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NHC pushes for prefabs to boost home ownership

Monday April 14 2014
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NHC engineers construct a sample house using Expanded Polystyrene (EPS) panels on the Agha Khan walk in Nairobi mid last year. Photo/FILE

In order to boost the supply of affordable housing, Kenya’s National Housing Corporation (NHC), the publicly-funded firm, is advocating for the use of a common packaging material, polystyrene in construction.

Polystyrene is commonly known by its trade mark styrofoam: The white, flimsy material used in the packaging of items such as electronic goods or in making takeaway food packs. This is to be used as a replacement for stones and bricks, potentially slashing construction costs by up to 30 per cent.

The use of polystyrene, one of the prefabricated materials — commonly referred to as prefabs — in the construction of homes has been gaining ground in Kenya’s building sector.

The use of such materials could cut the overall cost of construction, reduce the total time taken to put up a building and hence increase home ownership in a country grappling with a shortage of houses.

The NHC says the use of such material makes it possible to erect a three-bedroom bungalow in as short as 30 days. However, it is not an entirely new technology, having been used extensively in large-scale government housing projects in South Africa, Morocco and Egypt, as well as in Dubai and China to build skyscrapers dozens of storeys high.

When combined with steel and high-grade concrete, polystyrene’s apparent flimsiness turns out to be its greatest strength.

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“Polystyrene is essentially 90 per cent air, so it’s very light, and also provides great thermal insulation as air is a poor conductor of heat,” said Andrew Saisi, the general manager of NHC’s expanded polystyrene (EPS) technology factory in Nairobi. “It’s also stronger than building with conventional stones and mortar.

In a traditional house, steel columns provide support at the corners only. But with EPS, the mesh of steel and concrete provide reinforcement throughout the building.”

It is the combination of the light styrofoam and the strong steel and concrete that makes this material particularly suitable for tall structures.

The higher a building goes, the thicker its walls have to be at the base to support the increasing weight. For this reason, conventional brick and mortar rarely goes higher than 10 floors — the base walls become so thick that building upwards becomes highly impractical.

But skyscrapers are possible because structural support is provided by columns of steel and concrete, and combining it with polystyrene makes the structure not just light but also flexible — it can bend like a tall tree when hit with strong winds, tremors or shockwaves, unlike brick and mortar which would simply snap.

“In the industrialised world, walls especially in commercial buildings are built with much ‘less sturdy’ material — the modern buildings typically have a steel frame, and can use lighter materials for walls which are non-load bearing.

Even in housing in countries like the US you find wood and a variety of composite panels being used, whereas building with stone as you see here is increasingly less common,” said Dr Kamau Gachigi, a material scientist and lecturer at the University of Nairobi.

“Using a light material like EPS in a panel means that you gain all the functionality of concrete or stone, but at a lower cost because the lower weight means that the foundations don’t have to go as deep, as the structure remains light yet strong.”

It is what has made it possible to build so tall buildings in a place like Dubai, a city of skyscrapers essentially built on sand.

NHC is now manufacturing the EPS panels large-scale, and has already deployed the technology in the building of 44 police housing units in Ruai, on the eastern outskirts of Nairobi city.

Just a faint echo

The houses don’t look any different from the conventional ones; in fact, the only difference is that there is a faint echo when the walls are struck, owing to the air molecules in the Styrofoam wall panel.

Siphila Mumenya, senior lecturer at the University of Nairobi’s department of Civil and Construction Engineering agrees that EPS offers high quality housing material at a lower cost, faster speed and reduced labour costs.

“But the greatest bottleneck will be the resistance of people to change from what they know. Marketing the product will be the real challenge,” said Dr Mumenya.

Alternative building technologies are becoming increasingly popular in the region, and are one of the propositions that have been put forward to alleviate the perennial housing shortages.

Kenya’s annual housing demand for example is estimated at 150,000 units a year, but the combined efforts of both public and private developers results in an output of just 50,000 units a year.

Several low-cost materials have already been deployed in the market, including interlocking soil bricks which don’t require mortar to assemble, to pre-fabricated timber panels which can be assembled on site in as little as eight hours for a two-bedroom house.

But as a wholly government-owned body charged with providing housing for Kenyans, and with a Ksh1 billion ($11.7 million) factory already producing the EPS panels, NHC has the advantage of scale, averaging 1,000 units a year across the country — the highest output of any single developer in the market.

Rwanda’s Development Board has already identified EPS technology as the “most compelling new building material” according to a 2012 investor presentation, and is looking to build 4,000 units for the Rwanda Social Security Board and 250 units for Zigama Credit and Savings Cooperative, a financial cooperative with membership drawn from the National Army and Police.

There are about 1,000 new homes added each year to Rwanda’s housing market, but an additional 344,000 dwelling units will be required by 2022; as Kigali’s population approaches two million, the city has to build an additional 30,000 homes every year to meet the housing demand.

But a likely limitation to deploying the EPS technology in Kenya is the steel component, which Mr Saisi admits has been difficult to find in the local market.

“We import the steel from Europe and China; it’s made specifically for our machines and for house construction. We tried to source steel locally, but getting the kind of volumes we require with our specifications for strength and stability would mean a company stopping all other orders just for us,” he said.

Dr Gachigi proposes a more focused attention by government on the country’s steel industry, to ensure that high-quality steel can be manufactured locally.

“The government should consider taking up steel manufacturing as one of the flagship projects of Vision 2030. EPS technology needs very large volumes of steel, and the industry would benefit from government adoption,” he said.

But the greatest challenge to the uptake of the technology in Kenya is likely to be the “Kenyan mindset,” according to Mr Saisi: “Kenyans tend to think that if it’s not stone then it’s not good for building — just like the way we think that if it’s not ‘ugali’ it can’t be food.”

But Mr Saisi believes that with a strategic focus on the rental market first, it will be easier to convince Kenyans that they are not living in houses equivalent to cardboard.

“Kenyans never used to believe in buying apartments; people would reason that it was like buying a house in the sky. But apartments became common in the rental market, because when people are renting all they want is somewhere to live, without any of those hang-ups. With time, buying an apartment no longer seemed so bad. We hope to do the same with EPS — convince the developers of rentals, and the rest of the market will soon catch on,” he said.

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