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Buildings 2015, 5(1), 130-148; doi:10.3390/buildings5010130

Measuring the Weathertight Performance of Flashings

BRANZ Ltd., P.O. Box 50908, Porirua City 5240, New Zealand
These authors contributed equally to this work.
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Author to whom correspondence should be addressed.
Academic Editor: George Baird
Received: 25 November 2014 / Revised: 17 December 2014 / Accepted: 14 January 2015 / Published: 28 January 2015
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Abstract

Residential buildings are now better engineered to manage rainwater following the leaking building problem in New Zealand. The next challenge is to improve the weathertightness of medium-rise buildings which often use joint details widely applied on low-rise buildings but are subject to higher wind pressures and surface runoff rates. This study begins to address this challenge by measuring the water leakage performance limits of the following common flashings with static and dynamic rain and wind loads to see how their performance might be improved: (a) Horizontal H and Z jointers between direct fixed sheet claddings; (b) The window head flashing in a cavity wall; (c) A horizontal apron flashing at the junction between a roof and wall. At this stage, water penetration resistances have been measured but the data has not yet been discussed in the context of wind pressures and rain loads on mid-rise buildings. All of the joints were found to resist water leakage to pressures equivalent to the hydrostatic head of the upstand, so long as there were no air leakage paths through the joint. When vents were added, or openings were present that might arise due to construction tolerances, then the onset pressure for leakage was found to fall by as much as 50%. Vents, of course, are essential for ventilation drying in rainscreen walls and even with vents present, the onset of leakage was at generally at least twice the 50 Pa wet wall test pressure applied in New Zealand. Opportunities were found to improve the way vented joints deal with runoff by enlarging the gap between the cladding and flashing. This prevented the outer joint volume from filling with water and occluding the vents. The apron flashing was found to cope better than a window head joint with runoff, because of the larger 35 mm vertical gap between the cladding and apron. View Full-Text
Keywords: weathertight joints; flashings; upstands weathertight joints; flashings; upstands
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This is an open access article distributed under the Creative Commons Attribution License which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. (CC BY 4.0).

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Bassett, M.; Overton, G. Measuring the Weathertight Performance of Flashings. Buildings 2015, 5, 130-148.

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