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Flashing a sidewall
last updated 04/03/09
Summary of this page

Flashing a side wall can be achieved in many ways. The main aim is to produce an aesthetically pleasing and watertight detail. Custom measuring of flashings 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 flashings and the flashing length available may be restricted, for example 3 metre lengths. There are many variations to flashings, the following details represent a sample of suitable solutions.

Sidewall Flashing - Type 1
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Typical Sizes for Corrugated horizontal wall sheeting

  • A= 75mm
  • B= 20mm
  • C= 25mm
With a sidewall flashing it is important to consider the fixing points for the wall sheeting and the sidewall flashing. Measurement C in this example is only 25mm; this is to allow for a fastener through the sheet and flashing and into the wall stud. If the measurement for C was too long then additional framing would be required to fasten too. Measurement C can be extended to around 35mm (This may be an option if you wanted to cover more of the sheeting, but as mentioned, you may require more supports). Prior to installing the wall sheeting, the sidewall flashing can be secured to the end wall with suitable fasteners, this will ensure that the flashing sits squarely. Depending on the application, sealing of the connection of the flashing and the end wall may be required.

To help prevent any water penetrating the detail it is best to make measurement A at least 75mm long. Squash folds help strengthen the flashing edge and make a safer edge.

In the scenario that there are cappings at both ends of the wall sheeting, the tradesperson would order the wall sheeting slightly shorter to allow the sheeting to be inserted into one capping and then slide back into the opposite channel.

Profiled foam should be inserted to help waterproof the detail. Many people detail this foam behind the walling profile which is very hard to achieve in this detail, although it is the preferred option. A suitable solution in this case is to insert the foam between the flashing and the sheeting on the exterior wall side. This helps hide the end of the sheets and prevents spiders from nesting. Profiled, closed cell foam filler strips are available to match the top and bottom profile of the 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.

Suggested contractor recommendations: Like many details that we add to the system we like to discuss them with the industry for feedback that we can share with you. When we discussed this detail with one of our network of roofing contractors, their main concern when constructing such a detail was making sure it was waterproof. They insisted that sisalation always be used behind the wall sheeting and that the bottom of the wall flashing is installed behind the sisalation so as if water did penetrate, it could exit down the bottom and would not be trapped inside the building.

Flashing a horizontal corrugated wall sheeting with a sidewall type 1 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.