Learn all about the types of foundations and how to choose the most suitable for your building site!

Antonio Neves
Written by
Antonio Neves
Published in
31/5/2021
Updated
31/5/2021
Learn all about the types of foundations and how to choose the most suitable for your building site!

The foundation is the base of the whole construction, that is, it is the structure responsible for absorbing all the loads emitted by the building and distributing them to the ground. Do you realise that it is what gives support to the whole construction? Therefore, it is extremely important that it be executed correctly to avoid serious structural problems in the future. More than this, it is necessary to follow all the recommendations of NBR 6122, which concerns the whole process of execution of the foundations.

Thus, before starting any foundation project, read carefully the NBR 6122 to understand which are the correct procedures to be followed. By the way, whenever you are going to perform any procedure in a work, it is essential to follow the guidelines of the Technical Standards. In our blog, you can find summaries of several of them. Take a look there.

In this article, we will bring important information about foundations. Among them: what do foundations consist of, what is their function, what are their types, how to waterproof them and, finally, how to define the best type for your construction.

With all this information that I will provide in this article, you will be able to analyse and choose the type of foundation that best fits the needs of your work. Let's go?

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What are foundations?

Before we get into the more specific topics, let's have a better understanding of what foundations are. The foundation of a construction is nothing more than a structure that supports the entire load of the construction. Therefore, the execution of any work begins with the foundation, as it is from this that the entire structure will be built.

Thus, it must be done following all the recommendations and stages defined by NBR 6122, ensuring greater safety for the entire work.

Choosing the type of foundation that will be used in the construction is also a fundamental step that must be done in the project, before the execution of the foundation. To define which foundation will be chosen, it is necessary to analyse some variables, such as the type of soil and the weight of the building, for example.

Since it is a great responsibility to choose the type of foundation and how it will be laid, it is essential to have the help of an engineer or a qualified team to carry out this task.


What is the function of a foundation in construction?

We have already talked about what the foundation is for in a construction project, but it is worth pointing out so that there are no doubts about the importance of this stage during the initial phase of execution of a project.

The foundations are responsible for distributing the weight (load) of the construction to the ground in a safe way to avoid the occurrence of various types of problems, which can even compromise the construction itself. Among some damages, we can mention: landslides, cracks, cracks and other very serious problems caused by errors in the foundation.

A very clear example of serious problems caused by errors in the foundation are the crooked buildings in Santos-SP. These buildings were built many years ago with a very shallow foundation, with a depth too small to support the constructions in an unstable ground, with the most solid fragments of rock being more than 50 metres deep. You see this is a very serious problem, but fortunately, after studies and efforts of researchers, it was possible to keep the buildings inhabited without risk of accidents through the realignment of the buildings by hydraulic jacks.

It is not always possible to find a solution for the damage caused by errors in the foundation. Therefore, attention during the execution of a foundation is essential to avoid future problems and ensure a quality construction work.

What are the types of foundation?

Let's now understand what are the most common types of foundation used in construction. Remembering that each one of them has its own characteristics and, therefore, are suitable in places that require certain structures. Therefore, it is important to analyze the soil and the weight of the load that the foundation should support to define which type of foundation best fits the construction project.

Foundation types are divided into two major classes, shallow or direct foundations and deep or indirect foundations.

Shallow foundations are indicated for constructions with up to two floors, due to their better cost-benefit ratio. It transmits the load directly to the ground through its bases and has a depth of 3 meters or less. The formats of shallow foundations vary according to the type, but all are built with concrete and steel. The most common shallow foundations are:

  • Isolated footing: recommended for soils with firm and resistant soil, where the building load is transmitted to the columns, which transfer the weight to the footings, distributing it to the soil. Generally, they have a rectangular or square base and the top may be straight or pyramidal.
  • Flat footing: shallow foundation, with a continuous reinforced concrete structure located below the walls, with dimensions of width and height greater than the span beam.
  • Beam: this is a beam located below ground level and runs the entire length of the walls of the building and connects the isolated footings to distribute the weight of the building. It contributes to better locking the columns, but it requires a lot of time and work.
  • Radier: shallow foundation recommended for low resistance soils. Common in light structural masonry works, the radier is a reinforced or prestressed concrete plate that is below the building and in direct contact with the ground. The building is built just above it and the weight is distributed uniformly to the ground. One advantage is its fast execution and economy of materials.

Deep or indirect foundations are indicated for soils that do not have good resistance in the first 3 meters of depth. They transmit the load from the structure through the shaft resistance, through the side, and the point resistance, through the base. Most used in large projects, such as high-rise buildings. The best known deep foundations are:

  • Piles: indicated for soil with little resistance, where piles more than 3 meters deep are required to reach a firm soil to make the foundation. This type of foundation transmits the loads to the soil by lateral friction and its excavation is done with a manual or mechanical auger, commonly called a drill.
  • Jibs: suitable for works with very heavy loads, such as bridges, viaducts and large buildings. It has a deep foundation cylindrical structure, in cast-in-place concrete. It can be made of steel or concrete, with or without lining. The casings can be made in the open air or under compressed air. 

These are the most common types of foundations for a building. But how to know which is the most suitable for your building site?

How to define the type of foundation?

To choose the ideal type of foundation for a building, it is necessary to use technical criteria, that is, to analyse the type of construction, how much load will be transmitted to the ground and what type of soil. For this, it is essential to hire an engineer to carry out the construction's structural project. Only he will have enough technical knowledge to define the best type of foundation for each work. But, here I brought important information that can help you in this choice too.

How to waterproof the foundation?

Any foundation needs to be waterproofed in the right way and with the right product for that use. A lack or failure of waterproofing in a foundation can generate very serious structural problems, which can compromise the entire construction. Not to mention the inconvenience and unplanned expenses. That's why we recommend Blok EP 2, our semi-flexible waterproofing for negative hydrostatic pressures, which offers excellent waterproofing, flexibility, and resistance. To know more about this product and how to use it in your construction, talk to Blok's team. 

I hope this article has helped you learn more about foundations, their types and how to choose the best one for your project. And don't forget to use Blok EP 2 for your foundations! Until next time.

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