Foundations and Soil Considerations.

Chapter 2: Foundations and Soil Considerations.

In the construction of buildings, foundations play a vital role in providing stability, distributing the load of the structure, and safeguarding against ground movement. In tropical regions, where soil conditions can vary significantly, understanding the types of foundations and their suitability becomes crucial for ensuring the long-term durability and hence economic benefits of the buildings.

Selection of Appropriate Foundation System

The selection of the appropriate foundation system depends on factors such as soil composition, bearing capacity, groundwater level, and the structural requirements of the building. Let’s explore some common types of foundations used in tropical construction:

Shallow Foundations

Shallow foundations are typically used when the soil near the surface has sufficient bearing capacity to support the building loads. They include spread footings, strip footings, and mat foundations. Spread footings distribute the load over a larger area, while strip footings are long and narrow, supporting load-bearing walls. Mat foundations, also known as raft foundations, are suitable for large structures or areas with weak soil.

Deep Foundations:

When the soil near the surface is unable to support the building loads, deep foundations are employed. These foundations transfer the load to deeper, more stable soil layers or rock formations. Common types of deep foundations include piles and drilled shafts. Piles are long, slender structural elements driven or cast into the ground, while drilled shafts are cylindrical excavations created by drilling into the soil and then filled with concrete or reinforced with steel.

Retaining Walls:

In cases where buildings are constructed on sloping terrain, retaining walls are used to support and retain the soil. Retaining walls are designed to resist the lateral pressure exerted by the soil and prevent slope instability. They can be constructed using various materials, including concrete, masonry, or reinforced earth systems, depending on the specific site conditions and design requirements.

Soil Considerations

In tropical regions, soil considerations are of utmost importance due to the unique characteristics of the soil. The soil type often times determine the type of foundation; depth of foundation; types of foundation materials and size of foundation. Here are some key factors to keep in mind:


Soil Bearing Capacity:

The bearing capacity of the soil determines its ability to support the weight of the building. In tropical areas, where soil conditions can be challenging, conducting geotechnical investigations and soil testing is crucial. This helps in assessing the bearing capacity and selecting the appropriate foundation system.

Expansive Soils:

Expansive soils, common in some tropical regions, have the tendency to swell when wet and shrink when dry. These volume changes can exert significant pressure on foundations, leading to cracks and structural damage. Mitigation measures, such as soil stabilization techniques or the use of specialized foundation systems, may be required to address the challenges posed by expansive soils.

Groundwater Level:

High groundwater levels can impact foundation stability. It is essential to consider the depth and fluctuation of the groundwater table during the design and construction of foundations. Adequate drainage systems and waterproofing measures should be implemented to prevent water infiltration and potential damage to the structure.

Slope Stability:

Building on sloping terrain requires careful consideration of slope stability. Assessing the slope angle, soil properties, and potential erosion risks is vital to designing appropriate retaining walls or slope stabilization measures. Ensuring the stability of the soil and implementing effective drainage systems are key to preventing slope failures.


In this chapter, we have explored different types of foundations and the importance of considering soil conditions in tropical building construction. By selecting the appropriate foundation system and addressing soil-related challenges, construction professionals can ensure the stability and longevity of the building in tropical environments. Kindly note that you would the need the services of a geotechnical and civil/structural engineers to help you determine the type and nature off the foundation that is suitable for your proposed building.

In the next chapter, we will focus on structural systems and materials, examining the design principles and construction methods that are suitable for the tropics.

Continue to Chapter 3: Structural Systems and Materials.


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Engr. Okoye is a registered Civil engineer with interests in Engineering, Project and construction management as well as general management. He is currently the Managing Director of Conifer Konstruktion (Nig) Ltd, a Building construction/project management company located in Awka, South Eastern Nigeria.