Types of Foundations in Building Construction
Foundations are the most important part of a building. Different types of foundations have been used in a building to distribute the overall weight of the buildings. Shallow and deep foundations are the key types that have been used in different kinds of construction projects.
Shallow Foundation
The shallow foundation supported the entire structure of the building. This type of foundation helps to transfer the building’s overall weight to the surrounding soil. In this regard, the selection of the right types of foundations is necessary.
Importance of shallow foundation: A shallow foundation is cost-effective and suitable for the project conductions. This is most of the simple construction process which makes the building construction process quicker. Low-rise buildings including garages, houses, sheds, and others have been made with this type of foundation.
Types of shallow foundation
Figure 1: Different types of Shallow Foundation
Spread or Isolated Footing
Isolated footing supports the individual pillars and columns of the buildings thus distributing the structural load of the buildings throughout the soil beneath. The risk of the building sinking has been reduced by using this shallow foundation. This isolated footing is made with different materials such as steel and concrete. The plan of this spread footing is usually rectangular or square. This footing reduces the shearing forces and the bending moments of the buildings at critical sections. Isolated Square footing can be of three different types including Isolated Spread Footing, Isolated sloped footing, and Isolated stepped footing. “Isolated Spread Footing is usually square, circular, or rectangular in shape whereas, “isolated sloped footing” has been designed by maintaining an angle of 45 degrees from all sides. “Isolated Stepped Footing” is another popular type in which 3 concrete cross-sections are used to give the shape of the building.
Figure 2: Spread or Isolated Footing
Strip Foundation
Strip foundation has been used for providing the supports for the linear structure of the buildings such as for the building walls or building columns. The weight of the load-bearing walls can be distributed by using a strip foundation. This type of foundation is also quicker in construction and less expensive as compared to the deep foundation. Strip footing can also be applicable in poor soil conditions. Apart from the advantages, there are also some limitations of strip foundations as these are not suitable for all kinds of buildings. This shallow foundation type also has the chance of being damaged by water issues or flooding. Mainly Deep Strip Footing and Wide Strip Footing are the common types of strip foundations.
Figure 3: Strip Foundation
Mat or Raft Foundation
Ground has been excavated to a flat and uniform level to construct the raft foundation. In this mat foundation, a waterproof plastic sheet and a 3” layer of plain cement concrete have been used. These components are used to create a perfect flat base for the building foundation. After making the base level of the building, a waterproofing layer was also installed to chemically isolate the building structure. There is a chance of containing different types of chemicals into the soil which may impact the long run of the concrete. In this context, the use of the waterproofing layer adds benefits to the foundation structure.
Figure 4: Mat or Raft Foundation
Combined Foundation
The combination of isolated footing is called a combined foundation. This combined foundation is rectangular in shape and used in case the building columns are carrying the building loads. This variety of shallow foundations can be categorized into four different types which are Rectangular Combined Footing, Strap Combined Footing, Trapezoidal Combined Footing, and Raft Combined Footing. The “Rectangular Combined Footing” supports two or more columns, whereas, “Trapezoidal Combined Footing” has been used when one building column load is much greater than the other columns. In “Strap Combined Footing”, three or more column footing have been connected through the concrete beams. In “Raft Footing”, all the columns and walls of the building are supported and the full area underneath the construction site is covered.
Figure 5: Combined Foundation
Limitations of shallow foundation: In the case of using this type of building foundation, the soil needs to be strong enough to bear the entire building’s weight. Weak soil is ideal for this foundation. The shallow foundation is not also appropriate for very heavy structures which require deeper load distribution.
Deep foundation
A deep foundation is useful for constructing taller buildings, marine infrastructure, and bridges as it helps to transfer the building’s load into the stable and deeper part of the soil.
Importance of Deep foundation: A deep foundation helps to provide stability to the building structure which is built on poor soils along with higher water tables at a greater level. The uplift forces from wind can also be resisted by this foundation rather than shallow foundations.
Types of Deep Foundation
Basement Foundation
This structure provides space for storage and working at the ground level.
Figure 6: Basement Foundation
Buoyancy Rafts
This structure helps to reduce the net loading of the building on the soil.
Figure 7: Buoyancy Rafts
Caissons Foundations
This foundation has been built near the surface area and sunk into the soil as a single unit.
Figure 8: Caissons Foundations
Cylinders
The concrete cylinders help to create a level surface. This cylinder foundation is strong, easy to use, less expensive, and long-term durable.
Drilled Shaft foundations
This is also built into the deep excavations and filled with the pre-fabricated load-bearing units, concretes, and others.
Figure 9: Drilled Shaft foundations
Pile foundations
Driving performed units constructs pile foundations. The tubes in this foundation are filled with concrete. These foundations are relatively long and slender members as compared to the other categories of deep foundations.
Figure 10: Pile foundations
Limitations
Deep foundation is more complex and expensive rather than other foundations. There is also a need for the installation of better techniques and equipment for this foundation. Any kind of mistakes during the installation process can be costly during the use of a deep foundation.
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Video Source: QUANTITY SURVEYING ACADEMY
