By Fred S Crofts, Pr. Eng., Pr. ASS Valuer, structural engineer and masonry consultant
Advances in hollow concrete block masonry in the use of housing over the last four decades have alerted specifiers to its many uses. Concrete masonry has excelled past addressing the pressing need in affordable housing and in its heyday demonstrated significant possibilities for design and architectural masonry.
Much of the credit must go to the industry’s professional bodies that have shown the way forward through information programmes, conferences, technical publications and national standards organisations, such as the Concrete Manufacturers’ Association (CMA) in South Africa.
One of the most adaptable products known to man, concrete has long been a natural choice for any type of construction project. With advances in concrete manufacture, particularly in the United States of America (USA) and housing shortages in South Africa, hollow concrete block became recognised as a panacea for all kinds of designers’ headaches, since the need to build on large scale was paramount.
An unfortunate reputation
Through its vast number of applications, however, concrete block masonry acquired the tag of being a poor man’s product. The many Reconstruction and Development Programme (RDP) housing developments only added to its image as a soulless, catch-all product, and a lack of care in architectural detailing and structural specification in the design of housing, especially concrete block housing, became apparent in certain large construction projects.
Concrete blockwork had by the 1970s unfairly acquired the reputation of being a downmarket building material. During this same period there has also been an increase in crudely manufactured roadside concrete building blocks taking advantage of the demand for this product, which has further tarnished the reputation of the concrete block industry.
The current SANS 10400 XA energy usage requirements furthermore “knock the block”. Sometimes pursuing green building can have unintended consequences, especially when it becomes the overriding focus as opposed to focusing on the broader issues of sustainability.
But even with this unfortunate publicity, concrete blockwork has become unrivalled as a cost-effective method to provide a masonry envelope for housing, especially affordable housing.
The manufacturing of concrete masonry improved over the years due to the introduction of a national manufacturing standard (SANS 1215: The South African National Standard for the standard specification for concrete masonry units).
Its position in the market was further strengthened by rigorous product development, quality assurance and the improvement in dimensional manufacture of blockwork, largely due to the use of sophisticated block-manufacturing equipment. At the time, there has been a proliferation of reputable concrete block manufacturers as the demand for concrete masonry increased throughout South Africa, especially in the larger economic growth centres.
The industry today
Recently, the CMA’s membership has dwindled and currently there is not a single member manufacturing hollow concrete block. Most, if not all the block manufacturers in Gauteng, have ceased production and manufacturers elsewhere have become unprofitable or are finding it difficult to keep their doors open, with the Western Cape seemingly the exception.
There is simply not enough housing stock overall to meet the demand, and there hasn’t been for a while. The shortage is most pronounced in low- to middle-income suburbs in metropolitan cities such as Johannesburg and Pretoria. On the whole, the residential property market continues to look promising, yet concrete block manufacturers are closing their doors.
The reason for this conundrum must lie in the downturn of the economy and the effects of the rating downgrades that are beginning to hit home. Manufacturers state that there are not many low-cost housing projects on the cards and they as manufacturers are stretched to the extreme as creditors.
What about alternatives?
Innovative building systems are always mooted as a magical quick-fix solution to the housing problem, but in my experience none of these have ever been successful or economically viable in the long run.
The concrete block still has a place
The National Building Regulations (NBR) are generally functional in nature, in the sense that they do not prescribe how a building should be constructed, but rather stipulate the qualitative performance requirements that the building design or construction of the building must satisfy.
To facilitate the use and application of the NBR, the functional regulations are supported by a set of deemed-to-satisfy rules which are published in “SANS 10400, The Application of the National Building Regulations – Part K: Walls”. The deemed-to-satisfy provisions describe design and construction methods, materials and solutions, which if applied, will ensure that the building so designed and constructed will satisfy the functional requirements of the regulations.
Hollow concrete block masonry manufactured to a specified minimum standard fully complies with the NBR and the use thereof is accepted nationally by financial institutions.
Admittedly, when the economic upturn comes, there will be a couple of obstacles to overcome, such as enticing the concrete block manufacturers back and addressing countless masonry skill shortages. The one thing the market can depend on though is a “concrete” solution to the housing problem – the hollow concrete block, fully compliant with the National Building Regulations and supported by four decades of technical nurturing.
For more information, please contact Fred Crofts at firstname.lastname@example.org.
Caption main image: A childcare centre being constructed using concrete blocks.
Fred Crofts discussed the role of concrete blockwork as a modern building material, especially in housing.