27 March 2019

Uganda: Building With Steel, a New Way to Cut Costs - Experts

Steel composite construction is a new construction technology aimed at reducing the number of raw materials and costs incurred during construction.

According to designingbuildings.co.uk, composite elements are made up of two or more different materials, and the main benefit of composite elements is that "the properties of each material can be combined to form a single unit that performs better overall than its separate constituent parts." Steel-concrete composite is an example of a composite element.

Budgeting for more than Shs2.1b for the construction of eight-storeyed apartments, Siraje Makanga, a businessman and owner of Beverly Apartments Buziga, is one of the few people who have embraced the steel composite method of construction. He says compared to the conventional method of construction, steel composite is cost-effective.

"Initially, my budget was Shs2.1b but I was advised by a friend to use the steel composite method of construction. I might not have saved much but my budget was reduced to shs1.5b," Makanga shares.

Yusuf Kazibwe, an engineer at Nana Corp Limited, says steel composite method reduces construction costs by 35 per cent depending on what you want. However, he says the method is best used for storeyed buildings because in bungalows, a lot of material goes to waste, especially steel. When using this type of construction, Kazibwe says all construction materials are put to use, but they are calculated and in smaller quantities. For example, where you expect to use two trucks of bricks, one truck is enough. "When using the steel composite method, proper calculations need to be made, especially with steel. This is done to help you identify the right size and material to be used," Kazibwe advises.

Foundation and columns

I-beams are the widely used in this kind of construction and these are available in a variety of standard sizes, depending on what you need. In this case, steel I-beams act compositely with other materials such as concrete, timber, bricks among others.

Moses Walakila, an architect, says during the laying of the foundation, instead of using iron bars, rings, binding wire and aggregate, I-beams and concrete are used. For the columns, stainless steel hollow bars welded with I-beams are used.

"The difference in terms of cost is that one stainless steel hollow bar of six metres costs Shs250,000. An ordinary house has three metres, meaning one hollow section can be used to construct two floors," Walakila says, explaining that when using the conventional method, constructing a three metre column costs about Shs478,000 x 2, which is Shs956,000.

Slab

Kazibwe says instead of using the maxspan, nails, rings, iron bars, among other materials for a slab, with steel composite method, one only needs to use I-beam, timber, aggregate, cement, sand, cement, BRC and nails.

The cost of I-beams depends on how many you need.

For example, he notes that one I-beam costs around Shs280,000 and the span can approximately be 25 metres x 280,000, which is roughly Shs7m.

"The slab and brick work of a three bedroomed storeyed house costs between Shs16m and Shs17m," Kazibwe says.

Brick work

Walakila explains that in the conventional method, the walls are normally 150mm, which is about 52 bricks per square metre. Walls such as a 230mm composite wall takes about 32 bricks per square metre. He says the difference is in the brick arrangement.

"For the conventional method, bricks are laid in header format such that the small end only appears on the face. Stretcher, which is the steel composite way, bricks are laid such that the long, narrow side only appears on the face of the wall," Walakila shares. Stretcher makes the building lighter yet dependent on columns, I- beams and light weight concrete covers.

Here are the benefits of using steel composite building method:

Strength and safety

Herbert Butoga, a builder, explains that when you are constructing high storeyed buildings, commercial or residential, because of the I-beams and steel hollow bars, the structure turns out to be stronger withstanding earthquakes and strong winds. He says the entire building is solid, welded and bolted as a single unit.

"From the foundation to the roof, the structure is one whole unit with lighter slabs and stronger columns, which are constructed using hollow sections. In between the hollow sections, concrete is applied to enforce the strength of the I-beams and also sustain the number of floors you want," Butoga says.

It takes a shorter period

Makanga says one of the benefits of steel composite construction is that it takes a shorter period of time to construct and less labour is required. However, this is only possible when you have all required resources.

"It took me three months to complete eight apartments in Buziga," he says.

Limited material wastage

He adds that during construction, the site remains clean since less or no material is left to go to waste. Less and lighter materials can easily be moved around the site during construction. Kazibwe says every step taken in the conventional method requires patience, for example, you wait for 21 days for the slab to dry and before it does, you cannot proceed to the next level. However, this does not happen with the steel composite for construction is continuous.

Fire resistance

"Steel composite construction is resistant to fire and in case of a fire outbreak, the flames will not spread," Butoga says, adding that during construction, the timber is covered with mortar and plaster, which is an innovative fire-retardant coating. He explains that the chances that the building will collapse after a fire outbreak are less.

Maintenance

Herbert Butoga, a builder, says steel requires little regular maintenance and it is easy to repair. Mentioning that the costs of maintaining a steel composite structure remain low throughout the lifetime of the building.

When the construction is complete, he says it is advisable to conduct maintenance checks twice a year.

"Get a structural engineer or contractor to conduct the checks and make repairs whenever necessary," Butoga advises.

Noting that incase you come across any holes in your steel structure or a crack in the paint, it is best to not leave it for the future because any minor issues can in the long run turn into major ones that might affect the overall structure.

That is why it advisable to fill all holes and use paint to repair any scratches.

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