By Kingsley Adegboye

The lure to live in one’s own property has driven many people, particularly those residing in the cities and urban centres, into buying land even in very difficult terrains. Unfortunately, some of the people who buy these “difficult lands”, lack the financial wherewithal to develop them. Some have ended up erecting structures that are unfit for human occupation.

It is commonplace to find houses looking like airplanes about to take off, simply because the foundation works were improperly executed. In fact, most building collapses in the country have been attributed to poor foundation works. While the affluent can buy land on rocky terrains to build their mansions, experts advise those who cannot afford the huge funds required to build on such difficult terrains, to look for more suitable lands that would not require complex foundation works.

Built environment experts who spoke to Vanguard Homes & Property noted that  foundation laying or requirement differs from one terrain to another. For instance, it would be very difficult and expensive to do the foundation of a building on a sloppy site, a swampy land or hard ground under the topsoil.

Usually, the foundations in such difficult areas will be dug around the edge of the land with varying depths depending on the height of the terrain and the materials to be used. If the terrain is soft clay or rock, then specialised foundation methods such as piling or anchoring would be used.

A Lagos -based builder and engineer, Mr. Olatunde Jaiyesimi told Vanguard Homes & Property  that the first thing to be done before commencing foundation of building project is to test the soil of the land. He said the result of the test which will be analysed by soil engineers will give the bearing capacity of the soil.

Mr. Jaiyesimi a former Chairman of the Lagos State Chapter of the Nigerian Institute of Building, NIOB and current Chairman, Lagos State Branch of the Nigerian Society of Engineers, NSE,  added that based on the analysis, a suitable foundation can now be done. He pointed out that the foundation should be taken into consideration when designing a building, as this will ensure the stability of the house.

Another Lagos-based Civil Engineer, Mr. Afolabi Adedeji stated that foundations of structures vary from terrain to terrain. Adedeji who is the Chairman/Chief Executive, Ethical Business and Management Associates noted that  raft foundations are required in places like Victoria Island and Lekki Peninsula that have sandy subsoil conditions while places like Agege and Ikorodu  where there is firm laterite soil require minimal assistance from a foundation structure.

Adedeji added that what laymen regard as pillar pile foundation ( isolated footings or pad foundation) is required for  high rise buildings in areas where the soil is so weak such as Onike, Yaba. “ A more recent and modern approach is vibrofloatation.

“This is particularly suited to built up areas, where the impact of the pile driving hammer may damage nearby building structures. The soil, usually sandy, is treated through gentle vibration, to become very dense, so as to allow the building to more or less float on it after construction,” he said.

Adedeji advised Nigerians to avoid buying land in difficult terrains as only the affluent can afford to build lasting structures on such land.  He however reasoned that experienced architects and engineers can have plenty of leeway to please their clients with creative designs that fit into the existing rocky landscape, provided that it has adequate bearing capacity to support the superstructure or the house that will be visible to the owner and other people

“In reality, those that procure construction services may not have the luxury of being able to choose to erect their proposed buildings on land that has perfect sub-soil conditions for inexpensive foundation construction. This is a fact of engineering and a fact of life.

“Take for example, the highbrow areas of Victoria Island and Lekki Peninsula in Lagos State, which require expensive raft foundations for low rise buildings and sometimes pile foundations or the relatively new vibrofloatation method for high rise buildings. People are still paying a premium price to have an office or home in these areas,” he said.

Pointing out that structural designs are most crucial when building in difficult terrains, Mr. Kunle Awobodu, former Chairman, Lagos State Chapter of NIOB said with suitable foundations, superstructures can be built on them. He however noted that architects need to take into consideration while designing that only structures with light loads are suitable in difficult terrains, gigantic structures on the terrains will have problem with time.