Knysna-based light steel frame (LSF) construction company Rancor has completed the addition of a 570 m2 second floor to the Kaap Agri building in Paarl, Western Cape.
The requirements for the new structure were clear; it had to be cost-effective, comply with building regulations, be acoustically well insulated, be energy efficient, and be built as quickly as possible.
The initial design, before Rancor was called in, was based on brick and mortar with concrete beams to support the second floor. However, after the foundation footings were uncovered, it was apparent that additional footings would add such significant extra costs and time to the project that the design was not a viable option.
Rancor was then invited by architecture and engineering firm De Kock & Vennote to provide a solution in LSF that would comply with the requirements.
“LSF met all the requirements and, in addition, resulted in lower loading of the existing walls,” says Rancor CEO Charl van Zyl, adding that South African construction company Stahlbau Construction, the main contractor, accepted the solution.
Scope of the Project
Apart from adding a second floor to the building, the interior of the existing ground floor had to be totally refurbished. LSF floor joists, 350 mm deep, were installed at 300 mm spacing to support the new lightweight floor. The joists span 6.5 m and are supported by the existing brickwork.
The flooring consists of 21-mm-thick shutterply boards laid over the floor joists, followed by 12-mm-thick fibre cement boards supplied by Roodekop-based dry construction supplier Marley Building Systems. Special sound mats were placed between the joists to reduce sound transmission.
The sound insulation was further enhanced by installation of suspended acoustic ceilings with an ample ceiling cavity. Acoustic insulation was a non- negotiable requirement.
In addition, the walls for the second floor consist of LSF wall panels, clad on the outside with a magnesium oxide board and a tyvek vapour permeable membrane. Top hat sections, 20 mm deep, were then horizontally fixed to the structure, serving as brandering to fix the external diamond deck prepainted profiled sheeting and therefore providing a durable and robust external skin. Glass wool cavity batt insulation, supplied by thermal and acoustic insulation solutions supplier Saint Gobain Isover, was installed in the wall cavities created by the LSF, providing the required thermal insulation. The internal lining consists of 15-mm-thick fire-rated Marley Gypsum boards.
Light steel trusses were used for the roof structure, spanning 17 m, with openings onto the front deck over the exterior stagger glass doors. Top hat cold formed steel sections, 40 mm deep, were used as purlins to which the prepainted diamond profiled steel sheet was fixed.
“The LSF shell of the project, the floor, walls and roof, was completed in three months with internal finishing taking a further three months,” adds Van Zyl.
Southern African Light Steel Frame Building Association (Sasfa) director John Barnard said in a statement last month that it is encouraging that an increasing number of construction professionals are recognising the environmental benefits and long-term cost savings of LSF building. Sustainability in terms of buildings is essentially based on three criteria: social acceptability, affordability and energy efficiency, and LSF buildings rate highly on all sustainability considerations.
LSF buildings appear the same as conventionally built structures, except for the finishings with the former better in this regard. There is a rapidly growing acceptance of LSF for ‘affordable’ as well as upmarket buildings in South Africa.
Further, LSF is a cost-effective building method, with financial savings emanating from significant time savings to complete building projects, less rework, reduced logistical costs – which are of growing importance owing to the escalation of fuel prices and general construction inflation – and a drastic reduction of wastage and rubble on building sites, compared with the brick-and-mortar alternative.
LSF building is significantly more energy efficient than heavy construction methods; both with regard to ‘embodied energy’ of the materials and components, as well as ‘operational energy’ relating to heating and cooling of the building over its design life.
All three of Barnard’s criteria are met on the Kaap Agri project. In fact, as far as energy efficiency is concerned, the R-value (the measure of thermal insulation) of the Kaap Agri external walls is greater than 3 W/m2K which is more than four times better than what would have been achieved using a double brick wall.
Barnard says the Kaap Agri project is indicative of an area of construction where LSF is increasingly playing an important role.
“It is not only perfect for extensions of existing buildings, but, also, LSF building is becoming increasingly relevant in a construction environment that is striving to reduce the impact on the environment,” he concludes.