Aspiring property owners, developers and even professionals in building construction often assume that bungalows do not require extensive foundational details, but this is contrary to the opinion of experts in the geo-technical investigations and foundation design.
Often times, owners of storey buildings are always alarmed on noticing that their multi-million-naira property was sinking. Many reasons were adduced for the then unfolding “drama”. Neighbours and friends blamed some diabolical elements for the structural failure.
Upon enquiries, the owners are introduced to firms of geo-technical, civil and building works professionals who specialize in foundational design and construction and then start investigating the building’s foundation and the sub-soil structure. Investigations later revealed that the sub-soil was very weak to the extent that that piece of land had “swallowed” two other buildings previously constructed on it.
It is instructive to note that the foundation failed despite the fact that the developer utilized the raft design generally considered to be very strong and dependable in addition to being on two-metre-deep beams.
The experts eventually were able to rescue the building from total collapse by under-pinning the foundation, but that was an expensive job that posed some discomfort to the residents.
The importance of geo-technical investigation before designing and constructing buildings on any piece of land with the peculiar nature of Lagos as a littoral (by the sea) and riparian (by the river) state makes it susceptible to foundation crises.
It is regrettable that people don’t learn from other others’ mistakes. It is funny that years after independence and with many endowed professionals in the building construction industry, people still embark on construction without following the due process.
The due process involves subjecting the site to geo-technical investigation before even designing and constructing building in order to unveil the nature and type of engineering properties of the sub-soil.
After obtaining the necessary data in the form of soil test report, recommendations will be made by the geo-technical engineer as to the most suitable foundation type for the soil. The foundation could be strip, pad, raft or in some extreme circumstance, pile. This will enable the structural engineer, architect and builder to design according to the budget of the client.
If the cost of doing the recommended type of foundation is too high and unaffordable by the client, the builder should be advised to look for land on firmer ground.
When the underlying sub-soil material is weak, the number of floors may have to be reduced in relation to the soil’s bearing capacity.
It is observed that if clients and construction industry professionals have been observing this process, the crisis of sinking and collapse of structures would have been reduced to the barest minimum.
Experience on the field has shown a wild conflict between assumption and reality. In most prone areas, the sub-soil material is so weak that bungalows are subjected to sinking or tilting of foundations beyond settlement and consolidation. Experience has also shown that even fence walls that have to cope with only dead and wind loads do sink.
Every building design must achieve the design triad of function, safety and cost. If one is able to marry the three, the built environment will defy losses.
It is observed that most building owners that are subjected to sub-soil investigation are the multinational corporations who appear to be the biggest patrons of geo-technical experts in the country.
It is very important for buildings and other civil works such as road and bridge construction to have good and appropriate foundations. This is so because having a sub-soil investigation would have revealed the load bearing capacity of the soil beforehand.
The function of foundation is to spread the load of the super-structure evenly in order not to put too much weight on certain elements of the building.
In summery therefore, the following essential points of note can help check the spate of building collapse while engaging the services of experts.
- Don’t assume that one foundation type will suit all buildings.
- Get expert to conduct thorough sub-soil and geo-technical investigations.
- Follow expert’s advice in designing the appropriate foundation type.
- Under-pin the foundation of existing but failing structures.
- It costs more to correct foundation problems than to do sub-soil investigation before constructing the house. .