23 March 2018

What fixings should be used for fibre cement sheeting?

Profiled fibre cement roof sheeting should always be fixed with two fasteners per sheet per purlin and in accordance with the recommendations of BS 8219. 

Selecting the correct type of fastener is extremely important for the integrity of the roof covering to avoid premature failure, corrosion or leaking. You should consider the type of sheet being used, as well as the type of purlin or rail system, and the weatherproofing, with washers and caps.

What fixings should be used for Profile 6 roof sheeting?

For Marley Eternit Profile 6 sheeting, self-drilling, self-tapping ‘topfix’ style fasteners are generally used to fix the sheets to the purlins. These fasteners drill through the sheet, creating a 2mm oversize hole, and self-tap into the purlin. They have an integral washer to seal onto the sheeting. The fasteners are designed with different drill points and threads suitable for cold rolled steel (typically up to 3mm thick), hot rolled steel (typically 3-6mm thick) and timber. Fasteners for steel are typically 105 – 125mm long and for timber are 130mm long. 

When following the recommendations of the fastener manufacturer, you should pay particular attention to the minimum purlin thickness and maximum roof pitch.

Can I use traditional fasteners for profiled roof sheeting?

In certain circumstances it may be preferable to use traditional fasteners such as hook bolts, crook bolts and drive screws, instead of topfix fasteners. 

For Profile 6 fibre cement roof sheeting, 8mm traditional fasteners can be used with 10mm diameter holes pre-drilled in the sheet. Drive screws also require a pilot hole in the purlin to avoid splitting the timber.

If using drive screws, the holes must be located centrally on the purlins. For hook and crook bolts, the fixing should be positioned 4mm upslope from the back leg of the purlin. 

In all instances,  sealing washers and caps should be utilised with these traditional fasteners to ensure adequate weather protection. 

There are, however, additional health and safety implications to consider when using  hook and crook bolts as these are installed from underneath the sheeting but have to be tightened from above.

What fixings for Profile 3 roof sheeting?

Profile 3 sheets  can be fixed using 6mm diameter traditional fasteners with an 8mm diameter hole drilled through the sheet. Topfix fasteners are also available for timber purlins, but not for metal

Tools for fixing profiled fibre cement sheeting

It is important that the fasteners are installed using the correct power tools, which should have an adjustable depth-setting device to ensure the washers are tightened and seated correctly. 
All fixing holes should be drilled, not punched, and should provide adequate clearance for the fastener shank (minimum 2mm). 

Fasteners should be installed perpendicular to the plane of the roof.

For more information, please refer to our Profiled Sheeting Design Guide (Part One) page 33.

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