised. The consequence of this is that twin skin remains the first specification choice at architect level, although it is often not the most practical solution on-site.
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 a lot easier, which reduces the amount of wastage through breakages.
The objection relating to compromised performance is also totally unfounded, 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).
At present, twin skin is still the most commonly specified, because the majority of architects have tangible experience of it. However, as single skin terracotta rainscreen continues to prove its performance capabilities and ease of installation, alongside pressure from developers who recognise its cost benefit, the number of specifications for this system is expected to rise sharply.
Behind the rainscreen
Whether using a single or twin skin system, modern terracotta rainscreens should be used with precision calculated carrier systems, that are available in a range of grid formats to allow complete design versatility and fast installation.
One of the main shifts in carrier system technology is the development of vertical hangings. 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.
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.
The major advancements achieved in vertical carrier and terracotta rainscreen technology has significantly brought the overall cost of this façade system down, making a high quality and durable finish more affordable than ever before.
