Designing problems away


New Zealand’s building legislation still causing confusion for many builders and TAs


Leaky buildings have been a major concern in the construction industry in the past 10 years. But joinery system supplier Nalco believes sensible product design and building installation detailing can keep moisture where it belongs — on the outside of windows.


National Aluminium Ltd (Nalco) marketing manager Mark Gilbert says the Auckland-based company, supplier to the Nulook and Bradnams range, carefully considered possible moisture ingress via joinery.


“We took the approach that if we can design the problem away or reduce the risk then we would be one step towards providing customers with better outcomes,” he says.


Designers of the Nulook Nutech product pinpointed screws that penetrate the joinery frames at corners and, at times, transom and mullion connection points to be vulnerable leak positions.


They then replaced screws in these positions with nylon moulded corner blocks supporting crimped corners, and screwless transom connection blocks where possible.


In addition, they designed the Nutech suite’s platform using High Performance Drainage, a design system that focuses on drainage paths.


“This attention to detail, as well as rigorous testing, ensured errant water is diverted from hazardous areas where possible, exiting outside the window,” Mr Gilbert says.


However, he adds, the best quality aluminium joinery will not prevent leaky building problems if the installation detail is inappropriate.


“Today, New Zealand’s building legislation is still causing confusion for many builders and territorial authorities. Parts of E2/AS1 can only be described as incomplete and do not address all the issues thoroughly,” he says.


In his opinion, examples of these are that sliding doors and bi-folds are expressly excluded from AS1 – requiring specific design — particularly in view of their popularity, and that the treatment of sill support, recommended by all window manufacturers for direct fix and cavity installations, is only covered in E2/AS1 by “Note 3”.


“This provides builders with no clear direction as to how best to support windows when a support bar has been widely promoted to the Department of Building and Housing (DBH) as being suitable by the Window Industry Association of New Zealand (WANZ),” he says.


He also regrets the complete exclusion of timber joinery installation details from E2/AS1.


Mr Gilbert says Nalco contributed expertise to the WANZ technical team that developed an alternative solution to E2/AS1. Complete building installation details for a wide variety of cladding types are now available as a joint window industry solution.


To assists architects and builders, Nalco enhanced the WANZ solution, and now offers free installation detailing downloads in a variety of formats, including PDF, DXF, DWG and MOD on its web site.


The details cover the main cladding types and all door and window varieties, including rebated doorsill details.


This strategy struck a chord.


“During a recent promotion to architects, more than 50% of our target group responded by registering on Nulook’s web site. This, in part, indicates the need for clarity in this area.


“Nalco would like to see a review of E2/AS1 in this area to bring together the ideas of the WANZ technical team and the DBH to create one installation system solution covering aluminium joinery.


“For builders and territorial authorities, this would help clarify installation requirements in an area of building which is prone to serious problems if details are not adequate,” he says.
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