How to specify concealed fix roof systems

by Ofentse Sefolo
How to specify concealed fix roof systems

When designing and specifying a concealed fix or standing seam roofing system, there are several things that need to be taken into consideration. Safintra gives some tips.
When a concealed fix or standing seam roofing system is installed, the sheets are fixed to the purlin with a clip system, and are not pierced with any fasteners.

The clips that are used to fix the sheets to the purlin serve two purposes:
•    Firstly, they obviate the need for holes in the sheet, which prevents leakage through the perforation.
•    Secondly, they allow natural metal thermal expansion without restriction, which in turn reduces fastener wear as seen in pierced fix applications.

By being able to move over the clips, the sheets can be rolled in long unbroken lengths, averting the use of end laps and further reducing the risk of leaks.

The expansion of coated steel
Coated steel expands at a nominal 1mm per 1m, meaning that a 15m sheet will move by 15mm in heat. Best-practice installation is to not install a pierced fix sheet in lengths of more than 15m, and in large developments, concealed fix profiles become the obvious choice.

Aesthetical and functional benefits
When designing a low-sloped roof, a defined rib and a wide, deep pan are needed in order to deliver excellent water run-off at slopes as low as 2° or 3°. The height of the rib is important as it also provides structural strength, and acts as a water runoff catalyst preventing ponding.

The design of the clips further needs to be considered as this is the anchor that will secure the sheet to the sub-structure and hold it down in high winds. The strength of the clip will be determined by the material that is used as well as the thickness of the clip, which in turn helps to determine the wind-uplift resistance of the system.

Selecting the correct profile
One of the most widely specified systems available in the market is the Saflok™ concealed fix roofing system available in 410mm and 700mm effective cover widths. The two interlocking profiles are each designed for specific structural applications and together with precisely engineered clips and the dimensional consistency of the Saflok profiled sheets, it provides a robust and reliable roofing system.

Although transverse ribs, offered in various products on marketprovide marginal rigidity, the downside is dust collection and ponding that could cause damage to the protective material coating and eventual premature corrosion.

Getting support
Specifiers and other built environment professionals are encouraged to request full technical details of the system they intend to specify, and request technical support throughout the installation itself. Safintra offers this service free of charge to all customers from the company’s seven branches in South Africa (Johannesburg, Durban, Cape Town, Polokwane, Nelspruit, Port Elizabeth and Bloemfontein).

Safintra is part of the Safal group, with operations in Namibia, Mozambique, Botswana, Zambia, Malawi, Tanzania, Kenya, Angola, Uganda and others.

Tel: 011 323 6300
Website: www.safintra.co.za

Safintra’s Saflok 410® concealed fix roofing system was specified for the Value Logistics distribution centre in the Western Cape, showcasing the long-span capabilities of concealed fix systems

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