Is it necessary to lay a foundation for a building? You can build a building without it if you don’t need it to stand for a long time. Buildings without foundations have traditionally been simple structures built and not designed to last.
Although a structure may be able to withstand its load’s downward force without a foundation, it is the sideways motion that causes the issue. The earth expands and shrinks as it changes temperature with the seasons, generating instabilities that cause the building to move.
Unless the building is on rock-solid ground that will not tend to change much based-on climate changes. However, its stability depends on the structure’s foundation that sits on a level deep enough to maintain a consistent temperature. Then it will reduce the level of movement.
However, in most cases, buildings are not always built on rock-solid lands that are stable. The foundation of the building is what gives the building its strength. A poorly constructed base may also be dangerous potentially. With more and more skyscrapers in the modern days, stronger foundations are even more vital.
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Three main purposes of a foundation for a building
A foundation serves three important functions the first being, sustaining the weight of the entire building. At times of natural disasters, a sturdy and strong foundation keeps the structure standing. It also protects the residents safe in times of disasters such as earthquakes, floods, and storms. Moreover, it is important to construct the base in a way that the ground moisture does not leak and destabilize the structure.
According to professional engineers, the foundation is critical for supporting both “dead” and “living” loads. As the underlying structure remains constant, this refers to as a dead load. The living occupants of the structure, as well as any things that they carry, are the live load. As a result, it must be able to convey all this weight to the earth. If the project is to be completed on sloping land, it must be designed to be long-lasting.
What kind of constructions can you build without the use of a foundation?
You can for instance, construct buildings on piles or stilts without foundation. This is most common on flood plains or swampy coastal areas, although some buildings do have foundations, just not standard ones. The weight pushes down through the piles to a stable level, effectively performing the same function as a more traditional foundation, but with the increased load capacity provided by ‘skin friction.’
Types of foundation for buildings
You can categorize shallow foundations into individual footing, combined footing, strip footing, and mat foundation.
Individual footings: Individual footings, also known as isolated footings are the most used type of foundation in the construction of buildings. It is designed for a single column. They are constructed in a rectangular shape or square shape and are utilized when the loads from the structure are carried by the columns. The load on the column and the bearing capability of the soil determines the its size for safety.
Combined footings: These rectangular footings forms when two or more columns are close enough together that their footings overlap. It composes of individual footings, although their structural design varies.
Strip footings: these have a broader base and it distributes the weight of the building across larger areas, providing greater stability.
Individual columns, walls, and bridge piers with bearing soil layers within 3 meters of the ground surface are supported by spread footings and wall footings. The soil carrying capacity must be sufficient to support the structure’s weight over the structure’s base area.
Mat foundation or raft foundation spreads across the whole area of the building to support heavy dead loads of the walls of the buildings.
The mat foundation types are great for column and wall foundations where the loads from the structure on them are extremely high. This helps to prevent differential settling of separate footings. Therefore, it is hence constructed as a single mat comprising all the structure’s load-bearing parts.
Deep foundation types
This foundation type further divides into two. They are pile foundation and drilled shafts or caissons.
Pile foundation helps to transfer large loads from a structure to a hard soil that is many meters below the ground.
Drilled shafts are similar to foundations. However, it resists structural loads using shaft friction, toe resistance, or a combination of the two. We use an auger to produce drilled shafts or caissons as in figure 4 below.
We use drilled shafts when the depth of hard strata underground level is between 10m and 100m. Moreover, drilled shafts may carry more column weights than pile foundations. Moreover, drilled shafts does not suit where there are deep layers of loose soil or water-bearing granular soils. It is also unsuitable for soils with difficulties to stabilize cave formations, boulder soils, or spring water aquifers.