Steel roofing and cladding is often treated as a commodity decision. Specify a sheet, find an installer, move on. Johan van der Westhuizen, Director of SAMCRA, believes that approach is precisely where many projects go wrong. We spoke with him about what quality actually means in this sector, where the industry consistently falls short, and why the decisions made at specification stage echo for decades.
Quality is not one decision
For Johan, quality in steel roofing and cladding rests on three interdependent pillars: strength, environmental suitability, and aesthetics. Each informs the other, and none can be addressed in isolation.
On the structural side, the starting point is understanding base metal thickness, the thickness of the steel itself, not the total coated thickness. It is a distinction the industry frequently blurs, and the consequences show up in underspecified products. “People talk of thickness as total coated thickness, which includes the thickness of the coating,” Johan notes. “One needs to differentiate between the two.”
Base metal thickness must be matched to the design wind and point load forces the sheeting will face, which depends on purlin or girt spacing and whether the application is roof sheeting or side cladding. Roof sheeting is typically exposed to higher wind uplift forces than side cladding, and the two should never default to the same specification.
Environmental conditions then determine the correct coating. A coastal or industrial environment demands a heavier zinc or aluminium/zinc alloy coating than an inland or low-pollution rural setting. The consequences of getting this wrong are not immediately visible. They surface years later in the form of premature corrosion and costly remediation.
Where projects fail
The most common failures Johan encounters are denting and sheets being blown off. Both are largely preventable with better upfront design.
Denting typically results from underestimating foot traffic. “Sheeting is really a non-trafficable product,” Johan explains. “It’s not designed for traffic.” In high-access areas, measures such as tighter purlin centres or staging platforms that distribute load before personnel step onto the sheet surface are practical precautions that are routinely skipped.
Wind uplift failures are more serious and more avoidable than they appear. Perimeter and end-span zones experience significantly higher uplift forces than field zones, and design codes provide clear guidance for calculating them. The problem, Johan says, is that this step is sometimes bypassed entirely, leaving standard end spans in place where the application demands more.
Solar panels have added a layer of complexity the industry is still catching up with. Unlike standard wind loading, which is distributed uniformly, wind forces transferred through solar panel mounting systems act as point loads on the sheeting. Placing panels at perimeter or end-span locations can produce uplift loads that exceed sheet capacity. “If you go and calculate the point load uplift on that specific point, you might find that it exceeds the capacity of the sheet,” Johan warns. It is a risk that is calculable and entirely avoidable with proper design.
Design responsibility cannot be passed down the chain
One of the more pointed issues Johan raises is the tendency for design and supervision responsibility to be shifted onto installers or sheeting suppliers. In his view, this is both unfair and counterproductive. Subcontractors further down the chain rarely have access to all the information required for a thorough structural and environmental design. “The better you start at the top, the better your project is going to end up at the end of the day.”
This is particularly important on concealed-fix and clip-on systems, which require tighter manufacturing tolerances and more precise installation methods than standard pierce-fix sheeting. Not all producers have the equipment or quality controls to deliver a consistent product, and buyers who do not ask those questions at procurement stage are carrying risk they may not be aware of.
Workmanship determines the outcome
Even a correctly specified and well-manufactured product can fail in the hands of inexperienced installers. Johan is direct in saying that everything invested in design and specification can be undone on site. Incorrect ridge turn-ups, improper lipping at eaves, failure to account for an out-of-square building, scratched finishes from metal components dragged across sheets during installation are common and consequential.
“Experienced installers will see that immediately and talk, so that whatever correction needs to take place is actually done,” Johan says. Every concealed-fix system has its own installation method. Assuming general roofing experience transfers across systems is a false economy that project teams continue to make.
The maintenance question
Steel roofing exposed to the elements requires maintenance, and this is an area where Johan sees consistent neglect. Dirt and pollution accumulation accelerates coating degradation. Roofs where debris is never cleared are frequently blamed on the product when the real cause is a lack of maintenance. “You need to clean things,” he says simply. “If dirt accumulates on a roof with pollution, it will affect the performance of that roof.”
A basic maintenance programme is not optional. It is part of the system’s performance equation and should be factored in at project stage, not addressed reactively years later.
The industry’s underlying challenge
Asked about the biggest misconception in the sector, Johan points to a debate that continues to simmer. Is sheeting a structural or an aesthetic product, and who carries the design and supervision responsibility? “There are both requirements,” he says. “Whoever takes the responsibility needs to understand both sides.”
The answer, he believes, lies in doing the work properly from the start, investing in qualified people, experienced installers, and fit-for-purpose specifications rather than treating the envelope as an afterthought. “Cheapest is not always the best. Rather ask whether the product that you specify answers the required criteria.”
For those selecting roofing and cladding solutions and service providers, Johan’s advice is straightforward. Look at the track record. The barrier to entry in the sheeting industry is low, and not every supplier in the market has the manufacturing capability or quality controls to back up what they sell. Long-standing service providers have stayed in the market for a reason.
For SAMCRA membership details and to connect with qualified roofing and cladding professionals, visit samcra.co.za.
About the author
This article was developed from an interview with Johan van der Westhuizen, Director of SAMCRA.