CLADDING // CONCRETE // INSULATION // STEEL // THATCH // TIMBER // TRANSLUCENT // WATERPROOFING // COMPONENTS
ASSOCIATIONS
From page 8
10.5mm are the number of pitches between corrugations and the 76 is the pitch, or distance, between the crests of individual corrugations measured in millimetres. The depth is fixed at 18mm(± 1mm).
Recently numerous widths and / or depths as low as 16mm have been foisted on an unsuspecting public. There is a noticeable difference in the spanning capabilities of 18mm and 16mm deep corrugated cladding. IBR was a copyrighted name of a box-rib( trapezoidal) profile with a specific geometry that was introduced in the 1960s which has subsequently become the generic name for all box-rib profiles. The original profile has a cover width of 686mm, five ribs spaced equally at 171.5mm centres and the ribs are 37mm deep, 35mm wide at the top and 69.5mm at the base.
What you should know
Currently there are profiles with much shallower and narrower ribs being approved as IBR. Most reputable roofing profilers produce an IBR that complies largely with the original and market a variety of weaker profiles under various brand names. It must be noted that the spanning capabilities of a profile are directly proportional to the square of the depth of the ribs.
There have been several generations of concealed-fix profiles ranging from narrow standing seams to trapezoidal ribs or a combination of the two. Klip-Lok, although a copyrighted profile, is trending towards being the generic name( with numerous distortions of the spelling) for concealed-fix profiles with trapezoidal spring snap ribs.
Grades of material are now described, in line with international practice, by minimum yield strength measured in megapascals( MPa). Commercial quality( CQ) is now 230MPa and fullhard G550MPa. An intermediate grade of 300MPa has been introduced. Unfortunately, there is no uniformity in the prefix used to describe the grades, for example G550, ISQ500 and so on. Generally, material up to and including 0.53 / 5mm is 550 MPa, 0.55 / 8 is 300MPa and thicker material is 230MPa. Thickness is the total coated thickness of the coated material( steel core plus coating) rolled to a tolerance of ± 0.02mm. Some unscrupulous roll formers substitute 0.48mm material for 0.50mm.
In an attempt to address this problem, the National Regulator for Compulsory Specifications has agreed that the( soon to be published) revision to SANS 10400 Part-L will require all coil used for the manufacture of metal cladding to be indelibly marked 50mm in from each edge, at no more than three-metre intervals. Other data will also be specified such as the weight and type of the metallic coating and identification of any other coating applied to the coil. Local cladding manufacturers refer to this indelible marking as branding. Many people are not aware that galvanised, or more correctly zinc coated, material is available with different thicknesses of the coating ranging from Z100 to Z600. The Z denotes the coating is zinc and the number the total mass of the coating, measured in grams, to both sides of a square metre of material. As the durability of a coating is basically proportional to thickness, a Z275 coating has a service life expectancy 2.75 times that of a Z100 coating.
Zincalume, ZincAL and Aluzinc( which has effectively become a generic name) are all copyrighted names for 55 % aluminiumzinc coatings. Similar to zinc coatings they are available with different coating thicknesses that range from AZ100 to AZ200 with durability being proportional to thickness.
There are other aluminium-zinc coatings available with the aluminium percentage varying from as low as 5 %. These coatings are usually denoted as South African. Colour coated or pre-painted material is available with either a galvanised or 55 % aluminium-zinc coated substrate.
Not all paint systems are equal
The overall performance of these products in a given environment is dependent on the combination of the paint system, the thickness of individual layers, plus type and thickness of the underlying metal coating. Performance of paints is directly linked to their formulation plus the quantity and quality of the ingredients used.
Paint systems with the same formulation comprise lesser quantity and quality of materials and do not have the same durability as those made with better quality materials. The extremely high levels
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When considering the life cycle of products, never has the expression‘ penny wise, pound foolish’ been more relevant.”
of UV radiation experienced in southern Africa quickly reveal the quality of the pigments and resins used. It is therefore advisable to specify brands with a proven track record rather than accept an unproven paint system.
Prior to South Africa being a member of the World Trade Organization( WTO), cladding products available locally were comparable, however this is no longer the case. Our market is being flooded with inferior materials and products where price is considered over performance. When considering the life cycle of products, never has the expression‘ penny wise, pound foolish’ been more relevant.
While the first of the four components of an item of cladding, such as geometrical dimensions, are easy to check, the balance can only be reliably confirmed in a laboratory. The growing incidence of counterfeit documents pertaining to quality and composition of materials is cause for concern. Branded coil has been available in the country for more than 15 years, mainly as an option to the more reputable cladding manufacturers. Fortunately, two local and one foreign mill have adopted a policy of supplying branded products only.
By insisting that only branded materials are supplied is the most reliable and practical way to ensure you get the cladding material you specified. It eliminates onsite paper trails and is almost impossible to counterfeit.
THE MOST COMMON GENERIC COMPONENTS ARE:
• Cladding systems – corrugated( iron), IBR or box rib and concealed-fix.
• Grade of material – CQ and fullhard.
• Thickness – 0.40mm, 0.45mm, 0.47mm, 0.50mm, 0.53mm, 0.55mm, 0.58mm, 0.60mm and 0.80mm.
• Coatings – galvanised, Aluzinc( Zincalume), colour-coated( Chromadek), aluminium and stainless steel.
10
AUGUST 2018