When specifying roofing systems, the ideal is to understand the complete picture – from the largest roof sheet to the smallest screw, and everything that might be mounted on top – before starting to sort out the individual puzzle pieces.
Although a building envelope consists of many different elements that are manufactured and provided by several different suppliers, it ultimately forms one system. In order to ensure optimal top of wall functionality and longevity, it is important that a roofing system should be considered, designed and specified as a whole – from the longest roof sheet to the smallest screw or fastener and everything that might be mounted on top.
While professionals are well informed about the latest trends and developments, roofing manufacturers and suppliers indicate that there undoubtedly is room for increased participation and responsibility. Roofing accessories, especially, are rarely specified in detail from the start of a project, and instead are included in a design specification as “Roof sheeting to be fixed in accordance with manufacturer’s specifications”.
On the upside, according to Reitze Hylkema, managing director of Kare Industrial Suppliers, where roll formers in the past did not always specify roofing fasteners and left it up to the roofing contractor, whose decision more often than not was determined by price over quality, they are doing that today. “What we have seen changing over the years is that roll formers now clearly specify the type of fasteners that have to be used on specific types of roof sheeting and profiles,” he says.
“The more the fasteners and other items are specifically specified, the better. It takes away the choice of using the incorrect product and also levels the playing field when tendering,” Hylkema explains. “At the end of the day, everyone is compelled to quote on and use the appropriate accessories instead of leaving it open and vague.”
Flashing detailing is one area where professionals such as structural engineers should play a bigger role, according to an architectural specifier at Clotan Steel, Corné Nel.
“Flashings in particular are mainly considered as aesthetical features, but they play a critical role in diverting water off the roof and away from the roof cavity. We are often asked to assist with flashing detailing by architects in particular, mostly with little or no input from the engineer. Features such as flashings and fasteners have a very direct impact on the eventual warrantees of the roof, and the structural engineer most certainly must have greater participation,” he suggests.
Comparing apples to oranges
Not all fasteners and flashings are equal in quality and function. And since they are such a vital component of a roofing installation, Nicci Solomons, national marketing manager at Safintra, emphasises the importance of selecting products with service life warranties that match those of the metal sheeting used.
“The use of specialist products for a specific application is advocated. Even flashings can be customised for specific functionality and design aesthetics. With fasteners, factors such as the type of materials, coating, thickness, porosity and proper use all need to be considered when selecting the correct fasteners for the application. It should also be noted that the use of non-approved accessories often nullifies manufacturers’ warranties,” she states.
“In the case of pierced fix profiles, fasteners are exposed to extreme climatic variations and other elements such as pollutants, debris build-up and natural thermal movement, making it even more critical to select the correct class and material of fasteners for the sheeting material used and which also complements the structure. Technical advice is still recommended, as geographical location and environmental conditions such as seaspray, terrain and design all come into play,” she adds.
From a practical perspective, Hylkema points out that steel roofing components vary in thickness from very thin light gauge steel, to standard cold-rolled purlins, to very thick hot-rolled steel typically used on power stations and mining applications.
“Because these heavy-duty industrial projects are fairly uncommon, not many people know which fasteners to use. Often they specify and purchase standard screws, only to find that those won’t drill into the hot-rolled steel. Also, when it comes to very thin gauge steel, screws designed for normal cold-rolled purlins won’t work well. Instead, they pull out since they have no hold,” Hylkema explains.
Best practice: Thin gauge steel
Called “specials”, the fasteners used to assemble the trusses and the batons of a light steel roofing structure, and to fix the roof sheets onto the steel frame of light gauge steel purlins, are not the run of the mill fasteners used on normal roofing applications.
“Most of the screws have smaller drill points and finer, broader and flatter threads in order to grip the thin gauge steel better and offer higher pull-out,” Hylkema says. “Therefore using incorrect fasteners on thin gauge steel roofs will most definitely result in problems.”
What goes on top, should stay on top
Apart from the growing share of thin gauge steel products in the market, probably one of the biggest impacts on the roofing industry over the last couple of years has been the increased installation of solar geysers and solar photovoltaic (PV) panels on rooftops.
According to Hylkema, these are sometimes installed on existing roofs that weren’t designed to carry the extra weight. Another potential issue is that these PV panels cover sections of a roof that are no longer washed by rainwater, so dust and debris can build up and cause premature corrosion. Dust, which contains pollutants, also gathers on top of the panels and when it rains, causes runoff onto the sheeting below the panels, which can also result in premature corrosion.
To counter this, the roof maintenance needs to include rinsing the roof on a regular basis, especially the unwashed areas where rain doesn’t fall directly onto the roof. This is not only applicable to areas covered by PV panels, but also where an overhang covers a section of wall cladding, for example.
“These are things that I don’t think we’ve really dealt with before in South Africa. Now that the solar market is on the increase, people need to take these aspects into consideration from a roofing perspective,” Hylkema advises.
Nel further notes that as solar panels and geysers gained popularity, similarly the demand for compatible products and fixing systems amplified. “The industry has heeded the call for innovative and cost-effective solutions for mounting these products on existing roofs, without violating the structural integrity of roofs overall,” he says.
Best practice: Mounting equipment on roofs
Nel explains that concealed fix roofing systems are by their very nature not intended to be penetrated by fasteners, ventilation systems or any other objects such as communication systems, air-conditioning units and even television cables.
“However, since this remains largely inevitable, the fixing and installation of any product not linked to the roofing system itself must be controlled by the roofing manufacturer in close collaboration with the structural engineer. Most warrantees unequivocally state that any perforation of the roof surface will render that warrantee null and void. This certainly demands greater awareness and acute attention from developers and project managers,” Nel says.
“Light harvesting or any allowance for natural light by means of translucent sheeting must also be planned and designed in accordance with the roofing manufacturer,” he states.
Solomons adds that specialist clamps and brackets are available to avoid piercing metal roofing structures, particularly on concealed fix profiles. These products are compatible with common metal roofing materials and have been tested for load to failure results. Instead of piercing the roof sheet, it just dimples the profile to ensure water tightness.
In addition, she suggests that if piping penetrations are overlooked during the initial phases of a project, it can result in huge challenges down the line. “Waterproofing the holes with a relatively maintenance-free product that allows the natural thermal cycling of a roof is the ideal solution, and we recommend the use of products that are proven to prevent water ingress and withstand extreme temperature fluctuations – providing peace of mind to the building occupant and owners.”
Best practice: Constructing the overall roof
Ultimately, to ensure the expected longevity of the roof, all the components need to be handled correctly before, during and after construction. “A roof is not a walkway, and should never be regarded as the preferred point for foot traffic,” cautions Nel.
“Providing temporary or permanent walkways will ensure that the structural integrity of the roofing system will remain intact, and the warrantee unaffected. With demanding construction schedules, there is an increased activity and presence of construction crew during construction, and apart from providing walkways traffic should be closely controlled and monitored,” he advises.
Nel further emphasises the importance of using only specified material and to be vigilant against dissimilar materials that will negatively react with each other. Project managers and professionals should insist on verifying the origin of materials.
“Flashings are unfortunately very easy to under-gauge and the practice of using thinner than specified materials is regrettably quite common,” Nel states. “Possibly the best preventative measure one can take is to rely on a roofing manufacturer that can be closely involved with the design aspects of the roof and remain intimately involved throughout the construction phases. Relationships based on trust will inevitably follow, and the industry will heal itself over time from any negative practice and influence.”
Organisations such as the South African Institute for Metal and Cladding (SAMCRA) play a pivotal role in providing standards and guidelines for the industry.
Nel also points out that there is a very clear move towards safety in general. “Safety equipment such as nets, cables and anchor points are installed during construction and often remain part of the construction for subsequent use by maintenance staff,” he says.
Get the help you need
Because it is not always practical for professionals to be au fait with each and every technical, legislative and regulatory aspect of all the sub-structures that make up the construction industry, Solomons advises professionals to always partner with a reputable roofing supplier who can provide sound technical advice prior to, during, and after a project who can respectthe design concept, and deliver a functional and aesthetically pleasing end-result.
“In an ideal environment all stakeholders would be aware of future property lifecycle plans such as retrofitting, the additions of heating, ventilation and airconditioning (HVAC), satellite dishes, solar panels and more, and this would allow all technical factors to be incorporated into the initial design of a project, but this isn’t always the case,” Solomons states.
“This is why it is imperative to partner with a roofing supplier whose products carry a manufacturer’s warranty, who keep up to date with and inform regulation, and who complies with SANS standards.”
Full thanks and acknowledgement are given to Kare Industrial Suppliers, Clotan Steel and Safintra for the information given to write this article.
Highlights in this article
– Specifying roofing accessories.
– Fasteners for different functions.
– Thin gauge steel applications.
– Considerations for installing PV panels and solar geysers on roofs.
– Mounting equipment on rooftops.
– Sealing penetrations through steel roofs.
– Best practice for roof construction.
– Safety measures.
– Partnering with the experts.