Make The Right Choice On Site

Make The Right Choice On Site

By Gareth Griffiths

“Goedkoop is duurkoop” The original pre-painted galvanized roofing on this upmarket Cape Town home (seen on the right) needed complete replacement after less than 10 years in service and was replaced progressively by the contractor from the left using by Clean COLORBOND steel.

In this advisory article, a well-known steel roofing material supplier points out that both what happens on site needs to be monitored to ensure the right grade of steel as specified is actually used.

There is an old South African saying ‘goedkoop is duurkoop’. As a company worldwide, we have found that substituting a high quality roofing material such as ZINCALUME® steel or a high quality pre-painted steel such as COLORBOND® steel with an alternative material is sometimes done in error at the last minute to reduce building costs, without the specifying team being aware of it. We strongly advise against this practice” says Arno Hanekom, Regional Manager Africa, for steel roofing multinational company, BlueScope.

Following the old adage that form follows function, it is also true that the selection of materials used should mirror the intended function of the building, including elements of sustainability such as long life.

Sustainability starts with the roof”, says Hanekom. “By this, we mean that what covers the building is crucial to life and operating performance of the structure; and also that the right material needs to be specified during the design phase of the that building”.

But what happens on the building site is of critical importance. Misguided decisions by project managers, contractors and even built environment professionals can result in substitution of high performance steel as specified by architects with cheaper low grade options. These affect both performance and service life negatively” he says.

Look for the branding on the reverse side of the product

According to Hanekom, quality steels such as the ZINCALUME and COLORBOND steel brands have a dot matrix branding on the reverse side which clearly distinguishes the product concerned. This makes it easy to spot during construction site inspections.

He warns that substitution with cheaper grades of steel roofing often leads to two things happening:

  1. Corrosion and breakdown of the metal substrate at an accelerated rate compared with the BlueScope product. The company’s steel brands have been found to deliver a service life of more than four times longer than conventional galvanised or pre-painted galvanized steels, even where the substituted product contains a higher base metal thickness of steel.
  2. Colour and thermal performance. Premature fading and loss of infra-red reflectance are two key areas steel roofing of today. “There is no substitute for the performance of our ZINCALUME and COLORBOND steels when it comes to both the appearance of and a cooler roof”, adds Hanekom.

Reputation on the line

Hanekom asks: “Look for the brand that identifies the long lasting guaranteed performance of genuine ZINCALUME steel and COLORBOND steel from BlueScope. Why risk your reputation when you can enjoy peace of mind by using genuine ZINCALUME steel or Clean COLORBOND steel?”

Proof is in the testing

The pictured samples were exposed at BlueScope’s Bellambi Point Australian test site for the same period of time under a severe environment. The galvanized steel (left) shows a severe loss of zinc coating and consequent red rusting of the steel substrate, while the ZINCALUME steel sample (right) is still in good condition.

… and in real life
BlueScope’s local South African office has a number of case histories where COLORBOND steel was used to completely replace pre-painted galvanised roofing that had severely corroded after just 3 years. Now, 10 years on, those COLORBOND steel roofs are still intact.

There’s no beating an original

There’s no beating an original

Secunda Mall
Photo: Gareth Griffiths

By Gareth Griffiths

Over decades, ZINCALUME® has become a household name within the building industry. When specifying premium high performance metallic coated roofing and cladding materials, this original and trusted brand remains the roofing material of choice for specifiers, says the manufacturer.

First made in the late 1970’s, ZINCALUME has a long and distinguished pedigree, having been constantly improved over time. Manufactured and marketed by BlueScope, a reported 28 million tonnes of these zinc-aluminium coated products worldwide have been sold since inception – as verified by the Zinc-Aluminum Coaters Association (ZAC).

The 55% Al-Zn technology is licensed internationally by BIEC International Inc., a BlueScope subsidiary. In certain countries, the technology is marketed as GALVALUME®. In the mid 2000’s, the acrylic surface resin applied to coils of the product at the factory was upgraded, yielding significant advances in performance and formability.

A registered trademark of BlueScope Ltd, ZINCALUME steel was developed in association with Bethlehem Steel in the USA and perfected by Australian scientists at the Port Kembla research laboratories in New South Wales.

The choice of roofing material can affect the amount of solar energy that enters a building, affecting climate control inside the building and the comfort of occupants. To mitigate against heat ingress, ZINCALUME steel has an attractive, shiny appearance designed to keep heat out by limiting solar absorptance. All roofing products are subject to weathering, however, BlueScope’s product will stay brighter for much longer than alternatives, providing approximately twice the thermal performance of other commonly used materials such as weathered galvanised steel and fibre cement/asbestos.

ZINCALUME steel continues to deliver strong thermal performance throughout the life of the product. ZINCALUME is also extremely easy to form and work with”, says Hanekom. “It stays brighter for longer and due to its lightweight steel character. It is the architect’s dream material for curves and shapes, having been formed into a variety of curved surfaces. A good example of this is the roof over the departures terminal at Cape Town International Airport, completed in time for the 2010 FIFA soccer world cup and impressively shaped like an aircraft wing. Viewed from the air, this gives a stunning example of how versatile this product is.

The ZINCALUME roof at Cape Town International Airport is a stunning example of how versatile this product is.
Photo: Gareth Griffiths

The corrosion-resisting benefits of the product are considerable, and a special AZ 200 (both sides coated with 200 g/m2 of Al-Zn coating) version is available for use within the 5 km distance of the sea or in areas where there is a strong industrial fallout.

Because the metallic coating consists of 55% aluminium with the 43.5% zinc (the balance being Silicon), on a minimum coating mass both sides of 150 g/m2 in total, the user gets a highly effective degree of sacrificial anodic protection over the steel substrate meaning that the product may last at least four times longer than conventional zinc coated steels. ZINCALUME steel exhibits a more complex coating structure with both aluminium- and zinc-rich areas. The zinc-rich area provides excellent sacrificial protection, while the aluminium-rich area provides durable barrier protection. It is the combination of these two characteristics that make this unique product durable and effective against corrosion.

All this means that a special corporate warranty of performance can apply when product is fitted in an approved way”, adds Hanekom.

Mbombela Stadium
Photo: Grant Duncan-Smith

Noteworthy projects

ZINCALUME has been used extensively throughout South Africa on a number of high profile projects.

BlueScope customer, Clotan Steel expertly formed ZINCALUME into its Craft Lock profile in use at the Secunda Mall, as specified by architectural firm, LP Architects. The double-story mall was completed late in 2013.

Other examples of projects have included the Mbombela Stadium, Maponya Mall, Soweto, various integrated housing projects and more recently the roof over the massive Pepkor Distribution Centre in Hammarsdale.

Pepkor Distribution Centre, Hammarsdale Photo: Reinhard Swanepoel

If the good name of your practice is on the line, make sure our brand name is on the steel. Look for the brand that identifies the long lasting guaranteed performance of genuine ZINCALUME by BlueScope. It’s stamped on the underside of the roof sheet. Why risk your reputation by using generic Al/Zn coated steel when you can enjoy peace of mind by using genuine ZINCALUME steel?” he asks.

BlueScope Steel Southern Africa (Pty) Ltd

T: +27 21 442 5420