Press Information
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| Issued: August 2008 |
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What lies beneath?
In spite of the fact that carrier systems have a pivotal role to play in what can be achieved with rainscreen cladding design, this factor is often overlooked at specification, where the primary consideration is surface aesthetics over practicality and performance. William Harwood, director, T.I. Dynamic Facades, provides advice on selecting a carrier system and explains how correct choice of carrier can actually make a positive contribution to building design.
Where the subframe of exterior cladding is concerned, both vertical and horizontal systems are available, but it is the latter that is most commonly specified. Once the subframe has been selected, a decision must be made with regard to the carrier system that will actually hold the tiles/panels in place. Again, there is a choice between vertical and horizontal, but in the context of carrier rails, it is the vertical systems that are coming out on top.
Choosing a carrier
A recent innovation, vertical carrier rails have quickly emerged as the preferred option on a wide number of developments, attributed to the ease with which they can be installed, compared to a horizontal alternative. Some vertical carriers actually make it impossible for a tile/panel 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/panel.
When choosing a vertical carrier, the first thing to assess is the compatibility with the subframe, as this will dictate the options that are available. For example, some systems, especially those that work well with composite panels and SIPs, can only be used with vertical subframes. Carriers with this profile will generally only be suitable for use with a façade, because they have a tight construction which does not accommodate the minimum 30mm unrestricted zone required for a rainscreen. However, the advantage of using these ‘clinched’ carrier systems is that they deliver a high quality exterior finish whilst maximising the internal floor space of a development.
Where a rainscreen is being installed, the two main choices are either a belt and braces rail or an adaptive rail. While the selection between these will generally be determined by budget and project requirements, more often than not the belt and braces will be specified. This is because it can be fixed back to either a horizontal or vertical subframe, which offers greater flexibility in terms of total system approach.
Where there is a more complex rainscreen design, such as a mixture of tile/panel sizes, an adaptive rail should be used. An adaptive rail, as its name suggests, can easily accommodate the vertical joint variations associated with the use of different tile sizes. Higher performing adaptive rails typically achieve joints of 2mm to 40mm, which allows the rail to be adjusted to compensate for the difference in tile sizes. Even where the tiles/panels are homogenous or similar in size, an adaptive rail can be used to purposefully create joint variations, which may be specified by the architect as a design feature of the tiled/panel finish.
Practically aesthetic
Where a facetted design is encountered, any of the vertical systems are suitable, although smaller module sizes are recommended. Where a tight facet must be achieved with larger tiles, or a horizontal subframe incorporates large spans, specification advice should be obtained from the façade manufacturer.
The additional design advantage of a vertical carrier is that the system will preserve the aesthetics of a development, both initially and over time. For example, its design facilitates tile/panel removal, which means damaged tiles/panels can be efficiently and cost effectively replaced.
Vertical systems also benefit from minimal fixings, and those that are used, have been developed to be virtually invisible. As such, an apparently seamless elevation is much easier to achieve with a vertical frame. Moreover, a system with the fewest moving parts should always be specified. As well as helping to deliver a high quality finish, it simplifies installation and keeps site wastage through the loss of fixings, to an absolute minimum.
