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Flashing a Parapet Wall
last updated 16/01/09
Summary of this page

Parapet metal cappings provides an effective solution for preventing water from entering from the top of a parapet wall. The construction of the walls varies but the principle of capping the wall is basically the same.
Because of the array of different dimensions of parapet walls the parapet flashings are custom folded to suit the individual application.

 
Typical Parapet Wall Flashing
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Typical sizes for parapet wall flashing

  • A & C = 100mm - 200mm (typical)
  • B = to suit the application (outside of wall)

The "Installation Code of Roofing, HB39-1997; published by the Australian Standards" specifies a 3 degree minimum full to the top of the parapet capping. The fall is away from the front of the wall and is designed to divert water away from the visual side of the wall. Water running down the wall tends to create unsightly stains. The drip edge of the flashing is intended to get water to drip away from the wall.

The use of packing has been detailed in our CAD drawings to provide support for the top of larger parapet flashings. Without it, foot traffic and the weight of the flashing can result in the concaving of the top of the flashing; this leads to water and debris ponding on top of the flashing, which will reduce the life expectancy of the steel. The other concern with unsupported flashings relates to the silicone lap joins which can tear apart if the top of the flashing is damaged by foot traffic, allowing water to enter the building. Overall it is a good practice to include packing on larger parapet cappings.

The parapet flashings should be installed as per the relevant Australian standards and the Building Code of Australia and specialist advice should be sort that relates to your specific needs. As a general guide; the "Installation Code of Roofing, HB39-1997; published by the Australian Standards" specifies that parapet flashings be installed at intervals not exceeding 500mm with masonry anchors.

Where applicable, allowances should be made for longitudinal expansion and contraction (sliding bracket fixing); seek specialist advice.

A common problem with parapet flashing results when the width (B) is slightly undersize which causes the top of the flashing to bow when installed which leads to water ponding.

Fasteners
Fasteners/rivets used for fixing of flashings should be compatible with COLORBOND® and ZINCALUME® steel - refer Technical Bulletin TB16 - Fasteners for Roofing and Walling Products - Selection Guide

 

Parapet Wall Flashing to suit steel clad wall

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Technical Resources
  1. Acceptability of Drainage from an upper surface to a lower metal surface
  2. Material Selection
For a complete list of BlueScope Steel Technical Bulletins click here
 
Parapet flashing to suit 200mm block work

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Parapet flashing to suit 110mm brickwork

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Parapet flashing to suit 110mm double brickwork

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Parapet flashing to suit brick veneer

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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.