Roofconsult Website Fixing Horizontal Cladding by Peter Reilly of SFS intec
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Metal roofing for industrial and commercial premises, with the familiar ribbed profile from ridge to eaves, traditionally was complemented by metal cladding with the profile running vertically from gutter towards the ground.
The supporting structure for the roofing and vertical cladding is also similar in practice, with the vertical primary steelwork crossed by horizontal secondary steelwork. Skills acquired in roofing contracts are easily transferred to installing vertical cladding.
However, more and more building designs are incorporating horizontally aligned wall profiles and panels in contrast to the vertical orientation of the roofs. As a design statement, this has several effects, including reduction of the apparent height and bulk of a monolithic building by leading the eye horizontally.
Although, this might appear to be a cladding system on its side, there are several factors which the contractor should be aware of to ensure they are incorporated into the contract specification and price.
Loading the structure
One factor to consider is loading the structure.
For site assembled twin skin, using a typical "roof type" spacer grid for horizontal wall cladding can lead to serious problems, as the spacer bracket is generally designed to fit into the spacer bar at about 1m centres. However, because the spacer has to stand vertically to carry horizontal sheeting, the spacer brackets can only be fixed where the sheeting rails occur - usually at about 2m centres. Thus the spacer brackets are set too far apart and are too few in number to carry the dead load of the cladding system.

Picture 2

Typical spacer grid brackets rely on an interference fit in the spacer bar and this attachment is designed to resist loads acting at right angles to the grid bar, as happens in conventional roofing, rather than the parallel load applied when the spacer grid is standing upright.
The dead load of the cladding sheets have a tendency to pull the spacer bar downwards, loading the bracket/bar joint against the interference fit which in turn bends the bracket over.
Spacer system suppliers have overcome this design problem by producing more substantial "top hat" systems with screwed together connections that can resist the dead and imposed loads better than the lighter "roof" systems.
Fixing the panels
A second factor to consider is the placing of the fasteners. With a twin skin system, where the gaps between portal frames may be too great for the panel length, contractors may not be able to allow for sufficient fixings on the vertical edges. Pull out under high wind suction, sealing and airtightness are all potential points of difficulty. Picture 1
Where horizontal cladding is specified for aesthetic purposes, secret fixing is frequently desirable. Contract difficulties can arise as a result of insufficient fasteners or poor performance from fasteners not designed for high loading.
A better solution
To minimise distortion and meet aesthetic needs, composite (sandwich) cladding panels of insulation factory-adhered to metal skins, are often considered the better choice for horizontal cladding purposes.
With good inherent stiffness, perpendicular or lateral panel distortion is minimised. In addition, many composite panels are designed for secret fixing, with overlapping tongue and groove jointing which hide fasteners. Low profile, self-drilling fasteners within the joints and using fasteners with thread patterns designed to protect the insulation integrity, provide rapid, secure fixing of panels. Self-coring fasteners can also provide additional fastening security, with a minimal external appearance.
As with any external envelope panel, composite panels also need the security of 25 year plus warranted austenitic stainless steel fasteners, to prevent the risk of corrosion streaks on the once pristine fašade which would ultimately lead to claims for redress.
Additional considerations
If the wall is specified as a fire wall to BS 476 part 22, any horizontal cladding must follow the certified design detail with absolute rigour. The designs are more complicated and costly than normal work, but the potential for fire damage and even loss of life is so great that contractors who ignore the detailed design will face severe consequences.
Cladding contractors should also be aware of the special disciplines required for installing other external wall protection such as rainscreen cladding, which is often used in refurbishment projects. The essential discipline when installing rainscreen cladding is to ensure absolute flatness of the standoff support structure which carries the external skin panels. Training by the system manufacturers and recruitment of specialist fitters should be considered and is definitely recommended.
With horizontal cladding, just as with rainscreen installation, investment of time and thought into careful prior planning will help avoid pitfalls and ensure profitable contracts.
For further technical information, please contact: Peter Hamby, Product Manager at SFS intec Ltd, 153 Kirkstall Road, Leeds. LS4 2AT Tel: 0113 2085 500, Customer Service Fax: 0113 2085 573,or visit www.sfsintec.biz/uk
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