As Kenya races to house a growing population, the most efficient building technology delivered at the least cost will be the key to development.
In the market today, there are several extant and unfolding technologies that have worked well in economies that sought to deliver durable mass and affordable housing, especially apartments, at the shortest time, which the One Million Houses Agenda is seeking to borrow from.
The efficient technologies include the various aspects of Monolithic Construction Technologies and Mivan Shuttering Construction Technology.
Mivan shuttering
The Mivan formwork uses wall reinforcing steel to mold structures. The steel is precast at the factory and installed at the construction site. Both the beams and the slabs are poured at the site and the mostly aluminum formwork taken away after the concrete has cured and is strong. Other components are stub pins that join wall components and beam side panels, where the beams are placed.
Mivan Shuttering is notably being employed in the billion-plus population of India where it has come in handy because of its fast implementation. The Delhi Government embarked on one of the world’s most ambitious mass affordable housing projects dubbed: Housing for all.
The use of Mivan technology is mostly informed by the fact that it reduces construction time by half. A key marketing point for the Mivan formwork is the reduced need for skilled labour, which today is a major bottleneck to large infrastructure projects in Kenya, ranging from railways, roads to houses.
In particular, the walls and beams construction save on masonry and rendering services as it does not use bricks or blocks, aiding quick delivery at minimal labour deployment.
Apart from the cost savings, Mivan is reputed to be structurally superior in withstanding earthquakes and other seismic disturbances. Reduction of the number of joints in the construction process not only enhances longevity of the structure, but also maintenance during the lifetime of the housing unit. Equally, construction of the walls and slabs with fewer joints increases the uniformity of the structures and reduces leakages.
A key marketing point for the Mivan formwork is the reduced need for skilled labour, which today is a major bottleneck to large infrastructure projects in Kenya, ranging from railways, roads to houses
In terms of floor development, it takes seven days, compared with conventional construction that takes 21 days.
However, there are drawbacks, in particular for small projects, as the aluminum formwork — skillfully removed when the concrete is cured — tends to be expensive. It is thus suitable for large-scale projects like apartments. It is also noted that aligning the steel (timber and aluminum can also be used) is a skilled labour for the concrete to be poured correctly.
Monolithic technology
This type of construction is one of the oldest, having been recorded as early as 700AD in Jerusalem during the Zagwe kingdom. It was also deployed in ancient Ethiopia and India in various forms, hundreds of years ago.
But a major breakthrough would wait for centuries in 1908 when Thomas Edison registered the Monolithic patent that involved construction using only single concrete placement. The technology was a hard sell though, given the expenses involved despite a sales pitch that it was fire-proof.
The Edison technology failed the market test with his cement company losing dollars hand-over-fist, but some construction did take place to stand the test of time. Monolithic construction structures stand in New Jersey, USA, to date. The one-pour concrete technology has proved an important learning point and a practical method for mass housing, with India using it for vast and fast development. In particular, the country uses it for office and residential housing under the tutelage of the Central Public Works Department.
A major breakthrough would wait for centuries in 1908 when Thomas Edison registered the Monolithic patent that involved construction using single concrete placement. The technology was a hard sell, given the expenses involved
It has been picking up in the US also, while countries like the UK have used it for years, thanks to aspects like cost saving and speed of construction.
Unlike the step-wise construction widely practised in building single-dwelling residential houses to larger multi-storey residential and office blocks, the monolithic concrete structure saves on cost, right from the foundation. The so-called footing in Kenyan buildings takes a lot of mortar and steel to avoid structural defects in the future, as well as to withstand the weight of the building blocks.
The monolithic technique is much preferred in high-rise buildings where it is proven to withstand earthquakes of up to 8 points on the Richter scale. Among the advantages are sound isolation and high thermal insulation. With a lower weight, it can prevent cracking and extend the lifespan of a building.
How it works
Typically, it combines the footing and slab being poured at the same time instead of going through the time-consuming curing and layering processes. With footings taking about 12 inches and the slab just four inches, construction is much cheaper and faster. While excavation is required, it is shallower, given the depth of both footings and the slab.
Concrete mixing can be done with a vibrator, with due care taken to eliminate air pockets in the mix. To achieve good results, a wire mesh or rebar can be used to prevent cracks while laid over a gravel bed, on top of which proper preparation is needed for drainage purposes.
But even as the monolithic technique is appreciated for fastness and cost-saving factors, it has a number of drawbacks that must be considered before it is deployed, especially in colder climates prone to thawing. However, in the Kenyan situation where thawing is rare, fill-dirt or loose chippings can cause cracking, thus requiring stabilisation.
Besides being carbon-intensive in implementation, the construction is less suited to sloping terrain, where it requires much more concrete to stabilise. It can also crack under the weight of materials in large buildings or structures. In flood-prone areas where structures are supposed to rise well over the ground, authorities will not prefer monolithic construction, which is normally inches in thickness. Nevertheless, it is preferred for its fastness, given the reduced mortar volume and less thickness. It is a reinforcement through bars or wire mesh and strengthens the structure at lower costs.
In hard and rocky places, the monolithic concrete saves the cost of digging the foundation and back-filling, making it cheaper and faster.
Here, the monolithic construction wins over the step-wise technique, given that you simply have to pour the mortar as opposed to a complicated process that has seen many buildings crack in the country, owing in part to lack of skills.
The task is simpler and does not require sophistication and multiple curing.