The rate at which building collapses occur in Nigeria is quite alarming. In fact, we are convinced that the faster we take practical steps, the safer. Nigeria Real Estate Hub’s correspondent, Esther Adeniyi was able to interview a seasoned Civil/Structural Engineer, whose experience we can trust to guide us on practical solutions to reduce and in the long run, totally combat the frequency of building collapses in the nation.
In an exclusive and expressively informative interview, we get a grasp of the causes of building collapses, possible solutions and a thorough guideline to safest building and construction practices in Nigeria. Read the full interview below:
NREH: Can you kindly introduce yourself sir?
Engr Disu: I am Engr. Adedeji Disu, a Professional Civil/Structural Engineer with about a decade of Structural Engineering experience and a Senior Project Director with IAA Associates Ltd, a leading Structural Engineering firm in Nigeria. I am a Member, Nigerian Society of Engineers (MNSE), Nigerian Institution of Structural Engineers (MNIStructE), Nigerian Institution of Civil Engineers (MNICE) and a registered Civil Engineer with the Council for the Regulation of Engineering in Nigeria (COREN).
NREH: The rate at which building collapses is occurring in the country is quite alarming, what is the cause of this?
Engr Disu: As a Professional Structural engineer, building collapse, at most, should be a very rare occurrence. In other words, collapses should be once in a lifetime by circumstances beyond human control. But unfortunately, majority of building collapses in Nigeria are caused by human negligence and avoidable mistakes. The rate of collapse is now at a frightening frequency resulting in attendant loss of lives and properties and sub-consciously perceived by the society as ‘normal’. Just in July 2017, a mother and her baby died in a case of building collapse in Lagos. Two generations erased!
There are various factors responsible for collapse but to put succinctly, when a building cannot adequately support its own weight and other imposed and dead loads it is designed to carry, that building is already a candidate for collapse. This is why a Structural Engineer is saddled with the responsibility of the overall stability and performance of any structure during its intended life time. Poor structural design, which consists of inadequate structural sizes, unstable framing, over and under-reinforcement, detailing errors, non-compliance with standard codes of practice are most often the primary causes.
Another cause of building collapse is alteration of building usage by clients, say from residential to office without the structural engineer’s approval. For example, a residential building is normally designed for an imposed load of 1.5kN/sq.m while for an office it’s in the range of 2.5kN/sq.m to 3kN/sq.m. So when a building designed and constructed as residential is converted to an office by erecting additional floors without considering the adequacy of the existing foundation of the residential building , collapse is knocking on the door.
Also, with a building, though well designed but poorly constructed with sub-standard materials and workmanship, collapse is only a matter of time. This is where the supervision role of the structural engineer comes in to play in ensuring strict adherence to quality control and quality assurance standards.
Every structure is supported on a foundation and this foundation transmits the superstructure loads to the underlying soil. Another important cause of collapse is failure of clients to conduct sub-soil investigation. In this case, the building may not collapse at once but it starts to experience severe cracks, noticeable tilting and sinking below the ground level. Unfortunately, a lot people neglect sub-soil investigation despite the fact that the cost is less than 0.5% of the total cost of a project.
I am glad that Lagos State Government has made soil test report a requirement before building approval is given. Other states should tow this path. As a professional, I strongly advise clients to carry out soil investigation because without this, a structural engineer cannot make good engineering judgement on the foundation design.
Also, the proliferation of quacks in the construction industry is also another cause of collapse and it is really perplexing. There are people who call themselves engineers just because they are arranging blocks on site and there are people who are trained and certified engineers.
In fact, during supervision, some of these contractors argue that they have been constructing buildings in a particular way for the past 20 years and I always tell them, ‘you can be doing the wrong thing for 20 years’. They say that is how we have been doing it but I tell them the ‘ WHY’ of what they are doing. Another misleading assumption by some of these quacks is that they say because they constructed a particular building in a particular way and it has not collapsed, then they are confident their method is right.
However, from a structural engineer’s point of view, a building does not collapse immediately. It can take up to 5 years or more after occupancy. The sad thing is when a building collapses, not only are lives lost, generations are wiped away. This menace of collapse must be curbed with a real sense of urgency.
NREH: What are possible steps that can be taken to reduce or totally avoid this?
Engr Disu: The rate of building collapse can be reduced to the barest minimum but total elimination is a gradual process which involves appropriate synergy between various professionals.
First things first, people should ensure their buildings are designed by professional structural engineers. 80% of buildings in Nigeria are made of reinforced concrete. This means the quality of the two major materials, concrete and steel determine the structural integrity of any building. The concrete produced from constituent materials (cement, fine and coarse aggregates) must meet the required strength (N/sq.mm) specified by the structural engineer while the steel rods must not only pass tensile strength test but more importantly, elongation requirements. Elongation is often overlooked but should be given more attention.
Due diligence by the structural engineer at the design stage is not an option but a core duty. You must get it right at the design stage. However, beyond a good design, any building construction should be supervised by competent structural engineers who should be involved from start to finish. This guarantees adherence to stringent quality control measures during construction which goes as deep as using potable water for concrete works. Unfortunately, this is not often the case in Nigeria.
The choice of building contractor must be devoid of sentiments. While there are other selection factors by other professionals, the structural engineer should assess critically, the technical competence of proposed contractors and give an unbiased recommendation. The cheapest bid may not necessarily be the safest. However, if a Client decides to directly construct his or her building, a structural engineer should be their guide.
Rolling out sanctions to erring designers, contractors or even property owners involved in building collapse will serve as a deterrent and ensure things are properly done as it concerns buildings or structures in general. In other stricter climes like Asia, the engineer or builder or property owner is put to death. However, Nigeria as a nation is not at this disciplinary level yet but we can set the ball rolling.
NREH: What can the government do to avoid future re-occurrence of building collapse?
Engr Disu: The government’s pivotal role cannot be over-emphasized. As I mentioned earlier, until the Lagos state government took the bull by the horn by enforcing sub-soil investigation, it was taken with levity. There should be stable policy guidelines on building approval throughout the country, properly trained personnel for structural drawings approval in town planning offices, effective monitoring personnel in town planning authorities responsible for ensuring that plans approved are the ones executed on site, legislation of laws that prohibits non-professionals from undertaking building construction supervision, etc.
Relevant professional bodies, especially COREN, NSE & NIStructE should ensure increased sensitization to the public on the need to engage professionals before and during building construction.
NREH: What other things would you love to say about the frequent building collapses in Nigeria?
Engr Disu: Beyond the frequency of building collapse, my ultimate dream is total elimination of collapse. Is this an arduous task? Yes. But is it achievable? Definitely Yes. For this to happen, all hands must be on deck in order to nip all future re-occurrence of building collapse in the bud.
From the government, to the professionals in the construction industry, to the property developers, to the contractors, we all have roles to play. Permit me to quote from the ‘Man on the job”, leaflet a Cement and Concrete Association, UK publication, ” One man’s carelessness can let down the whole job; every man’s care can make it a job to be proud of. So, it really does depend on you”.