Metal Roofing: tips and tricks to avoid specification and installation failure.
August 8, 2019

The secret is in the fix

Your project is your most valuable asset. Choose Craft-lock® as your preferred concealed / side interlocking fixing system to withstand high wind loads.

When it comes to choosing a roofing & cladding system for your project it is important to keep in mind the structural performance of the roof covering system.

Roof covering systems are primarily designed to withstand high wind forces and all roof coverings need to be designed to resist these wind loads.

The resistance of the profiled roof sheeting, against uniformly distributed loads, depends on the strength-defining structural parameters.

Main parameters that determine the load resistance of the roof covering are within:

  • the resistance the profiled sheeting has against bending (Positive and negative bending moments) & the load resistance of the fastening system
  • the thickness of the sheeting profile,
  • the dimensions of the profile, especially the overall depth of the profile

From the above it is clear that both the sheeting profile and fastening system / mechanism play a crucial role in the overall wind load resistance of the roof system you choose.

Resistance against negative wind loading (suction):

Negative wind loads on roofs generally do not exceed 1.5 kN/m2.  Analyses conducted by one of the leading Universities in South Africa show that the Craft-Lock® side interlocking fixing system can withstand wind loads in excess of 280 km/h, depending on purlin spacing and other design factors.  Other concealed fixed roofing fixing systems generally fail at wind speeds of about 190 km/h.

Why choose Craft-Lock® for your project?

Craft-Lock® is arguably the best performing roof sheet in the country when it comes to performance in high wind conditions and turbulent weather. This was the sheet used for the Mall of Africa – recipient of multiple awards in the industry. Well over 4 million square meters of Craft-Lock® now features in the South African and African roofing landscapes.

  • Craft-Lock® can be installed on roof pitches as low as 1 degree. At this angle, the profile has enough flow capacity to withstand rainfall intensities in excess of 300 mm/h, depending on sheets lengths.
  • Craft-Lock® comes with a 5-10 year installation warranty if installed by an approved contractor and upon passing inspection.
  • Depending on material used, atmospheric conditions and building application, corrosion performance warranties are usually in the range of 10 – 15 years.

Our unique approach to fixing, improved purlin spacing, and other inherent product features make for a cost competitive concealed fix solution for your next project.

For more information on Craft-Lock® visit the Clotan steel website at or contact us for technical advice on your next project at

Get a Quote