Black cotton soil: The bane of Homa Bay town
5 months ago, 12 July 04:40
Homa Bay Town is grappling with a housing crisis. The crisis has been attributed to a chain of reasons whose solutions might be difficult to reach.
Ostensibly, the hosting of many tertiary institutions and the demerits of black cotton soil have contributed to the strain. Students and residents are paying more for accommodation because of insufficient houses.
Black cotton soil
Construction expert Methuselah Onyango says that the town’s soil structure makes building expensive compared to other areas in the county.
“The soil structure on the shores of Lake Victoria renders construction of foundations expensive,” he observes.
For example, he says investors who buy land away from Lake Victoria’s shores save on construction expenses compared to those who build near the shores.
“I have invested in constructing rental houses out of Homa Bay Town. I have realised that it is cheaper to build foundations away from the black cotton soil because the soil there is much stronger and holds houses firmly,” he says.
Mr Charles Ayieko, a civil engineer, cautions that there is need to take necessary precautions during construction in black cotton soil to avoid any damage to the foundation of a building.
“During construction on black cotton soil, the main wall of the building must be provided with all-round reinforced concrete ties or bands,” he says.
“Reinforced concrete ties or bands having 10 to 15 cm deep should be placed at plinth level, lintel level and eaves level. In case the depth of black cotton soil is only one to 1.5 metres, then completely remove the entire black cotton soil and place the foundation below that depth,” he continues.
He further notes that the construction should be done during dry season.
In Homa Bay Town, the percentage of black cotton soil found in total soil deposition is almost 15 per cent.
Black cotton soil has fine-grained clay particles that cause volume variation with change in moisture conditions; for instance, it swells when wet and shrinks during dry period.
Thus, structures built of this type of soil are primed for collapse.
As a precaution, it is important to evaluate factors such as swelling pressure, shrinkage index, consolidation (compressibility of soil) and strength of black cotton soil. It assists to realise the suitability of the soil.
According to Mr Ayieko, Homa Bay Town is also facing financial challenges such as poor circulation of money and low disposable incomes. As a result, many people in the town prefer to stay in informal settlements.
“Most developers avoid building permanent houses because of lack of tenants. They would rather accommodate residents in iron sheet structures so as to get a constant monthly income,” he adds.
More importantly, he says, a major hindrance is the absence of factories in the town. “Manufacturers attract huge populations, which translates to increased demand for housing.”
Homa Bay is one of the towns in Nyanza region where thousands of people reside in informal settlements.
Unlike the neighbouring Rongo Town in Migori ...
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