Specialised block provides practical seating arenas

News

Since earliest times, humans have felt the need to gather around a focal point to relax, negotiate and entertain each other. This has often been made possible by seating arenas or amphitheatres. Today, these structures are still very popular, however, the method of construction has become easier and building material more varied and versatile.

One of the more cost-effective ways of building a seating arena is to use pre-cast, solid concrete units or interlocking concrete blocks that are relatively easy to transport and install. In addition, concrete is durable, doesn’t burn and can be readily repaired or recycled. A specialised segmental concrete block has been developed by Terraforce, a local concrete product licensor with manufacturing outlets all over the world. This block, the 4x4 Step Block, is part of Terraforce’s large range of hollow core, reversible retaining wall units that offer a versatile segmental retaining system. They require low hardware input for manufacture, low transport costs and low inventory requirements at sales outlets.

Initially, the 4x4 step block was intended for low retaining walls and smaller steps, but soon became very popular not only for stairway access, but to provide comfortable, practical stairs and seating arrangements at leisure amenities and school sport facilities. The blocks can be stacked up without mortar, interlocking at the corners to form gentle curves and varying wall angles, but it is by turning the unit on its side to create steps that has made it so successful at creating small to medium-sized seating arrangements.

Flexible seating

Towards the end of last year, the block was used at the Tourism Centre in Kayamandi, Stellenbosch, to create an eye-catching amphitheatre – a simple neatly curved seating area required for viewing performances around a courtyard. Following the success of that project, two more arenas have recently been completed. Both were installed by Dassenberg Retaining, a Terraforce-approved retaining wall installer.

Acoustic excellence

The first amphitheatre to be completed is situated on Kronenburg estate, between Paarl and Wellington. Conceptualised by Robin Barnes, Architect with JHP Architects and Town Planners, it has become the ideal social gathering place. According to Barnes, it is designed on the same principfe as the traditional Greco-Roman amphitheatre where acoustics work on the principle that sound travels upwards. The centre of the circle is the origin of the sound, whether it be a play, a musical or an oration.

The sound travels outward and upward without losing much energy within the bounds of the stepped stair tiers of the amphitheatre. The people sitting on the tiers absorb the reverberated sound and have a dampening effect on the echoed sound. The clarity and quality of sound is carried in concentric sound waves to each part of the amphitheatre and experienced by each person sitting in any position within the amphitheatre in virtually the same way.

“We decided to use the 4x4 Step Block system as it provided flexibility and ease of construction. The blocks fit together nicely and provide the correct anthropometric sizes for seating and staircases. Ultimately, the client was provided a facility that could be used for weddings, musicals and seminars, whilst still maintaining a cosy and intimate atmosphere within the amphitheatre,” commented Barnes.

Designed on strict guidelines supplied by Terraforce the amphitheatre was built on a sturdy concrete foundation, followed by a row of concrete filled L11 retaining blocks, laid to the specified radius. Next, the 4x4 Step blocks, filled with wet concrete, were set on top of the L11 blocks in groups of four to allow for the insertion of two 1.5 m Y12 reinforcing bars, which facilitated the setting out of the radius. Behind each L11 and 4x4 block is a 400 mm wide layer of 3% cement stabilised sand, with space for a 350 mm wide strip of 50x100x200 Corobrik clay pavers. The above steps were repeated until the desired height was reached.

Indigenous installation

The second seating arrangement was conceptualised by Dassenberg Retaining, and is situated on the eastern bank of the Berg River Dam which captures water in the upper reaches of the Berg River and will augment the supply of water to the City of Cape Town by 18 percent. Hugo Pienaar, quantity surveyor for Dassenberg, says that the seating arena will provide visitors with a comfortable viewing platform to sit and admire the panoramic view of the surrounding area and the vast expanse of water.

“The Terraforce 4x4 Step Block was chosen for construction of the seating arena as everything was very environmentally conscious, seeing that the Berg River Dam is the first dam in South Africa to be designed, constructed and operated in strict accordance with the guidelines of the United Nations World Commission on Dams. The blocks and pavers blend in with the surrounding landscape, and are versatile and durable.”