The last is yet to be heard on the flooding in cities as concerns are mounting over its effects on submerged homes.
Built-environment professionals monitoring the development have reinforced the need for the Federal and state governments to embark on a post-disaster survey of buildings in affected states.
They’re also recommending structural integrity or non-destructive tests of the buildings, especially the ones above one-floor to determine their continuous fitness for habitation and mitigate building collapse incidents across the country.
The Federal Ministry of Humanitarian Affairs, Disaster Management and Social Development and the National Emergency Management Agency (NEMA) data revealed that as of October 24, 181,600 houses have been partially damaged and 123,807 houses totally damaged and 392,399 hectares of farmlands have been totally damaged.
Also, 3,219, 780 persons have been affected by the 2022 flooding, 1,427,370 persons internally displaced, 2,776 persons injured, while 612 people were killed.
Prior to the ongoing flooding crisis, cities across the country had recorded repeated structural failure with over 461 buildings collapsing between 1974 to July 2021, and more than 1,090 deaths, including billions of naira worth of properties lost to such disasters.
Out of the figures, Lagos as the busiest construction site accounted for the largest chunk. For instance, over 34 cases were recorded between January and September 2022 in the state according to statistics from the Lagos State Emergency Management Agency (LASEMA).
Speaking on the development, a past president of the Nigerian Institute of Building (NIOB), Mr. Kenneth Nduka told The Guardian that the greatest enemy of any building is water.
He said during flooding, water penetrates the structure passing through the capillary elements of the structure whether wood/metal or concrete.
On the severity of damage to buildings, he explained: “If water passes through the wood, it will eventually rot because water dries out slower in building materials. The material composition of the wood structure will decompose and you can have rot, algae growth and strength of the wood structure is compromised.
“If water enters concrete, it absorbs it and compromises the bounding power. The same thing if water goes into the block work, it becomes wet and loses strength. Then, the chemical composition of the block or concrete will be affected. If it is reinforced concrete, water will be retained in it and encourage rust.
“Afterwards, the building can experience concrete cancer as the rot would manifest, start leaking and showing on the reinforcement. Once that occurs, the integrity of the structure is compromised.”
Nduka observed that efforts are always made to ensure that the foundation of buildings is anchored on firm ground but, he said when the water content of soil is overwhelming, the soil will move and stability of the foundation will be compromised, thereby affecting the structural integrity of the building.
He said: “Everything installed in a building, including tiles and paints will be affected because of water. When the flood goes down, there is what is called efflorescent; water coming out of the block concrete will create moles, which have been proven to be carcinogenic, with health implications that reduce the life span of the building.”
On the environmental impact of the flooding, he noted that most reptiles and animals look for where to hide for safety and there may be openings created by the movement of water, reptiles may move into the ceiling of buildings and multiply. He calls for fumigation of affected buildings to ensure that the environmental health of the structure said occupants is assured.
The former NIOB’s boss said to avert collapse, buildings that are above one-floor need structural integrity tests to ascertain fitness before accommodation.