By Candace Sofianos King | Photos by SASFA
While light steel frame building has been around in southern Africa since 2006, this viable cost-effective alternative building technology is on the rise. SA Roofing investigates.<
Cranes continue to dominate Pretoria’s prime precinct of Menlyn Maine, a mega mixed-use development that’s taking shape by the day. What’s been dubbed as ‘Africa’s first green city’, the precinct is also home to several exquisite buildings that make use of light steel framing.
To find out more about this intriguing building method, SA Roofing explored Menlyn Maine with John Barnard, director of the Southern African Light Steel Frame Building Association (SASFA). A division of the Southern African Institute of Steel Construction (SAISC), SASFA has played the role of advocate for light steel frame building in South Africa for almost 12 years.
“I believe we have established an industry that’s here to stay,” says Barnard, adding that the association has been at the forefront of establishing the sector’s codes and standards since its inception. More than half of light steel frame building activity takes place in the roofing sector, adds Barnard.
With 30 years behind him as a structural engineer, Barnard is no stranger to the steel industry. Practising what he preaches, his very own home is a testament towards steel frame building. “I will never forget the first time I witnessed the construction of a light steel frame building – it was in 2006, before SASFA was born, when I saw this exciting project go up in Pretoria North. Since then this building method has grown tremendously,” Barnard elaborates.
Barnard point out that South Africa was shown the ropes of light steel frame building in Australia. “We have learnt quite a lot from the Australian market, although they used to focus on low rise residential building only. Development of the industry in southern Africa happened over a broader front – accordingly we are now making use of light steel frame across the board, ranging from residential to office and commercial. In some sectors we believe that we have grown beyond the Australian market.”
Amidst escalating construction and energy costs, the need for an effective and financially attractive alternative building methods is paramount in the grand global scheme of things. Enter light steel frame building, an exciting and feasible construction medium utilised for a growing number of building types.<
A closer look
From small residential and other low-rise structures to façade walls of large multi-storey office and commercial buildings, light steel frame building is garnering greater attention. “Light steel framing is being used for a wide range of building types including low-rise residential building, student accommodation and hotels, to office and commercial buildings, schools, hospitals and clinics, churches, community halls and more,” notes Barnard.
There are a number of reasons why light steel framing for roof structures is showing healthy growth, highlights Barnard. The speed of construction, accuracy, excellent thermal properties, logistical cost advantages and design flexibility is what makes this building method an appealing choice, he says, adding that it provides well insulated buildings and complies with building codes standards of best practise.
SANS 517 Light Steel Frame Building is the building code for low rise light steel frame buildings. It fully complies with the requirements of SANS 10400. As far as energy efficiency is concerned, SANS 517 complies with SANS 10400 XA, as well as the more stringent SANS 204.
Barnard notes the superior functionality of light steel frame building is a prized attribute. “It is lighter than timber and hence offers logistical advantages as well as ease of handling on site. Mechanical properties are guaranteed and will not change with time. Sections are straight and not prone to warping or insect attack. It also facilitates fast construction,” he points out.
Barnard continues, “Cold-formed sections are optimised, resulting in low mass of roof structures. The zinc coating of the galvanised steel sheet used to manufacture the light steel frame sections provides protection against corrosion for the design life of the building.”s
Coming into its own
While the availability of light steel framing for roof structures has improved, the design skills of South African light steel frame truss designers has simultaneously refined rapidly. “South African designers are excelling in the use of light steel framing for curtain walls for multi-storey commercial and office buildings. The sector is also well regulated – a certified structural engineer must sign off all light steel frame buildings,” says Barnard.
What makes this building method attractive, you may ask? Barnard says the major advantage is that there are very few disadvantages. “This building method boasts logistical advantages due to the low mass and transportability of light steel frame sections, ease of handling on site, the inherent accuracy, and the reliability of mechanical properties. All of these factors combine to make it cost-competitive.
Light steel frame building is often used for vertical extensions as the low mass of the floor joists and walls more often than not render the existing foundations adequate for the increased load. Barnard highlights that truss spans of more than 30m is possible, opening up competition with heavy welded hot-rolled structures. Where required, hot-rolled sections are used in combination with light steel framing for extreme spans, he says.
“Long span trusses are very slender and difficult to erect one by one. MiTek, one of the major light steel frame suppliers in this segment, has, in conjunction with their licensees, devised a process to overcome this problem. They box groups of trusses on the ground with bracing and purlins and then lift these clusters of trusses onto the building using a long reach, low mass crane. It is safer, as much of the work is done at ground level, and quicker. As an example, the roof trusses of the 3 200m² Kingdom Leadership Centre in Mpumalanga were erected in a single day!”<
Frame of reference
Provided the foundations or floor slabs have been cast accurately and level, installation of wall frames and roof trusses can take place rapidly, using a small team of artisans, says Barnard. “For instance, wall frames and roof trusses for a 250m² house can be put up in three or four days, by a team of four artisans. While it is easy to erect, it has to be done correctly, and SASFA strongly recommends the use of competent and trained builders.”
Most of the materials used are incombustible, and hence do not propagate fire, notes Barnard. “Fire resistant gypsum board is used for internal lining to protect the steel against the heat of internal fires. The light steel frames are designed to resist high wind speeds – from the roof trusses and their connection to the wall panels, through the bracing in the walls to the anchoring of the wall panels to the floor slabs or foundations,” he highlights.
“The materials used for light steel frame building are not cheap, but as a package, with all its advantages, it is cost-competitive – otherwise the use of light steel frame will not be expanding,” states Barnard. Having said this, he believes the future of light steel frame building in South Africa looks bright and promising.
“The steel industry recently hosted the Steel Awards, where 19 light steel frame projects were submitted. Apart from the light steel frame category winner, Gateway West, there were a number of eye-catching projects including a game lodge in Botswana; the vertical extension of Kaap Agri offices in Paarl; the roof of the Mediclinic in Stellenbosch; the Spectacle Warehouse in Pretoria; and several light steel frame houses built in Knysna in response to the needs after the terrible fires in 2017.
“We are busy with changing mindsets within the industry. I do believe that five years from now we will see light steel framing as a conventional and standard building method – let’s face it, it is the logical way to build, designed to overcome all the disadvantages of masonry building. It is quick, accurate and neat, with minimum wastage. Within a few years it will be the preferred way of building. It is the future.”