The activities of unskilled craftsmen in the building industry have really smeared the image of the building profession in the recent past. The incessant cases of collapse of buildings in some parts of the country have resulted in the loss of lives, property and left many people injured. Quite a number of factors are responsible for collapse of high-rise, reinforced concrete buildings in Nigeria. Albeit the blame game continues while the necessary steps needed to tackle the anomalies are not taken.
The need to provide shelter to man and his daily activities has always been an utmost priority. Buildings are constructed to serve as shelter for man, his properties and other activities therefore; they must be properly planned, designed and erected to obtain desired satisfaction from environment. However, recent events in Nigeria in places like Abuja, Lagos, Port Harcourt, Enugu, Aba, and other places in the country have seen these buildings as a growing cause of death, loss of property and left many people injured.
A nation’s development is usually measured by the strength of the building and construction sector of its economy as such this building industry must be properly monitored. The factors to be observed in building industry should include adequate stability to prevent its failure or discomfort to the users, durability, resistance to weather, fire outbreak and other forms of accidents. As new materials are being constantly discovered, so also is the style of building construction changing in the building industry. The selecting of materials, components and structures that will meet the expected building standards and aesthetic value is paramount. But if there is a non-occurrence, non-performance, breaking down, ill sickness and unsuccessful things or attempt in the building exhibiting any of the above characteristics, failure can be said to have occurred which can lead to building collapse. Quite a number of factors are responsible for this incessant collapse of buildings in Nigeria.
Building failure could also be defined as non-occurrence, non-performance, running short, breaking down, ill success, in solvency, and unsuccessful attempt. Failure in construction can be seen as negative consequences arising from risk actions resulting in obstruction of any or all of the appropriate benefits derivable from the construction project. Building failure is an unacceptable difference between expected and observed performance. A failure can be considered as occurring in a component when those components can no longer be relied upon to fulfill its principal functions.
Failure in building could be of two types namely; cosmetic failure that occurs when something has been added to or subtracted from the building, thus affecting the structures outlooks while structural failures affect both the outlook and structural stability of the building.
In Nigeria, building failures have been attributed to so many factors ranging from the use of substandard materials, poor workmanship, low quality of blocks, concrete and other factors. Also building failures can be attributed to the following causes; design faults (50%) faults on construction site (40%) and product failure (10%). While, environmental changes, natural and man-made hazards, improper presentation and interpretation in the design can also lead to structural failure.
Failure could occur in the form of partial or total collapse of the structure as is observed with sand Crete blocks. Sand Crete blocks are composite units made up of mixture of sand, cement and water in specified proportion. The quality of sand Crete block used in the construction of walls play a very significant role in the total strength of the wall. The quality of any sand Crete block is largely determined by it properties which include strength, durability, thermal conductivity, fire resistance, density, efflorescence and dimensional charges. However, these properties greatly depend on the type and proportioning of the constituent materials, mix ratio, mode of compaction and duration of curing. These constituent materials are first mixed and then compacted in moulds to form pre-cast units. On setting and hardening, the blocks attain sufficient strength and can be used as walling units.
The quality of block used in Nigerian building industries is a factor in building failure. For instance, the nine inch (9”) hollow blocks used for the construction of external walls of a building are to support the weight of the decking and other floors above it in conjunction with column. Since the strength of the blocks depends on the ratio of cement to sand used for moulding them, the right proportion must be used to ensure that they are strong and durable. Due to its high demands in the building industry, the block industries in Nigeria have equally increased the quantity thereby compromising the quality in the bid to get the most number of blocks per bag of cement; they use more sand than necessary which eventually results in moulding weak blocks. A lot of these blocks even break in the process of conveying them to the site. Most block industries in Nigeria do not meet the standard requirements specified by the Standard Organization of Nigeria (SON). The Nigeria Industrial Standard (NIS 87:2000) requires that a certain degree of quality for sand Crete blocks be produced. The basic requirements stipulate that sand Crete blocks should have the required crushing strengths, the required dimensional tolerances and the desired appearance; only blocks that are sound and true in shape, free from holes, cracks and any other flaws shall be considered good for use in the building industry.
Government, professional bodies and people are asking countless questions as to who should be held responsible and how solutions could be proffered while high rise buildings continue to fail.