When RIDBA raised concerns relating to slippage of traditional agricultural profiled sheets, EJOT UK took the call for action seriously and launched the first BAZ Screw developed specifically for the Big Six fibre cement roofing profile.
Once in position, roofing sheets are subject to natural movement created by the environment and the passage of time - which may cause the hole between fixing and purlin to enlarge, putting a strain on the securing washer. Tests carried out at the time across a range of commonplace industry-supplied fastenings endorsed the theory.
Another consideration was that the top fix self-drilling fastener for fibre cement sheeting was originally developed when steel supports were between 1.5mm and 6.0mm in thickness - designed for traditional hook bolts. As yield strengths of modern steel purlins have increased thicknesses have decreased, and it is common to see purlins of 1.3mm,1.4mm in some instances as low as 1.2mm being used!
Modifications and tests on EJOT’s traditional wing-drilling fastener set out to create a bespoke solution rather than provide a ‘fits-all’ offering. Re-engineering focused on eliminating any possibility of the panel ‘jacking’ and to look at the installation holistically during installation which can lead to an oversized hole.
EJOT’s Applitec development team achieved its objective by precise repositioning of the fastener’s ‘wings’ whilst shortening its length. The drill point and thread configuration was analysed leading to the development of a purpose designed fastener to accommodate and provide positive engagement into purlins of 1.2mm to 2mm thickness. Even the length of the fastener has been designed to ensure that the BAZ washer sits against the sheet sooner, to avoid any movement that could unduly elongate the installation hole in thinner purlins.
Pull-out tests carried out at Applitec showed the fastener recording an ultimate mean performance of 3.8 KN from 1.4mm steel purlins and an impressive 3.0 KN from 1.2mm galvanised steel purlin sections, clarifying that the fastener not only improved on the installation performance but also from a technical standpoint.