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Flashing a wall cladding external corner
last updated 02/07/15
Summary of this page

External corner flashings come in two main styles: trim and moulding flashings. Moulding style flashings are more common with domestic dwellings as they tend to provide a neater corner - the downside is that they are slightly more expensive (this is mainly due to the extra folds required to manufacture them). Trim style flashings are used in domestic and commercial applications. Both styles of flashings are in most cases custom made to suit the individual requirements, although, some manufacturers do stock standard profiles.

Because you can never guarantee where the sheeting will finish and you inevitably end with the problem flashing half sheets, custom measuring is the preferred method to guarantee a neater finish. When designing flashings you should be aware that the manufacturer's folders may have different tolerances for folding tight flashings such as mouldings. Flashing mouldings may be restricted to shorter lengths, for example 3 metre lengths. There are many variations to flashings, the following details represent a sample of suitable solutions.

 
Trim Style Flashing
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Break: Horizontal sheeting - typical break dimension for flashing a corrugated profile is a 10mm slight break (over folding can result in unsightly dimples in the flashing edge when securing with fasteners). A larger break would require the flashing to be notched to the walling profile. The break adds strength to the flashing edge, preventing the oil canning affect of unstrengthened material.
When using profiles other than corrugated, notching may be the preferred option for proving a neat watertight detail. In this case, a 135 degree break is suitable (some prefer a tighter break). The length of the break is to suit the profile depth.
Vertical sheeting - A 135 degree break is suitable (some prefer a tighter break), the length of the break is to suit the profile depth.

A & B: Horizontal sheeting - the length needs to be long enough to provide a neat and waterproof detail. A typical dimension would be 140mm, this would result in a total girth of 300mm (140mm x 2, plus 10mm breaks). Many manufacturers charge by flashing girths - hence it is best to design flashings to an economical cut size (girth), contact the manufacturer for their material cut sizes.

Flashing a vertical corrugated wall sheeting with a trim style flashing

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Flashing a horizontal corrugated wall sheeting with a trim style flashing

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Alternate profile flashings

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Moulding Style Flashing

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Typical dimensions for mould style flashings
Manufacturer's tolerances vary depending on machine capabilities. The example shown is available from our chosen supplier in 3 metre maximum lengths.

Dimension A height is dependant on the wall cladding profile height.
The minimum dimension for B is determined by the dimension A.
Dimension C is typically 50mm, the squash fold is typically 10mm.

A= 20mm minimum B = 35mm
A = 27mm minimum B = 45mm
A= 30mm minimum B = 50mm
A = 33mm minimum B = 50mm
A = 37mm minimum B = 55mm
A= 43mm minimum B = 60mm
The moulding style flashing requires the manufacturer to have specific machinery to complete the folds (measurements available may vary slightly from those shown). If you are experiencing problems obtaining this style of flashing please contact us for assistance.
Flashing a horizontal corrugated wall sheeting with a moulding style flashing

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Download 3-D CAD detail

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Resource Acknowledgements
Source: SteelSelect - author Richard Michael

Publication Details: November 05

Authors Disclaimers:  The information and advice contained in this article is of a general nature only, and has not been prepared with your specific needs in mind. You should always obtain specialist advice to ensure that the materials, approach and techniques referred to in this article meet your specific requirements. SteelSelect makes no warranty as to the accuracy, completeness or reliability of any estimates, opinions or other information contained in this article, and to the maximum extent permitted by law, SteelSelect disclaims all liability and responsibility for any loss or damage, direct or indirect, which may be suffered by any person acting in reliance on anything contained in or omitted from this document.