The South African mainstream building market has been cautious in accepting light-steel frame building (LSFB), unlike in the US, Australia and New Zealand where it is being used increasingly, yet the building method’s advantages – substantially faster construction time, energy and cost efficiency, and significant environmental benefits – are grabbing the attention of a growing number of industry participants.

It was, therefore, no surprise when, in March, environment-friendly building television programme ekoSTYL producer Francois van Wyk approached the Southern African Light Steel Frame Building Association (Sasfa) to participate in its 13-part series on ecofriendly building, which is broadcast on DStv’s KykNET channel.

The idea was that the ekoSTYL cameras would document the full-scale renovation of a masonry-built house – including the addition of a 140 m2 second storey using LSF – and broadcast progress in weekly installments.

“JVR Architects architect Joe van Rooyen knew we wanted to make use of green building methods, and since we were going to do the renovation in less than ten weeks, LSFB was really the only option for the second storey,” says Van Wyk.

“When we subsequently started researching LSFB, we came upon the many ecofriendly benefits of this building method, which were obviously right in line with the concept and format of the show.”

Sasfa director John Barnard explains that LSF is significantly more energy efficient than more traditional construction methods with regard to both the embodied energy of the materials and components, and the operational energy, which refers to the energy used in heating and cooling the building over its design life.

This is illustrated in a recent research project carried out by the Council for Scientific and Industrial Research, which indicated that a LSF building will require less than half the energy needed to heat and cool a masonry residential building to comfortable internal temperatures.

Meanwhile, steel is also a reusable and recyclable material, which means that it reduces the overall carbon footprint of the building project. It should be noted that a LSF building, built to the SANS 517 building standard for LSFB in South Africa, fully complies with the requirements of the SANS 10400 XA South African standard for environmental sustainability and energy use in buildings, and also that of the more stringent SANS 204 energy efficiency standard.

LSF is ideal for renovating or adding a second floor to an existing old brick house as it will usually not be necessary to strengthen the foundations and the whole process can happen much quicker.

Barnard explains that LSF can be easily used in conjunction with heavy structural steel, which may be required for long spans or large cantilevers, or to be exposed as part of the architectural expression.

Project Processes
When Barnard first visited the site of the eco-friendly, masonry-built house in Parktown, Johannesburg, in late April, some of the walls of the existing structure were still being broken down to accommodate the extensive renovations that were to be done to the ground-floor level.

“The television series had already started airing, with the final programme scheduled for June 25 – only two months away, which meant it was going to be a tight schedule, even for LSFB,” says Barnard.

Building contractor IKN Construction, owned by Ian Nyschens, was appointed by Sasfa to do the job. Nyschens has been involved in the building of some large upmarket LSF houses – including a 800 m2 mansion in the Xanadu Eco Park, on the Hartbeespoort dam, in the North West.

Nyschens, who has been involved with LSFB for about six years, enjoys working with steel because “there is less site rubble and the building process is extremely accurate,” he says.

Nyschens met with the architects on site and took detailed measurements of the existing masonry walls, since there is always some deviation from plan dimensions when working with brick buildings. “Accurate site measurements were necessary for the manufacturing of the light-steel floor joists and wall frames to ensure that everything fitted,” he explains.

The building contractor and its building team started in early May and by that time the first batch of floor beams, fasteners, shutterply or plywood, fibre-cement floor boards and rubber underlay had been delivered.

In the two places where the second storey would not be sufficiently supported by masonry walls, hot-rolled I-sections of steel provided an elegant support solution.

Flooring
Once the I-sections were in place, Nyschens was able to install the floor joists and the shutterply floorboards.

The light-weight floor was constructed using 18-mm-thick shutterply, followed by a 3-mm-thick layer of closed-cell foam rubber intended to absorb impact sound, and finished off with 15-mm-thick high-density fibre-cement board.

The mass of the lightweight floor came to only 50 kg/m2, compared with 350 kg/m2 for a 150-mm-thick reinforced concrete floor, and after only 17 days on site, the floor was installed and the first wall panels were being erected, highlights Nyschens.

Building Structure
The walls were covered on the outside with 10-mm-thick high-density fibre cement boards, provided by building products supplier Everite. This was followed by 10-mm-thick polystyrene strips placed on the steel frame to serve as a thermal break between the outer cladding and the frame, in accordance with the requirements of SANS 517.

The light-steel wall frames were covered on the outside with a vapour-permeable membrane to enhance the waterproofing of the building and to prevent any air movement through the wall panels.

Finally, the wall panels were braced by the use of strips of high-strength galvanised steel, strengthening the resistance of the wall panels to wind forces, explains Nyschens.

Barnard notes that this process took only a few days with only little cutting necessary and minimal material wasted.

“This demonstrates another way in which LSFB saves time, owing to the manufacture and assembly of the lightweight-steel frame to specification in the factory and only then being quickly erected on site. Once the steel frame is in place, the building can be enclosed and internal finishes, such as tiling and painting, can start much sooner than with a masonry structure,” says Barnard.

Time can also be saved when using LSFB as different disciplines can work in parallel. For example, LSF window apertures can be agreed upon upfront with the glass and aluminium contractor, even before the LSF walling is installed, as the framing system is accurate.

Roof Structure
Meanwhile, light-steel joists were used for the roof structure and installed at 1.2 m spacings. Purlins, consisting of cold-formed top hat sections, made using high-strength galvanised steel sheeting, are fixed to the roof beams using self-drilling screws.

The roof sheeting – Steel producer Arcelor Mittal South Africa's Chromadek was used for this purpose – was then fixed to the purlins, again using self-drilling screws.

“As with all the light-gauge steel used in the frames, the screws have to comply with stringent corrosion-resistance standards to ensure the long, maintenance-free life of the building,” explains Barnard.

Insulation in the ceiling under the roof is important for a well-insulated building to prevent losing heat in winter and gaining heat in summer. Sasfa specified the use of 135-mm-thick glasswool insulation, as required by the LSFB SANS 517 standard.

For the ceiling under the floor of the second storey, the contracting team used 15-mm-thick fire-resistant gypsum board to meet the fire rating requirements, and also installed 50-mm-thick pink fiberglass insulation in the ceiling for acoustic insulation.

Both the walls and the ceilings were then skimmed with a thin layer of gypsum cement to provide a smooth surface for painting.

Challenges
The particular challenges that faced the LSF building team was the difficult site which it had to work on. “It was very hilly and, with work only half-finished on ground level, we had to contend with deep trenches and uneven terrain. There were also two building teams working concurrently on a tight building programme. Despite this, the project turned out great,” says Nyschens.

Van Wyk says the ekoSTYL production team was impressed with Sasfa and its partners and were amazed by the progress of the LSF building each day.

“Now is a very exciting time for LSFB in South Africa, as people increasingly realise that LSF can be used for a range of different applications and recognize the benefits of the building method, both practically and environmentally,” says Barnard.

He believed that exposure on programmes such as ekoSTYL will increase awareness among the public and building professions about the advantages of LSFB and dispel beliefs that heavy masonry or reinforced concrete are prerequisites for quality structures.

He also maintains that Sasfa and the television producers have been receiving a steady stream of enquiries from architects and future homeowners since the ekoSTYL programme aired.

“There is no doubt that the prejudices in South Africa against unconventional building methods such as LSFB are decreasing,” says Barnard, adding that the more people see high-quality structures being built with light steel and realise its environmental and other benefits, the more they will open up to new methods of construction.