After the collapse of a building in the Nigerian city of Lagos that killed at least 11 people, including several students attending a school on the top floor of the building, we look at a few reasons why such tragedies are so prevalent in some African countries.
While investigations into the cause of this collapse are still ongoing, engineers have cited some common problems.
1. The foundations are too weak
Sufficient foundations can be expensive.
It can cost up to half the price of a building, notes Professor of Construction, Anthony Ede, at Covenant University in Ota, Nigeria.
He says that when building the foundations, there are two things to consider: the strength of the floor and the heaviness of the building and its contents.
In Lagos, the marshy soil requires a strong foundation. Far stronger than solid ground.
He says, however, that builders save money that should be spent building on foundations on the marshy terrain of the city. Many buildings have collapsed in the city.
Even on solid ground, foundations have to be strong enough for the load.
Insufficient foundations for a four-story building was one in three Reasons of the investigators for a building that collapsed in northern Rwanda in 2013, killing six people.
2. The building materials are not strong enough
Sometimes materials are used that are not strong enough to hold back the load, says Hermogenes Nsengimana of the African Organization for Standardization, whose organization met in Nairobi in 2016 to discuss why so many African buildings are collapsing.
He suggests there is a market for counterfeit materials – to the point that sometimes steel is used instead of steel.
In April 2016, when a six-story building collapsed in the Ugandan capital Kampala, the director of the city council suggested it had been built using counterfeit materials. reports on the Ugo News site,
Mr Nsengimana says there are even cases in which counterfeiters fake certificates of authenticity.
However, he suggests that contractors knowingly use the wrong materials to cut costs.
Therefore, they can use concrete to carry the weight of a one-story building in a four-story building.
Mr Ede adds that the regulators do not do this.
3. Workers make mistakes
Even if workers are given the right materials to make the concrete, they mix it wrong, says Ede.
This leads to concrete that is not strong enough to hold the load.
He accuses the developers of cutting costs by hiring unskilled workers, who are cheaper than trained construction workers.
This is one of the reasons by civil engineers Henry Mwanaki Alinaitwe and Stephen Ekolu to explain why a building in Uganda collapsed in 2004.
Their research shows that the workers misunderstood the mixing ratios of the concrete.
It has been suggested that people used wheelbarrows instead of cement meters to measure cement.
The five-storey new BBJ hotel collapsed during construction and 11 people died.
"There are bricklayers and even technicians who call themselves engineers," warns the president of the Nigerian institution for civil engineer Oreoluwa Fadayomi in Nigeria's The Punch News Site.
For those who want to save money for professionals, he advises: "One should not be wise and be foolish".
Nigerian building collapses
- According to the Nigerian Building and Road Research Institute, between 2014 and 2016, 199 people died in four collapsed buildings in Nigeria.
- 2012: 33 buildings collapse in Lagos and 22 in Abuja according to the Ministry of Housing
- 2013: 17 buildings collapsed in Lagos and 20 in Abuja
- 2014: 13 collapse in Lagos and two in Abuja
- In Nigeria, more than 54 cases of collapsed buildings were registered in 2017
- The last collapse was the third in 2019
4. The load is heavier than expected
Mr. Ede says a building collapses when the load exceeds the building's strength.
He gives the example of asking a baby to carry a heavy box: "The baby will not be able to withstand the load."
Although the foundations and materials are strong enough for what they were originally built for, this purpose may change.
If a building is designed as a dwelling and then turned into a library where boxes and boxes of books are stacked, the building can be under the weight.
He says, another reason why the load is often heavier than the original design, because additional floors are added.
In March 2016, a high-quality apartment building with more floors than planned collapsed in Lagos, killing 34 people the guard reported.
This happened two years after a church shelter for the famous preacher TB Joshua collapsed. because it had more floors than it could hold, In this case, more than 100 people were killed.
5. The strength is not tested
At all construction points, the strength of the building should be tested, says Ede.
"You have to be strict," he says of the police work.
"The law says you have to consider it is the enforcement of the law that is the problem," he says.
That's a big problem, he says, if there's anyone at any stage who has a strong motivation to save money or take money.
There are many physical reasons why a building can break down, but there is only one motivation for it, says Ede. That's money
And that's the real reason for the collapse of buildings – corruption.
The story does not end there.
Just because unsafe buildings are built does not mean that someone has to die – the buildings can be demolished.
And that happens next.
But even in these situations, things go wrong and lead to the loss of life.
6. People stay in convicted buildings
In the building collapsed on Wednesday, the building was classified as unsafe in 2017 and marked as a demolition.
That's why one of the most important questions to be asked about the tragedy is: Why was there a school in the building?
The State Building Inspectorate of Lagos said in a statement that it had been marked as desperate in 2017 and had remained empty, but "the recalcitrant owner renovated the building with gravel as granite, without conducting a thorough inspection of the building's quality and the building let it be used ".
It was a four-storey multi-purpose building with a primary school on the top floor.
One reason why the residents did not listen to the government's order in Lagos was stated by the engineer Felicia Nnenna Agubata.
She told the BBC that construction supervisors are not supported by security officials who can enforce evacuations.
So you can ask well, but these requests are often ignored.
This is an updated version of Article from 2016, why buildings collapse,