Types of Shallow Foundations and Their Uses

A shallow foundation is also known as the spread footing which helps to transfer the weight of the building structure to the surrounding soils which is close to the surface area. Other types of foundations go deeper into the earth, whereas, the shallow foundation have a depth which is less than its width.

The shallow foundation had been constructed in those areas where the upper layer of the soil reaches a maximum depth of 1.5 meters and thus possesses the capacity to stand with the structural load of the construction structure. This type of foundation helps to ensure stability on the surface level of the soil.

Design requirements for Shallow Foundation

Certain design requirements should have to be met for the shallow foundation which are:

➢ There should be safety against the load-bearing capacity, that is strength exceedance of the underlying soil.
➢ Excessive settlement which can be damaging to the overlying structure or affects the functionality of the construction structure should be controlled.

Importance of Shallow Foundation

There are several advantages to choosing a shallow foundation in the construction site which are as follows:

Simpler construction process

The construction process of the shallow foundation is relatively straightforward as compared to the construction process of other foundations which helps to make this type of foundation more quicker.

Cost-effectiveness

Fewer materials and excavations are required for the construction of the shallow foundation as compared to the deep foundations. This helps to save the overall cost of constructing this type of foundation.

Suitability for various structures

The shallow foundation is suitable for various types of construction structures such as houses, garages, low-rise buildings, or some bridges on solid ground.

Limitations of shallow foundations

Apart from the advantages, there are also some limitations of shallow foundation which are:

Restriction of the soil

Weak or compressible soils are not suitable for this type of foundation as this foundation requires strong soil to resist the weight of the structure.

Limited depth of the foundation

This type of foundation is not appropriate for every heavy structure as it requires deeper load distribution.

Different types of Shallow Foundations and their usefulness

There are different types of shallow foundations which include:

Strip footing

This type of shallow foundation is also known as continuous footing which is the common choice for the construction of load-bearing walls. This type of shallow foundation is narrow and long and spans the entire wall length. Strip footing helps to distribute the load from the walls to the underlying soil evenly. These types of foundations are effective in those areas where the soil has the capacity to bear a substantial amount of weight across its length.

The advantages of using strip footing are:

➢ This strip footing helps to provide the uniform distribution of the load along the wall length.
➢ The construction of the strip footing is economical to construct the multiple walls along with shard footings.

Isolated footing or spread footing

Isolated footing or spread footing helps to support the individual columns of the construction structure. This shallow foundation type helps to spread the entire load to the larger area of soil thus helping to prevent excessive settlement. These shallow foundation types are ideal in case the columns are spaced at a distance from each other.

The usefulness of this type of shallow foundation is:

➢ This type of foundation is appropriate for point loads or individual columns.
➢ This shallow foundation type also helps to minimize the impact of the settlements on the construction structure.

Cantilever footing or strap footing

The strap footing or cantilever footing has been used in the case of the building structure extending beyond the main footing area. This type of shallow foundation has been designed to counterbalance the uneven distribution of the structural loads with the help of the cantilevered portion of the building structure.

The usefulness of strap or cantilever footing are:

➢ Cantilever footing helps to maintain stability and balance of the uneven distribution of the structural loads.
➢ This shallow foundation type also helps to provide support to the cantilevered or overhanging sections of the building structures.

Combined footing

In this type of foundation, two or more columns are close to each other. Multiple columns have been served by this type of foundation which helps to distribute the construction structure’s loads effectively.

The effectiveness of the combined footing include:

➢ Multiple columns along with shared loads have been supported by this type of footing.
➢ This shallow foundation type also helps to decrease the requirement for separate footings for the adjacent columns.

Raft foundation or Mat foundation

A mat foundation or raft foundation helps to spread the load over a larger area. A thick concrete slab has been involved in the raft foundation which helps to cover the entire footprint of the building structure thus distributing the loads of the building structure effectively.

The advantages of using a mat foundation are:

➢ It helps to reduce the differential settlement through the distribution of the load over a large area.
➢ Raft Foundation also helps to offer stability in those areas, where the soil condition is challenging.

How to choose the correct types of shallow foundation

Several factors need to be considered while choosing the most appropriate types of shallow foundations for the specific construction project. These factors are as follows:

To learn more, watch the following video tutorial.

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The structural loads

The weight of the building structure or any kind of additional load that can be bear by the foundation structure needs to be analysed.

The local building codes

Specific requirements regarding the construction process are mandatory and need to be followed by the construction team according to the region of the construction site.

The condition of the soil

The types of soil, the strength of the soil, as well as the load-bearing capacity of the soil of the construction area also need to be analysed before constructing the shallow foundations.