The Difference Between Raft Foundation vs Pile Foundation

The construction industry serves as one of the formidable pillars of the progress of our civilization. Throughout history, various construction projects have shaped the face of mankind’s presence on Earth as we know it today. However, many of us do not deem it worthy of wondering about the intricacies in the world of construction. That brings us to the question of the most important part of any construction project.

The sole answer to the question is the foundation. Foundation is the most crucial part of a construction project, and its effectiveness is very important for the success of the project. Therefore, it is very important to understand the purpose of a construction project and the suitable foundation type for it. In the following discussion, we shall explore the differences between two noticeable types of foundation, i.e., raft foundation and pile foundation.

Defining the foundation

Before moving into the two types of the foundation under concern in this discussion, let us know more about the foundation. Every foundation structure consists of two parts, known as the superstructure and the sub-structure. The superstructure of a foundation is above the ground. The sub-structure of a foundation is the part that lies below the ground level.

The foundation works for transmitting the load of the structure to the ground soil. The foundation rests on solid ground known as foundation bed. The foundation transmits loads of the structure and its weight to the soil in a manner so that it does not exceed the ultimate bearing capacity of the soil.

Types of foundation

The different types of foundations are classified on the grounds of load transmission to the ground. As a result, we get two broad categories of foundation, namely shallow foundation, and deep foundation. Let us learn about them in brief before outlining the differences between the raft foundation and pile foundation.

Shallow foundation involves a lesser depth of placing the foundation than the foundation’s width. Shallow foundations are also known as spread footing because of transmitting a load of superstructure to the ground laterally.

Deep foundation, on the other hand, has a higher depth of foundation than the foundation’s width. The deep foundation ensures the transmission of a load of the superstructure vertically to the deep underlying rock strata.

Difference between raft and pile foundation

The raft foundation or mat foundation is a prominent example of a shallow foundation. On the other hand, the pile foundation is an example of a deep foundation. This is one of the first and the most general point of difference between these two types of foundations.

Raft foundation design

The design of raft foundations involves a mat of concrete that just sits on the ground or above the ground. The foundation is spread across the complete area of the building for supporting heavy structural loads of the columns and walls.

Therefore, the important factors for consideration in the design of the raft foundation include edge conditions, the variability of column loads, and mat stiffness.

The raft foundations are ideal for buildings with moderate size and a regular layout.

The design involves placement of the mat’s center at the center of vertical loads held by columns with uniform soil pressure. The horizontal column actions to the outside get neutralized within the mat, and inward reactions neutralize with the friction of mat on the soil. The weight of the concrete removes any concerns about uplift pressure.

Pile foundation design

The design of pile foundations is highly focused on two significant components. The components are pile cap and a single pile or group of piles.

Piles are generally installed in groups of three, and they can help in tolerating inaccurate column placement.

The pile foundations are made of steel, wood, or reinforced concrete and are available in the prefabricated state.

The design involves laterally braced columns piercing through weaker soil and reaching the suitable ground. The lateral loading receives resistance in the pile foundation through bending. The use of pile foundations is appropriate for areas that do not have sufficient land for construction, or the ground is soft.

Conclusion

Therefore, you can notice clearly that there are differences between the raft and pile foundations. The most prominent point of different lies in the types of buildings for which they are suitable. Both types of foundation are distinct in terms of design and offer different cost benefits also. For example, raft foundations prove cost-effective in the short-term while pile foundations are built for the long journey!