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New technology to deliver mass low-cost housing

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To accomplish affordable shelter for Kenyans, adoption of innovative and cost-effective construction techniques will come in handy

In February this year, Arcoverde Kenya Ltd broke ground for construction of Iguta Paradise Homes, a 62 four-bedroom town-houses project along Kiambu Road that overlooks Runda.

Five months later, much to the surprise of many, the first phase of the project comprising 32 houses is now complete and the houses are currently being painted in readiness for the market.

The project director, Mr Patrick Kamau, told DN2 all the 62 houses will be ready for occupation by December.

“If I was building on a flat ground, I would have handed over the houses even much earlier. The sloppy ground is derailing me because I have to erect gabions to hold the soil, but by December I will be handing over the keys to buyers,” he said.

A woman at the gate vending food to builders on the site says she thinks a miracle is happening there.

“One day there is no house on the site, the following day you wake up to find houses,” she says.

Unknown to her is that the developer for Iguta Paradise has taken a paradigm shift from conventional building techniques that would otherwise consume a lot of time to a more efficient reinforced concrete technology imported from Korea and the United States.

Patterned aluminium formwork set-up for a perimeter fense. In the background are shells for Iguta Paradise Homes constructed with alluminuim formwork from Korea.

He is using aluminium panels, steel, ballast, sand and cement. On the site, there are no building stones or wood. The houses are built using aluminium panels from Korea while the perimeter walls separating different units are being put up with patterned aluminium formwork from Wall-Ties and Forms Inc. (WTF) technology, a Kansas City-based global giant in aluminium forming systems.

According to Mr Thomas Muturi, an architect and a representative of WTF Kenya branch, this cast-in-place steel reinforced concrete is basically a construction technology where aluminium formwork are fabricated to take the shape of the entire building, then assembled on site, leaving a hollow space in between where ready-mix concrete is poured. This eliminates the need for brick and mortar.

Developed in the mid 1970s, the technology of using aluminium forms has been used in the construction of thousands of residential units for both low- and high-rise buildings.

It has proved successful in the construction of low-cost mass housing projects in various parts of the world.

In Ghana for instance, a leading homes developer in collaboration with the country’s Social Security and National Insurance Trust built 1,680 apartment units and sold almost all of them in less than two years.

In Kenya, no one understands the magic of this technology better than Epco Builders Ltd. Epco’s 315 low-cost homes for Ministry of Housing employees along Jogoo Road is a case in point. They started using traditional post-and-beam construction methods in early 2010, the project was taking too long to deliver each block of flats; one 600 square-metre level of seven flats was taking a month to complete.

But when the contractor used the aluminium post-and-beam concrete forming, the delivery speed was cranked up so much so that an entire block of 35 flats was done in 10 weeks.

But it is Epco’s second housing project in Langata that clearly demonstrates the speed at which aluminium concrete forming can deliver a house.

“We built 116 units in nine months. Typically, we were delivering a floor every four days. That means we were building a block that has four floors in just 16 days,” says Mr Muturi, whose WTF had teamed up with Epco Builders Ltd to execute this project in February 2012.

METICULOUS PLANNING

The goal of this technology is primarily to industrialise the entire building process. How this technology manages to achieve the goal, Mr Kilonzo, says, is by ensuring that every time there is an ongoing activity at the site.

This calls for meticulous planning as Mr Kilonzo explains:

“You have to roll out the programme in such a way that at every stage there is a different activity happening on the site. So excavators would need to be on the site probably one month earlier, after which masons will lay the foundation. Then you will have people come to tie the reinforcement steel and others to do the piping and wiring systems. Basically, from assembly to pouring the concrete we just need a day, depending on the size of the building.”

While slabs have to be cured for recommended 21 days, the use of high-strength cement with this technology ensures that the walls dry fast.

This means that about 90 per cent of the aluminium mould is slab, and making sure there are no time-outs during the construction.

For developers, saving on time will definitely save them money.

“If you are using borrowed money, it means you will repay your bank loan in say two years instead of five, so you save on interest payments and share the savings with the home buyer. If it’s for rental purposes, you start collecting money almost immediately,” says Iguta Paradise Homes developer.

The government intends to construct 500,000 affordable houses in five years and it has allocated Sh6.5 billion for the project. This translates to at least 100,000 units every year, making it a herculean undertaking.

Developers and experts in real estate concur that even with a budget and goodwill in place, pulling off such a project will not be a walk in the park and the government has to encourage developers who will put up the houses through public-private partnership to embrace alternative building technologies to deliver many houses within a short time.

“There is hardly any single developer who can build such a huge number of homes within the given time. Considering that the government wants to put up at least 100,000 units a year, it is imperative then that it will have to leverage on new technologies as traditional brick and mortar might come up short,” offers Mr Muturi.

Iguta Paradise Homes project director says: “This is the way to go. Reinforced concrete is the technology that the government should adopt to deliver the affordable housing dream.”

THE TRAINING

Architect Thomas Muturi.

All a developer needs to get started is to submit the architectural drawings to a fabricator like WTF. Aluminium formwork will then be fabricated to an exact architectural design and detail.

Notably, the contractor does not need a workforce with extraordinary set of skills to run the show. Mr Muturi says the skills employed in this building technology are easy to grasp and the developer only needs to recruit residents and train them on formwork setting and stripping on the site for 2-4 weeks depending on the simplicity or complexity of the project design.

“The beauty of the aluminium formwork is that it is easy to learn how to fix the panels,” says the architect.

“Actually the only tool workers on our sites require is a hammer since the forming is secured with simple pins and wedges.”

Prefab technology has caught on in recent times. But even this comes with its fair share of challenges. First, the pre-cast concrete slabs have to be transported from the factory to the site, presenting the risk of breakages and additional transport cost.

Also, prefab technology does not provide a monolithic structure per se considered sturdy and safe as there are joints. Still, the contractor would need to have a crane on the site to lift the heavy concrete slabs.

SAFE HOUSES

During the Kenya Homes Expo in April this year, most potential buyers of WTF formwork expressed concerns over the integrity and durability of houses built with this technology.

In response to the concerns, Mr Muturi told DN2 that since all concrete aspects of the building, including the walls, slabs and staircase are poured monolithically, eliminating joints, the houses are safer compared to conventional brick and mortar ones.

“The best example we give is that of a place in Peru where there was an earthquake. Everything around collapsed apart from one structure that had been done using our system. To put it simply, you are looking at an entire fabric of steel reinforcement and concrete that is all interconnected both vertically and horizontally, unlike the traditional brick structure that has the tendency to develop weaknesses at the joints,” he says.

He adds that another advantage of this technology is that there is no wastage of material on site. Also, the walls are so smooth that they do not need plastering, just some skimming and they are ready for paint work.

Just recently some building projects stalled following the ban on logging. Mr Muturi notes that if the government is serious about conserving the environment, especially with the rolling out of the mass housing project, it should encourage the use of construction technology that does not rely on timber.

The ban on logging brought to the fore the impact of the move on timber-dependent construction techniques. But unlike some traditional construction processes that require timber to execute, all operations under the aluminium technology are timber-free.

The million-dollar question any developer is likely to ask is how much money this technology saves them.

“This method results in cost cutting of between 15 to 20 per cent compared with conventional brick and mortar technique,” says Mr Kilonzo.

“While it may be expensive to buy the aluminium set for say the first housing project, one thing you need to understand is that the set of formwork can be reused up to 2,000 times. So considering all the other benefits, you save more in the long run,” says Mr Muturi.

The construction process

WTF aluminium formwork construction

The process begins with compaction of the site. Trenches are then dug, plumbing installed, and aluminium slab formwork is set.

Once structural footings are dug, slab steel is installed in accordance with local code. Concrete is then placed using local methods. Wall steel is tied in accordance with local building codes.

Electrical boxes and conduit are attached to the wall steel. When constructing mass housing projects, the architect notes, it is wise to prep slabs well in advance.

The concrete forms process normally starts in a corner or multiple corners depending on the number of workers and continues until all walls are erected. Once wall forms are set, decking can begin.

Decking like wall formwork is hand-set and begins in a corner.

Upon completion of decking, steel and electrical components are installed in preparation for concrete placement.

“All your electric conduit — the switch boxes, the water piping, all the drainage pipes, basically everything that needs to go into the walls, is installed before concrete is poured in,” notes Thomas Muturi, a representative of WTF Kenya branch.

When all prep work is complete, concrete is placed monolithically in walls and deck using a boom pump but this is dictated by equipment available in the local market; it can include trailer pumps, crane buckets, and even hand bucketing.

The formwork is removed the next day to begin the cycle again. For multi-story structures, scaffolding is then attached to not only support the weight of the workers but also the exterior wall forms.

Steel is tied, forms set, and concrete placed. After concrete placement and curing, aluminium concrete forms are removed leaving foam insulation permanently bonded to the concrete.

All decorative features, whether structural or ornamental that need to be captured on the external walls can be incorporated in the aluminium panels. This eliminates the need to have a mason make additional features on the exterior walls and comes as a cost-cutting aspect.

And there is no space for human error, he notes. “Our system operates like a jigsaw puzzle. The last piece of the aluminium panel will not connect with the rest if all around the house the vertical panels for walls are not precisely laid.

So even if the builder somehow deviated from the provided measurements, the pre-measured aluminium pieces will align the house back into the preferred measurements,” says Mr Muturi.

He adds that in terms of quality, the system all houses look the same.

 

-www.nation.co.ke

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