In this part of the world little emphasis is placed on soil test before a building is erected, hence, there is a need to bring this aspect of structural engineering under radar and this article attempts to do justice to that.
Not doing a soil test to determine the right kind of foundation for your building could spell doom for your home years later. In fact, deciding on any type of foundation for your home without a structural engineer carrying out the necessary soil test is having a death wish.
How would you feel when that house you spent millions on falls to the ground in the twinkle of an eye?
There really should be no excuse not to get the soil that beget your land tested before a building is erected on it. What you see on the surface is not indicative of what might be 10 or even 20 feet below the surface. Soil that feels firm under your feet may be very loose below the surface.
Soils vary in type, composition and strength. The differences can be significant. Some soils are very strong and can support significant weight, while other soils are weak and squish out the sides under light loads. The old buildings that are structurally sound that you see near your new lot undoubtedly have foundations that rest on high-quality soil or the weight of the structure has been transferred deeper into the ground where good soil or rock can be found.
Ordinarily, a soil test lets you know if your site conditions will attract additional building cost. For example, if it is a dump-site or they find deep fill. The idea of using the rule of thump which is prevalent in Nigeria is highly criminal and a disaster waiting to happen. Soil strength and texture can be unpredictable even within the same plot of land.
That notwithstanding, potential problems and costly mistake can be avoided in the future if you carry out a soil test on that land.
A soil test on a land is usually carried out to determine the following:
(A) Surface Texture: The amount of sand silt and clay in the soil.
(B) Permeability: The rate at which water enters and passes through the soil.
(C) Depth of soil to bedrock: This includes both topsoil and subsoil.
(D) Slope: Steepness and length of the slope.
(E) Erosion hazard: The amount of topsoil currently on the site and the potential for future losses.
(F) Surface runoff: The rate at which water flows off the site based on slope, drainage and texture.
(G) Shrink-swell of the soil: This involves changes in volume based on soil wetness.
(H) Water table: The depth at which water occurs in the soil both seasonally or permanently; and
(I) Flood hazards: The frequency that water from storm runoff inundates the site.
According to the Managing consultant, Lagos State Materials Testing Laboratory (LSMTL), Abel Famakin, since the inception of the Agency saddled with the responsibility of soil and materials testing, no incident of building collapse has been recorded from any of the certified buildings and materials tested by the Agency; pointing out that non-compliance to building standards and negligence by contractors has been responsible for perennial building collapse in the state. This information was divulged at the 8th anniversary of LSMTL last week in Lagos. This further lays credence to the importance of soil test before a building is erected on a site.
However, suggestions about a possible enforcement of soil and materials testing to curb the incidence of building collapse in the country is an issue for another day.
LSMTL was established eight years ago by the APC National leader, who was the then Lagos State Governor, Asiwaju Bola Ahmed Tinubu popularly called Jagaban.
So, before you start to build make sure you get a qualified person to do a soil test and an engineer to do the site classification.