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