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/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