12 COMMENT
When designing standing seam roofs architects should always consider the implications of the pitch and environmental conditions
the edge that is fixed with clips) and an ‘overcloak’ along the other. To make the joint, the overcloak is welted around the undercloak of the adjoining tray, covering the clips. The two trays are then seamed up using seaming irons or seaming machines. Since the trays are only fixed along their seams, the distance between trays is determined according to expected wind loading, and tied in to commercially available coil widths. Be aware that angle standing seam joints are limited to use on slopes pitched at least 25° or above.
Choosing the right cross joint
It is sometimes necessary to join standing seam trays end to end. This may be to introduce an expansion joint, as part of the flashing work around a chimney or skylight, or to produce a change in tray width on a conical roof.
There are different joint types available and the degree of roof pitch will determine which detail should be specified.
Fixing
Each tray is anchored using hidden clips that are hooked into the seam and normally screwed or nailed to the substrate below. If the length of the tray is under 1.5 metres, fixed clips can be used throughout. Trays over 1.5 metres require a combination of fixed clips and sliding clips to allow for thermal movement of the trays, and provision for movement at eaves and ridge. The distribution of the fixed clips depends on roof pitch – the steeper the pitch, the higher the band of fixed clips is positioned.
Avoiding pitfalls COAST BOURNEMOUTH
The apartment building is clad in elZinc Slate Advance which has a protective coating that makes it suitable for use in coastal locations
Roof build-up
Standing seam roofing can be installed over a ventilated or non-ventilated roof construction allowing you to choose the best solution for the characteristics of your project. Trays are not self-supporting and require a fully or almost fully supporting substrate against which they rest and to which their clips are fixed. Choosing which design is the most appropriate for a particular project depends on many factors and is best discussed on a project- by-project basis.
The standing seam joint
The longitudinal joint is a 25 mm high double lock standing seam. The double lock welt of the seam is raised above the water drainage part of the tray.
The standing seam is formed by profiling or folding strips and sheets into trays. An ‘undercloak’ is formed along one edge (this is
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When designing standing seam roofs architects should always consider the implications of the pitch and environmental conditions. For example careful consideration is needed when designing for particularly windy locations. The bay width of the trays will need to be narrowed otherwise an unwelcome fluttering noise can be generated by the movement of the pans of the trays or at worse, the standing seams can be lifted. We would always recommend choosing a supplier or manufacturer with comprehensive technical support. The supplier should be able to provide technical information, including details, NBS Specifications, 3D build-up, and warranties. It is also a good idea to look at the installation site with an experienced and accredited installer and take all these factors into account when determining joint type. A FTMRC registered and reputable hard metal roofing contractor should carry out the installation.
Want to learn more? Why not attend a RIBA Approved CPD such as SIG Zinc & Copper’s ‘Specifying Hard Metals: Choosing the Right Product for the Project’ which aims to help specifiers demystify the confusion surrounding hard metal specification.
Simon Walker is category manager at SIG Zinc & Copper ADF DECEMBER 2020
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