HDGASA V7E1.pdf

FastenersSANS 1273 – settinga new standard forroofing fastenersAfter many years under revision, amendments to the SANS 1273 standard“Fasteners for roof and wall coverings in the form of sheeting” have been finalised andthe standard was published late in 2009.The main changes to the revised standard relate to the corrosion resistancerequirements of roofing fasteners and the introduction of self drilling screwsand bonded roofing washers which were not incorporated in the old standard.The amended standard specifies the corrosion resistance and mechanicalproperties of the following fastener types:◆◆◆◆◆◆◆Hook bolts; Channel bolts; “U” bolts and “J” boltsSlotted mushroom head roofing bolts (also known as gutter bolts orveranda bolts)Slotted mushroom head roofing screws with rolled threadMushroom head drive screws with rolled threadCross recessed pan head self tapping roofing screwIndented hexagon head self tapping roofing screwSelf drilling screws for steel or timberCorrosion resistance and protective coatingsIrrespective of what fastener type is used, the appropriate protective coatingon the fastener must be determined by identifying the corrosivecharacteristics of the environment in which the fasteners will be used,according to the ISO 9223 classification (see table below).Corrosion resistance classAtmosphere of intended use1 General use in internal application2 General use in other than external applicationsbut where significant levels of condensation occur.3 External use in mild, moderate industrial ormarine environments4 External use in severe marine and industrialenvironmentsAt all times the corrosion resistance of the roofing fastener must equal orexceed the corrosion resistance of the roof sheeting. This will ensure that theroofing fasteners will not become “the weakest link” in the roofing system (asthey have so often been in the past).Once the correct corrosion resistance class has been identified the Standardspecifies the following plating / coating requirements:continued on page 12...Volume 7 Issue 1 2010 Hot Dip Galvanizing Today 11