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Flashing a wall cladding internal corner
last updated 05/03/09

Internal 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 wall 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.

 
IMPORTANT NOTE
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.
 
Trim Style Flashing - Type 1
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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. In this case, a 135 degree break is suitable (some tradesman prefer a tighter break). The length of the break is to suit the profile depth. If the detail is to be exposed to the weather, extra precautions can help prevent wind driven rain penetrating the flashing. They include; weathering the sheet ends, notching the break to the wall profile and the inclusion of an approved weathering strip (Profiled, closed cell foam filler strips are available to match the top and bottom profile of the a wide range of sheet profiles. It is critical to ensure that the foam used in the filler strips does not absorb water as this will lead to poultice corrosion of the sheeting and structural steel support. Filler strips made from ignitable materials must also be avoided, particularly in those areas prone to bush fire hazard as wind blown sparks may initiate ignition of the foam strip contributing to destruction of the building by fire - refer BlueScope Steel Limited, Technical Bulletin CTB-19 Roof Profile Closures).
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 (when using smaller rib height profiles such as Mini Orb®, this measurement would be reduced to approx. 50mm for aesthetics), 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 type 1 flashing

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Flashing a horizontal corrugated wall sheeting with a trim style type 1 flashing

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Trim Style Flashing - Type 2
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The trim style flashing - type 2 is basically the same as type 1 (above), except the fold to stiffen the edge is a 10mm squash fold instead of a slight break. It is typically used with horzontal wall sheeting. An advantage of using a squash fold is that you are less likely to experience any dimples or puckering of the edges due to the tension of the fasteners. The flashing is easy to install but offers little protection from wind driven rain. When used with higher rib height walling profiles, it doesn't hide what is behind the flashing and can spoil the aesthetics of the detail. The flashing does provide a safer material edge (squash fold) for "little fingers" (compared to a type 1 flashing).


Flashing a horizontal corrugated wall sheeting with a trim style type 2 flashing

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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. Dimension A is typically 50mm, the squash fold is typically 10mm.
Dimension B height is dependant on the wall cladding profile height, but should be a minimum of approx. 20mm. This style of flashing would not be suitable for smaller rib height profiles such as Mini Orb® because of the difficulties manufacturing the tightness of the folds (unless it was intentional that the height of B was to be a lot greater than the profile height).

Flashing a horizontal corrugated wall sheeting with a moulding style flashing

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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.