Sunday, 31 January 2016 09:02

Fasteners are the biggest cause of failure in metal roofing quality counts

Fasteners that keep metal roof sheets in place are just as important as the roof itself. As they are the only item actually securing the sheet to the substructure, there should be no compromise on quality to try to save costs.

Fastener failure is primarily due to inadequate or to non-compliant coating of the fastener. The coating is the sole protection provided to the fastener substrate, and as it weathers off, the shank and head become exposed to water and contaminants which rapidly eat away at the core steel, causing fasteners to fail.  

Bigger roll-formers have now started specifying the fastener type and class that will preserve warranties on their sheeting.

Roofing fasteners in short

Standard: SANS 1273.

Biggest reason for failure: The wrong class or type of fastener is used, and becomes a source of corrosion on roof sheeting.

Biggest challenge: Insulation being installed in thicknesses up to 135 or 150mm, which places enormous strain on fasteners.

What is law?

SANS 1273, which was revised in 2009, when more emphasis was placed on corrosion resistance of the fastener.

What are some of the biggest fastener challenges in the roofing industry?

Lack of knowledge of fastener standards:
We see roofing failures as a result of inadequate fastener usage, and while it is one thing to have a standard, it is another story for the industry to apply it or for building inspectors to correctly police it.

Insulation thicknesses:
Revisions to the energy-efficiency standards have resulted in insulation being specified in thicknesses never seen before, which requires extremely long fasteners. This can lead to instability of the entire installation.

Vendors make claims made for their fasteners which cannot be verified:
Many fasteners sold in SA are not compliant with our legislation, and are not manufactured to the standards required for the Class of fastener they claim to be.  Independent and credible testing verification of coating properties is critical.  

Traceability of fasteners:
If fasteners cannot be identified by manufacturer (usually as a distinctive head marking), they cannot be tracked back to the actual batch of manufacture, the responsibility for fastener failure will fall on others in the supply chain, and not on the fastener manufacturer. This has massive cost and credibility implications for installers, suppliers and professionals on the project.

When buying fasteners, what are the key points to consider?

  1. Understand the site location and corrosivity environment before determining the grade of fasteners to use. The lifespan of the roofing fastener should match or exceed that of the roof sheeting in that environment. Never use anything less than the minimum class as suggested by the sheeting manufacturer or roll former.
  2. Compatibility of the roof fastener with the roofing material is crucial. If not, there will be a galvanic reaction between the fastener and the roof sheeting material, causing premature corrosion of both fastener and sheeting.
  3. Follow the recommendations of the metal manufacturers or roll formers as to which fastener coatings and classes are appropriate for the sheeting in order to preserve warranties and life span on the sheeting.
  4. Only buy products from known manufacturers who can back up what they claim about their fasteners. This ensures accountability by the fastener manufacturer who should be prepared to stand behind his product for the duration of its service life. He must also be able to provide you with specifications and test reports to verify the fastener ‘class’.
  5. All screws must have EPDM sealing washings which are free of carbon fillers. Black carbon causes premature corrosion of coated steel.