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concrete Precast Concrete offers a housing solution – sa Housing Conference Precast concrete can reduce South Africa’s housing backlog dramatically. Just how was the subject of two papers presented at this year’s SAHF (Southern African Housing Foundation) International Housing Conference and Exhibition. These were delivered by CMA director, John Cairns, and Llewellyn van Wyk, a senior researcher at the CSIR. Staged in Cape Town during October, the conference was attended by 350 delegates, including a large overseas contingent. Keynote addresses were made by Helen Zille, premier of the Western Cape and the executive mayor of Cape Town, Dan Plato. Both outlined the immense challenges faced by the city in providing housing to a growing number of migrants and Zille presented a convincing case as to why spending R1 billion on a stadium for the 2010 World Cup benefited the city’s housing policy. Cairns focused on the means by which concrete can be effectively deployed to reduce the housing backlog in his address “The preferential use of concrete and precast products for the development of township housing and housing infrastructure”. He demonstrated how precast concrete has already made a positive impact on township housing by presenting a very Seen here in front of the CMA stand at the SAHF International Housing Conference and Exhibition are: Llewellyn van Wyk (left), a senior researcher with the CSIR; John Cairns, CMA (Concrete Manufacturers Association) director; Hanlie Turner, marketing manager of C&CI (Cement and Concrete Institute); and John Sheath, strategy and marketing manager of Ash Resources 22 Prestressed hollow-core concrete slabs manufactured by Echo Prestress, shortly after being lowered into position on one of the double-storied housing units at Pennyville attractive affordable housing development, Pennyville, south of Johannesburg’s CBD. Most of the building materials used on the project, including the bricks, the roofing, the paving, reticulation poles, and hollow-core precast flooring, were precast concrete based. “Speed of delivery and aesthetically pleasing finishes were the hallmark of this development and we believe that if there were more projects like it the housing challenge would be far less daunting,” he said. Cairns said one of the products which offers hope for the future is the precast hollowcore slab. “When combined in a foundation and flooring system it can be installed at a rate of 30 per day by a single team. This fasttracking and Agrément approved method allows building operations to begin immediately and speeds up the whole construction process.” SA Affordable Housing November/December 2009
concrete a brick. Corner blocks, reveal blocks, sill blocks, and half blocks are required to make effective use of modular blocks. Without the full set the advantages of modular construction are negated. “Thirdly, modular blocks are far larger and require a different set of skills. Because of this contractors and block layers must be taught how to use modular masonry. It’s encouraging to note that the educational process has already begun with CETAapproved modular training initiated by the CMA. High-quality affordable housing, most of it built using precast concrete elements, predominate at Pennyville. The picture shows houses built with Sedibeng concrete bricks and roofed with Monier concrete tiles, a path paved with Concor Technicrete’s concrete blocks, and prestressed concrete poles manufactured by Infraset Cairns also demonstrated how concrete roof tiles are increasingly being used on affordable housing projects, adding value to individual housing units far in excess of any initial purchase price. However, both the CMA and the CSIR believe that concrete blocks will remain a key component of low-income housing for some time to come. How its quality and performance can be enhanced was the subject of Llewellyn Van Wyk’s paper, “Maximising modular masonry”. Van Wyk based his address around the central question: “Can we build low income housing that performs as well as conventional housing at the same or a slightly higher cost than that of a typical poor-performing low-income house?” “Fourthly, using a full suite of modular masonry will solve another very prevalent problem, namely, cracked walls. And lastly, full modular masonry will also require the standardisation of components such as window and door frames.” Van Wyk says the CSIR is researching building technologies at an experimental site at the Pretoria Campus where several 40m² houses have been built to test different technologies. Two of them were built using modular masonry and the performance of both is being carefully monitored. “We are also working on the development of an innovative new suite of modular blocks which will offer performance and quality improvements. Concrete blocks will have to meet the new regulations for building efficiency which should be in place by April 2010. R and U values are going to be set which means producers will have to make adjustments in the manufacture of masonry blocks to meet these performance criteria,” concludes Van Wyk. Yes he says, but not just yet. A considerable improvement in the application of modular masonry must first take place. “Modular masonry offers a fantastic opportunity to not only improve housing delivery, but to build houses with zero wastage. But before this happens several measures will have to be taken,” says van Wyk. “In the first instance, houses will have to be designed with each and every block identified and numbered. If not, the system won’t work. This places certain constraints on design flexibility, but at this level the importance of building efficiencies far outweigh those of design flexibility. “Secondly, genuine modular designing will require a full suite of complementary blocks. One can’t treat the 390mm block like One of the houses at Pennyville which is being built with diamond-faced concrete bricks 23 SA Affordable Housing November/December 2009
Page 1: SA Affordable Housing Infrastructur
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Page 17 and 18: Marley EKONOROOF ®
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Page 42 and 43: ROOFING Turning shelters into homes
Page 44 and 45: news Another country, another Molad
Page 46 and 47: energy efficiency Service delivery
Page 48 and 49: news Extremely fast and precise mea
Page 50: news ‘Concrete for Housing’ pre

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