In the light of the recent collapse(s) in Lagos Island recently, that’s has killed at least 20 persons, it becomes rather imperative that the possible causes to these collapse are addressed. Experts have given 5 reasons for building collapse which are: weak foundation, building materials being not strong enough, workers making mistakes, the load being heavier than expected, strength isn’t tested. I added ‘old age’ is another factor for building collapse.
Efforts have been made to shed light on each of these factors.
1. The Foundation is weak
One of the major challenges faced by buildings is the strength of the soil in which it should stand. This usually determines the depth of the foundation. Prof Anthony Ede, Professor of Civil Engineering, Covenant University even suggests that they could cost up to half of the price of a building.
A common challenge that faces builders in Lagos Island is the high water table. This basically means that there little depth from the ground to underground water. So it’s very common for water to be pumped out from the site, and the foundation floor protected with damp proof membrane after foundation trenches have been dug.
These soil types in Lagos Island then require a proper raft and/or pile foundation. When not done properly or not done to the required strength, it increases the chances of an eventual collapse.
2. Workers make mistakes
It’s common practice in Lagos to have people loiter around bus stops with shovels and ‘pon-pon’ waiting for a ripper to drive by so they can hop in to wherever construction site the ripper is headed with the hope of getting hired by the contractor for that day.
The problem with that is, some of these men might not be trained – at all ! So even in a case where the proper materials are available for that site, if they aren’t mixed properly, like say using a 3:6:4 (cement:sand:aggregate ratio)for an M2 concrete grade mix as opposed to the standard 3:4:6 that’s required would only be setting the pace for future problems. Usually, these problems in themselves are not always capable of causing any severe damage to the building, not to talk of a collapse. But when done over and again, human errors either in mixing and application of crucial materials, it could become devastating.
So it’s no surprise that the president of the Nigerian Institution of Structural Engineers has cautioned that bricklayers and even technicians are not referring to themselves as engineers.
3. The Load is heavier and expected
In the case of the Lagos Island Collapse, it was said that the owner of the building at Ita Faji in Lagos Island actually added a pent-floor without any further structural support to the existing building – not like that’d have helped much.
Structural drawings from the engineer are results of calculations based on the generic use of the building, total number of occupants and equipment and temporary load like wind (live, dead and dynamic load) all acting on the buildings. They usually end up over-designing to accommodate a possible case of sudden overuse.
This overuse however is assumed to be temporal, like say a flat that should accommodate 6 persons, housing 14 for a night party. The drawings usually accommodate this load, but not an extra pent-floor load that’d last the remaining lifespan of the building.
So a change of use, from say a mixed use building (commercial + residential only) to an added school with over 100 pupils without a corresponding change in foundation isn’t exactly a smart idea.
4. The building materials aren’t strong enough.
The standard curing time for concrete is usually around 3 weeks, so it should be a surprising thing when one hears a story Building has been completed within a month, but then, it happens !
Unreasonable standards by clients, the fear of being caught up in the rainy season before being able to roof a building are part of the reasons for the rush. This doesn’t give enough time for buildings to cure.
The use of low grade materials especially of those that should serve structural purposes like re-bars, and scrap metals to serve as steel are part of the problem. Contractors also take a share of the blame in this regards as they are found to intentionally purchase and make use of substandard materials to cut costs.
5. The Strength isn’t tested
Professor Ede advises that the strength of the building should be tested at all points of construction.
He implies that corruption is the major reason building collapses, and this is rightfully so. This is because buildings usually do not collapse at early stages of construction. The common case is the building reaching about half way before collapsing.
In a case where strict policies are out in place and enforced that ensures buildings are tested at various crucial points of construction, it would reduce the number of collapse drastically.
6. Building is Old
Experts have stated that there are about 1000 distressed buildings in Lagos. Buildings that if they aren’t demolished soon enough could result to more calamities in the state. In fact, the Ita Faji Building was marked for demolition 3 Times But was never demolished till it came down itself. The Building Control Agency would need to do better to ensure the building policies are enforced to the latter in a bid to end the incessant building collapse in Lagos State.
But if we’re to narrow down the reasons, we’d easily see just two:
- that the owner of the building and/or the contractor are just greedy bastards (yes I said it!)
- The building eco system in Nigeria is definitely not functioning as it should.
As far as I know, no one has ever been convicted for any building collapse in Nigeria. The worst that’s happened are a few arrests here and there. The most popular was the VGC collapse, then we also had the one in Portharcourt, Ibadan (around the same time as Ita Faji) and now two collapse in Lagos Island within a week!
We’d have to do better as a People, to hold ourselves accountable, to hold the Professionals in the Built Environment accountable, to hold the government accountable or these collapse won’t end.