Dineo Phoshoko with input from Greenlite concrete
SA Affordable Housing has an in-depth look at alternative building materials currently available on the market and we consider the pros and cons for the affordable housing sector.
With the growing demand for social and affordable housing in South Africa, exploring alternative building materials is one of the smarter ways to reduce the housing backlog and the cost of delivering homes.
Traditionally, buildings are erected with conventional bricks and mortar. Although such buildings are reliable and strong, they are costly and take more time to build and some of the materials used to build with can be harmful to the environment.
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One alternative – Greenlite concrete products – are suitable for building low cost housing units. These products are made from 100% recycled expanded polystyrene (EPS).
The jumbo block and the lightweight aggregate can be used instead of conventional bricks and mortar. The lightweight concrete blocks are Agrément SA approved and have a 2-hour SABS fire rating. The blocks are a good alternative to conventional masonry as they offer lightweight walling which is cheap to transport along with impressive insulation and acoustic performance. The concrete blocks manufactured with Greenlite concrete are light, weighing a quarter of typical concrete blocks.
The lightweight aggregate comes in 250 long ton (lt) bags and is made from recycled polystyrene beads that are pre-coated with a Greenlite concrete additive. Four bags of lightweight precoated polystyrene aggregate is mixed with eight bags of cement, and 240ℓ of water to form one cube of lightweight screed mix. These screeds offer impressive weight savings over conventional screeds as well as combining the screed and insulation application into one process.
“We recycle post-consumer polystyrene back into beads through our recycling plants. This material is then used as aggregate mixed with cement and additives to form insulated, soundproof, fireproof, water-resistant lightweight concrete blocks and screeds,” explains Greenlite’s technical director, Hilton Cowie. The lightweight material that is not only able to reduce the structural concrete and steel requirements but offers excellent insulation ensuring significant energy savings.
Alternative materials and the environment
Using alternative materials such as recycled EPS not only has advantages for affordable housing sector, but also for the environment.
“With climate change looming and the rising cost of energy, using recycled polystyrene in building and construction applications is an increasingly popular solution for architects and material specifiers. Last year alone, more than 2 036 tons of polystyrene was recycled countrywide for this use in a wide variety of different types and sizes of buildings — ranging from schools, shopping malls, state-of-the-art museums and designer homes, to low cost housing solutions, schools and community clinics,” says Adri Spangenberg, director of the Polystyrene Association of South Africa.
The jumbo blocks from Greenlite Concrete used during the construction of a building. Credit: Greenlite Concrete
The highly insulated walls from the jumbo blocks have the added benefit of conserving energy over the lifespan of the building. In addition, Cowie says that removing polystyrene from the waste stream has a positive impact on the environment. “Polystyrene is probably the most versatile construction material on the market in terms of carbon footprint. The fact that we only use recycled polystyrene is even better,” Cowie adds.
Cost effectiveness of alternative materials
According to Michael Page, a committee member at the South African Affordable Residential Developers Association (SAARDA), there is not much of a difference with regards to alternative building materials and cost. Page’s experience with more than 15 suppliers of alternative building systems over the past three years has found that most of the products realise savings on labour and time, rather than cost.
“Let’s say it takes you four to six weeks to erect a normal brick and mortar house, they claim you can do it from three to seven days,” Page explains. He also says that when it comes to costs, sometimes the use of alternative materials works out to be the same or even higher as using conventional building materials.
“At the end of the day, the product is geared for volume. To date none of the suppliers could provide proof that there is a true material cost saving of an acceptable alternative method over traditional bricks and mortar.”
Page does however highlight that using alternative building material that saves time and labour would be effective for a project that requires the delivery of many housing units in short amount of time. For example, if you need to deliver 500 housing units monthly, then using alternative building materials and methods for that project makes sense.
Alternative building materials and socio-economic factors
There are other factors to consider when looking at using alternative building materials. One of them is the market’s perception around alternative building materials, as Page explains clients traditionally favour bricks and mortar to alternative materials. This is due to the market perception that bricks and mortar is a strong product, with no other to compete with it.
Another factor is the social component within a development. Page’s example of this is the use of less labour with alternative building materials. For an example, using alternative building materials in a low-cost housing project could employ 50 people compared with 200 plus people with bricks and mortar.
“For the same price I would rather employ 200 plus people and put food on their tables,” Page explains. Ultimately the only saving in Page’s view relates to using less labour in the construction and erection of a house during a low-cost housing project.
Page also adds that market perception is unlikely to change any time soon — unless the client and purchaser is well-informed that they don’t need bricks and mortar to have a strong house. He adds that costs related to alternative building material needs to be accurately re-looked.
Page concludes, “At the end of the day, we as developers are not biased when considering the use of alternative building materials versus traditional building methods. We constantly review alternatives that may enable us to provide a cost-effective home to the market and pass on savings to buyers. We need to find synergy on cost and acceptance from all parties involved — ultimately delivering and selling a product that satisfies potential buyers’ needs.”
Regulations around alternative building materials
Agrement architectural technical group leader, Sammy Skosana, explains that if that alternative building material has an Agrément South Africa certificate, so stakeholders can be rest assured that the product has gone through stringent tests and meets all standards and requirements.
“To comply with the National Building Regulations, one can go the deemed-to-satisfy rule as stipulated in SANS 10400 — namely, the conventional way of construction,” says Skosana.
An engineer can be approached to do a rational design, where they take full responsibility of the structural integrity of the building or you can approach Agrement South Africa, that will issue a certificate that is fit-for-purpose for the intended use of that innovative or alternative building technology.
Skosana also adds that there are ongoing tests and research locally and internationally by reputable research organisations to determine if recycled building rubble can be used in certain construction environments without compromising structural strength or integrity of the building.
“Certificated alternative building materials is the way to go. These are used extensively all over the world and even in seismic conditions. Most are affordable and easy to construct as many them involves the use of an unskilled labour force and therefore provide employment and are quicker to erect. Currently there is a shortage of conventional building material exacerbated by the housing backlog,” he concludes.
There are alternative building materials available on the market for use not only in low cost housing, but also in other areas of construction, including roads. These building materials have been found to be less labour intensive and save a lot of time, however they are not really cost effective. The market has yet to fully latch onto the use of alternative building materials for low cost housing projects.