When Kaap Agri wanted to add a second floor to its building in Paarl, Western Cape, the expansion plans took a few turns.
The initial design, which involved brick walls with concrete beams supporting the second floor, turned out not to be a viable option after the foundation footings were uncovered and it was determined that additional footings would be required, which in turn would compound the cost and delay the project too much.
Architecture and engineering firm, De Kock & Vennote, then approached Rancor, a light steel frame (LSF) construction company, to come up with a solution for adding 570m² to the floor area by vertical extension, that also met the client’s requirements: It had to be cost-effective, comply with building regulations, be acoustically well insulated, energy efficient and had to be built in double-quick time.
“LSF met all the requirements and, in addition, resulted in lower loading of the existing walls,” says Charl van Zyl, chief executive officer of Rancor. This solution was also accepted by Stahlbau Construction, the main contractor, who eventually completed the project on time and within the budget.
How was it done?
Supported by the existing brickwork, LSF floor joists, spanning 6,5m and 350mm deep, were installed at 300mm spacing to support the new lightweight floor. 21mm-thick shutterply boards were laid over the joists, followed by 12mm thick fibre-cement boards supplied by Marley Building Systems.
To reduce sound transmission, special sound mats were placed between the joists and suspended acoustic ceilings with a big ceiling cavity were installed.
The walls for the upper floor consist of LSF wall panels, clad on the outside with a magnesium-oxide board and a Tyvek vapour permeable membrane. Top hat sections, 20mm deep, were then horizontally fixed to the structure, serving as brandering to fix the external Diamond Deck pre-painted profiled sheeting, providing a durable and robust external skin.
Glass wool cavity bat insulation, supplied by Isover, was installed in the LSF wall cavities, providing the required thermal insulation (R>2,2 m².K/W). The internal lining consists of 15mm-thick, fire-rated Marley gypsum boards.
Light steel trusses used for the roof structure span 17m, with wide openings on the front deck over the exterior staggered glass doors. Top hat cold-formed steel sections, 40mm deep, were used as purlins to which the pre-painted Diamond Deck profiled steel sheets were fixed.
“The LSF shell of the project (floor, walls and roof) was completed in three months, with the internal finishing taking a further three months. The client moved into his new head office on the planned date,” adds Van Zyl.
3 criteria for sustainability
John Barnard, director of the Southern African Light Steel Frame Building Association (SASFA), says that sustainability with regard to buildings is essentially based on three criteria and that LSFB rates are highly based on all of these.
1. Social acceptability
“LSF buildings appear no different to conventionally built structures – in fact, the quality of finishes is often better.
“It is a cost-effective building method, with financial savings emanating mainly from significant time savings, less rework, reduced logistical costs, and a drastic reduction of wastage and rubble on building sites, when compared with the brick-and-mortar alternative.
3. Energy efficiency
“LSF building is energy efficient – both with regards to the embodied energy of the materials and components, as well as the operational energy relating to the heating and cooling of the building over its design life. In fact, the R-value (the measure of thermal insulation) of the Kaap Agri external walls is greater than 3m².K/W – considerably higher than the 1.9 – 2.2 required by SANS 10400 XA. ”
Barnard also points out that the Kaap Agri project is indicative of an area of construction where LSF plays an important role. “LSF is not only perfect for extensions of existing buildings, but it is also becoming increasingly relevant in a construction environment that is striving to reduce the impact on the environment,” he states.
Main image: The completed Kaap Agri building after a second floor was added thanks to a light steel frame building solution.
Courtesy of SASFA
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