Public interest in light steel frame building (LSFB) continues to grow, despite the slowdown in the building industry in South Africa, which is operating at about half its prerecession capacity, says Southern African Light Steel Frame Building Association (Sasfa) director John Barnard.
“Currently, everybody is pricing just to survive,” says Barnard, who expects rapid growth in the LSFB industry once the international economy has stabilised and the local building industry has recovered.
Citing the results of Sasfa’s most recent biannual survey, which is carried out to quantify the level of LSFB activity in the market, he reports that 290 000 m2 of floor area was built using light steel framing (LSF) last year, which included residential and office buildings, classrooms, hospitals and expansions on existing structures.
Light steel roof trusses are becoming increasingly popular, according to the survey, which indicates that 1.1-million square metres of roofs were erected last year, using LSF roof structures. Barnard says this comprises some 16% of the total local roof truss market.
“It was always predicted that light steel roof trusses would be the low-hanging fruit for the construction industry, owing to its efficiency from a handling, installation and cost-efficiency point of view,” he says.
Further, Barnard believes the increased interest in LSF is the result of its energy efficiency and sustainability – both with regard to the embodied energy of the material and components, as well as the operational energy of the building over the course of its design life – compared with traditional masonry buildings.
He explains that the embodied energy of an LSF wall, which includes all the energy that goes into that wall – from mining the iron-ore and coking coal to manufacturing the steel and transporting the product to the construction site – is a quarter of the embodied energy of a double-layer plastered brick wall, based on Australian figures.
Moreover, LSFB has significantly lowered logistics requirements, which is also factored into embodied energy. Comparing the mass of building materials required for a 200 m2 brick-and-mortar house to that of an LSF house that has the same floor space, Barnard has calculated that the mass of materials required for the brick-and-mortar structure would be about 180 t, which will need 18 trucks with a delivery capacity of 10 t.
“When the same building is constructed using LSF, however, it would require 11 t of material, which demands only two 10 t trucks. The benefit of transport efficiency is therefore obvious,” he says.
Embodied energy constitutes about 20% of the energy required for a building in its lifetime, says Barnard. He believes this figure could increase as newer technologies are devel- oped and the construction industry becomes more energy efficient.
He cites a research project carried out by the Council for Scientific and Industrial Research in 2011, which indicated that an LSF structure required about half of the energy needed to heat and cool a masonry residential building to a comfortable internal temperature.
This statistic underscores the advantage that LSFB has over traditional building with regard to operational energy, which accounts for 80% of a building’s energy consumption in its lifetime. Embodied energy makes up the remaining 20%.
Barnard maintains that the growing energy efficiency requirements of new buildings will ensure the growth of LSFB from affordable and upmarket residential buildings to commercial and office buildings.
“There’s little doubt in my mind that LSFB will eventually become a mainstream building method. Twenty-first-century demands on sustainability, including energy efficiency, as well as handling and logistics, will ensure the growth of LSFB.”
Sasfa aims to eventually capture 20% of the low-rise building market and believes that once the LSFB industry has reached the 10% mark, the fire will fuel itself.
While multistorey commercial and office buildings offer exciting prospects, Barnard believes housing projects are still the largest area of growth potential for the LSFB industry in South Africa.
He says more people are expanding existing structures instead of building new ones and that vertical extensions are made possible by LSFB.
“With LSFB, one can expand by adding a floor or a level to a building, normally without having to worry about the foundation of the structure,” says Barnard, adding that this cannot be done with conventional construction because of the increased weight and its impact on the foundation of the building.
He adds that, while there are far fewer multi- storey buildings in South Africa than new housing projects, the country is progressing well in the housing construction market.
“The LSFB industry in South Africa started off by focusing on residential construction because it involved smaller and simpler projects.”
Barnard says that, when LSFB construction first started coming to the fore, South Africa followed Australia’s lead. However, South Africa has added some multistorey buildings to its portfolio through the innovation of local architects and designers.
“This is something Australia is not really doing, so we’re surpassing them in this regard,” says Barnard. He admits, however, that South Africa is still constructing two- or three-storey LSFBs, whereas the US has already managed to construct LSFBs of up to nine storeys.
Projects in Progress
Barnard tells Engineering News there are currently a number of significant LSFB projects under way in South Africa, one of which is a three-storey, 800 m2 residence at Xanadu Eco Park, overlooking the Hartbeespoort dam, in the North West province.
Insulation was the owner’s number one priority for this residence, which was achieved by constructing two layers of LSFB with a 100 mm gap in between. The walls were then clad with 60-mm-thick polystyrene, backed with galvanised steel sheeting, which formed the external layer of insulation.
Glass wool inside the inner wall provided a second layer of insulation.
Barnard believes that, if the same project had to be built in brick and mortar, with the required insulation in the walls, it would have been significantly more expensive and construction would have taken even longer than the estimated nine months it will take to complete this LSFB project.
In addition to optimal insulation, the Xanadu residence boasts an underfloor heating system that pumps hot water through pipes in the floor, which significantly reduces electricity consumption when it comes to heating. The air space between the two wall layers also allows for the piping of a central vacuuming system.
Barnard reports that the Xanadu project is about 85% complete, the construction phase having started in October 2011.